need a little help with my wooden go kart, bearings and axles

[The Cabinetmaker]

Hi guys I've made myself a wooden 1920s race car which was for a gravity race in my local carnival and now I'm looking to put a 36v 800 watt electric motor I've got lying around from previous electric bike builds I've done but I'm unsure what bearings and axle I should get, I want them to be very smooth so I can take off the motor for future soapbox races and if it's tough enough maybe try it in the red bull soapbox race here in the UK, the body is 550mm wide and I'd like the wheels (which are 20" bmx wheels) to be about 850-900mm apart, other than that I'm easy hopefully I've attached some pictures of the go kart, New to this forum lark

Edit* I think I'm after/wanting a live rear axle if I can bolt the bmx wheels to it ��

 

[ezcome-ezgo]

That is a sweet ride. Very well done. Welcome!

 

[The Cabinetmaker]

Thank you ezcome-ezgo it's made from mahogany for the frame and and 4mm beech ply for the panels, it looks cool but isn't very fast lol, I came 10th out of 26 karts so really want it to go quicker but I'm a cabinetmaker and had very little to do with go karts so looking for some advice, it doesn't have a rear axle right through at the minute, just bolted the small bmx axles to the body with a metal plate on the inside so not very strong so it's a blank canvas really,

 

[ezcome-ezgo]

I can certainly tell you are a cabinetmaker. You will definitely need to use a live axle. Perhaps there is someone here who has converted wheels like those before. Good luck with it!

 

[itsid]

Well, let's be honest..

I read the topic and thought :
"Oh another one of those... go tell him to stop even thinking about it..."

Here I am amazed by the beauty of it...
Well done sir!

Now the bad part...
bicycle wheels are not exactly the best choice for rides like that, even soapboxes (aka gravity racers) can produce enough inertia to crash on wheels like that...
and even worse: the larger the diameter the easier they will collapse on side loads.
(say a narrow curve or precisely too narrow for your speed )

So please be very very careful, it'd be a real pitty to crash that thing;
it's too georgeous!

You can camber them slightly; so that the spokes have an easier job of deflecting the forces.
Or what I'd do.. upgrade the wheels.

If you insist on that wheelsize a perfect replacement would be spoked Moped wheels with 16" rims
They do often come with a drum brake which is a nice convenient add on for your kart
Since you're in the UK, check for older MBK, Herkules, Simson, Kreidlers, Puch etc...
front wheels preferred
like this one:
http://www.kalaydo.de/kleinanzeigen/technische-geraete/vorderrad-16-felge-rigida-nabe/a/39132502/
(yes it's expensive, I'm sorry )

If you cannot find them, at least get bigger spokes (2.4mm if you can) maybe the rims need to be drilled out to allow the larger spokes to fit,
but the additional strength is really helping
(BMX ordinarily come with 1.8mm spokes, rarely 2mm)
If the hubs fail to allow the bigger spokes... get different hubs; you'd just move the weak spot down to the axle (and the longer lever would make it worse)

A wheel like the one above (here's just the image)


should help staying safe;
on the red bull derby you should STILL STAY AWAY from the jump they always include in the track

I wouldn't convert to a live axle btw.. not for a gravity kart.. makes no sense at all, just makes steering a lot more difficult.

Instead, find Wheelchair hubs and bearings;
they're meant to be single sided and thus come with a larger bearing.
well that is, if you stick with BMX rims

'sid

PS don't put an engine on it.. an electric motor no bigger than 500W maybe (twice the power the sinclair C5 had) but nothing bigger than that IYAM.

 

[machinist@large]

I'm with Alex on this one; I was expecting the usual death trap, only to see something that was totally thought out and rendered well. I'll have to let Alex do the talking on potential upgrades though; not my area of expertise......

 

[The Cabinetmaker]

Thank you Sid there was a lot of useful information there, that was why I included pictures, so you could tell I wasn't just "one of those" people again lol , I'll keep an eye out for some wheels there is a motorbike breakers yard near me so I'll try him, I guess the steering would be better because the wheels wouldn't be locked together like they would with a live axle and can spin independently of each other,

I have a 36v battery with a 30 amp controller so that would be 1080watts (1.5ish bhp) so would be a lot more than 500 watts but would be fun, I did have it drifting a bit under heavy braking, only having a rear brake is the problem there but I only had 6 weeks to get it made so I ran out time to get everything working properly or fix mistakes, front discs will be next upgrade if it goes fast enough

Can I pick your brains about suspension? I've come to the conclusion that it isn't worth the work or money as it wouldn't make it go any quicker and if I didn't get it right I'd just make it handle really bad, there is 4" of leather covered foam to save my bones from shattering which was plenty for what I used it for,

Edit* I've got lots of wood filler in case of a crash lol

 

[landuse]

Edit* I've got lots of wood filler in case of a crash lol

I am not too sure if wood filler is going to work for the holes in your body that the wood splinters have made

 

[itsid]

I guess the steering would be better because the wheels wouldn't be locked together like they would with a live axle and can spin independently of each other,

exactly!

I have a 36v battery with a 30 amp controller so that would be 1080watts (1.5ish bhp) so would be a lot more than 500 watts

No, in fact a 36V 1000W motor needs a 60 amp controller, the 500W model is fine with 30-35Amps.
(do not mistake electical Watts peak with rated mechanical watts of the motor.. two very different things)

Can I pick your brains about suspension? I've come to the conclusion that it isn't worth the work or money as it wouldn't make it go any quicker and if I didn't get it right I'd just make it handle really bad,

And I would agree..
small heavy springs to detach harmonic vibration from the wheels to the chassis is the max suspension I would be doing.

Edit* I've got lots of wood filler in case of a crash lol

Yeah, you made it and you can do it again.. still it'd be a pitty to see it crashed

'sid