Board logo

Changing Wishbone Geomtetry
scootz - 20/8/16 at 02:11 PM

So you have a chassis and the wheelbase is 3cm too long for the bodywork you want to use. The front-end is ok, so any mods are going to happen at the rear.

It's a full bodied car, so lengthening the bodywork is out.

You also can't shift the rear suspension mounts.

That leaves changing the rear wishbone geometry to reduce the wheelbase. I know the square route of bugger all about geo, so is this a workeable solution, or is it a sure-fire way of completely screwing-up the rear suspension?

mark chandler - 20/8/16 at 04:01 PM

Well within the tolerance of the cv joints, the pivot points remain the same.

Analogy time

Look at locost fronts, even length, then look at some other types with the front bone at right angles and the rear 45 degrees.

Only concern then is the shock will now lean a bit, can you modify the brackets to put back in line?

Sam_68 - 20/8/16 at 05:23 PM

quote:
Originally posted by scootz... is this a workeable solution?


Short answer: yes absolutely.

It will change the handling of the car slightly, of course, but in a fairly easily predictable way, which is why some old F1 cars were designed to do exactly this to suit different circuits.

If you can alter the 'sweep' of the wishbones without running into tangles between driveshafts, dampers, etc., then it's pretty straightforward.

I know you said the changes are at the rear, but worth noting that you'd have to be more careful at the front, since if the fore-aft relationship between the uprights and the rack changes, you'll be altering the Ackermann geometry.

scootz - 20/8/16 at 06:02 PM

Thanks for the replies guys!

Neville Jones - 27/8/16 at 09:12 AM

Hi Scot,

What sort of car is it, to start with?

You might not be able to change the body length, but cutting the arches, moving them, and glassing/filling in between, then fairing it up and painting would save a lot of headaches and maybe cause a few more?

Cheers,
Nev.