Rack And Pinion exploration

icehouse · Post by **icehouse** » 11 Oct 2007 16:28

I didn't use the stock column due to the fact that the steering shaft falls out without the steering box there to hold it in place. I used a silvia column, the blinker switch fits to. When I redo it I plan on using the skyline column, it has tilt and teliscope.

xlr8r · Post by **xlr8r** » 11 Oct 2007 22:20

I fabricated a simple little bracket that supports the middle link (between the steering column & the Rack) & this prevents my steering shaft from sliding out. I'm actually using a greased up sway bar bushing that wraps around the middle link/shaft to keep it in place. I also had to do this because the angle needed to get from the steering column shaft to the R&P, required one additional linkage than normal. The one additional linkage allows a whole lot of flopping around w/out the bracket/support I made. I may switch to a more modern column with tilt later on, but it currently works well for me.

FYI: I'm using a Manual R&P that came out of most early to mid 80's BMW's (mine is off of a 320). I don't know where I put the measurements, but I do remember that the rack pivot points are 1/2" further apart that the LCA upper pivot points. This isn't optimal, but it's as close as I could find at the time. I do experience a little bit of bump steer, but it's much tighter than the steering box ever was. It attached great to my reversed crossmember & worked well with the KA & looks like it will work well (after a slight mod) with the VQ.

sdterrible1 · Post by **sdterrible1** » 12 Oct 2007 08:57

xlr8r... would you have any pic's of yer set up showing the column section you had to mod??

Post by **S15DET** » 12 Oct 2007 10:03

I guess some of you were waiting on me to chime in, since I've been working on the MR2 rack install for a while. I don't have a lot of time to work on the 510, that's why it's taking so long. Here's a photo that I just took of what I'm working on today...
It's a jig that I made for the testing and measuring of the MR2 rack.

more to come...

Post by **S15DET** » 12 Oct 2007 10:14

One concern was the width of the rack. Here's some measurements...
The center-to-center of my reversed crossmember is 560.8mm (22.08").

The outside of the MR2 rack is 555mm (21.85"). But you have to add to that the width of the inner tie rod ends. I don't have them at work, but I'll guess maybe 10mm per side, so that puts the width of the inner pivot points 15mm wider than the inner pivot's of the LCA's

Here's an installed picture...

More to come...

JeffGreg · Post by **JeffGreg** » 12 Oct 2007 10:27

Im down to throw down on the group buy

JeffGreg · Post by **JeffGreg** » 12 Oct 2007 10:30

I do know someone that does R&P swaps. He can do them for regular, or reversed crossmember. His name is Nelson, and he owns a shop called Altered Motives in Sherwood, OR(USA)

They have a website,
http://www.alteredmotives.com

Post by **S15DET** » 12 Oct 2007 10:36

As you can see, the Z position (vertical height) is spot on. These mounts were measured and made on the granite table, so the offest in the picture is just paralax from my holding of the camera.

important note!!! The motor mount uprights shown are positioning this motor 40mm rearward of the stock mounts. I've got the rack as far back as possible before it contacted the underside of the oil pan, and it's still a little shy of where it should be to match the stock position. This will effect ackerman a little, but it's very close. The point is, if you're using the stock motor perch on the crossmember, I think that it won't be possible to move the rack rearward enough, without lowering it. Lowering the rack will effect bump steer.

I'd really like to model this with a 3D cad program, or better yet a real suspension design program. This way we can determine the right place for the rack. You see, I'm just trying to approximate the locations of the stock inner tie rod points, but there's nothing saying that these are the "right" location. I don't have these software anymore. If someone else wants to do this, I have all of the measurements you'd need. Once my car is drivable, I'll be able to give subjective feedback on the rack, and the mounting position.

Post by **brknrekord** » 12 Oct 2007 10:53

Great input there S15DET. Thank you. I need to go look at my KA oil pan. Two inches forward of the stock location will be no good. I have nothing productive to add, just wanted to say thanks.

Dimebag · Post by **Dimebag** » 12 Oct 2007 10:54

Woodward Steering has a very informative tech page where you can download .pdf's all about custom setups.

Post by **S15DET** » 12 Oct 2007 10:57

Sure, that's why we have this forum. I have plenty more pictures if there's something else someone wants to see. I'll be sure to add pictures to my gallery of the finished rack mount.
My next task is to figure out where to mount the sway bar. I'm trying to find a way to have it trailing the front axle, rather that leading, but we'll see.

Post by **benz-tech** » 12 Oct 2007 12:28

I have 2 questions:
what is the length from center to center of our inner tie rod pivot points on the stock drag link?
what is th distance traveled at the pitman arm per 1 full revolution of the steering shaft? - I realize this is "ratio" but i can measure a rack at the yard more easily with tape.

I expect to get to the wrecking yards next week to search. I was thinking something like a Suzuki swift or Geo Metro type thing. Stop me if you've tried these already. any narrow car you can think of also, plse suggest.

xlr8r · Post by **xlr8r** » 12 Oct 2007 12:31

sdterrible1 wrote:xlr8r... would you have any pic's of yer set up showing the column section you had to mod??

I'll take some pics this weekend & post them up, though the technology that went into my rack install is much more crude/basic compared to what S15det is doing. It would be nice to get some input though since I can make some changes as needed, especially after I can read through that Woodward stuff.

P.S. Someone mentioned possibly using a rack from a CRX & I'll just say that the pivot points are way too far apart. I have a rack from a 90 Civic hatch (same as CRX) as well as one from an older Prelude, both of which are not suitable for 510's.

Dimebag · Post by **Dimebag** » 12 Oct 2007 13:23

S15DET wrote:One concern was the width of the rack... the width of the inner pivot points 15mm wider than the inner pivot's of the LCA's

If I'm understanding this correctly, your inner tie rod pivot points will be an estimated 15mm closer to the wheel on each side than the LCA pivots. On page 70 of the Woodward tech document, this scenario is illustrated in figure 11. Their illustration has the tie rod pivot ~91.4mm closer to the wheel than the LCA, perhaps to exaggerate the resulting geometry that occurs in this situation.

However, a little or a lot - a rack that is too wide predisposes the vehicle to overteer in a bump scenario which can be caused just by negotiating a curve in the road. I've also read that vehicle manufacturers deliberately design their cars with a touch of understeer to be more stable (within the realms of a driver of average ability) if a violent change of direction occurs.

It sounds like the MR2 rack is not quite right?

Dimebag · Post by **Dimebag** » 12 Oct 2007 13:59

benz-tech wrote: any narrow car you can think of also, plse suggest.

79 - 84 VW Rabbit, 79 - 84 Dodge Colt, 78 - 83 Dodge Omni, 87 - 94 Subaru Justy, 76 - 87 Chevrolet Chevette, 81 - 90 Ford Escort, 81 - 85 Mazda GLC, 86 - 89 Mazda 323, 84 - 87 Pontiac Fiero, 88 Pontiac Fiero, 82 - 88 Toyota Tercel

I don't know if these are feasible, just suggestions of small cars that have rack and pinion steering