akitagandy
Member
Has anyone ever thaughttp://chassisengineering.com/enlargephoto.asp?ProductId=1718ht about Rack and pinion on a bucket
steering
- Thread starter akitagandy
- Start date
Unisteer would be the way to go with a rack and pinion.
Sets up like a cross steer on Vega box mounts
Unisteer Performance Products Cross Steer Rack and Pinion : JC Whitney: Auto Parts & Accessories
Sets up like a cross steer on Vega box mounts
Unisteer Performance Products Cross Steer Rack and Pinion : JC Whitney: Auto Parts & Accessories
donsrods
Member
A buddy of mine had a rack setup in his T bucket and I drove it home for him one day from a show.........it was white knuckle time all the way. Worst handling car I have ever driven because every irregularity in the road steered it left or right. I know some have been made to work ok, but this one didn't.
Don
Don
TRoadster
New Member
Since no one else has brought it up, you can mount the pack and pinion directly to an I-beam axle. There are kits available for older trucks that do this. As for tube axles? I guess you could weld a plate on back to use as a mount. I'm not sure. The other question is whether or not there is room underneath the front leaf spring (if your spring is mounted behind the front axle as in many T's) you would have to check. The good thing is there's no bump stearing at all... according to those who use this set up. The bad thing is that you have to use a slip joint in your steering linkage and some people don't like that idea. The final question is would you be able to see it and if you could, would you mind. I believe most buckets use either side steering or vega cross steering because its simple, well proven and concelable.
Bump steer is just that. When you hit a bump the toe changes because the geometry is not correct in the car. With the type steering most of us use and suicde front ends. What seems to change the bump steer the most is the location of the steering box in relation to the frame mounting point of the front radius rods. When the radius rod and the drag link are different lenths it makes for bad bump steer.
With cross steer it does not seem to have much effect. The picture of the rack I posted is a half rack. I would locate under the car just behind the radiator. It is a cross steer and links to the right front wheel. There are 2 guys from Hermans that have it and they work out great.
With cross steer it does not seem to have much effect. The picture of the rack I posted is a half rack. I would locate under the car just behind the radiator. It is a cross steer and links to the right front wheel. There are 2 guys from Hermans that have it and they work out great.
Hotrod46
Member
Rick
Here are some links that describe it better than I can. Some of it deals with 4x4's, but the principle is the same.
What Causes Bumpsteer?"
How to Build Hot Rod Chassis - Google Book Search
Solid-Axle Suspension - History & Technical Specs - Rod and Custom Magazine
Street Rodder's Chassis & Suspension ... - Google Book Search
Basically, it means when you hit a bump or a pothole(anything that causes suspension movement), the car will dart or veer off the path you are steering. How bad depends on your suspension. It is usually caused by poor suspension geometry, such as:
Drag link and raidius rods(or 4 bars) different lengths so that they travel in different arcs
Different angles on radius rods and drag links
Extreme angles on steering and suspension components
It can also be caused by cross steer setups with no panhard bar or dead link, so that the axle moves from side to side on the spring shackles.
This is certainly not all the possible causes, just the ones that come to mind.
Mike
Here are some links that describe it better than I can. Some of it deals with 4x4's, but the principle is the same.
What Causes Bumpsteer?"
How to Build Hot Rod Chassis - Google Book Search
Solid-Axle Suspension - History & Technical Specs - Rod and Custom Magazine
Street Rodder's Chassis & Suspension ... - Google Book Search
Basically, it means when you hit a bump or a pothole(anything that causes suspension movement), the car will dart or veer off the path you are steering. How bad depends on your suspension. It is usually caused by poor suspension geometry, such as:
Drag link and raidius rods(or 4 bars) different lengths so that they travel in different arcs
Different angles on radius rods and drag links
Extreme angles on steering and suspension components
It can also be caused by cross steer setups with no panhard bar or dead link, so that the axle moves from side to side on the spring shackles.
This is certainly not all the possible causes, just the ones that come to mind.
Mike
Hotrod46
Member
Rick
No stupid questions when you're trying to learn.:lol:
The car will need constant steering correction. Every little bump will have some effect on your direction, depending on how bad you're setup is.
Really rough roads and/or really bad setups will have the car darting all over the place. You will be forced to "drive" the car all the time, no relaxing. Can get pretty "white knuckle" the faster you go.
Some of these same symptoms can be caused by worn steering and suspension parts too.
Mike
No stupid questions when you're trying to learn.:lol:
The car will need constant steering correction. Every little bump will have some effect on your direction, depending on how bad you're setup is.
Really rough roads and/or really bad setups will have the car darting all over the place. You will be forced to "drive" the car all the time, no relaxing. Can get pretty "white knuckle" the faster you go.
Some of these same symptoms can be caused by worn steering and suspension parts too.
Mike
Ok... I have played with racks on drop axle cars several times. And here is what I have learned. First, they do work, and work fine. The first T I built, had a rack mounted to the chassis, and it did not have any bump steer. Everyone said it wouldn't work, couldn't work... Well after completing it, and seeing how well it did work, I went looking for answers. Answers as to how I got it right, when everyone else got it so wrong. And the guy I turned to was a friend of a friend, that happened to be an engineer at visteon (visteon is, or at least was at the time, a tier one oem supplier). But not just any ol' engineer. An engineer in the steering department. He had 7 us patents on steering gear design and had written sae tech papers. He was a for real steering expert. So I sent him photos and asked lots of questions, and what I got back was interesting... at least to me 
. The first thing he shot down was the theory that the axle moves straight up and down, and the rack ends move in an arc, causing toe change and bump steer. While that is true, in reality, you are not going to have both front wheels hit the same bump, at the same time, to make the axle go straight up. In the real world, you are more likely to have one wheel hit a bump, or drop in a pot hole. In which case, the axle moves up and down in an arc, because it pivots on the spring that is center mounted. Where people are having problems with the frame mounted rack, and the transverse spring, is the spring shackles. As the rack pulls on one side, and pushes on the other, the shackles and the spring deflect, shifting the whole front axle. A simple panhard bar is the answer there. I never had this problem, as the car I built had a torsion bar front end. The 3/8" thick chrome moly arms held the axle in place. In wasn't until later that I discovered this.
The next thing I found interesting, is that there is no set number of toe change, that will cause bumpsteer. You can't say " if you get over 3/32 of toe change it will bumpsteer". Right from someone that designs the parts in the cars we drive... He said they have no firm numbers. It depends on many variables. With all the sophisticated computers, and programing, and all the education, blah, blah.... At the end, they make thier best guess, and build it, and drive it. I was also told that rack placement can be very critical. Sometimes moving the rack as little as 1/8" can make a big difference. This is where I think the swap isn't for everyone. If you do not want to take the time to make sure it is 100% the best it can be, move on to something simpler.
The next time I did a rack on a straight axle, I mounted it to the axle. This I did NOT like. This was on a Model A with air ride. Because of the large amount of suspension movement, mounting the rack on the frame would not work. So on the axle it went. The thing I didn't like about it was that The steering shaft has to move as the axle goes up and down. Everyone I spoke with suggested a slip joint. I did not like that because it introduced play. It can't be set up tight, or it won't slide freely. And I was afraid if it didn't slide freely, that it would bind the steering or possibly causing bump steer. The other option was to put in a u-joint and have it pivot to match the suspension. This might be OK on a car with headers out side the frame, like a T, but on a model a with a full hood, not so easy to do. I can't find a picture of this set up. I found the air ride pics, but none showing the rack.
And the last one... I didn't do much on this, outside of maching a few parts and a little tig welding. My father did all the fitting etc on this (it's his latest car). It is a rack mounted thru the frame, and only one side is used to push the drag link. Works pretty good. He's got one cruise season on it, and is happy.
You may be wondering why all the work with the racks ? Well 2 reasons, one... they have better leverage ratio's than the typically used boxes. Which means easy steering. All the ones I've done have steered very nice. As close to power steering as you will get without the pump and all the hoses. And two, they are cheap, light, and compact. We have been using geo metro racks. They are $40 at my local pick n pull.
Is it for everyone, NO. If you are not willing to put in the time to make sure it is installed properly, and willing to do some testing, I would walk away. And it is not a simple install, machining, fabricating, and welding (sometimes on delicate parts) are all part of the deal. But, If you are willing to do the work, and it can be some work. You can end up with a nice system. My father wouldn't own a T without one. Me? My car has a vega box :razz:
. The first thing he shot down was the theory that the axle moves straight up and down, and the rack ends move in an arc, causing toe change and bump steer. While that is true, in reality, you are not going to have both front wheels hit the same bump, at the same time, to make the axle go straight up. In the real world, you are more likely to have one wheel hit a bump, or drop in a pot hole. In which case, the axle moves up and down in an arc, because it pivots on the spring that is center mounted. Where people are having problems with the frame mounted rack, and the transverse spring, is the spring shackles. As the rack pulls on one side, and pushes on the other, the shackles and the spring deflect, shifting the whole front axle. A simple panhard bar is the answer there. I never had this problem, as the car I built had a torsion bar front end. The 3/8" thick chrome moly arms held the axle in place. In wasn't until later that I discovered this.
The next thing I found interesting, is that there is no set number of toe change, that will cause bumpsteer. You can't say " if you get over 3/32 of toe change it will bumpsteer". Right from someone that designs the parts in the cars we drive... He said they have no firm numbers. It depends on many variables. With all the sophisticated computers, and programing, and all the education, blah, blah.... At the end, they make thier best guess, and build it, and drive it. I was also told that rack placement can be very critical. Sometimes moving the rack as little as 1/8" can make a big difference. This is where I think the swap isn't for everyone. If you do not want to take the time to make sure it is 100% the best it can be, move on to something simpler.
The next time I did a rack on a straight axle, I mounted it to the axle. This I did NOT like. This was on a Model A with air ride. Because of the large amount of suspension movement, mounting the rack on the frame would not work. So on the axle it went. The thing I didn't like about it was that The steering shaft has to move as the axle goes up and down. Everyone I spoke with suggested a slip joint. I did not like that because it introduced play. It can't be set up tight, or it won't slide freely. And I was afraid if it didn't slide freely, that it would bind the steering or possibly causing bump steer. The other option was to put in a u-joint and have it pivot to match the suspension. This might be OK on a car with headers out side the frame, like a T, but on a model a with a full hood, not so easy to do. I can't find a picture of this set up. I found the air ride pics, but none showing the rack.
And the last one... I didn't do much on this, outside of maching a few parts and a little tig welding. My father did all the fitting etc on this (it's his latest car). It is a rack mounted thru the frame, and only one side is used to push the drag link. Works pretty good. He's got one cruise season on it, and is happy.
You may be wondering why all the work with the racks ? Well 2 reasons, one... they have better leverage ratio's than the typically used boxes. Which means easy steering. All the ones I've done have steered very nice. As close to power steering as you will get without the pump and all the hoses. And two, they are cheap, light, and compact. We have been using geo metro racks. They are $40 at my local pick n pull.
Is it for everyone, NO. If you are not willing to put in the time to make sure it is installed properly, and willing to do some testing, I would walk away. And it is not a simple install, machining, fabricating, and welding (sometimes on delicate parts) are all part of the deal. But, If you are willing to do the work, and it can be some work. You can end up with a nice system. My father wouldn't own a T without one. Me? My car has a vega box :razz:
benT
Active Member
Good Stuff LKE! The rack and pinion setup that my dad has is frame mounted. He is running carerra coil overs and when you hit a big bump, hang on! I agree with LKE that with proper engineering, testing and some luck you could get a rack and pinion setup that would be slick and work well. I perscribe to the K.I.S.S. method most of the time; thus the vega cross steer on mine. I do like the idea of the torsion bars...maybe on the next one!
EX JUNK
Moderator
LKE does not post that often but when he does, he speaks volumes. His posts are always VERY informative and to the point. His knowledge comes from designing and building suspensions and vehicles for many years. We are indeed, very fortunate to have him participating on this board.
