If you attach the rack to the frame you'll have all kinds of serious problems, especially bump steer. AND, massive toe changes which will cause erratic steering problems. Attached to the axle eliminates the bum steer if it's mounted correctly. BUT everytime the suspension moves, the steering shaft has to telescope. I don't think is too great of an idea. But folks do both of the above and live to tell about it. Usually it's done because these were the parts we had laying around.
I'll mention that mounting to the axle may work out, but must be done considering first, all loads the steering will encounter. The precise location of the rack matters, since you will be building in some ackerman geometry, (inside wheel turns sharper, outside wheel turns less.) The post above mentions the need for column length change, allowance due to suspension movement is also true.
The best setup is to have the rack mounted on the axle and have a universal joint in the steering shaft. This uj needs to be inline with the radius rod attaching point on the frame.
You need more than a u-joint . Think about it for a minute. Just like with a driveshaft, you need a slip joint connection, otherwise everything goes into a compression bind. I swivel ball connection like an old Ford torque tube set-up might work, but is it worth the trouble.
Quote: Originally Posted by ray-jay The best setup is to have the rack mounted on the axle and have a universal joint in the steering shaft. This uj needs to be inline with the radius rod attaching point on the frame. ================================================= This set up is on our drag race car..has run 9.60's.. R. =====================================
The driveshaft analogy doesn't work. The suspension instant center is way behind the front uj, therefore they work in different arcs. By having the steering uj inline with the instant center of the front suspension the arcs are the same. The torque tube analogy does work as that is what you accomplish with the uj at the radius rod pivot. I think relying strictly on a slip joint would be asking for trouble although on a light vehicle it would probably not be an issue. Hitting a bump while in a turn with lots of load on the steering shaft could cause binding. How much suspension travel the vehicle has a lot of bearing on the issues that can crop up. The less suspension travel the less issues with geometry. You should still have a compressible section in the column for crash safety.
This is a disaster waiting to happen. There are a number of posts already warning of the various problems associated with the steering shaft coupling in this idea. Combined with the unknown power steering ratio and the steering arm lengths this could be a hand full to drive. A further look at the picture will indicate that the chassis will potentially hit the rack steering rod when in a body roll mode. As it stands now the axle will go up without hitting the frame but should the chassis go over a depression where the axle drops the steering will hit the frame. The suspension is best suited for a side steer application. Junk that rack, dumb ass engineering.
If there is some sort of bearing where the torsion arms attach to the axle then that set up will sorta work becuase it probably doesn't have 2" of total travel. If there is no bearing there then the front end is probably rigid. Also, the failure of one of the undersized looking bolts would be disasterous. I am talking about the pic of the drag car in post 8.
The reason I asked about the rack is because, I installed a 4" axle with a Toyota PS box. When I sit the truck on the ground it looks impossible to hook up the drag link.
Looking at the pictures, most seem to refer to the install being on a completly different suspension design. Being that it is on a truck, i think that the travel of that axle will be signifigantly different that of an A or hairpin style front end. NO LIMIT makes a kit for it. of course there are no install picture that I saw looking on their website real quickly. http://www.nolimit.net/prodinfo.asp?number=PS-SA-
I was looking at the same thing and after talking to Speedway Motors tech guys they pointed out that 2800 lbs was the limit for a rack and pinion. Also if there is a transverse spring being used you must have a watts link to keep everything from shifting. I went with a vega box and a cross steer setup. We have that installed and are now doing the king pins
I've got three running rods in the garage right now, all with rack & pinion steering units attached to the axle. All have a slip joint in the steering shaft. One is a double D sleeve/shaft with 6" of engagement. The other two have a splined shaft and sleeve. The total amount of movement on bumps and dips is 3/8". That's why some people get by without a slip joint. In two of the cars I removed another form of steering and am very pleased with the improvement. The heaviest of the 3 cars weighs 2,500lbs. I built my first hot rod in 1959, and have been building ever since, so I have a bit of experience and am very comfortable with this arrangement.
If you mount the rack to the axle, put a u-joint on the end of the rack AND on the end of the steering column, then use a splined slip joint between them and keep it greased, you will not have any problems. I talked to a rep from Flaming River about this idea, and they said as long as its greased, its not a problem. And of course, they sell the parts. And yes, it is just like a driveshaft setup, only difference is the slip joint is between the u-joints instead of at one end. The end results are the same.
Do you think for one minute that Bubba knows what an "instant center" is? AND, I think you think I said use a slip joint instead of a u-joint. Wrong, you'd have to use both. But as Dick Spardaro said. "Jack the Rack". Crappy idea. To quote Nader, "Unsafe at any speed". And I do agree with a compressible steering shaft when doing this deal. But for two reasons: 1) Technically to try to make the system work. 2) Cause you'll need it when ya' crash with this Rube Goldberg set-up. And, comparing a dragster front end to something for street driving doesn't work. Look at many drag car door slammer rear suspensions. Good for goin' straight, but a disaster otherwise.
As long as the tie rod end mounts to the steering arm on the line drawn from the kingpin axis to the midpoint of the rear axle centerline, ackerman will be correct. Mounting the steering rack directly to the axle eliminates bumpsteer because doing so eliminates toe change. Keeping the length of steering shaft joining to the steering rack relatively horizontal at ride height will minimize the distance it needs to change to a minimum and can easily accommodated by double D or splined shafts, or a factory coupler (the oblong one with the pins inside) for that matter. Russ Meeks, for one, was mounting rack and pinion steering boxes to straight axles with great success as far back as thirty years ago.
The pics that I posted were in mock up. The frame hitting the rack was a problem that is now fixed. The set-up is from No Limit and has been on the truck for a couple of years with NO problems. Usually the people that say things won't work are the ones who have never tried it. Anybody that tells you a steering box is better than a rack, will try to convince you that drum brakes are better than disks too. The rack mounted to the axle WILL work... with NO problems! Later, Kevin Ooltewah Speed Shop
something like this http://www.flamingriver.com/index.c...ategory_ID=120/home_id=85/mode=cat/cat120.htm
Also late model chevy truck I or GM vehicles in general have slip joints but you have to make sure you keep it well lubricated. I have had my rack mount to my frame with no issues for some time now. Recently my brother went to a chassis suspesion setup at Alston in Ill. and brought my steering up in class. The instructed noted the same issues with wether or not the rack is mounted to the frame or the axle. I does work well for me, and have driven the truck on some pretty crapp roads. Personal I like things to be mounted solid that is why I didn't go with a slip joint setup.
I didn't need a slip joint my rack is mounted to the frame like it supposedly isn't supposed to be. Sorry not the best pictures. During mock up...
Actually a Ford Festiva rack, but your right about it being a Mustang slip joint. It works pretty good, but I'm not sure I'd do it again just because it was kind of a pain in the ass to set up. At the time it was done, I was still a grad student and was really limited to using stuff I (or my father) already had. Combined with the underslung suspension, it does corner exceptionally well
This afternoon friend of mine sent me the attached pictures of the chassis he is building for his Model A coupe. You will note the rack and pinion steering mounted to the front axle. The work was done by Richard Carter, a pro builder in the Dallas Ft Worth area. In addition to rack and pinion upgrades on numerious 50s and 60s cars Richard has reportedly done 8-10 rack to beam axle conversions like this one as well. He uses a slip joint in the steering shaft. My friend tells me they drive well and have less bump steer as compared to traditional and cross steer drag link and tie rod set ups. I personally have no experience with this set up and I am not recommending its use. Simply sharing the pictures and info.
Fast41 to answer your question about the toe in out. I am sure that as I hit a bumb it is pretty obvious to most on here that the wheels will turn in or out. Hence I supposedly have bump steer, if I do I don't notice it. But also found that examining an A arm set I would have similar issues. Is it a problem? Not for me... The truck goes nice and straight down the road, and it turns just fine as well. I have taken this turck down some of teh crapiest roads in WI (I mean old farm roads) Other than the truck rides pretty stiff, I am happy with it. Bib, that setup looks very similar to how mine is mouted if I had a rear view shot.
The Jalopy Journal
