Cowl steering geometry

I've been through a list of threads here concerning cowl steering installations. Each has constructive information and some are downright amazing, however I have yet to find a definative design criteria for cowl steering geometry on a car using a split bone front suspension. The mechanics of building the system are straight forward however I want to make the system work as well as is possible. I know the parallel to the bones theory is shot full of holes.

Your input gentlemen?

 

Similar arc in the movement of the bones and the drag link.

 

Exactly...but without a REALY long pitman arm you won't get that. Parallel to the pitman arm and not too much higher looks right and performs descent.

 

Ideal would have the tie-rod end at the pitman arm the same height and fwd/aft position as the rear point of the radius rod so that there was zero change in distance between pitman and steering arm with suspension travel. That would amount to both the radius rod and tie-rod swinging on nearly identical arcs. Tough to work out in practice.

 

I have my draglink and split wishbone within 1/2" in length of each other and they are nearly parrallel of one another using a Schroeder box and I get virtually NO bumpsteer.

 

Hi Kirk could you post a pic of your setup ???

 

Here's a very good example of what to shoot for.

 

You can't get much better than this. Russ Daly's tub.

 

That is the only cowl steering job that I have ever seen with perfect geometry.

 

Yep. If you're looking for the definitive answer, you just found it. That tub cannot possibly have any bump steer. Good job. However, mine is a lot like the one in Johnny Fast's pic and it performs very well.

Pete

 

From OZ manual, consider length too

 

Where did you find that?

 

http://www.infrastructure.gov.au/roads/vehicle_regulation/bulletin/pdf/Street_COP_sec_5.pdf
You can find other chapters in my post here
http://www.jalopyjournal.com/forum/showthread.php?t=282490&highlight=modified+28&page=9

 

I have the whole manual but I'm surprised to see it referenced from your side of the planet

 

Here' the US one, but yours is more user friendly
http://www.vesc.org/Media/VESC V-12...n and Equipment of Special Motor Vehicles.pdf

 

Not the greatest shot but the split wishbone is attached up inside the cowl directly beneath the centerline of the pitman arm.

 

Thanks Kirk, Lovely truck.

 

You call that cowl steering? Looks to me like a conventional box mounted inside atop the frame at the base of the firewall under the footboards.

I'd like to see the box, steering arrangemnt on that car, hope it is not sprockets and chains.