Gravity Racer Suspension - Is 3 The Magic Number?

Post here information about your own engineering projects, including but not limited to building your own car or designing a virtual car through CAD.
jimcroisdale
jimcroisdale
0
Joined: Wed Nov 09, 2016 11:47 am

Gravity Racer Suspension - Is 3 The Magic Number?

Post

Hi all,

I'm designing my gravity racing car for the 2021 UK season. This car will be the culmination of all that I've learned with my previous builds, and I hope to be able to compete with the very best cars out there.

The car will feature a suspension system with a small amount of travel. The roads we race on can be rough in places and suspension will help, but it has to be well controlled. Sloppy suspension seems to slow gravity cars down.

The first design stipulation is that the wheels (front and rear pair) must always face in the same direction. Gravity cars roll best with no toe, no camber, and a few degrees of caster. This originally got me thinking about beam type suspension. Initially a traditional beam with panhard rod and control arms - but this system seems so complicated for what may end up being an inch of travel at the wheels. So I looked at simpler torsion beam designs, before alighting on my idea.It will have caster gain on bump, but that's okay.

Imagine a triangular piece of card on a table. You can lift any of the three corners, and the other two will stay touching the table. The magic of three :-) The suspension works in a similar way - it is essentially a triangle. A corner each for the wheels, and one corner for the chassis mount via a rose joint. A single panhard rod locates it laterally, and shocks or viscoelastic polymer pucks are mounted off the "triangle" to give the suspension travel required.

I've spent a few months looking at it now, and to my eyes it's the simple and effective solution I was hoping to find. However, I welcome your comments and suggestions on this. :-)

Image

Image

Greg Locock
Greg Locock
179
Joined: Fri Jun 29, 2012 11:48 pm

Re: Gravity Racer Suspension - Is 3 The Magic Number?

Post

Looks OK to me. I'd terminate or raise the structure at the axle allowing a longer panhard. Bump castor really isn't an issue unless you have a driveline.