Hacker News new | past | comments | ask | show | jobs | submit login
A DIY E-bike Conversion on the Cheap (ieee.org)
223 points by PikelEmi on Aug 22, 2021 | hide | past | favorite | 258 comments



A word of warning. I started looking a little into motor assist bike mods a few years ago, and very quickly you find that the biggest mistake people make in this area is not altering any of the other systems of the bike. That is, they'll put in the motor, and then just ride. Which works, but then you find that your brakes aren't quite good enough to stop quickly at the new higher speeds. Shocks are no longer good enough to prevent certain issues as well. Maybe the frame needs reinforcing... I don't quite remember the whole laundry list.

I don't know how important some of these improvements are, I just remember reading this advice more than once, and safety is important. So be smart and do your research.


I made an ebike from a brand new Decathlon "rockrider" MTB 3 years ago, and have ridden about 10k km on it since. I changed brake pads often, and tires a couple of times, etc. but the frame is fine.

It's really life changing. I used to ride a motorcycle, and I still own one, but I seldom use it anymore; the ebike is absolutely perfect for short commutes (under 20 km each way).

That said, complete ebikes are more available now, and at good prices, so conversion kits are becoming less relevant.


Don't complete ebikes cost as much as used cars?


In France they start at about €800, or €500 when they're on offer.

Depending where you live, how much paperwork you can cope with and how much you earn, the government will give you up to 50% of the purchase price back.

Most of the cost of a used car comes after you purchase it, though : )


> Most of the cost of a used car comes after you purchase it, though : )

Very true! French cars are certainly no exception to that rule :-)


> how much paperwork you can cope with

This. I gave up after reading the list of documents I would have to produce.


Vive la paperasse ;)

It varies by metropole. Here in Nice it seems straightforward.


Not if you factor in insurance (especially for young males) and budget ebikes start at $1000 and even at entry level they are still very capable. Plus car repairs and gas.

Besides people always get suckered into getting way nicer/newer cars than they really need (myself included). Financing is a difficult thing to keep at the low end. So in practice it’s not really comparable. But cars obviously have plenty of other benefits.


High-end complete ebikes cost as much as a car.

So do high-end non-e bikes.


I bought a decent e-bike for $1800. It’s got good components (shimano) and disc brakes. I’ve put about 2000 miles on it so far and use the pedal assist 30% of the time, turn it off to get more of a workout when riding home.

You can get cheaper and way more expensive but I think this is the sweet spot. (For comparison My non ebike is a hybrid commuter which was about 600)


There is a hugh market for a reasonably powerful ebike.

The ones I like are $2000 to $12,000.

I'm waiting for a Henry Ford type of guy to bring those costs down. I guess the lithium batteries are a big factor in costs?

In the mean time, I'm sticking with my old Zapp bikes. I need a battery though.


I'm really baffled at (e-)bike prices remaining so high. There's certainly not more research than what goes into cars, admittedly amortized over smaller production runs, and battery packs should (should, but don't) cost very little (at 100$/KWh, my bike's pack should be a whopping 43 bucks, let's say 100 if we include the frame mount, the lock, the wiring and the charger).

There is SO LITTLE material overall in a bike, with 99% of the tech having changed little since the '70s, so I guess it's not patents or IP either. It's not the wheels, I can buy replacements for little. It's not the shifting system, a crappy one is 100 EUR and a decent (low-end) Shimano is under 200. It's not the chain, those are 10 bucks, maybe 25 for the higher strength ones appropriate for an e-bike. It's not the motor, as I can get a conversion kit off ebay for 150-200, which includes a wheel and electronics.

Yet, 25kg of ebike costs 12% of 1000kg of a low end city car, while using 40 times less material and not having to undergo all the same rigorous testing, homologation and what else.

What am I missing? Is it all in the frame? Is it all profit? Am I looking at this from a completely wrong perspective ?


Regular non-electric bike pricing gives some good clues. There are decent bikes made by Asian ODMs quite affordably, with simpler but good enough parts like steel frames and 3 or 7 speed IGH. They're not that easy to find on the market because it's hard to tell them apart from the crap ones, and this state of affairs is profitable to people selling bikes.

Also there's been a lot of consolidation, and there aren't many big bike manufacturing companies, so some illegal collusion is not out of the question.


Another factor is used bikes. It's hard for a company to compete with that on price.


Retail batteries are not $100/KWh. If you source high capacity cells from China, you can get maybe $140/KWh. That doesn't include a BMS, enclosure, labor, etc.


I completely agree with you on prices for bikes being to high. I think the reason for it is that bicycles are considered luxury items. They cost so much because people are willing to pay more and there isn't enough volume in bike sales to justify large economies of scale that drive down the price - used bikes eat up that part of the market.

If you look at bicycle parts then it seems like half the parts get updated once or twice a decade. Yet the old stuff was mostly fine.


When someone does come along and create an e-bike that's fast and comfortable enough to coexist with cars on every road short of a limited access highway it will instantly be regulated into oblivion with a bunch of hand wringing about road safety. See mopeds for an example. As soon as they got both good and cheap they got regulated to the point where a crappy car has a better value proposition.

You can already see a litany of comments expressing support for regulating ebikes so they remain a novelty niche in this very thread.


In my locale, mopeds / scooters had a very narrow niche, among college students and some employees, because they could be parked for free. You didn't want to be driving through the campus in between classes because of the scooter traffic. When the university started restricting and charging for scooter parking, the scooters vanished. At the same time I've seen practically no e-bikes in the racks on campus. Most student housing has no indoor bike storage, and they're hard to carry up stairs so it's a problem to find a way to charge them. On the other hand, as I've told my kids, "you were born with feet, you can pedal a bike." Conventional bikes have returned to their proper place at the top of the student transportation food chain.


In trafic a moped is better than a car, and an ebike better than a moped, regardless of regulations. If they impose a full helmet for ebikes I will hate it, but still choose that over a car.


You can buy a shitty car for the price of a decent e-bike.

The e-bike has maintenance costs close to 0.

Cars need insurance and fuel at the very minimum.


> The e-bike has maintenance costs close to 0.

Not perfectly true. You have to renew brake pads, tires, chain and cassette at regular intervals if you ride a lot. They cost way way less than car maintenance though.


An Ancheer ebike from Amazon cost around $1k, and while possible, it would be hard to get a car for that price. It seems pretty well made for the price, but it doesn't include the best quality shifters. I can set the saddle high enough for my 6'5" self, but I do want the handle bars raised as well. I suspect that for people 6' and under, it would be fine as is.


Depends on what kind of used car you're thinking of. (I'm being anal; it's a weird analogy given you can probably get a used car for <$100)

Anyway, the cost of ebikes has gone down a lot over the years, especially as more and more competition shows up and production of various parts (batteries, motors, control units) has scaled up. I just had a quick boggle, ebikes start at around €1200 at the moment (cheaper too, but those are folding bikes).


Possibly. Sky's the limit, as usual...and there are some dirt-cheap _very_ used cars available, so that's not a very useful comparison.


I'm reminded that my college roommate traded his unworking truck for a case of good beer.

He got the better part of that deal. (You have to put a price down on the title when you sell. In this case it was technically $1...)


I think ebike is a misnomer. These things are really e-(motor)cycles. This confusion is making it really hard for me to search for what I need. All I want is an assist to take the edge off of hills. Don't need to cruise at 30mph for an hour.


This distinction is becoming a big problem in our local mountain biking community.

Most of us really wouldn’t mind if people who needed a little extra help (older people, injured people, people new to the sport) were riding bikes that provided a small assist to help out with the hills. It’s actually great to see older people being able to ride again with some help from a motor, for example.

But instead, we’re seeing a lot of e-bike builders abusing the concept to hack or build bikes that are basically electric motorcycles. It gets old fast when your local mountain bike trail is now crowded with kids motoring up the mountain on their modified e-bikes without even pretending to pedal. It’s even worse when they end up deep into trails they’re not qualified to ride with a dead battery and no natural ability to pedal back out.

The end result has been a blanket ban on e-bikes on most trails and a lot of animosity toward e-bikes. I wish there was a better compromise, but after watching all of the dumb outcomes play out on my local trails from a small handful of people abusing the concept, I understand why it had come to this.


58 year old MTB’er here. I was looking forward to getting an eMTB in a few years to keep riding. Feels like the window is closing as many place around me ban eBikes for the same reasons you describe. It’s going to be pretty disappointing if I can only ride at the “eBike Park” full of kids on Sur Rons (basically an electric dirt bike). Oh well, I can still ride for now.


if you get your doctor to right you a note, it can be an assistive device which is not covered by a ban. i am not a lawyer, this is not legal advice, but i am middle-aged.


I think if this is true it highly depends on who owns and mamages the land.

I am pretty sure this is not currently true on almost all US National Forest land. Anything with a motor qualifies as for motor vehicle there and you will only be allowed on trails marked for motorized use on the MVUM maps. This includes mobility devices


Do bans work? I could probably build a bike that you really couldn't tell unless you took it apart.


Partially. My local trail bans e-bikes and off-leash dogs, but I still run into both on a regular basis.

Occasionally there will be someone waiting at the trailhead writing tickets to people who come off the trail with an e-bike or an off-leash dog. This seems to work as word spreads through Facebook groups and people stay away. Also generates some decent revenue when someone can write tickets for an hour and hand out a couple thousand dollars in fines for blatant violations (they stand right next to the very clear signage at the trailhead)


If it's indistinguishable from a regular bike, it's probably not one of the 1500kW bikes their organization had a problem with.


1500kW bike, that's a beast.. with wings and a pocket fusion engine, I presume .. xD


It powers the neighborhood.


EPAC or Pedelec is a term used for bikes that meet the EU regulations, assist should cut off beyond 25kph (15.5mph) and you only get power when you cycle. I think there's a motor wattage maximum too so that might help your search.


yup, and 250W continuous

And the great bit is that if you are ignorant of these laws and get caught on an electric bike doing higher speeds then you get a penalty as if you are riding a motorbike without insurance or a license - aka penalty points on your regular driving license, plus all the other court shenanigans.


Those seem to be the magic words to find what I'm looking for, thanks!


I'm all in for sensible regulation, but don't structure in a way that it's impossible to buy mid-speed ebike because no one knows how to certify or suddenly it costs 4x more for no apparent reason.


We call it a class 1 ebike and they are easy to buy in USA.


I think the phrase e-bike generally refers to a bicycle, with operable pedals, that also has an electric motor to assist when peddling, and possibly a throttle.

When I think electric motorcycle, I think of something that does not have pedals at all.


One issue is that the pedals could be practically cosmetic, if the power added by the motor is such that pedaling is unnecessary. This was true with some early mopeds too -- the pedals were pretty much good for starting the motor and nothing else. I'm seeing more of this as e-bikes evolve towards smaller diameter, wider tires and heavier frames.

The US "class" system seems useful, inasmuch as it more or less specifies the capability of the bike with and without pedaling. I'm all for adding a new transportation / recreation option, and have adopted a wait-and-see attitude for how the technology and its use will evolve. So far, e-bikes have not affected my use of a conventional bike, except for people asking me when I'm going to get an e-bike.


Huh, I've never seen a moped that you could pedal like a bike even in a photo. Apparently the "ped" is from "pedal," not "pedestrian." I wonder if eBikes will follow the same path? I don't think they will, a gas motor is already disruptive enough that you may as well become a motorcycle.


I wonder if electric starters killed the pedals. I grew up in an area that was pretty heavily car-centric, so we didn't see a lot of alternatives. The Schwinn store got the Solex Horse, which had pedals, but they were really only useful for starting as there was one gear with a low ratio.

The only next thing we saw was the Honda Spree, which as I recall had an electric starter and whatever qualified as an "automatic transmission," and I think that class of scooter is still more or less the standard today. It seemed like a big step forward in terms of ease of use.


I've never seen a moped that you could pedal like a bike even in a photo.

As an example, https://en.wikipedia.org/wiki/Puch_Maxi


In Sweden there are different classes depending on if the motor can drive when you are not pedaling.


This could be a market problem, like trying to buy a small car these days. People are demanding bigger, faster, more range. I know several people with e-bikes, and most of them are on their second or third bike in pursuit of more speed and power, fatter tires, shocks, etc.

A used bike might fit your bill. Or the DIY route. The friction motor might be a bit iffy, but you might be able to buy an electric front or rear wheel for not too much and use the same electronics.


Friction motors are not great in the rain. The tire tread type and width, the pressure on the tire and the material of the friction drive surface are all difficult to get right. These kinds of motors are very noisy too.


Search for a 750 watt motor. That is the upper limit in many countries for a standard commercial ebike. Bafang and Tongsheng both produce popular motors.


Google says those cruise at ~30mph.


I had guy in lycra overtake me at that speed (slight downhill). He smiled and took off.


You can get really nerdy and calculate this the way triathletes/time trialists do with a tool like this[0]. I plugged in what I think my numbers are for mass and my relaxed ride CdA and on my road bike and you're on the money.

[0] http://www.aeroweenie.com/calc.html


That's really helpful. It predicts 534 Watts to get me (110kg, 0.4 CdA) to the 45kph limit for Class 3 California bikes.

The Grin Technologies motor simulator https://ebikes.ca/tools/simulator.html predicts (the "Load Line") 837 Watts for "MTB upright", 648W for "MTB, Tuck" and 570W for "Road, Tuck".

I do find that in an upright position it takes 100-200W of human power in addition to 750W power measured at the input to the motor controller. The controller's pretty efficient, but the motor (GMAC) is only 85% max, so there's maybe 570W at the axle. The US CPSC and California laws aren't clear whether the 750W/1 horsepower limit is power in or power out, but power in is what shows on the display, so I limit it to that. Also, even a mild grade will cause the motor to approach the 70 deg C limit I chose after 1 minute. I live in the flattish Santa Clara County, but I'd definitely want a mid-drive if I lived in a hilly area. A 250 or 350W Riese & Müller Delite https://www.r-m.de/en-us/bikes/delite/ I test rode needed a lot of human power to hit the 45 kph max, but it climbed hills in Larkspur like a goat.

750W will have no problem getting a recumbent bike to 30MPH, but don't count on it for an upright.


Oh, and to see what 700W from a human looks like, an Olympic track cyclist toasts a piece of bread: https://www.youtube.com/watch?v=S4O5voOCqAQ


Yep. Bradley Wiggins's 2015 velodrome hour world record was 440W (since eclipsed in distance but not power). This puts into perspective how cheap power is in the industrial age. His hour record was the equivalent power of 35 grams of gasoline. Or it's about 5 not great power tool batteries (eyeballing eBay listings). It's gonna be tough when we have a world built for nearly free energy and we don't have the free energy anymore.


It's plausible. Pro riders put out 400-500W to do ~30 mph, but are likely in a more aerodynamic position than most ebike riders (or drafting).


Pro riders can do 30mph at around 270-300W on a flat surface as they’re typically very skinny. I need about 350-450W to do 30mph as an 88kg/1.88M male.


Hm. You’re right. Bad suggestion. Overkill.


The shocks on most cheap bikes are questionable at best. Lots of stiction and you're lucky if there's any dampening at all.

Downhill mountainbikes are popular conversions. They are designed with high speeds and impacts in mind. The cost may be prohibitive to many DIYers though.

For high speed (50km/h), adequate tires are also necessary. E50 rated tires are now widely available that can handle the speeds and loads.


"Downhill" mountain bikes is a term of art and, as an avid mountain biker, I'd guess not actually the type being used for conversions to commuter bikes.

You're much more likely to target a "trail" full suspension mountain bike or fixed tail bike. You'll have a lot more cost options and they're more suitable for a commuting purpose, they'd still have plenty of travel and braking compared to a standard commuter or utility E-bike. As a note, my mid-level trail bike came with a better set of brakes then my high end cargo hauler e-bike which weighed about 10 times as much.


Yeah there’s no way you could use a DH bike as a daily rider, even with an electric conversion. The geometry and shock travel is just wrong (when you try to pedal a DH bike on the flat, you look like you’re riding a chopper with the added bonus of your knees going up to your waist)


The implication is that most DIY ebikers don't bother with pedalling. Hand throttle keeps you at 50km/h fine.

Long seatposts that bring you up to a typical height are fine. The suspension is doing the work, no need to leave the saddle.


DIY downhill ebike is around $4000 NZD, while the cheapest, lowest spec downhill ebike from manufacturer is $6000 or so. There's a sizeable savings to be made.


Yeah I think you don't need to do this to an expensive bike. Mechanical disc brakes and just a front shock are probably fine if you want to go 50km/hr. A heavier sturdier frame and burlier tires are ok because it is powered.

I wouldn't recommend converting a road bike as they are more fragile.


I’d love a utility ebike but afaik they just don’t have enough weight and hence - the grip at high speeds to be safe.

I’d guess e-scooter/moped is next best thing tho parking is an issue in some places.


Mechanical grip is entirely a function of tire compounds. In fact, ebikes can have even more tractive grip because you can make them AWD! This makes them much safer in snow and ice compared to other two wheeled vehicles.


They are fine at 45-50 km/hr. That keeps pace with car speed on residential roads fairly well. Any faster and I agree you could look at scooter or moped.


What is this "shock" thing you speak of? Is this a nasty side effect of "e" bikes?

A "cheap" bike is just a rigid frame with rigid forks.


In the US midwest at least, almost everyone who buys a cheapo bike from Walmart, Target, etc buys what is basically a terrible hardtail mountain bike. Front fork suspension, wide knobby tires, etc.

My assumption is that people buy them since they are a touch more comfortable than a full rigid bike frame.


Imperfections in the road at 30mph are very different than at 15mph. Especially on a cheap frame.

A fat tire can stand in for a shock, but "cheap" bikes don't usually fit 3" of rubber either.


Relatively cheap electric fatbikes like [1] are currently very popular in Italy, as far as I have seen on a recent holiday:

[1] https://elettrica-bike.it/en/product/fat-bike-vulcano-s-tipe...


Shock absorbers = Suspension

I don’t see any ebikes being sold without at least a 50mm front shock. The added weight of the battery+motor makes it essential


I have a Trek Allant+ 9.9S that is shockless.


Wow carbon fibre, and the tyres don't seem too thick.. How does it ride?

Ahhhh I think I understand - it's a "speedbike" right? So only for driving on roads like a car, so there's no question of forest tracks or gravel walkways.


I upgraded from a Trek xm700+ with a front shock. Both served me well but I don't miss the shock.

Yep, they're both commuter/cruiser type bikes, so probably not best offroad.

Both have the top end Bosch Class 3 motor, so they're usually against the rules on trails in my area.


Being pedantic, the suspension of the xm700+ doesn't have a shock. Its a simple coil spring that gives the wheel some room to wiggle. Shock absorbers actually dissipate that energy with oil/air/rubber.

If you ride it like a bicycle and try to avoid potholes and curbs, simpler designs work great.


Another big issue is stealability - as a cycle commuter I considered an electric conversion right up until I remembered my office is in one of Oxford's black spots for bike thefts (the whole area is bad to be honest, but I'm in one of the worst places for it). The key to preventing your bike from being stolen by some fifth generation product of inbreeding isn't to have the best lock, it's to make it less worthwhile to steal than the bikes around it. The crappier your bike looks the less likely it's going to be stolen, an obvious electric bike parked with any regularity is going to vanish pretty quickly to a thief with a bolt cutter no matter how good your lock is.


So true. I spray painted my bike a flat black and put crappy looking fenders on it for wet riding. It looked like hell on the bike rack.


Put a lojack into the frame and have fun catching them.


Yeah so fun to have to figure out a way home, how to get to work the next day, having to deal with the police, retrieving the bike, hours spent on fun


The police don't want to help retrieve your bike, even if you know exactly where it is.


Or AirTags.


#1 rule people forget is: how fast can you stop. You see it with young car guys vs old ones. Old dudes upgrade the brakes before the turbo and visa versa


Some of that may be because brakes on old cars (drum brakes, undersized discs, etc) were often terrible. I think stock brakes have been quite good on most cars in the last 15 years or so.

For example, a 2021 Chevy Surburban is a HUGE SUV, but does 70mph-0 in 166 feet. Better than a 1999 Camaro Z28 or Mustang GT, at 184 and 182 feet, respectively.


It's a trope from the days when you could still get vehicles with manual brakes with no power assist. As you can imagine enabling such a vehicle to go faster greatly increases the workout the operator is going to be getting to the point where if you want to drive aggressively in stop and go traffic the operator is the limiting factor.


I wonder how the 20 year old GT cars would do on modern tire construction and compounds?


Probably pretty good but not better than modern cars.

In the 2000s one of the car magazines tested top trim (big engine, race package, etc) classic muscle cars on modern tires and they put down respectable numbers, not better than 00s cars, but respectable.

Suspension and chassis stuff hasn't come all that far since the 90s so high end cars of that era should be able to handle very respectably compared to modern stuff. The differences are more apparent at the low end. Modern crossovers handle very respectably for what they are.

Obviously modern stuff will always win in a straight line because power levels increased massively over the past 20yr.


Are those numbers with threshold braking or engaging the ABS?


Not sure, but here's the sources:

The article with the Suburban data: https://www.caranddriver.com/features/a35048882/tahoe-yukon-...

Mustang and Camaro:

https://www.caranddriver.com/reviews/comparison-test/a151408...


I really, really, really, really hate this trope.

You have to go back to the days of drum brakes and no power assist for this to even be close to true. Yet it gets tossed around in every comment thread about modifying anything that rolls because it gets easy virtue points from the safety crowd.

OE brakes on damn near every vehicle made in the last 50yr from a Walmart bike up to a semi truck are more than capable of stopping harder than even nice tires can grip the road. Will you go through more consumables if you use the vehicle harder (enabled by having more power on tap) sure? You'll also go through more tires too. That doesn't mean the brakes are insufficient.


#1 rule people forget is how fast you can stop isn't determined by the brakes as long as they're already strong enough to lock the wheels or cause loss of control, which they always are on cars and often on bikes.


The bigger concern on cars is, how many times can you apply the brakes before experiencing fade or overheating. But yeah - there's a reason old guys use expensive tires too!


Your statement reminds me of my concerns over electric scooters. They don't go superfast - maybe 30kmhr(18mph) - but the centre of mass(hips) location compared to the front wheel looks like a bad braking scenario...


You learn to shift your weight appropriately, but yes - definitely something to be aware of as it throws you if you're not expecting it. I'm speaking from experience on an electric longboard, but ridden both. I find the scooters you're more instinctively likely to brace on the handlebars.


I did a couple of conversions but mostly just replaced the rear wheel with a built in motor. It is a dirt cheap mod and it is very modest optics wise. Unlike other options. In general it is very advisable to look for spots on the frame where the power of the motor will be attacking. Most parts are designed to handle stress just from one direction only. That is why I am not a fan of conversions that utilize front wheel motors and/or big guns like 500W+ motors - even for the rear wheel.


If you limit yourself to like 25mph thats a nonissue though, all bikes are built to handle that speed.


European city bikes are most definitely not built to go 25 mph. A Dutch step through bike with a backpedal brake at 25mph would be very sketchy.


You'll add approx 20-30 pounds with the battery and a hub motor to the frame and that can make stopping more difficult, it's not the same as a heavier rider.


Not sure what you mean. The range of weights on any given adult bike beyond, say, extra small, are much wider than 20-30 lbs. It's exactly the same as a heavier rider as far as stopping distance.


The handling of the bike with weight added on the frame (especially if it is high) is quite different under a hard stop than just adding a heavier rider with the same weight.

You can shift towards the back of the bike with your body for instance.


> especially if it is high

Like the body of a larger person or a person wearing a backpack?


I mean where you mount the battery pack on the bike. On a rear rack above the tire is probably the easiest but its not great for stopping or handling, especially if its more than ten pounds.

On the down tube is better. Carrying the batteries in a back pack can be done. I did that for a few months.


Since the battery and the motor are usually low on the bike, it's actually a little better than a heavier rider.


This is a good point. I bought a used bike for about $100 online and have now done about 5K KM using a cheap conversion kit online, with minimal maintenance. However, I was lucky and also bought a low power kit (250W, while 1000W kits are available). It is a great way to get around but some caution is required. In the wost cases, front wheel drive motors can bend/break the front fork on a ride - not a good situation.


I think the biggest mistake people make with eBike conversions is putting in too powerful of a motor. If your motor lets you bike faster than the brakes or other components can handle, then it's too much motor.

Get an electric moped/scooter/motorcycle if you want to ride faster than you can pedal.


Yes, also include the added weight though. The converted bike will take longer to stop at the same speed just because you added a motor and battery.


Safety is definitely important but I have a hard time lining up this advice with how I ride my current bike. I ride downhill at up to 40 mph and my brakes, frame and shock work fine. On my mountain bike, I jump off 6 foot drops regularly. Maybe it's a matter of wear and tear over time being greater because your average speed is higher? I have a hard believing it's the added weight of the motor and battery either since I'm 50 pounds heavier than my brother in law and we have swapped biked a few times with neither bike having issues.


It can actually be much worse and void your insurance.

There are kits available to convert a low performance e-bike into a high performance one, which runs much faster and needs a registration and a number plate.

But cause an accident, which doesn't even needs to be your own fault with such a revamped bike and your insurance will tell you that you're shit out of luck and you will have to pay for the whole damage. Potentially ruining your life.


Also, at least in the UK, unless the e-bike meets certain conditions it is legally a motorcycle - which comes with the requirement for a licence, insurance, vehicle approval etc.

https://www.bbc.co.uk/news/uk-england-london-51707616


Yes this is a better link.

https://www.gov.uk/electric-bike-rules


Yes, another important one is the chain, if used for transmitting motor power. The additional torque can severely shorten it's life span if it is not adequately strong.


Hopefully your motor will also work as a regenerative brake. But perhaps not every controller offers that?


As I understand it, that's actually rare.


Not rare at all. Most direct drive motors, which is almost all over 750w, can do it, and their associated controllers generally have a setting for that.


It is. Motors that can regen also 'cog' if you're out of power, which sucks. It turns out it's a lot more comfortable to just have a freewheel system that can coast without any extra friction. The extra energy recoverable otherwise just isn't worth the tradeoff.


It should scarcely cost any power to cancel the cogging torque though, wouldn't it? Can't you just keep a small percentage of the battery in reserve for that purpose?


No matter what you do, you still have the ultimate potential endpoint of being stuck out somewhere with a dead battery pack and an annoying ride home compared to a freewheel system.

(It's worth mentioning that the other main reason you don't see regen used much on bikes is that freewheel systems allow the use of gearing, which greatly improves starting torque, which really is what matters for ebiking comfort. Direct drive systems are less efficient, so they are already starting from behind the curve with regards to making regen worthwhile.)

https://www.bikeberry.com/pages/direct-drive-vs-geared


Absolutely. The weight of batteries and increase speed will quickly tell you you need hydraulic brakes, and not a crap system either.

I was thinking, the one in the linked article uses friction against the back wheel. What happens the moment you get a good chunk of debris in there? It could get painful very quickly.


Before you get on one of these, it’s good to check your perspective on safety: https://youtu.be/wM8Xli2KTzI

As a motorcyclist, electric bicycles make me very nervous.


Somewhat irrelevant in places where motor assist is limited to 25kph (EU for example).


I dunno if it's truly irrelevant,

didn't a celebrity spin out of control in a backyard and break his back at less than that? https://www.theguardian.com/media/2020/aug/09/simon-cowell-b...

I think part of it may be familiarity perhaps, which I assume is higher in Euroworld.


No.

That would not even remotely be classed as an electronic bike in the EU.

It is far too powerful for that.

His electric motorcycle had a top speed of 60 mph (97 km/h) and a motor power of 15 kW.

The legal limits for a pedelec cycle in the EU are a maximum assisted speed of 15.5 mph (25km/h) and a motor of no more than 250w.

The motor in Simon Cowell's electric motorcycle is 60 times as powerful as the legal limit in the EU


thanks for this info!

When I first read the story I had assumed the accident occurred at very slow speed or full stop and mashing the throttle - so the 60mph v 25 would not have been something I would consider..

but 15kW vs 250w - now this is something that makes sense in this scenario for sure!

glad to have learned to eye this metric for this.


The issue is naming - term e-bike is used for everything while most if not all consumer "e-bikes" are actually pedelecs (no throttle, limited to 25kph and 250W, assisting only when pedalling). Every other e-bike is classified as moped/motorcycle which might require licence plate, registration and insurance. At least it should be like that in EU.


It turns out that wasn't an e-bike, it was an electric motorcycle capable of 60 mph.


Nancy the Van Seat, a comfy DIY e-couch conversion vehicle created at the Stupid Fun Club, had tremendously overpowered electric motors, a handheld remote control, could turn on a dime, but had no seatbelts.

https://www.youtube.com/watch?v=fvXG4gQ2FWI&ab_channel=Digit...


I wouldn’t want to go faster. 15 mph is probably faster than I’ve ever gone.


A bicycle goes downhill faster then that with little to no pedaling involved. Doesn't even need to be a steep hill.


I wouldn't worry too much, I have routinely done about 50-60 km/h on a motorized bike and had 0 issues. Always had the best disk brakes I could buy though.


Anekdata doesn’t prove much here. Some things you might not be considering:

1. At 60 km/h you are going the speed of a car but car drivers don’t expect you to be going that fast and as a result aren’t wired to look for you. Doesn’t matter how fast you were going when a car going 60-90 km/h didn’t see you and ran you over.

2. Brakes are only half the equation. If your tires start slipping your brakes will lock up and then you go splat.

3. If you do happen to get off at 60 km/h you will have road rash that will take off large chunks of skin even if you wear an armored jacket and armored gloves. In spandex you’ll be looking like Deadpool pretty quickly.

4. Your tires will heat up pretty quickly at these speeds. That will affect how they handle quite a bit.


>car drivers don’t expect you to be going that fast and as a result aren’t wired to look for you That's why I use hi vis jackets and reflective motorcycle helmets. I am not going like a run of the mill bicylist. I use all terrain tires, I never had an issue and I am certainly not the only one that uses motorized bikes like this, in Argentina and Brazil for example, there are lots of people using them daily for their commute and nothing really happens.

>If you do happen to get off at 60 km/h you will have road rash that will take off large chunks of skin even if you wear an armored jacket and armored gloves Wouldn't that happen with a motorcycle too? I don't see your point


All fair points but it is quite an undertaking to build an ebike that does 60km/hr with a useful range. Heavy motor, serious AH high discharge battery and a controller that can handle those amps. Your battery system will need to be above 48volts. Pushing wind above 35km/hr requires a lot more energy for each 5km/hr gain.

45-50km/hr idea fairly easy though with a 48 volt system.


Re #1 - If you are driving at places without bike lanes being able to move together with traffic flow is essential. Which then you can ask - do you also not expect motorcyclist to be on road either?


A motorcycle is an order of magnitude more visible than a bicycle and goes in the traffic, not next to it.


Motor cycles get treated with a lot more respect than bikes. I had a 50km/hr ebike with red back light, front white blnky light. Cars turning left into your opposite lane of travel were the worst. They never judged my speed correctly and there were many instances where I had to emergency brake to avoid a t-bone many times.

I only road residential roads and bike paths, planned my route carefully to avoid highways. Key things are to take the lane if you can do the speed limit and only give it up if safe to do so. Avoid driving close to parked cars that will open their door and kill you. Watch left turns in front of you.


Note that as a cyclist I would also be very pissed if a 50kh/h bike was on a bike lane. Maybe outside the city on long stretches it’s fine.


A road bike on a bike path with a rider worth their salt is a bit silly as well.

The thing with riding that on a bike path was that I had no concerns slowing down amongst pedestrians or on blind corners as it was no effort to get back up to speed. I was less inclined on my road bike due to the effort. Road bikes can get up to that speed, had a few that came close to pacing me. I understand the sentiment but I had zero incidents in four years of commuting. I was courteous, used a bell. Half my ride was up hill on the path and it did 30km/hr there. Everyone went pretty fast down of course.

I'll admit, I did enjoy passing spandex on expensive bikes with my beater bike wearing jeans. This was a decade ago when ebikes were not at all a thing.


> The thing with riding that on a bike path was that I had no concerns slowing down amongst pedestrians or on blind corners as it was no effort to get back up to speed. I was less inclined on my road bike due to the effort.

Many bike paths seem to discourage slowing down for junctions by putting them in dips - the opposite of how some train stations are on a hump as "gravitational regenerative braking".


How so? If you got lights and hi viz you are about the same. Yes motorbikes are slightly bulkier, but not in a way that's going to make a difference.

Motorbikes are certainly louder which IMO why we should ban motorbikes altogether. I hate visceral hate to them.


Have you ever seen videos of how invisible you look despite all the high viz stuff? In some cases it becomes urban camo. Take a look at this video, especially at 2:30 or so. It’ll show you just how little visibility you’ll have:

https://youtu.be/eqQBubilSXU

Your best bet is to have all your clothing match your bike, Power Rangers style, to increase your chances. And lots and lots of very bright lights. One little handlebar mounted light is going to look like a reflection or a flashlight.


Cyclists going 60 km/h are in traffic, not next to it.


And at the same or greater risk of being rear ended as a car or motorcycle while wearing a foam hat and spandex underwear…


Motorcyclists get killed very frequently.


I have to plan for what cars might do at 15 mph.

I certainly wouldn't casually ride the shoulder of a US highway at 35 mph.


I've already noticed that many cars don't expect cyclists to go 25-30km/h...


15mph is nothing in terms o safety (granted no break problems). On flat lane I hit that regularly without pushing hard, most people can handle that outside crowded areas.


If the builder of a DIY bike choses to adhere to that....


But that is not an issue with e-bikes as a whole (it is also illegal and fineable in places where restrictions apply).


I kind of think that the difference between electric bike and motorcycle is that electric bike ideally should be used on bike lanes within speed limit. So if the intention behind making an e-bike is to use it like a motorcycle then yes, motorcycle will be safer. But if the intention is to use it as a bicycle, using bicycle infrastructure (which arguably is very limited in America unlike how things are in Europe) at bicycle speeds but just without coming to your job covered with sweat then bicycles are safe.


In America, bicycles are allowed to use car lanes ...


This guy is wrong when he says the UK "has a culture of commuting on two wheels." We have a huge problem with cycle infrastructure, as evidenced by the stats he presents. Ok, London's probably decent but transport everywhere else in the country is built around cars.


Compared to Canada (where Fortnine mostly films), anywhere in the UK is cycling heaven.


Picking a country like the UK who have stats available would be fine then, but suggesting it's a better case scenario with that comment about culture is just trying to skew the conclusion. It doesn't help that the stats show a massive difference in injuries/deaths as well. By all means, everyone should choose your favoured transport, but the video really seems like FUD.


It’s kind of a thing for me as a cyclist. Like I had to get good at handling a bike every speed slowly because I didn’t get faster overnight, I didn’t just go walking to 40 overnight.


It’s not just about how fast you are going. When you drive a car, do you look out for pedestrians running at 40? Would you be surprised if one showed up in front of you? Now imagine the same thing with a bicycle.


Wait you lost me. Is the cyclist the pedestrian or the motorist in this scenario?


The cyclist. If anyone on the road does something that the soccer mom or SUV dad texting while driving don’t expect, they are going to be in much greater danger than if they didn’t do the unexpected thing.


The same channel proposed using a similar kit with a donor motorcycle. You get the advantage of a stronger frame, better brakes and better tires: https://www.youtube.com/watch?v=O2zlYpy6QCM&t=300s


> As a motorcyclist, electric bicycles make me very nervous.

Riding one yourself, or others riding them? And if you could elaborate, why do they make you nervous?


They make me nervous, bc, as other commenters have pointed out- brakes, suspension, and traction matter a lot.

The difference between the cheap version of a motorcycle and the sport version isn't the engine, it's the brakes and suspension ( and now electronics).

But the main thing is the lack of helmets. One motorcycles, the center of gravity is low. You are more likely to fall and slide than go head over handlebars. At motorcycle speed, you should be wearing a full face helmet. I very rarely see the guys on e-bikes wearing full face helmets.

Then you look at the wheels and tires, higher speeds means more acceleration and faster stops, means more wear- which means much more maintenance. That most people aren't really paying attention to. Maintenance on two wheels is more than just a reliability issue, it's a safety issue.

Finally, people give no respect to bikes on the road. Especially in the US. You could be cruising along at 30 mph at the speed limit and someone will feel the need to pass you because you're on a bicycle.


People feel the need to pass you when you go the speed limit because they are used to driving much faster than the speed limit, not because you're on a bicycle.


I assume the commenter was talking about situations where it wouldn’t be possible for a car to pass another 30mph car (or the overtaking car driver wouldn’t be bold enough to try).


Feeling the need to pass because of speed plus the ability to pass because it's a bike, is pretty different from feeling the need to pass because it's a bike. At the speed limit both of those things will happen. At 5 over the former will be much less common.


As in I would rather ride a motorcycle on the road than a bike. On bike trails, a regular bicycle is great. Where there are very few cars or very good bike lanes, electric assist bicycles make sense to me. But when you have bicycles going at car speeds mixed with cars, but without good brakes, without turn signals, etc. I would be very nervous to get on one. They aren’t built for that speed and roads aren’t designed to handle them. Moreover, most drivers don’t expect them. I can be on a 900 lb motorcycle and still be invisible to some drivers. Now imagine what I look like on a tiny bicycle that’s zooming at 3x the speed most expect from it.


Here in North America, most ebikers just wear bicycle helmets. Bicycle helmets are only rated for a fall from 2.0m onto the ground, or about 22km/h. [0] Ebikes tend to go much quicker than this.

[0]https://www.astm.org/Standards/F1447.htm


If you are serious about diy ebike be sure to check out these two links: https://endless-sphere.com/forums/viewforum.php?f=21

http://ebikes.ca


If buying from ebikes.ca, be sure to write them with your planned purchase and ask them to verify that it makes sense and if they're seeing any issues with it.

Some parts/combinations have known issues that you're just better off avoiding.


I can’t believe I’ve seen a link to ES in the wild! I used to love this website. Back in 2010 it was like a second home to me. That was before electric vehicles had undergone the revolution that was brought by Elon musk. If you wanted an electric vehicle that was good you had to literally build it yourself. I think the white zombie will always be the pinnacle of that era. And the countless ebikes that people made.

I haven’t been keeping up with the forums lately. The last I checked, the bottle neck for performance was people’s motors overheating. So there was a general effort to take a stock motor from China and drill coolant channels into it and attach a cooling loop. Dr base had some promising progress but I’m not sure anyone ever finished it.

There used to be this guy who you could send your inverter to in SF who would add extra solder to the power traces and modify it from stock to juiced up and ready for tons of current. The atmosphere in that website was just perfect because it was just a bunch of dudes who were a weird combination of speed freaks and electronics nerds. Amazing times.


Yeah I remember that guy and I did do the easier controller mods for better power.

That site really defined how good the internet could be. I remember Justin documenting his trip across Canada on one thread. So many cool builds.

I moved eight years ago and turned my ebike into a rope tow for the kids to use on my very small back yard ski hill. So haven't followed it after that sadly.


A fellow ES guy! My old friend, god bless you!


God bless you too! We shared a lot of good times and e grins on there I'm sure.


It's a shame the Copenhagen Wheel never went anywhere. It looked so promising.

https://en.wikipedia.org/wiki/Copenhagen_Wheel


I used to work for the company. I came on during the pivot to scooters, so this is just my (probably wrong) opinion.

IMO the reasons it never took off were:

- Expensive. You can get an electric bike conversion kit for $500 or less, compared to $1000+ for the Copenhagen Wheel. Don't get me wrong, the engineering on the Copenhagen Wheel was amazing, definitely worth the extra money, but it was too expensive for delivery guys to use.

- No replaceable battery: again this rules out delivery guys, as well as all-day rides.

- Requires a smart phone to use it. This was the biggest reason I stopped using my Copenhagen wheel. You needed to use your phone to unlock it or change the speed settings. I don't want to need my phone to ride my bike. What if I lose my phone or the battery dies? What if the server goes down or the company goes under?


Any idea why it was pulled?

I would imagine the common issue with integrated systems applies and makes it expensive: the lifetime and quality of the whole wheel is dictated by the lifetime and quality of the worst part. E.g. the brushless motor may run for years, but a battery cell, or crappy ic breaks in months in bad weather.


I followed Copenhagen in the early years, it seemed like the product was always in "beta". I was waiting to get one once it went into production, but that never came. My guess is something like what you said.

It seems like they have since pivoted to scooters.


I believe you can get a system like that (all-in-one motor + battery + controller)

I've seen those used on electric kick scooters that are still supposed to feel like a kick scooter, i.e. no throttle lever or controls on the handlebars.

Kostka, the local kick scooter manufacturer sells those: https://www.kostkakolobezky.cz/hill/920-elektrokolobezka-kos...


Perhaps mod this into an airline-compatible e-bike?

Airlines which will happy carry a non-motorized bicycle as a standard checked bag, won't touch a motorized bicycle at all.

So a conversion which can be easily and unambiguously removed, might leave you with a checkable non-motorized bicycle, and unrelated, a small motor, some electronics, and perhaps a TSA-compatible small battery. Then add say a commonplace "portable power station" battery shipped to/bought at your destination.


The problem is probably the battery. They worry about a battery fire int be luggage compartment.


Yes, and two possibilities came to mind for doing the battery differently.

A TSA-compatible 99 Wh power brick or two, suitable for checked and carry on, providing limited duration and assistance, but being at hand.

And a COTS "portable power station"[1], which can be ground shipped to meet you at your destination, from home, or from a store.

The ideas are to optimize the bike for shipping by removing any trace of the battery from it. And to optimize the battery for shipping and availability by going generic.

EDIT: Another comment[2] observes the battery in the post is available from Home Depot, so that might suffice for COTS generic availability. So an airline story might reduce to: leave the battery at home; attach the conversion with velcro instead of zip ties (or bring snips and a bag of ties); unbolt and remove the conversion before check in, and bag it separately from the bike; get a new battery at the destination, by visiting or shipping from Home Depot; and put the conversion back together.

[1] eg https://www.amazon.com/s?k=portable+power+station [2] https://news.ycombinator.com/item?id=28270285


Good luck getting usable range out of two 99Wh batteries with such an inefficient drivetrain.


https://ebikes.ca/product-info/grin-products/ligo-batteries.... 98Wh each, can be hooked up in series (already 10s = 36V nominal, max is 2 of them for 72V nominal) and parallel.

"While most airlines do not have a firmly defined maximum number of batteries under 100 Wh that can be brought aboard, we'd suggest travelling with no more than 4-5 LiGo's per person in order to avoid extra scrutiny. We have had customers travel by air with as many as 12 LiGo modules on them, but we wouldn't recommend that as a matter of course."

People traveling with folding bikes and LiGos: https://www.bikefriday.com/folding-bikes/the-only-electric-b...


Ah, interesting, the article doesn't seem to mention range.

This comment[1] reports the article battery as 160 watt hours, so 2x 99 Wh might be an upgrade.

One use case I pictured was last leg after airport arrival when traveling minimalist and budget. As a transportation alternative/supplement to mitigate last-miles time/$/hassle cost.

[1] https://news.ycombinator.com/item?id=28273273


Exactly, get a removable battery and bring that in your carry-on and it should be fine.


Are you joking? Lipo batteries in a carry on?


The rule is under 100Wh per battery, usually without a clear limit as to how many batteries.

https://www.tsa.gov/travel/security-screening/whatcanibring/...


If you read the article, it specifies lithium-ion batteries, which just about everyone brings inside the pressurized cabin.

So no, I am not joking.


I just know that most ebike batteries only ship by ground and even that isn't easy. See this for example: https://entrepreneur.indiegogo.com/education/article/how-to-...

Sorry for the tone, I honestly thought you might be joking.


Yeah, all lithium batteries ship via ground, but that's generally because cargo planes are basically like shipping things in the cargo section of passenger airplanes, which generally isn't advisable.


That's because shipping is more restrictive than carry-on and because of the capacity. People carry all kinds of lithium batteries onto planes.


People bring small batteries in the cabin. It also makes a difference if they're integrated into a product or not. E.g. you're allowed to being a laptop with a medium sized battery on board, but not a standalone lipo battery even if it is smaller than the laptop battery.


The only rule that differentiates between integrated and spare batteries is that you can't check spare lithium ion batteries. For carry-ons, the rules are exactly the same for both.

https://www.faa.gov/hazmat/packsafe/resources/media/Airline_...


There is a big difference between cellphone / laptop batteries and some random enormous 72V battery you might buy from AliExpress. I have used those big batteries and the word I would use is “scary.”


The battery in the article is 160 watt hours, the kind that slaps into yard equipment. You can get permission to carry that, or use two 80Wh drill batteries instead.


Yes absolutely. Those are in the minority of the home-made ebikes that I’ve seen, though - mainly due to range and power output. People love a bit of power, and they think any battery is just a battery.

I’ve seen a couple of “spicy pillows” smoke out, never a full thermal runaway fire - thank god


My battery pack could have been easily mistaken for a bomb. It was duct taped together, wires coming out of it, heavy and blinking lights on a home made exposed circuit board for the battery management system.

I tried a 72 volt setup for about a week. Too fast lol.


I’ve seen these. All fun and games until they’re forgotten in the basement for a while. Big puffy batteries just waiting for an excuse!

I went through an airport with a home-made LiPo in my backpack. Fortunately one of the TSA recognized it was just a battery but it was a really scary few minutes. Lots of very silent stares


If you don't want to be permanently tinkering, there's a whole range of e-bike conversion kits which work well.

I've got a Tongsheng TSDZ2. You remove the pedals and chainring and slot it in place, and your bike is electric. It's got built in torque sensors so pedalling is amplified - a very natural feeling. There's a range of similar motors made by a company called Bafang (BBS02, BBSHD) which generate more power and are more robust, but don't have torque sensing. For a bike in the EU, where you don't really want more than 250-300W anyway, the TSDZ2 is fine.

There's cheaper kits which use hub motors. Often you get the wheel pre-built so you just remove your existing wheel and insert the one with the motor.

The bike conversion kit is fairly straightforward if you're mechanically minded / have done any bike maintenance before. Sourcing a battery is actually the hard part - good batteries are expensive, and shipping from China is complicated. Once you have the battery it mounts where a water bottle would go. Mounting the kit and wiring everything up took an afternoon.

All in, the equipment cost me around £500. I already had the bike.

[1]: https://ebikechoices.com/tongsheng-tsdz2-review/


> The approach I adopted is mechanically as simple as you can get. It uses an "outrunner" motor designed for electric skateboards. With such outrunners, the case of the motor rotates. Driving the bike with it merely requires mounting it to the frame in such a way that the case is in contact with the rear wheel.

I haven't crunched the numbers, but this[0] Low Tech Magazine article from 2011 about the reverse process (generating electricity with stationary bikes) gives me the impression this adds quite a bit of inefficiency to this set-up:

> One reason [for inefficiencies] is the use of a so-called friction drive - the rear bicycle wheel acts upon the small roller of the motor/generator. While chain and belt drives (used in late 19th century pedal powered machines) have an efficiency of up to 98 percent, a friction drive is only 80 to 90 percent efficient (and wears much faster).

Whether or not you think that this is important is a different discussion of course, but I think 10-20% less range is quite significant.

[0] https://www.lowtechmagazine.com/2011/05/bike-powered-electri...


In Germany you'll need a speed limitation on such a construction (25 or 20 kmh, I think). And it must only assist pedalling, never drive the bike on its own. Otherwise this will count as a motorized vehicle and must be registered accordingly and needs vehicle insuramce. Don't know how hard it is to get it admitted for street use.

I'd love to see a minimal setup for these requirements :) Does anyone know of something?


> The lack of noise, combined with the discreet positioning of the motor and other components, makes it hard for anyone to notice that I'm on an e-bike.

Sorry, buddy, but in your dreams only. It is blatantly obvious for anyone if you are riding on your own, or if you have assistance - your body position is different, the power exerted looks different, not even mentioning the battery pack on your back wheel, and the motor behind your bottom bracket. So "OK Boomer" indeed.

On the other hand the real problem is that people who cannot really ride bikes now get easy access to speed. I regularly see them on my daily commute here in Vienna, where - despite the 25kph limit - these boomers ride in a way that scares the hell out of me. They go fast when they shouldn't (combined bike paths with lots of pedestrians), go slow when they don't have to (downhill), and generally are visibly uncomfortable on a bicycle.

I cannot imagine what would happen if you took an elderly person with an old bicycle and converted said bicycle using an unrestricted motor... that's really just asking for trouble.

I mean, people can be generally stupid - just last week a 78 year old driving a moped (!) was caught on the motorway driving in the wrong direction (!!!) in the inside lane (!!!!!) for a few km's before police caught him. And he wasn't even drunk.

Perhaps the solution is to introduce a driving licence category for e-bikes. And if they are unrestricted then they should be banned from cycle paths too.


Yeah, at least someone not used to using a normal bike is very obvious on an e-bike, as their cadence is often waaaay too slow. That speed with that cadence would basically translate to doing non-stop 100kg squats. Bikes have gears for a reason.

I do think the regulations in EU are fine as they are. 25 km/h max speed before it cuts the power etc. It happens that I see someone that should've "earned" their speed by getting used to lower speeds first and then naturally progressing, but I don't think adding a new license for that is worth it.


> people who cannot really ride bikes now get easy access to speed

Let's say there was a speed restriction: if you go above, say, 15km/h, the electric assist turns off and you have to pedal on your own. This would still be iffy in some situations, for example a busy combined cycle/footpath.

Maybe it would work OK if the electric assist was some function of cyclist's own effort. The more power you put out, the more the electric motor adds on top. But you'd need some sort of a power meter and more complex controller, so would not be cheap any more...


It would be quite interesting to see how these “tire contact” motors will perform once it starts raining or your tires get really dirty.

I think there is a reason, why crank or hub located motors are the norm now.


You are right about this.

This article does a much better job of exploring friction drives on bikes. https://www.electricbike.com/friction-drive/

The Kepler drive is the best design I've seen and the build/design thread on that shows you all the issues and challenges. It's quite impressive. https://endless-sphere.com/forums/viewtopic.php?f=28&t=25645


> I was able to come up with an e-bike conversion that cost me less than US $200 and yet functions impressively.

... excluding the cost of the battery. The battery costs $150 in HomeDepot


True, but the core is reusing existing batteries and I suspect IEEE readers are more likely than average to have battery lawn mowers, leaf blowers or (lower voltage @18-20v) battery power tools.

I suspect one of the links in there would have info on repurposing those as well.


Cool project. Would love a list of part URLs + repos to get set up. Wouldn't mind tinkering with something like this as a getting started guide.


Very interesting. I would love to see a video where someone does it from start to finish.

I would also like to make my own battery for the bike. I made a cheap DIY spot-welder from a microwave transformer and spot-welded my first 12V 20 Ah battery last week for a 3d printed robot lawn-mower project.


Building the battery pack yourself would give flexibility regarding size and shape of the battery pack. Maybe you could put them inside the seat tube?


You can often find faulty drill packs and harvest the good cells from those and cobble together a pack. Charging it safely isn't easy but can be done. There are battery management systems you can integrate. It's difficult to put inside the seat tube but putting it in a custom container on the down tube works well and that's a great place to put the added weight.


Doesn’t sound like a good idea to me… a malfunctioning battery would turn that into a blowtorch aimed at your nether regions.


That's a great hack. But I'm a big guy, bordering on 285lbs. That kind of low power traction doesn't seem enough to move me. I know European 250w motors are never enough for me.

I've build my first ebike a few months ago. I went for a 1000w Bafang mid drive geared motor with a 48v 20a battery, on an old used Peugeot mountain bike. Adding some new/used bike parts (wheels, tires, chain and rear gear), total project cost arrived at C$1800, less than half the price of a new ebike with similar specs.

Considering my weight, 20 to 23 kph is my speed of choice in pedal assist mode, which is quite safe. It does extends my range a lot compared to other use cases.


Your typical high output pedaling will produce about 100 watts of power, which for your weight will get you about 13 miles per hour. Pedaling hard with a 250 watt motor should get you around 23 mph.


One can't argue with precise calculations. Then the whole point for me is limiting my output and go farther.

One's mileage may vary!


> One can't argue with precise calculations.

I would have rounded off, however the numbers change quite a bit with small changes (according to the random online bicycle wattage calculator I was using).


250W pushes my 220lbs fat ass along pretty swiftly

edit: I wonder if we're experiencing the difference between 250W continuous rated motors, which is what the legislation covers, and 250W peak rated motors, which is what a lot of people end up incorrectly obtaining.


Well, there's probably something magical happening between 220lbs and 285lbs ;) ... and/or new motors perform better.


Here is my tutorial to de-car (unfortunately in Swedish but google translated): https://translate.google.com/translate?sl=auto&tl=en&u=elhju...

The biggest issue remaining is the wear of tires, and no good alternatives really exist for bike rims in terms of thicker tires.


Calculating the battery as given feels a bit like cheating for the 200$ number: A cursory search on Amazon puts the cheapest battery at 100€ and most in the 300€ range. Quite unfortunate, as I had hoped the author found a cheap option.


Cool to share battery with a lawnmover. Seems clever to share parts between appliances.



"cheap" and "ebike" don't really belong together.

A cheap bicycle is extremely dangerous, so a much faster cheap bicycle is crazy.


> A cheap bicycle is extremely dangerous

this is not really true, especially considering the second-hand market.


Having the motor casing drive the edge of the wheel is clever since it provides the necessary mechanical advantage without gearing.


“While it would have been nice to engineer some sort of spring-driven mechanism to control how forcefully the motor pushes against the tire, I kept things simple: I just deflated the tire somewhat, bolted the motor solidly in place, and reinflated the tire.”

I think Solex (https://en.wikipedia.org/wiki/VéloSoleX) did that better.

It uses the weight of the engine to press the powered wheel to the bicycle wheel, accounting for variation in wheel diameter due to tire pressure or tire wear. This could use the weight of the battery pack


Assuming his motor is mounted tight enough so that the tire loses traction before his friction drive does, he's likely halving his tire life.

That's fine for a project, but hub motors and mid drive motors are widely available now.


cyclone have been selling cheap conversion kits for around US$300 since at least 2005 https://web.archive.org/web/20061212021226/http://cyclone-tw...


USD200 can buy me new e-bike in China, so I can hardly see how is this cheap


400 Euros is all it takes for a 500W battery, 500W+ direct drive motor E-Bike conversion.

200 Euros just for the battery pack. And we're not talking some shit 7Ah pack that will last half an hour. An hour at full power is the minimum, anything else is unacceptable.

Whether used for constant speed, acceleration only or pedal assist, what's the point of an E-Bike that's deadweight after less than an hour?

I actually have made a design using a 1KW brushed motor that replaces the pedals and uses the hub gear. It is cheaper, but harder to install (needs at least a custom frame for the motor) and is illegal on bike lanes as the pedals are removed. Could share it if anyone cares.


> Whether used for constant speed, acceleration only or pedal assist, what's the point of an E-Bike that's deadweight after less than an hour?

I'd like to see some data on power usage for different percentages of user-assist for people doing average biking speeds. e.g. 25% of total power being motorised/assisted, the other 75% being human-powered, on average.

After all, using it at full power always isn't a bicycle, it's a motorcycle. The idea of e-bikes is to assist the user, on accelerating from a stoplight, on a hill, after a break, in a particularly strong gust of wind. At these short moments assist can be >90%, but when you're at speed it can be say <10%, averaging to perhaps 25%. The assist can be higher on warm days to prevent them becoming too sweaty days, but it'll still be to assist regular biking.

But yeah less than an hour is not really acceptable, I agree. Unless there's some kind of ubiquitous and convenient charging infrastructure, but I don't see that happening anytime soon.


> The idea of e-bikes is to assist the user, on accelerating from a stoplight, on a hill, after a break, in a particularly strong gust of wind.

To me, the idea of vehicles is to get me from point A to B faster and with less effort than it'd take on foot. If muscle power isn't enough, then adding some battery juice seems like a great idea to go further and faster while maintaining the agility, simple construction, and cheap operating costs of a bicycle. Electric assist for hill climbing and acceleration is a thing for some reason, but it's totally fine to want and expect more than that from a machine.


Agree, I used mine for commuting and to save money on parking. I used my pedals on the way home for exercise. Going 50 km/hr was a necessity as I wanted to keep pace with cars so they wouldn't pass me.


Sounds to me like you actually want an electric motorcycle then.


A bicycle will get me to places even when I don't have the battery, or don't have a place or the time to charge it. Now are you going to go down the rabbit hole of arguing about definitions?


It isn't definitions, it is about safety for other road users. If you don't want licensing or testing or inspections or insurance requirements, you need to accept certain limitations so as to not be a hazard. Riding fast on pedestrian paths and bike lanes is simply unacceptable. You are a different class of traffic, and you're trying to shirk the responsibility that comes with it.


Well, yeah, but it's a quiet electric motorcycle. Once you get used to just a hand throttle and zero pedalling (keep that as a backup and for legality on bike lanes), you may not want to go back heh.


Exactly. TFA is disingenuous since the author repurposes a battery from their lawnmower. A basic standard ebike conversion kit, with battery and a central motor, starts at €400.


I like nerds but man is it out of touch/socially awkward to posture based on how often you use the front brake and link to a decades old blog post doing the same.


Why is it socially awkward to link to an old resource? As far as I can tell, Sheldon Brown's blog is a fairly well-known resource, and it is frequently linked on other biking forums.


Could use two of those to turn the wheel by the aluminum rim (same one used by the brakes). More power, more traction, less dirt.


i've seen someone attach a pulley to the side of a thin rim and use only 1 motor. It looks pretty solid [1]. Only thing stopping direct drive of the rim is probably tooth material strength/weight/cost.

[1] https://youtu.be/Vc5kHuZoNoM


Maybe the author was intending it as a PSA. I certainly learned how to brake better by reading what he linked to.


Interesting, but to be completely honest, I think a two stroke motorized bike is better and a lot more fun to build


I live next to a bike lane, and there's a few assholes with two-stroke motorized bikes who use that bikelane regularly. I absolutely hate it, they make so much noise.

I hope the police catch them and take their bikes away.


I mean, they shouldn't use the bike lane. I agree with you. But, here's the thing. If they are not modified they are very quiet, noise codes should be enforced, but asking for their property to be pretty much stolen isn't a bit much?


A motorized “bike” is loud, smelly, expensive, much worse for the environment, and bad for your respiratory system.


I'm sorry, but I'd rather use a two stroke kit than dealing with all the ethical concerns of (for instance) the lithium batteries on ebikes. Also, when using the stock muffler and a right oil mix they are absolutely not smelly or loud. An argument could be made for the respiratory system, but I don't see how would that be an issue when these are used outdoors


Two strokes (and any other small engined scoot) qualify as low speed motorcycles here in Ontario. They require license, registration, and insurance. As a result, there is no market for them.

Ebikes on the other hand are legally bicycles. As long as you have pedals and officially limit yourself to 500W/32km/h, there are no restrictions.

At these low speeds, even a "small" 1kWh battery can run for two hours. That's 60-70km of range. Good for most commutes inside the city. Any further and you can take it with you on public transit that supports bicycles.

Really hard to make a case for two strokes here, maybe you live somewhere more forgiving.


I do, here they require no registration at all and they are considerably cheaper than ebikes. Also, I stated earlier that I don't feel entirely comfortable with the implications of lithium mining so I do try to minimize that as much as I can.


I contemplated something like that 20+ years ago, but also saw that there was at least one option with a small 4 cylinder engine that was reportedly quieter and able to run on straight unleaded IIRC.

Edit: a quick search shows those still available in 38, 49 and 79 cc models depending on the power needed. 100-150 mpg


I used to have one of those! I built it using a cheap 49cc conversion kit.

Honestly I'm not sure it was purely better: I had to pedal a bit before engaging the clutch to not stall the motor. It also became hard to breathe when stopped because of the fumes from the engine idling.

Was kinda fun to ride around though, but they outlawed them here. Guess other bike path users don't like smelling burnt oil...


Hi! I have a small 49cc kit too and never had an issue with fumes? Perhaps your oil mix is wrong? The one on the manual is way worse than using 40:1, perhaps you could try it if you get a chance. About the clutch issue, it sounds like you need some to make some changes to the flower nut maybe? I can start my bike without pedalling if I kick the floor to get some momentum.


They keyword there is "get some momentum"...it may not take much but definitely not as good as an electric motor that gives you full torque from 0. I actually managed to get it going from a dead stop by easing in the clutch and giving it a bit of gas but it smelled like burnt clutch afterwards :)


Lol at the downvotes, but yeah, nothing beats that for energy density. Could even carry a 1L bottle of petrol with you or something.

They're loud as hell and illegal in some places, though.


I'm actually a little curious about how great the practical energy density would be in this case with a 2-stroke engine compared to a modern lithium ion battery and motor. 2 stroke engines are pretty famously inefficient, expelling quite a bit of unburned fuel.

That and I'd guess that the engine itself is pretty bulky compared to the electric motor, so the total bulk might even out compared to an electric setup for the same amount of energy, but I'd have to look at the actual numbers.


I'm wondering what's the smallest possible fossil fuel _generator_ you could make, you could effectively make an ebike "hybrid" and it could be way more efficient since you can just run the engine at optimum speed constantly. Off-the-shelf units are 1000W, but a 200W constant unit would be the best.



Batteries are still worse. Power to weight of a two cycle is extensive. In ideal conditions a two cycle eninge is more fuel efficient than a four cycle, but you only get about 50 rpm range where this is the case, and you need to be near full throttle. (Read you can prove this in the lab, but not in real world use)




Consider applying for YC's Spring batch! Applications are open till Feb 11.

Guidelines | FAQ | Lists | API | Security | Legal | Apply to YC | Contact

Search: