pushrod suspension question

[Keegan]

I've been thinking about a suspension for a kart for a small chlid. My son is 4.5 and he's pretty light, about 35lbs. My idea is a offroad style kart with front suspension. My concern is that he's so light and the kart would be small in size, so there wouldn't be enough weight to compress the springs.

My idea is a pushrod suspension using a shared, single coilover. I did a quick drawing, so use your imagination to fill in the rest. I'm not a suspension guru, just brainstorming how I can get some usable suspension on a little cart for a little driver.

Thanks.

 

[robotmickey]

What you could do is have A-arms on either side like usual, then have the coil over mounted close to the pivot point on the kart. The idea is to move the fulcrum, making it easier to compress the spring. It's like a teeter totter with a fat kid on one end and a little kid on the other end. If the fulcrum is in the middle or closer to the little kid, he will never be able to pick up the fat kid, but if you move the fulcrum closer to the fat kid, then the little kid will be able to pick him up just fine.

 

[stargazer7467]

google cantilever coilovers, im actually planning on this design with air ride on my car.

 

[Keegan]

That's a good point about moving the fulcrum. I'm going to keep that in mind. That would also increase the travel of the suspension.

 

[Doc Sprocket]

You betcha! You can alter the travel and the spring rate that way. That single horizontal concept could work too. I had an R/C car years ago that used that design on the front. The only liability is that it renders the frontend no longer "independant" by definition. To illustrate- if you drive over a hump with the left tire, the compressing spring will apply more force to the right side, possibly causing the front end to rise. Conversely, dropping one tire in a hole will decrease force on the other side, causing the front end to lower. In reality, I don't think the effect would be very pronounced on a relatively low performance kids kart. It would look really cool, and be a decent enough solution for springs that are just too stiff.

If you have room, you can simplify your design by welding an upright member directly to the A-arms and attach the coilover directly to those members, saving cost, complexity, and weight.