R&P on a BJ front end?

[volkdent]

The gas tank is fine on the suspension box and the rack EXCEPT where the input shaft goes into the rack. In that location, as this is a prototype, I've had to "adjust" the tank with a rubber hammer to clear. As it turns out, it would have needed less adjustment than I gave it, but things still go back together. In kit form, I would imagine that you'd be able to do the adjustment with the tank in the car, and the whole install wouldn't take more than a spotty day. More cutting is involved than I had originally hoped for, this is going on a '68 pan, so I think the earlier ones would be fine, but I had to cut the webbing that extends from the frame horns to the front bulkhead partially out. It's very easy with a cheap jig saw. The other cuts will involve shortening the 1960 steering column and steering shaft. Otherwise it's totally bolt in.

Jason

[GS guy]

The bolt-in front suspension idea is great, have you compared overal weight compared to the original beam suspension? A hefty increase in weight would be a concern - otherwise it is neat!

From the pics it's a little hard to tell - but why can't you rotate the rack to better position the input shaft angle? Aim it more towards the steering column?

[volkdent]

Weight is still up in the air, because not all the parts are built, but I think it will be similar to or just slightly heavier than stock. Personally, I don't mind a little extra weight over the front tires anyway, considering the lovely understeer bugs have with stiffer suspension. Besides the 4 arms which will be much ligher than the trailing arms, there is only 2 laser cut plates of 1/8" steel sheet and 4 1.5" tubes running between them. Add lightweight coilovers and the rack, and that's about it.

As far as the rack is concerned, the rotation has already been taken into consideration, and there may be some. But if you look at the line between the stock steering arms on the spindle, you'll see that the rack has to sit very close to the bulkhead, so rotation won't help with that kind of angle. The suspension I'm building is also dropping the ride height considerably, and that helps with decreasing the angles of the U joints to the steering column.

Jason

[GS guy]

FWIW, on another board it was suggested that an English RHD (front steer) rack could be flipped over and used in a LHD/rear steer situation. Maybe that's one possibility for converting a ball-joint front end to use R&P steering? Maybe even a Super Beetle rack could be swapped in this way? That certainly opens up new possibilities.

Jeff

[volkdent]

The weight of my setup currently (without wishbones and not including the rack) weighs 13.79kg (30.34 lbs) I don't know what the stock one is, but I think that is much lighter.

[Michael Ghia]

I think that unless you can mount the steering rack so that the track control arms work in parrallel with the suspension arms, you'll always get bump steer.
The trailing arm suspension runs in an arc, so if you were to mount the rack to the bulkhead, you'd get terrible bump steer IMO.
Just thinking aloud

MG

[GS guy]

I agree with your assessment Michael, there's really no "right" design steering box or rack that works perfectly (geometrically wise) with the trailing arm suspension design. Even the OEM steering box and pitman arm falls short in this area. In the original design I believe the geometry is as best it can be - given pitman arm length and tie rod placement, spindle arm length, trailing arm length, etc. It's all designed to work as an assembly with all the angles worked out to minimize bump steer during travel (and steering). But, as soon as anything changes - like ride height settling or lowering, all that carefully created geometry starts going out the window. Rotating the steering box on the beam brings it back somewhat, bump-steer kits for the extreme lowering, etc - But from what I can see it can never be even as good as it was originally intended once you change anything. But, with all the succesfully lowered cars on the road for the last 30+ years, it's still not too bad!
Straight line - I don't see the different whether the driver's side inner tie rod is mounted to a pitman arm or rack end - as long as the mounting points are the same, bump steer should be unaffected. Things will change when you add steering into the equation, and this is where I think the rack will fall short. However, re-locating the inner tie rods to near the center of the beam (or car centerline) apparently goes a long ways towards minimizing the unwanted effects - as evidenced by all the off road cars that have been successfully running this design for decades. Just need a similar rack with offset input shaft to run it on a road car.
Jeff