Im building a '40 chassis and was thinking about using a Rack and Pinion for my steering with a straight Axel. Has anyone used one on a heavy car, what do the readers think of them, and who's unit would you recommend. Your pros and cons are appreciated.
As I remember, if you use a rack and pinion on a straight axle car the rack has to be mounted on the axle otherwise the steering geometry changes at every bump. The axle moves and the rack does not if you mount it on the frame. Racks and straight axles are generally thought of as a bad idea.
Mavel Unisteer uses a vega mount based bracket to mount their single actuating rack. I have 2 friends that use them on their cars and absolutely love them. They are not traditional, but apparently have very light steering effort and good road feel. Sent from my iPhone using The H.A.M.B. mobile app
I've done this many times, all you need is a sliding joint in the steering shaft to allow slight movement and it will work great Here's a pic of my old model A with rack on tube, I drove that car hard for years 10 sec street car Sent from my iPhone using The H.A.M.B. mobile app
I have a flaming river Omni Rack mounted solid an my tube axel with a slip joint in the steering shaft to allow for in and out movement as the axel goes up and down . I have had this system on a few cars and has always worked great.
Good friend has one on a '41 Convertable and says it's not good. Steers hard, rides rough and not a lot of room for power steering with 351. He's a dropped axle guy too, but is thinking MII.
it sounds like you are mixing eras and will end up with a street rod. It sure isnt traditional hotrodding
Had a customer try the unisterr rack after his Vega box was worn out. He hated the loss in turning radius. It's got a mustang 2 in it now. This was a 35 ford Tudor. Sent from my XT1585 using The H.A.M.B. mobile app
The issue with a rack on a solid axle is, as has been said, you have to have a sliding steering shaft to make up for the change in length as the axle goes up and down. The other issue that no one has brought up is you also have to have more room around the steering shaft as it moves with the axle which means tight header clearance just got a whole lot worse.
Tha Maval Unisteer unit is not what we normally think of as a Rack and Pinion. It is a cross steer steering box that instead of using a worm gear uses a mini rack set up inside the box. You still end up steering the right spindle with a drag link operating the left spindle, unlike a true rack that has the tie rod ends coming out of each end of the rack and operating each spindle directly.
Not at home now or I would post a picture of mine. The absolute best driving 40 with a beam axle I have ever driven ( I have driven a few ) has an Omni rack on a dropped axle. I am doing the same on my 40 sedan project. Borgenson has the shaft you need.
Two issues that i could see with mounting the rack to the axle, first these cars already have too much unsprung weight and now your going to add the rack to it? Sure seems like even with the sliding shaft you would get every little bump telescoping into the steering wheel.
Yes, the telescope joint would be a high action part. It better be equally high wear in durability or easy to change.
Not if it's setup right, the picture of my car I posted is when I did a slalom shootout for a magazine and my car handled the slalom course 4 secs faster than any other car there, enuff said Sent from my iPhone using The H.A.M.B. mobile app
Actually not "enuff said". I have no reason to dispute the handling qualities of your particular car, I'll take your word for that. However, saying there is no addition to unsprung weight "if it's set up right" is totally in contradiction to the definition of unsprung weight. The rack, mounted to the axle, most certainly adds weight to the axle assembly, which along with the wheels tires, brakes etc., ARE unsprung weight in a straight axle suspension. How critical that additional weight is could be debated, but it is additional weight nonetheless.. Ray
Sorry Langy but I'm not buying that as a reasonable answer to his comment. First, a slalom course is typically very smooth where unsprung weight is not much of an issue. Second unless you compared your car back to back with a cross steer setup, you really can't attribute it to the rack. Third what were you competing against, maybe you were just a better driver or willing to push your Hot Rod harder than the other fellas. The conclusion is not a logical one. I'm not knocking the rack conversion based on this either, personally I think the negatives outweigh the positives but your "Proof" is from it. I was riding a 1000cc sport bike down a local mountain twisty road at a pretty fast pace. I got passed by a guy on a Honda XL350. Using your logic all the sport bike riders should go out and buy old Honda Dual Sport bikes. The reality was the guy was a professional road racer while I was merely a club level racer.
I never said no additional weight, please point out where I did ? of course there will be but it doesn't have to massive weight increase if you chose the right parts, my rack was manual aluminium so added very little. Sent from my iPhone using The H.A.M.B. mobile app
There have been a few threads on the topic. Try a search. The good reason for a rack and pinion is precise steering that stays that way for a long time. There might also be an overall saving in weight. There are lots of ways to run a rack and pinion with a beam axle. Mounting the unit on the axle is viable but not ideal. Alternatives include cross-steer via an idler arm, which offers the opportunity to quicken or slow the steering, or a drag link to a rack and pinion alongside the driver's side frame rail. The latter is easier than it seems because the pinion axis is usually around 75° to the rack, so an intermediate shaft with two UJs will get you to the column angle easily. Traditional? Certainly the typical traditional hot rod didn't run a rack and pinion, but outside the USA it was established automotive technology throughout the era. BMW had been using it since they put transverse-leaf ifs on the front of what was basically an Austin 7 chassis in the early '30s. Whether it will fit any given build depends how you look at tradition.
Have you looked at the Chevy Cavalier rack? It is mounted to the frame, and is a center steer with two tie rods that mount on a bracket in the center of the rack. It looks like it might lend itself well to a I beam axle because it would be solid mounted on the frame not the axle, and the tie rods could be lowered so that they were parallel to the ground to help with any bump steer. The column would be common shafts and U joints , no slip shaft needed.
Problem is, the tie rods don't stay parallel to the ground as the suspension moves. This could work if you use only one tie rod from the Cavalier rack as a crosslink as in a cross-steer set-up, with a Panhard bar of near enough the same length and angle. Offset the rack as far as is practical to the driver's side: the longer the crosslink and Panhard bar, the better.
I agree bud, if you really think about the design right from the start it's quite easy to design without the slip joint also . Not a true slip joint in itself but if you look at a Jaguar IFS steering uj it looks like a regular uj but has about 1/2" of movement in and out which is just spot on on a rack conversion and very precise. By the way I wouldn't put one on a traditional car either as I've never had a problem with an early ford setup but the OP asked so I tried to help with my experience. Sent from my iPhone using The H.A.M.B. mobile app
Yup I get what your saying bud but at the end of the day my system worked extremely well and handled better than any early ford front I've ever had, and this was a street car used over 10 years of daily driving, but it's not a trad car it's was prostreeted Sent from my iPhone using The H.A.M.B. mobile app
Have built several rack to axle setups and found it a light weight, responsive steering. A recent one used a VW Rabbit GTI rack. Jag sedans offer a heavier donor-car for the OP.
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