Serious suggestions for reducing understeer??

[Island kart]

Just built my first metal kart after my previous wooden kart build, using my knowledge from my A level physics and inspiration from my old mini cooper I am a little afraid I may have gone too light (somewhere under 50 lbs including the engine), I put the driver and the engine right over the back axle and i know thats a bad idea but the engine's got some kick and i needed the traction. Well anyway the kart is too crazy (great fun, but crazy) it understeers and the front wheels lift off and there's a lot of countersteering on pain of death that has to be done. Anyone got any reasonable ideas for getting rid of it, cant move the engine, cant move the seat so i was thinking of putting in a floor at the front made from plywood to weigh it down a bit. Think the kart will be fine on tarmac, just on the grass its a crazy beast.

 

[Doc Sprocket]

Examine the sticky thread on Caster, Camber and Ackermann, and see how this is applied to your kart. Horrible weight distribution being what it is, try the above. You may also get some positive results by altering tire pressures.

 

[OzFab]

Plywood weighs next to nothing; if you want serious weight, throw some lead in...
But serioulsy, add some more metal, try to make it look like it's meant to be there, not just extra weight. Instead of just hollow tubing, use solid bar; it looks the same but weighs a lot more

What material did you use for the frame?
Did you employ the Ackermann Principle in your steering setup

 

[souperman000]

Is it a live axle?

 

[Island kart]

Well the thing is living on an island metal's expensive and i'm on a budget so thats why i was going to go for a couple of layers of plywood. As for all that camber and caster stuff my steering setup is to basic for anything other than toeing in or out and they're toe'd slightly out. As for the Ackermann principal I did not use it feel it would make a very marginal difference, what about an external fuel tank or water ballast tank. or maybe two layers of ply one on top one on bottom with a couple of bricks in between. Or maybe I'll just live with it kinda like riding rodeo or something... and fun's all I was really after. Got cars to go fast in.

Let me know what you Go kart guru's think

Thanks

and its inch square tubing

 

[Island kart]

and no its a single drive which again doesn't help when your front wheels lift

 

[Doc Sprocket]

The reason I suggested it is because you asked! If you want to throw some bricks in there, be my guest. But there's no substitute for proper geometry (and weight distribution). Unnecessary weight simply robs power.

EDIT- What do you mean by "single drive"? Live axle (both wheels driven, no differential)?

 

[OzFab]

Speaking from experience, Ackermann makes a huge difference but, if your front wheels don't touch the ground, it makes no difference at all

 

[Island kart]

Haha sorry guys I know it's a good idea but tbh my karts a little rough in places so I'll just do what I can and let you guys know. And my front wheels touch the ground but not on rough ground.

And sorry I meant fixed axle with drive to a single wheel.

Don't think I'll do the bricks by I'll play with the steering for sure

 

[slideways]

So you built a metal go kart that weighs just 50lbs WITH a seat and motor? And it does uncontrollable wheelies?

I gotta see some pics of this... I think the first concern is with it breaking in half lol

 

[Island kart]

Hahaha! I shall post some photos when it's painted, it's just a basic rectangular frame needed the most go kart for the least steel possible. I doubt it'll break in half.... Maybe thirds. No but I think I might call it the death trap, if it doesn't kill me before I get a chance just get it on my headstone instead...

 

[landuse]

If your kart is just basically a rectangular frame, I would add some cross bracing for support so that the frame does not warp

 

[qtband]

Adjust your front to have a little toe-in instead of toe-out. It'll make a big difference.

 

[anderkart]

Most karts can transfer more weight to the front tires by simply extending the pedals/front bumper area out further so your legs are nearly strait/not bent. You'll be transferring more of your lower leg/feet weight the front tires, it can make a huge difference. Doing this can also make the kart comfortable to ride with the seat moved forward more for even better results.

Transferring your body's weight so your closer to a 50/50% (front to back) weight distribution is one of the reasons why racekarts turn so well: