I hope this is the right place to ask about this set up. I bought a 39 Ford with this set up and have never seen it before. I got it from my friends wife after he passed away. It is basically new and has been adjusted, not sure correctly! I drove it about 1\4 mile to get it home. wondering if anyone has used this system, and how hard it is to get it set up correctly? Also any feed back on this set up would be greatly appreciated. Thanks Ron P S, almost ready to try it out.
Flaming River sold a single side r&p a few years back, maybe still. The only downside I remember reading about was the turn radius was not short enough. Guys did come up with fixes for the problem.
I don't have a dropped axle, and lt is a unisteer rack and pinion manual cross sreer for 1935-40 ford
A Unisteer centre steer rack is never going to get rid of bump steer as the operating arcs are not right. The fix is to set it up like any OEM R&P steering. This can be done by moving the inner pivot of the steering arms out to the correct position by mounting them on a bracket/rod/bar mounted to the centre steer mounts. It isn't hard to do, I have a centre steer set up exactly like that in a Suzuki. A bit of research on the net will show what's needed.
I have a Unisteer on my 32. Love it, drives great. Don't recall any setup issues. Set the steering wheel and rack centered and then fit the arm/drag link adjusted to fit. Some say that restrict the turning circle but I've not noticed that to any degree. There is some bump steer that I've noticed but only on severe drops like on some freeway joins, but nothing to be concerned about, a bit like a sidewind wiggle. Chris
I have the Unisteer with 4" dropped axle in my avatar. Sixty plus thousand miles, I've never noticed any bump steer. I like it.
I was talking to a wise car builder at a show the other day about his R&P on his Ardun roadster. He siad if the rack is attached to the axle, there can be no bump steer. I have no knowledge of it, just passing it along for discussion sake. You can see it if you look hard enough.
BB; True, but you *must* include a sliding steering-shaft solution 'twixt the rack & whatever steering u-joint used at the firewall. Even the ford pinto-flex-shaft won't work for that. Rack n spindle-arms do need to be aliened in a straight line, or you'll get varying amounts of *odd* wheel-angle in the turns(all fairly small, but if you're gonna do it, may as well do it correctly). Also have to look at the steering "throw" & compensate for (usually) less travel w/shorter spindle steering arms. Then there's the extra sprung-weight added to the axle-assembly, & some folks think it's really ugly(not fond of the looks myself). All in all, as usual, it gets "interesting". . Marcus...
The sprung weight, yes. And if there is a fair amount of suspension articulation, roll motion can feed back through the steering.
The Jaguar XJ6 and XJS had an articulated joint at the end of the steering shaft to accomodate some fore-aft movement of the suspension subframe and rack. Something similar might help attach a rack to an axle.
Never seen one of these before! Interesting. I doubt there'd be much movement as I'd imagine it's purpose was to allow some flex required as the subframe would be rubber mounted for isolation / comfort. That being said, a well designed rack on axle shouldn't induce much required elongation of the steering shaft. Chris
Sounds like most responders are not familiar with the Unisteer cross steer rack & pinion. It replaces a Vega type unit. A direct bolt in. Should not be any bump steer. I'd say check all the alignment numbers and go from there.
I was never really feeling attaching a rack and pinion to the back of the axle, so I never gave much thought to the pros and cons of the idea. I gave it more thought after revisiting some of the threads I listed here; specifically this one. Advantages are that, as the guy @Bandit Billy spoke with said, there can be no bump steer, as the entire system is rigidly mounted to the axle, and the only relative movement between the rack and the front wheels is due to steering input. It also frees up all kinds of ways to locate the front axle, unlike the Unisteer type which restricts you to Panhard bar location, and therefore gives a lot of freedom as to where to place the front roll centre. Disadvantages are the aforementioned gain in unsprung mass, though with a manual rack it's a matter of perhaps 15lbs, which may or may not be a small price to pay, depending on how much the rest of the build can be simplified as a result. As for the roll feedback I mentioned before, assuming that you're unlikely to see more than about 1½° of roll in ordinary driving, assuming roughly half of that feedback would be felt at the steering wheel rim and the rest would manifest as roll steer, and assuming a 15" steering wheel, that's 3/32" (2½mm) motion at your hand on the steering wheel. Depending on the steering ratio, the roll steer would be negligible at <0.05°. I don't know if the looks of the thing are really a problem. It's pretty much out of sight? And, I suppose, it's susceptible to some creative refinishing. Little more than a bit of polishing would be needed to match the look of this 1934-on Citroën rack-and-pinion: Now, after pondering again on chain drive steering, if a slow 24:1 manual rack (available) were driven through a 2:1 steering quickener (timing chain and sprockets), that would give sporty-quick 12:1 steering and only 3/64" (1¼mm) of feedback at the steering wheel rim. That's two turns lock to lock on a lightly-loaded early Ford front end: sounds practicable to me?
Not so. The rack may be relocated up or down and the tie rods adjusted to suit, with no effect on steering geometry whatsoever — which may be useful. Relocating the rack fore or aft bears on Ackermann: closer to the axle reduces it and further away increases it. I did a quick geometric exercise this morning, and I couldn't get the rack physically close enough to the axle to get less than 13% Ackermann. And as @Kerrynzl has pointed out on a number of threads, partial or even zero Ackermann may be desirable, depending on the kind of driving you're envisaging. At the very least, mounting the rack directly to the back of the axle would free up a bit of space at the bottom front of the engine.
We're talking about 2 different ideas here, the Uni-steer half a rack, mounted like a Vega box, with which I have no experience, and an axle mounted regular rack and pinion, which I have lots of experience-about 70,000 miles in the Willys on the left. I put my system together in my Willys because even with all new steering parts, the thing wasn't comfortable to drive at speed. Too twitchy even with 9 degrees caster. I blame it on this Willys' relatively low weight (about 2600), short wheelbase, high CG, and large cross sectional area. It really transformed the way the thing drives. Effortless one hand interstate drives. I won't tell anyone to do it, or not do it, for liability concerns, but mine works beautifully. Yes, a telescoping shaft is needed. I made mine from a dirt track splined steering column. If you like to ponder theory, yes unsprung weight goes up, but not as much as a typical 4wd differential adds, and somehow all those cheap smaller old SUV's go down the road without bursting into a ball of flames because of 20 extra lbs. on their front axle. And Zero Bump-Steer or Death Wobble. Just please, whatever you do, don't mount a regular rack to your frame! Bump Steer disaster. I've seen it done, but likely the car has basically no suspension travel, or doesn't get driven.
I added another scenario to the exercise I mention in Post 15. I set out the steering motion with the rack moved about 3½" off-centre, i.e. with the left tie rod 7" longer than the right tie rod, because a certain speculation was going in that direction. There was no more than 3-4% difference between left and right steering inputs, not enough to be perceptible in use. Edit: I could dial out the difference by tilting the rack 2°, left side forwards.
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