Go Kart Racer From Reused Old Scooter Wheels

There are two fun reasons to make a Go Kart / Soap Box Racer using up-cycled Scooter Wheels:

First is that Scooters are really popular, but also vary in durability... so much so that I often see one left in the street outside someone's house, that has been outgrown or broken - but there is much to reuse, up-cycle and repair!

Second, is that Soap Box Racers are traditionally made with large-ish 'Buggy Wheels'...and the problem with that is that 'old-school' Prams like you'd see in Mary Poppins are all but non-existent today, and to buy them new (or equivalent BMX wheels) costs a small fortune.

So if you can find some old pallet wood, and some busted scooters, and with some basic household tools - chances are you too can make a Soapbox Derby Car (US), Go Kart (UK), Billy Kart(NZ) - or whatever you call a DIY Car for kids, made on the cheap! Perhaps when they are older, they can go to this legendary Soapbox Derby!

Tool Time & Tear-Downs.

As you can see from the photos, this is also an amazing project to get kids familiar and confident with tools: I noticed my 6 year old son being fascinated by 'tear-downs' (carefully taking stuff apart), and as an adult, one can easily forget how much products are 'off limits' to kids to explore, and although I was keen to stress that my son does not take apart any electrical appliances, or other such stuff without my supervision, the experience or exploring the steering mechanisms, bearings, springs, levers, and plastic moulding assemblies - were all great fun (and perhaps educational by stealth!). I think the basic build took about 3 hours, but there was about 1 hour of questions while taking stuff apart! So it's a full day / weekend project if you're new to this sort of thing, but fundamentally very doable as history will attest. As you can see, we then iterated over subsequent weekends; painting, adding a speedometer, etc.

You may also like this video about kids tools: YouTube Link

A Wheely Good Idea?

I also did a bit of 'research' on Instructables, and was surprised to find not many SoapBox Racers that used 'small wheels' - and certainly none reclaimed from Scooters. So here I am writing this up as it seems pretty novel (or at least my search terms are poor choices!). I can confirm after a good few months of using this, the wheels do in fact stay on and it's pretty effective on flat paved/tarmac surfaces.

That said, I do want to give a shout out to two projects that really inspired me:

https://www.instructables.com/Wooden-Downhill-Racers/ - which inspired me to figure out how to make simple brakes (generally a good idea if riding in a park or public space!), and hinted that small wheels could work okay.

https://www.instructables.com/skate-buggy--soapbox-derby-in-rural-china/ - for proof positive, you can have fun with a very basic design.

As a final note, Scooters (from the fancy Micro brand to cheap knock-offs) all seem to use the same size of bearing and wheels - so you can interchange the parts if you find more than one!

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Safety/Disclaimer: Please do not attempt to build this if you are not confident using tools shown here, and supervising your child(s) taking part. If you do go ahead and race your creation, do respect this is by definition a DIY effort, and things may be unstable, come loose, or fall off - so do keep an eye on the kart so you can see any faults before they become an issue.

Lastly, don't go down too steep slopes (ours is probably 1:20), and I would advise at least wearing a helmet and perhaps any knee/elbow pads if you wish, as crashes and tumbles will happen! However, so far most of my son's friends - both boys and girls - have brushed it off and had another go...but the choice and indeed ultimate responsibility is yours and I cannot accept any responsibility for your building and/or riding it, or any bystanders...(you'll see I added a Bell - seriously a very good idea in hindsight!).

Further Reading on Risk: This is not a 'wrap your kids in cotton wool' project, and suits parents and kids willing to make mistakes and suffer some bumps and scratches as part of learning to learn about risk. If this elicits a "heck yes" from you - you may enjoy reading LEGO, Montessoriand seeing what Danish Forest Schoolsget up to... the latter is not for the faint-hearted, but is good calibration if you need to see what kids are capable of with guidance! Take care and enjoy... I post quite regularly on IG some other minor projects you might like also @BoredSmart.

Wheels: Most of this project is down to keeping an eye open for old scooters. You can of course purchase scooter wheels new, but it's really expensive. Interestingly I found 'stabiliser wheels' are less pricy and also include the necessary fitting etc. So the choice is yours!

Wood: I happen to have a collection of various grades of pallet wood, which I've got from dismantling pallets. Arguably one can buy timber cheaply, but if you are trying to impress on your kids a spirit of resourcefulness and adaptability (not all pallet plants are equal!), then this is a good way to start. I have some tips on reclaiming wood safely here.

Metal: I used various steel brackets, and scrap metal pieces for the build. Although you can buy these, they are fundamentally interchangeable with whatever else you have that will do the job. This can be part of the fun of reappropriating things to do the job.

Tools: I used a circular saw, for quickness. However, a handsaw will work fine also (if you want kids to have a go). There are no 'fancy' or intricate cuts, just straight lines throughout. A Screwdriver (or ideally impact driver if you have one) is handy - with hex/torx bits (Even though the main size you need is a M5, it's actually cheaper to buy a set (or two) if you don't have them already!). A hacksaw is needed to cut threaded bar (studding). Various wood screws are used (some ~15mm to not go through plants, and some up to 50mm or 70mm to screw planks together) - depends on the thicknesses you have (a multipack is likely best). Pliers are handy also.

Misc: I used some scrap foam (from a playmat) - also found in the street, as a seat. If you have any rope, wire etc. this is useful for creating a steering handle.

A Few Key Purchases:

Studding: Although most of the above you can scavenge for / may have in the shed anyway, chances are you may need 1m of M6 studding to fix the wheels (cut in half).

Carriage/Coach/'Hefty' Bolt & Nut: I used a M12 x 75mm bolt (eg), but essentially you need a bolt which can pass through two planks of wood, for steering, with enough to screw on the nut, as well as having some washers in between. Chances are if you go to a hardware store you'll be able to get a set of 1 for not much at all.

Truth be told, there's no need to remove the pink cover, but hey - it was great fun and good practice! There is a lot to be said for being able to carefully un/screw thing 'that don't matter', before you move onto those tasks which do.

As an adult you may take for granted that you know the inside will be hollow with structural ribs, but this was new to my son, and it was interesting to talk through how it was made. For those of you who are not engineers by trade, it's worth saying that you do not have to have all the answers, as a. you have Google, and b. just saying 'I dunno, why do you think it's like that?' - tends to get as much fun and learning as telling them (some might say - more!).

Safety Tip: This is a nice clip from Wallace & Gromit - and it's worth explaining to your kids that although Gromit has done the right thing and clamped the piece to be drilled, the drill can still 'kick'. So do be aware of this, and start slowly.

As mentioned before, the bearings seem to be exactly the same across all scooters. This is kinda fascinating - and illustrates how when one or two companies 'set the template', China et al really don't see the need to 'reinvent the wheel' and will naturally use what is being made in abundance. This means you can nearly always switch out a good bearing in a bad wheel, for a good wheel with a worn out bearing.

To do this, pry out the bearing carefully (wear googles), as shown with a small flat screwdriver, and work round as you go. Or you can push it out from the other side/hole.

You can also see me using a hex key and driver to remove the 'locking bolt' / axel from the wheel. Take care not to get 'whipped' by the hex key if you do this (see Gromit's mishap above). Watch your eyes (googles!) and hands (gloves!). Go slowly...

Some Wheels you don't need a second hex key to take out as they are mounted/fixed at the other end (more on that later*). So you can just unscrew these easily. They may have a red or blue 'paint' - which is called thread locker. If you are very safety conscious you can re-apply this stuff, here, to reduce chances of working loose.

*If the corresponding bolts are fixed in plastic, it's a little laborious, but you can cut/melt them free. That said, chances are if you have enough junk scooters, you may not need to! I'm just showing you this to make the point, but we actually had enough.

You may also find some Bearings need repair, and this is pretty tricky if the bearing is cracked I would avoid. However, most of the time is is just rusty, and soaking it in some oil and re-greasing it will likely get it spinning again. We got two such bearings going again, after thinking they were stuck for good. Also WD40 is useful, but be aware - this often flushes out thicker grease, so be sure to add some more in place once cleaned up.

Threaded Bar is a good idea as it essentially 'extends' the wheel mechanics/pins to be 50cm apart! If you are unfamiliar with this, it might seem a bit exotic, but luckily it is cheap - as it's a widely used component to hang AC ducting (you'll spot it now I mentioned it!), so you can happily pick up a 1m length for very little.

Cut this into two 50cm pieces using a hacksaw (or a rotary tool). Remove burrs.

It's worth noting that when on a Kart, you tend to 'pull your legs in'. This is funny to see kids set like they are in a car, yet they of course have not really. It seems this semi-squat position just feels natural. So asking your kid to sit comfortably - take some rough measurements.

Likewise, the studding should be wider than shoulder width as a rule of thumb. 50cm was fine for my 6 year old boy.

(You don't need 3 planks - it's just the ground was wet).

Next we can make the steering pivot. This is pretty straightforward, but the key tip is to start 'snug' fit, rather than loose. If your bolt is M12, you may drill a 11mm hole or a 11.5mm hole - just to check.

My bolt was a bit too short by about 5mm, so I 'recessed' the bold in the wood a bit. You have the benefit of hindsight and may well buy a longer bolt, but if you're 'making do' - this is a useful workaround ;o)

It should be said, putting the bold 'downwards' is safer than 'upwards' as any failure means the bolt will still hold things together long enough to spot, even if you need to hunt for the bolt. However, to avoid this - I added some metal 'stoppers' to prevent the bolt and nut from rotating with vibration and coming loose. You can also use thread-locker if you prefer.

Next up is to fix the studding to the wood. You want to observe to not 'collide' with the steering bolt, so this will be sightly off-centre.

I used some angle brackets I had lying around, and hammered them partially-flat, such that the middle 'popped up' and this 'arch' housed the studding and the bolt from the wheel. I added some washers to stop the wheel rubbing against the wood.

Lastly, I added a 'stop out block' - to prevent oversteering. This is a seemingly trivial addition, but I STRONGLY advise doing this, as the wood can 'scissor' if left to rotate 360 degrees. It need not be fancy and angled like mine, but should prevent turning more than ~25 degrees either way.

You may notice the 'longness' of the central plank. I didn't cut this to the end, as I wanted to not make it too short. (Theoretically it means it could be extended if your kid has a growth spurt, or you gift it to someone else who's taller.)

I started with the steering, but now I set the distance of the fixed rear wheels - adding some extra bracing as shown.

I didn't have any thick rope (typically used in karts), but instead used wire. I figured this will do ok, and I'd replace it with rope in due course, but ironically, it turned out to be a nice variation as it gave some good 'feedback' in steering. I slid a off-cut of PVC tube over it as shown.

To anchor the wire (or rope) I took a screw hook, and hammered it round to an eyelet (round, closed loop) - in a scrap bit of wood first. Or you can buy them like this of course!

For the Brakes, I cut some 'strapping' (thin metal strip) and drilled some holes, but even food tin can would probably work if cut carefully. This then created to sprung 'flaps' of wood, which could be pressed down with the kid's heels to create friction and slow down.

I've never pushed for high speed, but it seems to work intuitively, and my son and a bunch of his friends seemed to master this in minutes...funny how our brains/bodies just 'figure it out' so fast (when adults would likely take longer!).

Truth be told - my son was so excited to try it out, that we actually made the brakes the following morning. He was able to brake with his shoe-heals, but of course we know how popular I'd be at home if I let that carry on ;o)

The original deck was fine - just some angled cuts as shown. It need not be angles, and can be square.

Interestingly, the backrest is usually never used, but it is handy to have as a means for friends to push. (Also I suspect as he goes faster, corners, and such, one would 'root' oneself more into the seat for stability...? So chances are with more speed and skill, the seat may well need to be upgraded, but for now it's working well!).

So the surprise for us was finding two of the big wheels lit up - and this made it extra cool!!

When this started it was winter, so got dark early, but lights really helped.

Although this might seem just a nostalgic thing (We had three Americans come up and chat about it on day 1!), it really is just a fun build, and there are not many simple woodworking projects which kids can do and really experience how the trail-and-error comes together.

I didn't set out for this to be a STEM project, but purely by organic growth it has been a continual work of improvement and experimentation - "this bit squeaks - how do we stop it", "can I have this bit shorter/longer/different", "what if we do this / put that on it / change this for something else" and on and on...I'm pleased to say although I have of course lead the heavy work of the build, it is getting 'taken over' by and personalised one bit at a time by my son, and this is a great thing to see it slowly morph into his own creation. I had not appreciated this was going to evolve this way, but I'm pleased it has - and will continue to do so...and I hope yours does too!

Please share any pictures - stay safe and have fun.

One thing I learned from my time at LEGO, was that kids have great imaginations and enjoy fantasy, but they also crave realism - so of course in no time, wanting to add 'real' start/finish lines, but also 'fantasy' Mario Kart style icons as you can see later...

Despite having not played Mario Kart, kids in the playground somehow all know what it is, and the vague notion of driving over stuff that gives or takes off points... so with a bit of chalk one can also create Monsters, Power-Ups, Slow-Downs, etc. And yes, 'Poops' are a feature, highly recommended for giggles.

If you've read this far, chances are you are part of that group of parents, educators or other evangelists who think the school curriculum can - and should - be taught in real life applications. My son has only a vague notion of speed before this, but no had a pretty thorough appreciation for how many mph or km/hr he can walk, run and zoom on a go kart!

All of which is to say, I was really pleased that a speedo can be added to your go kart wheels. Depending on your instructions, you need to measure the circumference of the wheel, and input this into the memory (only once and you're done!).

Tip: You can do this by putting a mark on the wheel and rolling it down a ruler for 1 revolution (or again, if you want to explain the utility of 2πr to use the proper maths). Be fairly accurate about this, as it's in mm usually.

The next bit might seem tricky, but you need to put the magnet into the wheel, as this is what 'triggers' the sensor to count the revolutions and calculate the resulting speed. You may find like me it's simpler to drill a small hole in the plastic and add some magnets of your own, that will do the same job. Safe to say be carful not to split the wheel, and as shown remove as little material as possible. Press-fit, or glue in place, (after checking it triggers the sensor).

As with some of my previous co-creations with my son, I try to get him to plan what we're doing, partly for mental preparation (makes it less chaotic!), but also it gives him some agency over what parts of the project he is totally in charge of.

Really. Get a Bell. We got out in the park, went down the hill, and really needed to warn people we were coming. Although most people looked round - expecting to see a Bike - they were conditioned to take the 'ping' seriously, and so I'm sure many bumps on people's feet were avoided!

And away you go!!!

If you look closely at the pre and post-painted versions, you'l see that some of the design changed. I mention this to make very apparent that keeping an eye on your design, both early on for near immediate failures, and also ones that may occur much later.

As an engineer, there is an easy graphic to illustrate this: The Bathtub Curve. If you're curious - check out more here, but it explains a lot about how you might want to evaluate risk with projects like this and kids. Indeed, it applies not just to products, but also humans: Often trainees make a lot of mistakes, then the become experiences and make very few - but ironically they then get complacent, or goof around with friends, and mistakes increase again!

Night-time, Rain, or Shine. Park and Skatepark. We've been out in it all, with friends and sometimes just us. Brace yourself for a LOT of enthusiastic use a few tears and cuts, but some great memories!

Thanks for sharing any similar projects you've enjoyed making, and/or any tips for this one.

Jude

Links & More...

• I share fun stuff like this on IG here: https://www.instagram.com/boredsmart/
• I can be contacted via my website: http://www.judepullen.com/
• Aside from working in Tech and Design, incredibly, I get paid to do stuff like this for education companies, and have worked for companies like LEGO, Dyson, Sugru, Bare Conductive - so please get in touch if you are interested in collaborating: https://www.linkedin.com/in/judepullen/

Have fun!