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Drivetrain Design for Boosted's Electric Skateboard (boostedboards.posthaven.com)
121 points by skdoo 1544 days ago | hide | past | web | 48 comments | favorite

Any chance these will ever get down to ~$300? I guess what I'm asking is if this is the Tesla Roadster and there's an economy model a few generations down the line? Or will this always be for people more serious about using them for commuting, etc?

It's possible to get something like an electric Razor scooter for ~$300, but the parts they use to hit that price, like lead-acid batteries, make it a lot less appealing.

Just like a car or motorcycle, right now there's a floor to how cheap it can be and still be great. If that gets lower over time, all the better.

It looks amazing, but I'm having trouble understanding where the power comes from.

The Kickstarter says 20 mph, 6 mile range, 2000 watts, which gives an energy of 600 watt hours.

A Macbook battery is around 60 watt hours, and weighs about 1.5 pounds; 10 of those would weigh 15 pounds - and take up a ton of space. I don't see the volume of even ONE in any of the photos I've seen.

Where's 600 watt hours of battery hiding?

The battery is just under 100 watt hours. The motor power lets you accelerate uphill, but the range is calculated from riding at a constant speed on flat ground.

I wonder what sort of grade it can climb, and how far. As a "last mile" vehicle this looks quite promising but for me the "last mile" of my commute is my entire commute (well, two miles), and it is straight up a hill.

Eh, walking is probably good for me...

I rode one of these at SXSW. It has a lot of torque. I am 230 lbs and it had no trouble getting to top speed in a hurry. I didn't try it on a hill but I bet it'd do fine.

They're designed to climb SF hills - so I'm guessing you'd be fine.

I think 2000 watts is peak, not nomial power.

I love this post because it shows some real engineering. The fact they put so much effort into the test equipment shows that there's some serious characterization going on vs. just throwing together parts.

I really wouldn't call this "real" engineering. As a mechanical engineer it really sounds like they literally threw it together and hoped it fit after they tested the motors "...models were assembled together in the CAD software to check for fit, clearance, and interference." I saw no mention of fatigue analysis or FEA, both are now days required for "real" mechanical engineering. Without that just cross your fingers the motors don't fall off after 1000 miles. Other than that it is pretty comprehensive.

Our engineering team spends much of its time and effort on failure analysis. FEA is one of many tools we use during the design process, and we left out some details in this post for the sake of brevity and clarity.

>I really wouldn't call this "real" engineering.

Throwing stuff together and seeing if it works is the essence of engineering.

How so?

Properly engineered stuff will work as designed. Imagine an A380 falling out of the sky on the test flight and engineers exchanging betting money based on whether it flew or crashed. "Well, that didn't work.".

Engineering does everything to take the uncertainty out of design as much as possible. It's the anti-thesis of throwing things together to see if they work.

Ok, there are some things that don't lend to the iterative approach. Airbuses, bridges and skyscrapers would be three examples.

When you are designing the wing for the A380, probably a good idea to bust out the FEA software. But it's still going to be tested with hydraulic rams.

As far as I am concerned, bridges have fallen, buildings have broken, and airplanes have crashed. I guess its a different iterative process then software, but neverthless, it is an iterative process.

Vibration is the real killer for stuff like this. Hard to model for and with potentially catastrophic consequences.

Real engineering [compared to software development]

I really hope the link between the remote and the board is secured properly, it would be a really nasty prank to overpower the transmitter from some vehicle and to cause it to accelerate or come to a sudden stop. Griefers are not limited to being active online.

I think this is still, by far, one of my favorite "last mile" solutions. It's got a pretty slick look, it'll do basically all of the work for me, and I could carry it inside somewhere pretty easily.

Biggest downside I'm wondering about is only being able to use it when it's dry out (not sure there much to be doe about that while staying reasonable).

I'm a fairly avid cyclist, though. I think than between a boosted board and my trusty bike, I'd cover a pretty huge swath of my use cases.

Really interested in this.

I've ridden a long board in the rain. My legs have never been so wet. FAR wetter than biking or walking in the rain.

With this at least you could wear boots because you wouldn't have to kick/push/coast.

One of the reasons for which motors in scooters and other electric vehicles are large and bulky is that they have to be designed to last a long time in real world environments.

The motors being used for this project are hobby model aircraft motors. These motors put out a lot of power per unit volume but are most definitely not designed for continuous duty at anywhere near to full output. They are also not sealed against the elements and have bearings selected for reasonably balanced loads with relatively low radial loads.

I have piles of these on my workbench ranging from cheap Chinese units to top of the line German designs. I use these on our planes, helicopters, multi-rotors, boats and cars. At the top end you have amazing hand-crafted quality with a prohibitive price (unless you want to pay $8,000 for a skateboard). At the low end they are cheap and they are junk. I've seen everything from magnets coming off, coils burning out, power leads coming off, bearings going bad prematurely and shafts bending.

In short, while the design process is interesting, I think the most fundamental flaw is being ignored: The motors are not designed, nor are they suitable for, this kind of an application.

Obligatory: http://xkcd.com/139/

What are the safety concerns of something like this? A top speed of 20mph will definitely be unstable for general usage, and even 15 seems more like bicycle territory, where you're seated and have an aerodynamic shape.

We might see many people falling off of these in the future...

A longboard turns in the direction you're leaning and so is dynamically stable. In fact (counter)steering is more intuitive than on a bike because you don't have to coordinate lean and handlebar angle.

The main issue with skateboards is 'speed wobble' vibration in the trucks, but a well set-up board generally isn't prone to this.

Most wipeouts I've had on my longboard are when the board stops suddenly from debris and you continue moving forward, usually with your feet trailing slightly behind. Its a recipe for injury, and its why this mode of transport is only for those capable of taking a good tumble every now and then. The solution is to not travel faster than you can run, and to always be vigilant for small rocks, twigs, sand, and especially things that will jam under a wheel but continue to slide forward like pinecones.

The length of the longboard mostly prevents speed wobble which is an uncontrollable side to side swaying which tends to increase in amplitude once it starts.

A few addendums, from someone who spends too much time and money on longboards built for going fast. You generally only encounter the issue of the board stopping suddenly on small debris (referred to by street skaters as 'chalking') when you are traveling close to walking speed on small wheels. I personally skate around 3x walking speed, and these boosted boards would make that even higher.

Secondly, speed wobbles are caused by riders primarily, with gear only impacting it slightly. Put a new rider on a fantastic downhill setup, and they'll probably get speed wobbles, whereas experienced riders can have no trouble riding short, turny board at highspeed. (Look up Maryhill for more info, it's a race where slalom boards are commonly used).

Can you elaborate more on what newbie riders are doing wrong to induce speed wobbles?

(I'm a snowboarder, and am thinking a lot about getting a longboard for my ~4km commute that I'm currently riding)

It's partially about weight distribution, and partially about confidence. For the most part, biasing your weight distribution towards your front foot, and making sure you lead your steering with your front foot, and you'll be fine. The rest comes with experience. Does your commute contain any downhill sections?

Absolutely correct. On a longboard at speed, you have to keep your weight forward. This is partly to keep the front truck under control, and partly because flex in the board means that the end of the board with most of the weight steers more.

If you panic and lean back, you're effectively only steering with the rear truck, which is not a dynamically-stable situation. Things go wrong very quickly at that point.

Ah, I tend to keep my weight fairly centered at speed so I'm stable if I have to break tuck. Also, I don't ride a deck with any flex, and I ride split angle trucks so I inherently have more turn in the front. But yeah, for beginners, weight on the front.

Good point. A centered stance might be ideal, and may just seem 'forward' in comparison to the typical shortboard stance.

And now I think about it, it might not be board flex that limits front-truck turning when leaning back - rather, the lack of weight on the front truck might allow the outside wheel to lift. Either way, it's a bad situation.


There is a slight downhill for the first 300meters or so, then it's basically dead flat. I don't expect to ever be going super-fast or anything on the commute, more like only when I actually go a seek out a steeper hill.

Right, okay. When you do start hitting hills, make sure you have a helmet, slide gloves and optionally pads. Your first priority should be learning a shutdown slide. Search "coleman slide" on Youtube, safest way to stop a longboard.

This is why it is important to keep your weight closer to the tail and never stand directly over the trucks at high speeds. This will help to be less rigid as the wheels pass over the debria.

Can you apply this to folding kick scooter?

Lightweight electric kick scooter could be useful to larger audience as a "last mile" solution.

For more than a year, I commuted to and from work (3 miles each way) on a lightweight electric scooter I bought on Craigslist for $100. It's been a while, but I used to skateboard, surf and snowboard, but having the handlebars of a scooter in an urban environment is huge for me in terms of control and safety. I used to call it the poor-man's Segway.

Edit: Not mine, but these look nice: http://www.goped.com/products/Electric.asp

They are extremely heavy.

My current kick scooter weights 12 lbs and i consider it heavy. I can't imagine handling 35 lbs, my bike is lighter :)

I think that taking this [1] rather insane idea for a "longboard stroller", and replacing the child(!) with one's laptop bag and maybe some kind of fairing would be a pretty sweet solution for those of us not agile enough for regular longboarding.

[1] http://www.blessthisstuff.com/stuff/living/misc-living/longb...

A child shaped crumple zone. I already feel pretty squeamish with kids on the bike (2 kids, one adult, one bike).


A go pro video of going from Filbert and Lyon to Filbert and Van Ness, now that would be rock: http://goo.gl/maps/OlHc7

For those that don't live in the city, it's one of the steepest streets in the western hemisphere.


The 11% average over 1km isn't too bad, but the start looks pretty steep. Strava shows it at up to 40%. That's not exactly 100% accurate, but I've ridden 25-30% slopes on Strava and they are hard enough that on my road bike I can't stay seated (the front wheel comes off the ground) and if it is the slightest bit wet the rear wheel slips when you stand.

I'd be very impressed if this can make it up there with a person on it.

I'd love to see a mountainboard/pneumatic tyre version of this for us poor souls cursed with terrible road surfaces. I'd also love to see compatibility with Original Skateboards spring trucks.

But anyways fantastic product, I'll definitely be picking one up at some point.

On the image showing the brushed vs. brushless... How much of that size difference is due to gearing? A scooter shaft's output is much lower RPM than a skateboard. Your gearing seems to be via belt drive.

Any chance you'll sell just the motors...? ;)

You're right, there's a gearbox on the brushed motor and not on the brushless one. The gearbox is the part with the shaft sticking out, and the motor is the part with the heatsink fins.

And you can buy the motors already! We are using a slightly modified version of a RC airplane motor. Our first prototypes used motors we bought at a local hobby shop.

Can we buy a kit of the motors and drive train and put it together ourselves?

I really wish the city I live in has much better bike lanes or sidewalks so I could use this thing to get from point a to point b further than just my suburban neighborhood. I can't wait to see people riding these things in the city.

I wonder if they ever considered hub motors for better efficiency and quieter operation (no belt), or would it be too big technical challenge to custom-build (basically the wheel and motor would be single integrated unit).

Great video about boosted


Interesting, but I'm still waiting for hoverboards.. 2 years to go :)

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