So my cousin has a China Inc dirt bike that he bought a few years back and the previous owner was supposed to "get the Title to him" and well, as you can guess, that never happened. At this point he doesn't want to go through the hassle of doing a "lost title" at DMV for a 200cc China Inc. dirt bike that isn't worth as much as my shirt. But it got me/us thinking about building a tiny Go Kart size off roader with the engine. 200cc, 15-16HP, five speed and electric start on a 48" +/- wheel base maybe 42-46" track (I'm thinking 1960's size) that would fit in the bed of a small pickup. Hell, maybe even source a few more engines (link to cheap engines
) and have 3 or 4 we could race on his 80 or so acres. So there is the premise.
I have been thinking about it in the evenings and it definitely needs suspension at all four corners, maybe 4 to 6" travel, just enough to soak up some bumps to save the butt and back. The front is easy, little double A-arms (as long as will fit), a spindle and a spring and shock. The rear however, is another issue. The whole motor mounted to the swing arm thing like a lot of the cheap China karts is out, it's just a crap Idea, way too much unsprung weight and the motor gets beat to death. Swing arm with a jack shaft would work but it's not independent and that's a ton of bearings, chains and shafts and whatnot and all that stuff takes power to turn. I really like the Idea of IRS, super low unsprung weight, the bumps only affect the one wheel and it would just be trick on a tiny kart.
There seem to be a few ways to go about it, the first is the jack shaft with parallel trailing arms and chain drive down to the wheel. Like so...
Again lots of chains, shafts and bearings and it doesn't get any camber change,etc... But it would be OK.
Then there is a swing axle like old VWs used but again no camber control and a lot of possibility of wheel jacking in turns. (no picture because I think everyone knows what I'm talking about here). And you still need at least one CV or u-joint.
Then there is the trailing arms like they use on full size dune buggies which gives great travel but needs an axle shaft with a lot of plunge. This is a possibility but CV joints are $$$.
And of course the last is Double A-arm but again I am looking at CV joints and thinking this ain't gonna be cheap.
These images are all just yanked from a Google image search.
I would love to do a little version of one of the last two pictures but the CV axles are a huge stumbling point because of their Price $$$ and really with 15 +/- HP i think that all the ones I can find (like the type 1-4 or 930 CVs) that are easy to make attachment flanges for are way overkill strength wise and way too long. So I have been wondering about PTO type shafts and U-joints as they can be had for reasonable money and (on my tractor at least) they can take a hell of a beating. U-Joint.
And a square bar and square tube slip-joint, like they do for long travel drive shafts. So has anybody built a little suspension like this? And what did you use for the axle shafts? Or does anyone have a source for small and cheap CV shafts?
Hell if nothing else this might just spark some conversation and get this forum moving again. And if you've got any pictures of your buggy or suspensions please post them up, everyone like pictures.
Thanx for any input you might have.