Rack and pinion mounting to drop axle?

[Screaming Metal]

OK Guys, I've been over in the motor section a long time, helping out....now....I need your advice so pay up!
I've built my frame, fits the body perfectly. I have all the steering shaft material, and enough flaming river ujoints to do it.
I was tossing the idea up in the air about mounting my Mustang II Rack and Pinion to the front axle, with a floating steering shaft to a small pillarblock mounted to the frame. I have a small spline shaft that I can attach to the R&P, and from that shaft at the pillar block. I have the female spline sleeve that'll allow it to float.
Do ya'll see any problems with this? I'm interested in the pro's and Con's....

 

[railroad]

I like the idea. The rack and pinion assembly would have to be spaced off the axle the length of the steering arms on the spindle. That may look a little odd and need some sure nuff spacers and bolts. The next thing would be the male/female splined shaft. I am sure this is done all the time in some sort of way in modern cars, but I would check for wear often, until convinced the wear would not be an issue. Post some pics when you get the parts on the floor. I was visualizing that with an I-beam axle, but a tube axle with the brackets welded on would simplify the rack and pinion mounting. I'll bet you were already past that obstacle.

 

[Screaming Metal]

Its a older tube axle, I just got thru drilling and tapping for a zerk on the female spline tube....so when the front end articulates....it'll slide in and out. I realize there won't be alot of travel.
I've read over the years where you guys worry about the in and out movement at the tires when the R&P is mounted to the frame, Like in PotvinGuys T. I'm anxious to hear his opinion.
In this one, I'm running a cast block and headed 460....it looks like I'm gonna have to run 3 leafs up front to handle all the weight. I'm building this to be a daily driver here.

 

[Screaming Metal]

I'm thinking on mounting the R&P close to the axle, with offset tie-rods going to the spindle arms. That way, it wouldn't look funny from sticking way on out there.
I'm going to make the tie-rods out of some 4140 hex bar. I already have to stuff drilled out. Tomorrow, I'm going to tap them out, then I'll slit the tube, then turn the ends down for the clamps.
I have realized on paper, that the further I turn the wheel, the closer the tie-rods will move to the axle as the spindle pivots on its pin. So, I was going to make my first ones about 15% shorter in offset than the spindle arms are long.

 

[lincolnuT]

You do know Flaming River now makes a rear mount R&P? That is what I used on the 26 coupe I am making. I mounted it with 6061 Alum brackets off of the back of a Lucky 7 Drilled I beam axle.......

Mike

 

[Gerry]

Well after reading your many posts Im not sure you need any help but here goes.

I think that if you 'bolt' the rack to the axle it may well mess up the 'ackerman'. Got a feeling that if the rack is not in line with the end of the steering arms you may well find that on full lock the inside wheel (of the turn) will have too much angle on it. That is instead of it turning to the radius of the corner, as if its in line with the center of the rear axle it will be turn to a much smaller radius as if its in line with the center of say, the firewall.

Also as the axle is moving up and down (vertically, if you go for a leaf spring) the input shaft of the rack will also move up and down. It would need a UJ to take up the movement, but in effect it would also lengthen and shorten.
Im just cutting the breeze here as i have not sat and worked it out. I looked at many ways of mounting a rack and due to my obsession with an uncluttered look, decided to mount it along the chassis and directly under the steering column. Only clean mounting for a rack at the front end I have seen is where its mounted inside the front X member and that is normally worked to that it has a straight line through the rack to the steering arms.

Be interesting to see what you come up with.
Gerry

 

[Dino]

Rack mounted to axle wont work. When axle moves up on one side ( bump in road ) and the steering shaft will turn the wheel just enough to send you for a ride. rack needs to be mounted to frame .

 

[stroker]

Using offset tie rod ends will not correct the geometry problem created by mounting the R/P ahead of the steering arms. It may look better but the effective line of action is still from the steering arm to the R/P regardless of how you get there.

 

[benT]

Not a fan of the rack-mounted to the frame in a straight axle. Dad's '27is set up this way and its got a lot more bumpsteer than my Vega cross-steer setup.

 

[lincolnuT]

My coupe sure drives good with the R & P mounted on the axle so I don't think I will change anything .......If you have ever driven on New Mexico roads you know I have some bumps.....OK for me.....

 

[Screaming Metal]

My coupe sure drives good with the R & P mounted on the axle so I don't think I will change anything .......If you have ever driven on New Mexico roads you know I have some bumps.....OK for me.....

Does the steering wheel jerk any when hitting a big bump? And is your unit mounted close to your axle or have you mounted it out the length of the steering arms? I'm interested in all the pro's and con's with this setup.....Thanks!

 

[Ma_n_Pa T]

Screaming, if you shorten the steering arms the ratio will be way too quick, either way you mount it if you can go longer with the steering arms to slow down the ratio. Mine is frame mounted and we have no problems with it, love it other then it is a little quick on the ratio.

Jerry

 

[lincolnuT]

This is what I have on the Coupe today. I have Airbags on the front and I needed to keep 5 or 6 inches clear around them so I used a Lucky 7 Drilled axle for the holes.........I think being this far back and the tierods with a slight angle to the front helps with any bump steer that might happen. This car is a bit quicker than the T Bucket with a Flaming River gear box but nothing that I would consider unsafe........

Otherwise I would not let her drive it............SMetal I have not felt any jerk on even driveway and dips......Several times I have set the Orings on the shocks to see how mich movement and it never has been over a 1 inch travel........

 

[Screaming Metal]

LincolnuT, hey thats a Killer ride there. With the body on, you really can't see the bags and the R&P just at a glance. Nice Rod!
I appreciate the info and the pics....helping me alot with the design of mine....

 

[NicksT]

I will be the bearer o GOOD NEWS......it will work just as you think it will !!!!! I have allmost an exact setup on a T Bucket i have owned or about a year. It was allready complete when I got it so I cannot take any credit for the idea or the assembly but it works well. No bump steer, no wheel turning on a bounce, and rides as true as a caddilac. It will tend to pull to full lock if your are backin up with a large amount of turn on the front wheel, but I have been careeful and no problems yet.

 

[PotvinGuy]

Hey, Screaming, I've been running the frame-mount setup for 20 years:

My first set of tires went 15 years without noticeable wear or handling problems, so I wouldn't worry about that. Now any R&P, frame or axle mount, is gonna have a lot of road feedback compared to a standard steering box. That's why sports cars use them. Around town and on good highways it's no big deal, but it can be a pain on bad roads. I have a So-Cal steering damper that I keep planning to install and that should help. And don't worry about Ackermann; it only comes in play when turning and doesn't have any effect on handling. I checked mine and it would be correct...if the wheelbase was 41 ft!

And I've known cars with an axle-mount R&P with a flex shaft to the frame and that works fine too. Knock yourself out and post pics.

 

[Screaming Metal]

Thanks NicksT, and Welcome!!!! And to PotvinGuy....I already have the steering Damper on order. Will need one on these roughass roads around here. And my Thanks to everyone, I really appreciate all the input!

 

[Gerry]

I was tossing the idea up in the air about mounting my Mustang II Rack and Pinion to the front axle,

I took this to mean bolted to the axle. I also referred to the set up pictured above on the blue T as the way I knew would work. Sorry I disagree about ackerman. For me its got to be right.
Gerry

 

[Hot Rod Todd]

PotvinGuy that looks really interesting. Are the arms off the r&p parallel to the axle and in that photo, I cant see the arms from the front hub to the ends on the r&p. Maybe its just my old eyes.

Down here, for the past forty or so years, we get a r&p (usually from an old English Mini or something similar as they were very common) and mount it to the chassis where the steering column goes thru the floor (we used to have upright steering in true T bucket style but its not legal to build them like that anymore).

One end of the rack was attached to a steel arm that went forward to a bracket off the front brake on the drivers side, and we ran the usual arm across the front to the passenger side like you guys are used to. We just cut off the other end of the R&P as it wasnt doing any work, and covered it with a $10 r&p boot.

But I like PotvinGuys setup more & I have just bought anther project - a steel & rust 37 Fiat Topolino and will try to figure how to do steering like his. The Topo chassis will just be a short T bucket style with a cage to hold it together.

 

[PotvinGuy]

The steering arms are integral to the spindles (original old stuff). Here's a better shot:

The R&P arms lean forward a bit. Here's an underside view:

It's a Honda Civic rack. Let me know if I can help with your project.