Hi All,

I'm not sure that this is the "done thing", however, have any of you ever had any experiences with fitting a small steering rack with centre pinion on to any monoposto type A7's. I'm just curoius as to how this is done and whether anyone has done a conversion like this, would love to see some pictures of said conversion and talk to anyone who has physically done this, and whether a centre mounted centre pinion rack helps with bump steer.

And whilst I am on the subject of steering, what about tubular beam axles does someone actually offer this a s a conversion?

Hope to hear back from some of you.

Regards,

Mark

To avoid bump steer, the geometry of the track rod has to match that of the suspension, so as not to have conflicting arcs. So, with a beam axle, anything other than a one-piece track rod will introduce some degree of bump steer.
Having said that, a centrally-mounted rack using one end only to operate a steering arm, preferably on the side opposite the rack end, will minimise the effect.

Location: Richmond, Texas, USA

Mounting the rack on the chassis will have exactly the effect that Roger says.

The bump steer effect disappears if the rack is solidly mounted to the front or rear of the axle, the rack then mimics a rigid track rod in use. However, to accommodate suspension movement, a sliding joint will be needed as well as a pair of Universal Joints (UJs) in the column. Quite difficult to make this work well and reliably, which is probably why you don't see it very often.

On an A7 single seater that I worked on, we left the late type A7 steering box mounted to the chassis in the standard position. I shortened the steering column at the box end to a stub, and mounted a Mollart style UJ onto it. this joint had a piece of tube running across the car to a second Mollart style joint which connected to the top of an A7 steering column which positioned the steering wheel to centreline of the car. Can't find a photo of this setup sadly. Mollart joints here -generic versions are available for a lot less money from any power transmission supplier. http://www.mollart.net/File/land_products_universal_joints_single.aspx


Re. Tube front axles, I think Tony Betts (on here from time to time) still has a couple of these.

Location: N W Kent

Best way to solve all this is to fit the engine behind you. That eliminates swivels in the steering in compensation for the driver protecting the engine

I've a prewar BMW 328 powered car that is mid-engine built just after the war. They used an early VW setup in the front including a centrally mounted wheel. Entire thing came out sort of "Auto Union GP" style

One of our Lotus MK9 LMs had half a Morris rack mounted on the RHS of the frame with an arm that went to a center pivot
It was pretty easy to get everything in the same arch

So there were L&R Arms going out this pivot ..... this resulted in a arch of each that gave very good feedback to the driver and limited bump steer. It took a bit id fiddling to get it all correct but bump steer wasn't really a problem. I should mention that we made and fitted a rollover bar that attached all over the chassis. Making a subtle chassis with this. Second we located the De dion tube in an Alfa inspired sliding block ...... All using uniball type joints in place of the rubber bush. Net result was a much stronger/safer car. We even replaced the shock rubbers with these resulting is a ton more bump travel.

Sorry to get so far off topic but wanted to show what could be done with a little thought and effort.

Location: POLAND

Bluto, that rack mounting is fine for a Ballamy-style swing axle, but not for a beam.

Location: Richmond, Texas, USA