Attaching motors to wheels on the super-cheap

[bmscott]

Hey all - new here, but have been skimming some relevant threads. I'm cobbling together a vague plan to build some kind of fun electric kart over the next few months, and as an exercise, see how inexpensively I can do it.

Most of the process seems pretty straightforward - I have plenty of time, tools, and modest expectations to make up for my lack of kart experience. I'm technically inclined, comfortable enough around electronics generally. I've actually got most of the stuff I need already, in fact (lumber for frame, etc). Two areas I'm not sure about yet would be how to design the steering, and how to connect my motors to the wheels.

I'll be using 24v, 500 watt brushed DC motors from used electric lawnmowers. I can get them very cheaply (anywhere from $1 to $20), and I have 3 so far but will probably start with just 2. I also can get good quality 12v SLA batteries for next to no cost, so that's a solved problem. I'll have to buy a proper motor controller, but there appears to be plenty of affordable choices in that area, no worries.

Wheels seem to be shockingly expensive to a newbie like me, even used! I've got some free substitutes I'm hoping to start with - hand-truck tires and jogging-stroller wheels - but of course they have no cogs. My motors have a screw-tipped shaft, which I assume gives me some flexibility in how to attach the load, but they don't come with cogs either. I considered using wheels from kids' 5-speed bikes, but they wouldn't get me the gear ratios I'm probably going to need (wild guess, at least 10:1)

What I'm wondering about is what alternatives there may be to a conventional cog-and-chain arrangement. Let's assume I won't be welding anything. I have a 3D printer but it's mainly for custom shaped plastic parts, nothing load-bearing. I can post pics of my motors but I'm prepared to dump my wheel candidates so far anyway if another idea presents itself.

Remember that the point of this is cheap, or free when possible. My motivation here is that anyone can build something cool for $3,000, but if I can bring this in for $150 that'll be an accomplishment!

Crazy idea #1 I've had: fill stroller tires with solid foam, and drill all around the rims to create a sort of inward-facing spoke system, around which I could stretch a belt/strap. Stroller tires resemble these https://sep.yimg.com/ay/albee-baby/...lick-connect-jogging-stroller-tangerine-7.jpg

 

[mckutzy]

If they'll withstand the initial torque, they won't withstand much or any side loading which will occur. So ya no stroller wheels...
Best for this is get proper wheels from a riding mower or the like... They're built for it...

Or just use those and find out the hard way... But often I see people find out this the hard way.. The Expensive way..

Past that, bike sprockets won't do as they too aren't meant to handle the torque....

 

[itsid]

hmm.. friction roller (think velosolex)
heck, even buying a size 8 chain and sprockets would likely be cheaper than the foam to fill the tyres...

you can print belt pulleys rather easily (T5 should work well) but the size you'd need takes about 14-16hrs for the large one and ~6'ish for the smaller one.
ABS 40-50% infill should do (colorless works best since the dye itself does not fuse)
BUT T5 belts are not cheap either....
certainly not as cheap as 8mm pitch chain
and you need continuous belt in matching size of course...
So if you don't salvage a matching belt from somewhere.. chain is still cheaper.
to print the pulleys you'd use a few hundred grams of filament ... twice that if your print fails, right? and if you buy small spools that's again 10 bucks perhaps (less if you buy 2.5kg spools but still not free)

Now wheels:
kart wheels are not expensive, certainly not used..
think about it this way:
a 10 buck dolly wheel lasts maybe an hour .. three if you're lucky..
three of those can buy you a used kart wheel that lasts maybe a year until you need a new tyre
(in your setup)

yes, 120 bucks sounds alot... throwing 40 out the door sounds like alot more to me though
AND I've seen sets for as little as 60 bucks on the local classifieds..
gumtree I say!

for a 500watt motor, consider a used pedal kart as a donor vehicle..
you might need to alter the chain ratio of course, but if you find a sturdy one that got steel rims and air filled tyres for cheap, you should have taken a good step in the right direction.

what controller do you intend to use?
(and if you say none... frankly, I'm out of here )

'sid

 

[KartFab]

Wheels seem to be shockingly expensive to a newbie like me, even used! I've got some free substitutes I'm hoping to start with - hand-truck tires and jogging-stroller wheels - but of course they have no cogs. [/url]

heard it a million times

Parachute material is expensive, why don't we go use a bed sheet and some fishing line?

So in all honesty here, you cant 'afford' the $70 barebones brake and sprocket and rim and tire assembly here?
http://www.gopowersports.com/145x70...mplete-with-5-8-bearings-sprocket-brake-drum/

Instead of new, you can just go to a JUNKYARD please for the love of god go to a junkyard or a scrapyard and look for used GO KARTs. You could pick some up for NEXT TO NOTHING and have axle, brakes, tires, rims, sprockets, etc etc.

 

[bmscott]

If they'll withstand the initial torque, they won't withstand much or any side loading which will occur. So ya no stroller wheels..
[...]
Or just use those and find out the hard way... But often I see people find out this the hard way.. The Expensive way..
Past that, bike sprockets won't do as they too aren't meant to handle the torque....

Umm, how much torque do you think I'll be putting on these wheels at first?? 500 watts pushing (what I'm guessing will end up close to) 400 lbs isn't exactly burning rubber. If I get 10kph on level ground with version 1 I'll be impressed... side loading I get, spoked wheels not built for that, but bike sprockets not meant to handle torque? I can stand on my pedals and shove down with all my 200lbs and they hold up fine! My legs output far more than 500 watts.

Thanks, though, you've underlined some points I'll run into sooner or later. The idea here is to get something that at least rolls at first, then upgrade step by step as the mood strikes. We have a highly sloped plot of land at our house and it's a cinch I won't have anything that can ride around in our yard until I'm up somewhere past 2 kilowatts (and my kids are piloting instead of me), f'rinstance...

---------- Post added at 02:43 AM ---------- Previous post was at 02:29 AM ----------

hmm.. friction roller (think velosolex)
heck, even buying a size 8 chain and sprockets would likely be cheaper than the foam to fill the tyres...

WOW - yes, just what I was hoping for, an idea I'd overlooked... I'd need much larger rear wheels, ideally with a textured surface of some kind - but yeah that's definitely an angle to consider. I also thought about a screw drive, but that would mechanically tie the rolling of the kart to - well, a gear that'd be stripped pretty quickly, I reckon...

I'd certainly prefer to go with cogs and chains if I had a cheap way to attach them. I have access to people with welding equipment, even forging equipment, but my goal is to see how simple I can keep this first build. I've got a few tricks I've learned on getting really inexpensive parts and if I can turn that into a tutorial on building (let's say) a $200 gokart from scratch, it could be of interest to a lot of folks. If they need to weld something along the way, that's gonna limit the appeal...

BUT T5 belts are not cheap either....
certainly not as cheap as 8mm pitch chain
and you need continuous belt in matching size of course...

I actually do have a motor with a toothed pulley and matching belt salvaged from an old battery scooter, but at 100 watts it isn't pushing anything more than that old battery scooter. It could someday make a really cool power steering system though!

for a 500watt motor, consider a used pedal kart as a donor vehicle..

I'll keep an eye out but as far as I know electric bikes over 250 watts are illegal here. Of course there's always a grey market, but I don't know enough about that to recognize them on sight (like when you're cruising the streets during Hard Rubbish week...)

That's why I'm sticking to lawnmower motors. I just picked up another one today for $20 (whole mower, w/charger and batt, actually). They're not cogged but the price is hard to beat!

what controller do you intend to use?
(and if you say none... frankly, I'm out of here )
'sid

Oh of course I'll need a proper PWM motor controller - and you can get 'em starting pretty cheap online. I've been dealing with cheap Chinese electronics for years now (used to work for an importer, in testing and after-sale support...) so I know what I'm getting into there. I've already got very good quality wire and circuit breakers, even some solenoids.

I'm not planning to finalize my controller choice until I have a clear path on how to deal with the mechanical side of things. Ultimately I hope to have 4 of my 500W motors powering the kart, but that'll be a whole 'nother level of "interesting" since I don't think it's gonna be practical to make it a 4WD, and I've even less of an idea how to attach 2 motors to each rear wheel! But by then I'll have something like a year of tinkering experience under my belt...

---------- Post added at 02:48 AM ---------- Previous post was at 02:43 AM ----------

Parachute material is expensive, why don't we go use a bed sheet and some fishing line?

So in all honesty here, you cant 'afford' the $70 barebones brake and sprocket and rim and tire assembly here?

Yes, a bed sheet and fishing line is fine if you're planning to get started by jumping off your doghouse. Then you jump off your deck, and then off the roof, and you sprain your ankle and decide OK, time to upgrade. Low expectations, learn as you go, just like when we were kids.

I can afford a whole automobile if I want. I'm not trying to win any contests by building the greatest thing right off the bat. Gotta have some limitations to push against.

Simply buying stuff is no fun any more. The most fun I had last year was making voice-activated powered roller blinds - not because it was technologically difficult, but because I did it with under $12 in parts. (sure, they only lasted about 2 weeks, but that's not the point... yes, my wife wants the blind put back up over the kitchen window, but I have upgrades planned - already bought a larger stepper, you see...)

As for your suggestion - I never thought junkyards would have gokart wreckage. There are a few near me, I guess it's worth a phone call! Thanks -

---------- Post added at 02:54 AM ---------- Previous post was at 02:48 AM ----------

Oh by the way, that "$70" rear wheel unit is $87 and will turn into about $260 in Aussie dollars after postage from Texas... that said, I did not expect to find a new, cogged, pneumatic wheel with brake for under $100. Still out of range of what I want to pay starting out - still more than my car's tires cost! - but not quite as bad as I'd have guessed.

 

[Functional Artist]

If you want to stay "low cost" then Mckutzy's right find ya a used riding lawn mower
You should be able to pick them up for $0 - $50.00

For a small investment, you get
Wheels (heavy duty rims with a keyway & turf tires)
Axle or transaxle (with a key way that matches the rear rims)
Steering components (complete set up)
Switches (key switch & sometimes toggle switches for lights)
A seat, levers, pulleys

Here is a kart I built for my son, using riding lawn mower parts

Lawn mower parts:
4 wheels & tires
rear differential
& the seat

It runs on a
24V motor
500W speed controller
2 - 12V12AH SLA batteries

https://www.youtube.com/watch?v=YZ6bcBy1O1M

I am all for low cost & DIY but, it has to be well thought out & well designed.
or
You end up spending a lot of time & effort on something that only lasts 2 weeks

 

[TT540]

FWIW, I too went cheap for wheels. By only saving $5 a wheel, I ended up with an exploded bearing after minimal use. Granted it was not a catastrophic life threatening failure. but it was wasted money.

And if you fill it with foam, the out of balance/round will be ever more pronounced in the seat feel. A semi-flat tire that deflects/changes can help absorb a lot of that.

 

[KartFab]

I can afford a whole automobile if I want. I'm not trying to win any contests by building the greatest thing right off the bat. Gotta have some limitations to push against.

Simply buying stuff is no fun any more. The most fun I had last year was making voice-activated powered roller blinds - not because it was technologically difficult, but because I did it with under $12 in parts. (sure, they only lasted about 2 weeks, but that's not the point... yes, my wife wants the blind put back up over the kitchen window, but I have upgrades planned - already bought a larger stepper, you see...)
.

From what we have seen over the years, this is what happens with cheap parts

1) dollies/moving kart wheels: thin steel esp around hub breaks. has resulted in serious injury. These arent designed for side loads at all. Cheap bearings fail. 'rubber' tires is more like a greasy substance that lasts no more than 2 hours of drive time. I'm not making this up. I have also personally witnessed one of these moving dolly wheels break at the hub when my nephew was borrowing some cheap dumbass's mini bike that he wanted to 'test out' the thing CRASHED. its just DUMB to put on these moving dolly wheels, even if you can get four of them for $20.

2)plywood/wooden kart. breaks, again resulting in serious injury.

If your blinds break, not a big deal. But if the go kart breaks, when your kid is on it, then that's a huge deal. Large go kart manufacturers have been put out of business because of small oversights in safety that resulted in serious injury and death, which includes (unguarded clutches and axles) flipping, etc.

Just think about safety. You are basically going to put your inexperienced kids in a miniature moving vehicle and hope for the best. Please also consider

1) brakes
2) steering wheel mounted kill switch
3) remote kill switch.
4) helmets
5) supervising them while they ride.

have fun with your project!

 

[landuse]

I'm also all for cheap builds, but I am also all for paying slightly more so that I am not repairing stuff constantly and paying more in the long run that what I would have if I just bought bottom of the line "decent" stuff

 

[bmscott]

Just think about safety. You are basically going to put your inexperienced kids in a miniature moving vehicle and hope for the best.

OK guys, thanks for the advice but you're not really hearing me either. My kids aren't going anywhere near this thing, not the first few revisions anyway. My wife was an ER nurse, she won't even let me ride a Honda scooter...

You've made some decent points - I should have mentioned that I already have a source for decent wheel bearings, they're not a worry - and I've gotten an idea or two towards solving my basic question, which is appreciated.

I'm not trying to make something perfect on the first go, nor am I trying to save a few bucks for the sake of it. I'm intending to make (what you're calling) mistakes, test failure modes, and learn where the boundaries are. As has been said, if all your tests succeed, you're not testing properly.

And I'm not making a 100mph death trap. If I get it operating at more than a brisk walking pace, I'll go doublecheck my insurance coverage. Meanwhile I'll find some other places to discuss the project.

 

[landuse]

I'm not trying to make something perfect on the first go, nor am I trying to save a few bucks for the sake of it. I'm intending to make (what you're calling) mistakes, test failure modes, and learn where the boundaries are. As has been said, if all your tests succeed, you're not testing properly.

But if we can help you not make certain mistakes before you even make them....isn't that a good thing?

 

[mckutzy]

Ok then...Build what ever it is you want to build, you already seem to know what you want to build.... And how..

You can find plenty about steering and driveline attachment in the search...have to wade through a bit but hey... That's research...

Leave/stay if you want too... But one thing about the culture here is... Safety... If we think it isn't, were going to mention it...

 

[itsid]

You're not letting your kids near that contraption alright,
the question is can you stop them?

there's plenty of kart shops in australia; want steel rims:
https://www.gokartsaustralia.com.au/collections/parts-and-accessories?page=3
there, one googly away..
(they even have the drifgter chassis in parts.. should be a great donor and it's cheap)

again: gumtree.. local classifieds you'll find cheap reliable parts with only minor patience even

It's okay not to make a perfect kart at first of course,
it's just NOT okay to make a terribly unsafe kart at all!

cheap wins, I get that... but if cheap costs you a broken limb... what for?
And I repeat:
if you throw twenty or fourty bucks at a part you'll throw out within hours
just to by the 120 dollar parts you were afraid to buy at first...
then those will be 160 dollar parts essentially, not?

So cheap is fine, but make wise decisions...
just as you wouldn't print a motorcycle helmet to safe some bucks

ride on mower wheels are often times cheaper than kart wheels and similar in size,
get those if it saves you a few bucks, but stay away from hand truck, dolly wheels and everything you cannot support between two beams horizontally and jump on the axle/hub,
no matter if kids bike, stroller or whatever..
if it doesn't hold that it will collapse within a few turns.

'sid

 

[anickode]

My wife was an ER nurse, she won't even let me ride a Honda scooter...

I feel your pain. The one advantage of having a tiny yard is that aside from the occasional test run up the block and back, I have to take things elsewhere to ride them, so he has no idea how fast they actually go.

 

[KartFab]

Meanwhile I'll find some other places to discuss the project.

Looks like you moved along. Nothing wrong with what you are doing. We have just seen countless individuals try to save as much money as possible and end up hurt, or with a broken or unusable 'final product'. Feel free to post up your progress with pictures here. Dont take any advice that we give out as an insult. E.g. if you are putting wheels on a go kart that break and can only be used for two hours, we arent going to say thats a good idea and give you a high five, we are going to say its a bad idea. Dont take it personally.

 

[bmscott]

But if we can help you not make certain mistakes before you even make them....isn't that a good thing?

The goal is to learn from making mistakes. Everything I've had someone teach me, I only know superficially. Stuff I've taught myself, mistakes and all, ends up being the fields I've built my 2-3 careers on. Ideally, of course, you combine the two, but I haven't mastered that trick yet! (I've wasted quite a bit of money trying, it must be said)

cheap wins, I get that... but if cheap costs you a broken limb... what for?

Again, I don't see where the prospect of broken limbs comes from. You're too used to high-speed vehicles. Relax, I won't hold anyone here responsible... I'm making a Rascal scooter, not a nitro-methane funny car.

Just yesterday I came across this, right in my neighborhood: https://www.facebook.com/marketplace/item/173360906796809
A definite bargain, perhaps a bit TOO big, but none would deny their kart-worthiness... but it leads me to the other question I was posing here, or was about to: is it feasible to put more than one motor onto a single loop of chain drive?

Provided the motors are identical to one another and powered from the same, or identical sources, it should be mechanically OK to do. And with wheels this big I'd need 2 of my 500w motors just to get rolling, and 4 to do anything radical like trundle gently around a corner. But if there's some really obvious thing I'm overlooking, feel free to chime in!

Getting back to the earlier posts, I don't think I was expressing myself properly. Spoked wheels from a child's bike - sure, they're not intended to be robust to sideways loading. Exactly how will they fail, at what point, and which part(s) will fail? What if I use two on each side, like a "dually" truck? What if I mount them to tilt with turns? What about solid polymer wheels? Can I find a ridiculously cheap means of making a cushioned suspension, such as with cut-up pool noodles? What kinds of bearings stand up best? These are all questions I will eventually answer for myself, assuming I get far enough into this project. (note that I have a boxful of digital temp probes I'll be installing in key positions for testing - bearings, batteries, wiring, motors, the works)

We all got off track - what I wanted to ask was about alternate ways of getting power to the wheels, when cogs aren't available. Whether or not X makes an adequate wheel is a separate set of questions. I should have been clearer on that, and I appreciate the advice offered (esp. the tip that was on-target for my actual request!)

If I have a talent in life it's finding surprising and cheap new ways to do things. It was incredibly useful back when I was a broke kid. These days it's nearly useless, so I'm turning it to a new hobby. And if I discover some interesting new way to accomplish something, it could help other people. At worst, I'll have put to use some of these tools I've been watching collect dust.

 

[itsid]

Well, we cannot stop you from making mistakes of course;
still we strongly advice you to avoid them (in case we see them beforehand)

Live with that!

Keep in mind that we do have teens around here, that do not quite have the selfresponsibility an aduld has just yet,
and any chance a kid gets to reason towards a stupid mistake or risk of health (however minor)
it will likely label it a "good idea".

Not your fault? not your business? well... it's OURS!
So, we keep on pointing out the flaws that may or may not cause you to bruise your knuckles

Once you slightly feather a curb at 10mph and that flimsy ten dollar wheel collapses, you'll perfectly know that you got what you paid for

When do they fail? we can't tell, too many factors, what we do know is,
that they usually fail once you got confident they won't (and thus speed up a notch or take tighter turns, hit a curb by accident, a pothole... you name it)
Think "worst possible occasion" and you'd be at least close

And yes, one could power a single chain with two motors, in fact if you face one motor the opposite way it can even double as chain tensioner ...

It's not a suberbe idea, those motors are unlikely to run at perfectly identical speeds at perfectly identical loads etc..
but.. 5-10 bucks a motor... and you're obviously not too concerned about a perfectly reliable setup,
so yeah it'll do for a while, if you keep track of the motor temperatures you might not even ruin one

Said it before, but like to say it again:
a full sized car needs no more than ~300 Watts to cruise at low speeds;
a fellow DIYGK'er build a 1000W go kart at school at hit 40+mph with it (racing kart frame btw.. kart wheels... extra cheap being a school project and such)

So no, I doubt you'd need 2kW to have fun...
but feel free to check the calculation thread over here
to find out what power would be needed for what weight of kart

'sid

 

[bmscott]

a full sized car needs no more than ~300 Watts to cruise at low speeds;
a fellow DIYGK'er build a 1000W go kart at school at hit 40+mph with it (racing kart frame btw.. kart wheels... extra cheap being a school project and such)

That's pretty remarkable - I've been doing my wild-guess estimates based on my wife's electric bike, which at 250 watts is pretty anemic except on gentle downhill slopes. Meanwhile my electric car draws about 6 amps just to idle (it's that stupid feature that simulates a torque converter's creep-forward effect) which works out to around 2kw, given the battery pack is around 380v. It weighs about 8x what I expect my project to weigh, but its rolling resistance is rather lower...

If 500 or 1000 watts is enough to boogie even with a 200+kilo load, then it'll just be a matter of working out a gear ratio that will enable me to use that power climbing up our back yard.