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Show HN: Hacking a Mercedes GLA Class Ride-on kids car (ihackshit.com)
221 points by AnnoyingSwede 5 months ago | hide | past | web | favorite | 83 comments

> I also decided this build will need welding. Having never welded aluminium, i ordered a 200Amp TIG/MMA welding machine, rebuilt the main fuse-box in my house to be able to run it without burning my house down. I am currently waiting for a tube of Argon gas before i can start climbing that hill.

I think this is about the point where my wife would have killed the project.

I'll bet that could be one of the easier sells in the long run. A full rack of servers? Not sure that will be the most pragmatic investment. The ability to weld stuff that breaks in the future? Seems like a solid investment, and I wouldn't be surprised if he had other uses in mind already.

Sure, the trigger isn't some major value-add project, but if it builds a practical skill and makes other practical repairs/upgrades possible, I'd bet you could convince most people pretty easily.

The escalation was a bit unexpected, though, and definitely made me laugh.

Also, OP sounds like the kind of person who would have been talking about a welder for years. And among the woodworking tools, auto repair, painting equipment, electronics, and computing, it's not that out of place. Most people would start with a stick welder and steel tube, but if you're going to end up wanting a TIG and buying one a few years down the road, why not buy the right tool now instead of two tools?

Next step is the mill, lathe, grinder, strip sander...

> Most people would start with a stick welder and steel tube, but if you're going to end up wanting a TIG and buying one a few years down the road, why not buy the right tool now instead of two tools?

Have you priced a multi-process welder (plus all the extras) by a decent brand lately?

Most people would "nope" out of there seeing such prices, especially for a tool which they may not even manage to get the skills to use effectively.

While it is cheaper to go that route, vs going stick, then wire MIG, then TIG (and needing the room to store each machine) - if you purchase new equipment - it still is a big chunk of money to swallow.

The cheapest route is to instead make friends with someone who has welding equipment; learn to use everything there, then when you get to whatever point you're best at - buy your own equipment.

Myself, I've done a combo - I purchased a used cheapo 120 VAC buzz-box stick welder, which worked ok for small jobs - but I had learned on my brother-in-law's Lincoln Tombstone 220 VAC/DC system. Later, I met a friend who has a complete shop, and I can do just about any process I want there.

Back home, I purchased a HF cheapo 120 VAC flux-core wire feed welder (mainly because I wanted to see what an $89.00 wire-feed welder could do - it's actually not a bad piece of kit, and people do all kinds of mods to it, too - including conversion to DC).

One of these days I plan to get a 220 VAC line run to my garage, but that won't be any time soon; at that point I'll probably purchase a decent MIG welder w/ CO2...

I'm a metal fabricator by trade, twenty years next year! I've owned a couple of $2000+ inverter TIG / Stick welders, but not any more. My work place still buys the name brand units for reliability and serviceability.

The DC TIG / Stick inverter unit I have at home is a AU$280 one off eBay. It even has high-frequency start for the TIG.

I rent a tiny bottle of argon from one of the industrial gas supply places in town for $5 a month, just to have argon at hand if I suddenly want to TIG weld something, and can get a larger bottle delivered next day if I need it.

This is the unit I bought about 18 months ago, they're currently selling for less than when I got mine: https://tinyurl.com/ebay-dc-tig-au

I've done a little welding, using the really nice TIG setup at my work's machine shop. I've contemplated getting a cheap TIG setup for home, but was wary that they'd be unusable compared to a nice unit.

Sort of like soldering irons, where the <$40 ones are typically trash, the $40~$100 ones are probably fine for home use, and the ones that I bought for work start around $500 (JBC btw, I've convinced our entire engineering lab that they're the best).

When you go really cheap on soldering gear, overall power, tip temperature regulation, tip plating quality, and iron longevity are all reduced, sometimes to the point of unusability.

What do you lose when you go cheap on TIG machines?

not too much really. power. 200A gets you pretty far, but 100 isn't enough for some things. if you don't get AC you can't weld aluminum. without a water cooler you have to make sure not to run the head too long without a break, but for personal use its not too bad. if you get one without the argon valve and control its a pain, but its usable (you have to stopcock open the argon before use and turn it off, so you go through more gas). cheaper ones might not have the HF start so you need to scratch start, which is a pain, but livable.

the only thing to really be wary about with the cheaper deals is that they often don't include the head, sleeve, controls, ground clamp, argon fittings and regulator. so those might add some hidden cost. regardless you need to budget another ~$300 for a tank and gas.

but the difference between low end and low end professional is alot of money, so I would definitely recommend skimping a little. since the tips are consumed there isn't much of a wear issue really.

a super cheap option is a used stick machine with a tig head if you can live with all of the above limitations. if you upgrade you can carry forward the tank, regulator and head.

This comment does a pretty good job of covering the important things.

My work has an AC TIG so I'm covered for aluminium welding if I need it.

I think the only other thing I've noticed about the cheap DC TIG I've got is the build quality is, well, cheap, but if you handle it with a bit of care they seem durable enough. I've accidentally dropped one of the name-brand ones from 6' up a ladder and it just bounded and kept going. Not convinced I'd want to do that with my ~$200 unit.

Probably a good idea to let the unit run for a good 5 minutes after you've finished welding to make sure it has a chance to cool down. I had a MOSFET blow out on the first one I bought, I think because I was switching it off immediately after doing quite a bit of welding and the fan didn't have a chance to blow away the heat build up. But even after buying two of them I'm still a good ~$1000 in front of a high end unit.

Wanted to respond to this for a week but been home, sick as a dog and didn't have my HN credentials. This is spot-on, and next step IS a mill :) It's a bit scary how close you got. hehe. I updated my post with the last few pieces on the electric side now.

No woman, no cry ;) UHM: Don't get me wrong. I wish it would have worked out better between my ex and me but stuff happens in life. I am sure she would not have allowed the sawing and welding either, as we lived very confined. Anyway, i stand corrected on this. Sorry if i offended.

> I think this is about the point where my wife would have killed the project.

Small anecdote. My wife grew up in a house with no tools, I grew up in one with lots of tools. She is also much more fiscally responsible than I am. So early in our life together she would push back on tool purchases (I have a habit of creating projects that always require at least one new tool).

However, the experience over a few years of how much easier and more reliably a project was completed when the right tool was available, eventually won her over. And now she is perhaps more of a tool advocate than I am!

>I am currently waiting for a tube of Argon gas before i can start climbing that hill.

Pfffft. Spool gun off an engine welder or GTFO.

Just add a transfer switch and you can tell your wife it's a standby generator. ;)

Also, maybe I'm to used to thinking in terms of big things made from thick metal but 200a seems really small for aluminum.

200a is ok for 1/4" Al. warmup takes a while, and you do have to run it at max.

disagree about the spool gun. tig is alot more useful for smaller work and crafts projects. its a stupid choice for structural, but up to 1/2" its fine. and you can do really small work in materials like stainless, brass, Al, cast iron, and bronze. it also requires less prep and cleanup to get a pretty result. (again for non-structural applications)

>disagree about the spool gun

That was a joke. It's apples to oranges. Most people wouldn't prefer a spool gun over TIG given the choice.

> it also requires less prep and cleanup to get a pretty result. (again for non-structural applications)

This couldn't be further from the truth. Assuming you're not using exotic consumables that are very contamination tolerant/intolerant TIG is far more sensitive to contamination than other processes.

it is, but you dont have a grind a bevel to get basic penetration, and if you dont need it perfectly flat and weld clean you dont need to grind down the weld to get rid of all the slag.

obviously its all dependent on what you're trying to accomplish

This is a great project but it sounds a little ambitious. I suggest stripping down to the bare minimum to make your kid have fun and adding new things over time. I am going through a similar line of development for my kid but I started with a cheap power wheels and decided to forego remote control to let him drive. I started putting him in the car at 13 months and he was able to control steering and acceleration himself and direct himself where to go at about 16 months.

In time order my mods have been: 1. Soft start (R/C circuit, heat sunk MOSFET)

2. Replace lead acid with 18650 batteries

3. Reverse switch (they make these for big fancy power wheels, they just reverse the polarity to the motor)

4. Bluetooth remote kill switch (Lazybone - I don't recommend it, the ios app is crap)

5. Turbo button, adds a 18650 in series with the 2 other when the button is pressed

6. 2 batteries in the turbo button for a total of ~16v

He drives very well himself now, with 2 big issues - it is hard to get him to pay attention to what's in front of him at all times and go slowly around pedestrians (that's where the remote stop comes in), and it's so fast now that I need to figure out how to add brakes (maybe I'll just move him to a real go kart with rubber wheels and mechanical brakes). But he's an excellent driver at just over 2 years old and people are always very impressed. Kids are capable of a lot more than we give them credit for.

I've been putting my three year old in her car to drive since she turned two, but she still drives like a drunk. How did you get him to understand that he has to keep the wheel pointed in a straight line to go straight?

It took quite a lot of sessions before he started understanding what to do; at first, he really preferred to push it from behind rather than sit in it. So I just kind of let him do that for several sessions and gently coaxed him into the car for a minute or two at a time. I felt like if I got frustrated he would get frustrated, and he would just reject the car altogether, so I basically let him do whatever he wanted with it at first.

Once he was sitting in there and messing with the controls, I would run and dance around in front of the car to get him to chase me, which he thought was hilarious. As soon as he was able to go where he wanted and clearly enjoyed it, I thought he would be ready to listen to me tell him what to do, so we would take longer trips with a destination in mind, to the playground or to the drum circle. I would verbally tell him what to do (stop, go, turn left, turn right, reverse, forward, etc), and if he doesn't do it within a couple of seconds, I stop the car with the remote start and hunker down and explain to him what I wanted him to do and show him on the controls. If he continues to not listen to my instructions we take a few minutes time out out of the car and sit on a bench or run around or whatever.

Anyways, keep trying! it's a lot of work but so much fun.

Jerkstate, this is one of the best DIY posts ever. You sound like a great parent.

My 4yo never had a car like that, but maybe she thinks turning the wheel is "driving" ? I might try having her keep her hands off the steering wheel in a straightaway for a bit then gradually introduce turning. Or push it yourself if it's safer and slowly go through turns when she has the wheel pointed in the right direction.

Good luck!

I let my kid drive around the backyard for a month. After a month he could do it at 2 (edit:years old) with no problem. By 5 it was truly amazing with what he could do with the car! Glad he had forgotten about it by the time he could get his license!

> Bluetooth remote kill switch

Wouldn't a Bluetooth keep-alive signal be better suited.

man, I can't even find a kill switch with a decent iOS app to control it, I would love if there were more options, but since that isn't the primary focus of the project and I have a basically-working solution, I'm not going to put in the couple dozen hours it would take me to implement my own.

A BLE fence maybe?

> and it's so fast now that I need to figure out how to add brakes

Why not use electric brakes first? Take some high-load resistors, and use a high-current relay to switch the motor positive line from the 18650 controller to the resistor bank. For more fun, make a stepped resistor bank so you can control brake power.

I've thought about doing something like that but I'm not sure if the plastic wheels and gear box can handle it, and I'm not sure how much more effort I want to invest in a limited platform. In the situations he's in now, anticipation is just as good as brakes; being able to see that he's going to run into a person or obstacle and slowing down is what I'm aiming for. In a "racing" situation, braking is necessary to slow down from high speed quickly in order to take a corner without losing traction, but the plastic wheels already have so little traction that we would exceed the performance envelope of the wheels before really getting much speed advantage out of it. Probably what I'll do is upgrade to a basic electric kart at the next birthday and leave this car as it is for Sunday driving and/or the next kid (it'll be easy to reduce the power again by reducing the number of batteries)

> I've thought about doing something like that but I'm not sure if the plastic wheels and gear box can handle it

As long as the braking power does not exceed the power for acceleration, no need to worry (and you can always start with low braking load). Reversing the motor while the car is in motion is the dangerous thing.

Don't show your son Lila Kalis videos yet :P


Is children's powerwheel competitive drifting going to become a thing?!

I don't know if I should show you this...


Edit: I didn't realize they were doing autonomous cars now. Past races were definitely done with humans in the cars.

Is this still active?

I also did not know about the autonomous competition, but the last blog post is three years old, and the 'register today' button takes you to a form for 2015.

I only see 'autonomous' once and no further details.

If anybody has additional info, I would greatly appreciate it.

I totally missed this! Thanks a million times. By the time Chris is 5, he will beat her on the strip.

That’s crazy. She’s awesome! I just hope she stays safe. I worry about jutting out into the street like some of those videos showed — she is only 5 after all even if she drives like a champ.

Update: A few safety concerned readers mentioned: Top speed: My aim (until he is older) is 7-10km per hour, but with a torque that allows burnouts and donuts. A safety cage might become part of the build, just because better safe than sorry.

Will make sure this post can be read as soon as i can contact my webhosting company, hopefully tonight. Sorry about this!

I'm also concerned for your son's safety. Is he strapped in? I seriously hurt myself when I was a kid in a dodgem car at a fairground when my face hit the steering wheel.

7-10km/h may not sound very fast, but trying jogging face-first into a lamppost at that speed and you'll soon change your mind.

A helmet is a must. I also added a seatbelt to mine, but it really doesn't make sense, the most common thing that will happen is it flips if he drives off a tall curb, and in that case you want to be able to easily get out from under it.

Agree got one. A wider wheelbase of the car, lower center of gravity, and wheels 50mm-100mm wider will help keeping it from tipping over. I have a seatbelt but like a few pointed out that might make the car more dangerous without a roll cage. Both are taken into consideration now.

Please consider some kind of roll cage if you're going to put a 2-3 year-old into this. In the United States we see a tremendous number of toddlers who are very, very badly injured (or killed) in ATV rollover injuries. Obviously an ATV is a much bigger and heavier vehicle than what you're doing (which is cool) but the mechanism itself of rolling a vehicle over onto a child can lead to a very devastating injury pattern.

Posted a link to this page the other day, but it sunk to the bottom so fast, noone noticed it. I figured this is actually a Show HN, and worthy for others thinking of doing something similar. I would be very happy to see what others have done on the same subject, or to get inspiration on topics i am struggling with in this build.

Problem with modding plastic stuff like this is that as soon as you make one thing stronger, something else becomes the weakest link, so then you have to replace that with something stronger, and so on, until you've replaced nearly everything.

At some point you'll probably need rubber tires or you'll get a lot of wheel spin.

He already talks about this at the end of his current post - it sounds like he's basically going the route that full-size drag racers do, and building a tube-frame (or in this case, angle-aluminum) chassis which he is just going to put the plastic body over the top of for some resemblance to the original car.

First off: Thanks for showing interest in the post. To counter the weak plastic i vested in a MIG weld and the aluminum profiles seen at the last photo of the post. My intention for the next part will be constructing this support. Finding wheels have proven expensive (but not impossible), and as late as yesterday i was given 2 go kart tires that will become the rear tire set. I was also hoping people interested in this post could suggest other wheels that both are functional and look good. Even though i searched for a few weeks, i am sure i have not turned ever stone possible.

Possibly too big for your project (though the project does seem to get bigger), but wheelchair motors are great - they are cheap, have the gears built in and often come with nice wheels.

If only the rear wheels are powered then you can make plenty of compromises on the front wheels. On that note, make sure to have plenty of weight at the front to prevent your kid from being thrown off when the thing does a wheely on acceleration.

Out of curiosity, why aluminum? Isn't steel much easier to work with?

I want to keep the weight down, and i have other applications of this once this build is completed. Also people told me aluminum was hard to weld, challenge accepted. :)

Be aware of the safety issues with aluminum too; aluminum has a nasty habit of looking 100% healthy until the moment it completely breaks.

Thought the same thing as well. Ship of Theseus.

Great Scott! If my calculations are correct, when this baby gets an 1 kW motor... you're gonna see some serious shit.

Human beings on a bicycle who generate that kind of wattage can (give or take) hit speeds approaching 40mph. Allowing that the final product will probably weigh more than a race bicycle, but the vehicle is carrying someone much lighter than a bike racer, I'm kind of curious what the final top end will be. Some commenters are recommending a seat belt. I recommend a five-point harness.

And a roll cage.

My friend built an electric motorcycle years ago (we call it a "mootorcycle" because it has a metal cow skull with glowing red eyes on the front - and a ribcage, and other "bone" work); a couple of months back we upgraded the motor to one of these larger 1 kw beasts.

We use 24 volt lead-acid gel cell batteries - the thing easily gets up to some scary speed (well - scary when you're in nothing but a t-shirt, shorts, and no helmet) on the flat. Plus considering the homemade nature of the whole machine...

I can't imagine what a motor like that in a kids ride-on would be like, at full-throttle...

If you like this format of DIY posts (which I do) I'd recommend checking out Reddit's DIY subreddit:


Not sure why i havn't considered reddit, will have a look around and many post there when the build is getting closer to an end.

Obligitory link to the ppprs


I have done 24V on my sons ride, but I blew the gearbox. Time for an upgrade! Also did LED lights and other stuff. https://www.instagram.com/p/BY3X_zhAyY0/?hl=en&taken-by=chjo...

My webhosting provider removed the tiny video that seems to have slashdotted them a tad after yesterdays exposure here on HN. This video is now on youtube, hopefully i will be within my bandwidth limits going forward.

I am also very grateful for all the good and constructive comments made here, this is exactly what i was going for.

A lot of concerns about safety was lifted, and a few comments made me reconsider some choices i was about to make.

In order to make sure the car does not flip over i will be: Widening the axle base and wheelbase with 100mm. The new suspension will lower the the car quite a lot, and also lower the point of gravity.

As i mentioned the motor is a 48 volt running on 12 volt until the little guy grows older and more used to the strength and speed.

He will have no control over steering or gas until he understands the very principals of what he is doing.

In case of loss of radio control, the servos controlling the brakes will lock up.

I made a lot of progress on integrating a signal horn into the steering-wheel yesterday, will show this off in a small update in the end of the week.

As for welding, i got a lot of good advise on top of what i knew from researching the subject. If i go for steel or aluminum still remains to be seen, but my Argon gas delivery was postponed 2 weeks, making it likely i will go with steel at least for now.

Thanks again for all feedback! If you think of more, feel free to let me know here or on the blog.

Kind regards


This got met really interested:

I went above and beyond the original motors when i bought a 48 volt 1000 watt motor of amazon. The motor is meant for a e-scooter, is 200 times stronger than the original engine, so the frame will have to be reinforced.

Too bad it's just part 1.

> I went above and beyond the original motors when i bought a 48 volt 1000 watt motor of amazon. The motor is meant for a e-scooter, is 200 times stronger than the original engine, so the frame will have to be reinforced.

This made me laugh.

My Dutch is not that good, but looks like the bandwidth limit hit. cc: AnnoyingSwede

I tried to replicate this, but have not managed.. Also you seem to be the only one that got it? Are you by any chance in Russia?

CRAP! Will downsize the images when i get home. Did not see that one coming :(

Another blog added to my RSS feed.

I've been missing the old web for years now and this makes me a bit happier.

I also started writing a web page again recently after throwing away any ideas that it needs a theme or a cms or even a static page generator.

I'm a big fan and owner of a Land Rover Defender, so my kiddo car of choice is the Toylander:


These are really fine (and expensive) ride-on car kits. The little Land Rover can easily carry two kids and pull a trailer.

I never bought one, though, and I'm kind of glad I didn't. Once you get your kid an electric car, they'll never want to ride a bike again. I see overweight kids riding around the neighborhood on electric scooters and my wife and I swore we'd never buy ours an electric vehicle.

I've always wondered why they don't make these things with remote kill switches for parents to control while their kids drive around the yard/sidewalk.

They do actually, that's the Stop-button on the control. Since i tossed all that out, I will make sure the brake-servos lock up the front-wheels if it losses radio on mine. As my son is very young, i will be in full control until he is getting older, removing the ability for him to just hit a switch and ride off into the sunset.

They do now - that’s one of the uses for the remote control these come with

I use a lazybone bluetooth relay for my kid's power wheels. I would like to find one with a better iOS app, though, the lazybone app is very unreliable and crashes constantly.

Because they mostly go slow and you can simply walk up to the car and stop it. It's not until people modify it to go fast that a kill switch is needed.

People in Puerto Rico modify and drag race these cars (mostly kids of racers). They use brushless motors, ESCs, and batteries from R/C cars. They end up being ridicoulsy fast. Some even add rubber tires from gokarts for grip. But like any hobby of the sort, it gets expensive fast. Electronics can run you $300 easily.

awesome project!

another feature idea I just had: put a couple of ultra sonic sensors on the front and back.

on the back: to emulate the reverse parking "beep-beep" indicators.

on the front: to prevent collisions - if you rapidly get too close to something (a wall, another child), it cuts the power to the motor.

Great ideas, might steal a few of them. Thanks for the inspiration!

Geez, dads are awesome. This is some shit that mine would have totally done for toddler me, had he the money and time.

Besides my interest in builds and electronics, this is why i am doing this. I never had such a dad either.

It's a bit odd how the word "pimping" has come to mean "embellish". I know how it happened, from "pimp my ride", a show that tried to use "street" language for effect. I can't shake the awful connotations of pimping, though. Nice hardware hack problem, but I hate to think of you pimping your son.

Agree, that word isn't the best, but as long as we are clear i'm pimping the car and not my son it's all kosher to me ;)

If you're going to rant about how the word has taken on new definitions at least be accurate about how it was used.

Pimping my son != Pimping my son's ride

As individuals, we don't have much personal agency over the evolution of language, so sometimes it's best to just let words change meaning. We wouldn't be speaking English today if people got in a fit every time a word changed meaning.

People have been using "pimp" as a verb in this context since at least the 70's, so I'd say this is a lost battle. The phrase did not come from Pimp my Ride.

edit: my interpretation of your use of quotations is one of many, but I should give you the benefit of the doubt here

A more generous interpretation of the quotes around street is that the commenter thought the language on the show was inauthentic (i.e. not real street language).

> putting quotations around the word "street" implies a certain attitude about urban culture that I'm going to assume you don't actually wish to convey.

I read those quotes as simply indicating that they weren't sure if "street" was the most accurate way to convey what they meant (urban, etc.). It is common to use quotes around a word that is an approximation of the intended meaning.

Better than the use of "porn" on sites like reddit to signify fancy photos.

Yeah, I don't like that much either. :-)

Thankfully, that usage seems to be petering out?

The author doesn't appear to speak English as his first language, so it's completely possible he's far more familiar with the informal definition of the word, especially in the context of cars.


words are thought. thought forms knowledge. knowledge is power.

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