TA22 + rack and pinion

[Sam_Q]

have a good look at this guys thread. hes running a full house 9 second ta22, tubbed and all the fruit. read the whole thread as it seems to be a good conversion.

cheers mat

say what you like lots of rights don't make up for a wrong and unless that rack is shorted it's wrong.

[bigmat]

Sam can you share what you have found out about a ta22 conversion please. im very interested. thankyou

cheers mat

edit just read a litlle more and found some wonderful information. thankyou. looking forward to your complete wright up!

[Sam_Q]

what information did you want specificly?

as for this guy "You need a rack from an 83 Corolla rwd car or similar."

so he is trying to not only sell one but instead a group buy for his product which I don't think he is letting people know about the downside of it, that pisses me off.

[bigmat]

edzact reason for his flaw. for my knowledge.

cheers mat

[Sam_Q]

oh right, the distance between the pivots on the steering rack has to be identical to the distance between the lower control arm pivot points. It also has to be in the same direction and the same lengths or else they follow different arcs of axis. The result of this is changes in length relative to each other and hence a steering action occurs/ie: bumpsteer

[Sam_Q]

forgot to mention that my second modified crossmember that I was working on has been finished and is now in the hands of Shelldrake. This means just about everything is now in place and ready for assembly. Pics soon of the crossmember as soon as it's cleaned up and painted.

[jeffro ra28]

Tidy idea, just needs some refining i think...............

[TA22 GT]

I like the way he has mounted the rack. Looks tidy and then no need to modify the cross member.
Surely there is a rack from a donor car that is the right size for a TA22?

I'm no expert on this, but would like to understand the whole bump steer issue? Eg I understand the pivot point on the rack needs to be the same as the control arm position, but when you turn this point on the rack changes so is this any different to having a rack that is slightly wider to start with?

[Sam_Q]

yeah but it only works on a front crossmember not any normal one.

If the rack is wider it will mean that it will have shorter steering arms and hence more sideways movement when it goes through its arc of travel than the lower control arm of the longer length. This will mean that if the suspension goes up the wheels will get get pulled outwards and hence toe out.

[LeeRoy]

oh right, the distance between the pivots on the steering rack has to be identical to the distance between the lower control arm pivot points. It also has to be in the same direction and the same lengths or else they follow different arcs of axis. The result of this is changes in length relative to each other and hence a steering action occurs/ie: bumpsteer

That's not entirely correct.

Even in standard applications the steering rack (if mounted behind the crossmember) has pivot points slightly longer than the LCA/crossmember pivot points. If in front of the crossmember then the rack is shorter.

This is to allow toe in under suspension compression (eg braking), which in turn makes the car more stable under these conditions.

[Rob KE25]

That's not entirely correct.

Even in standard applications the steering rack (if mounted behind the crossmember) has pivot points slightly longer than the LCA/crossmember pivot points. If in front of the crossmember then the rack is shorter.

This is to allow toe in under suspension compression (eg braking), which in turn makes the car more stable under these conditions.

I know what you are saying LeeRoy about toein for stability. That seems to be a common thought here.

However in every car I have dealt with (even though that's not very many) they toe out on compression, which makes more sense when having to go around a corner. Just yesterday I was talking to a wised up engineer friend who was talking out this subject. He too agreed toe in in compression takes away confidence in a corner. It becomes an unstable situation as it makes the car turn sharper, causing more compression on the outside wheel, which in turn causes more toein etc.
I tried driving like this with my shortened (toein) rack. Yuck.

If you have a car with very soft springs, just get a few big guys to bounce the front up and down. You'll probably be able to see the toeout occur under compression.

I think I've written something about this in this thread earlier. As my car has no toe out in compression, I actually have my car set up with some static toe out in my wheel allignment. That said, I think alot of the static toe in is cancelled out when a car is driving, so dynamically most cars possibly have zeroish toe due to the soft (compliant) bushes being pushed back by the friction of the tires. This is possibly why some racers actually run quite different static toe measurements with their rose jointed bits and pieces. And why custom (read zero toe movement in compression) steering settings will require unorthodox static toe settings. My theory anyway.

I think we need to see/think what is actually happening at the wheel dynamically, taking into account how much braking force we have, how much suspension bush compliance, what happens in compression etc. This makes it a bit of guesswork on standard bushes, and a bit better with nylothane bushes, and excellent with rose joint suspension. Just like we see suspenion as a package, we need to consider all the elements of our steering.

I'll put a link to what I did with my rack and pinion in the KE25. Has a bit of my reasoning too. The car was definately a few seconds quicker and more 'precise' in it's steering around the race track after the conversion. I'm no expert racer, more like I guess most of us are: enthusiastic drivers who enjoy a car that grips well and also handles well (fairly confident and pricise to drive).


Rack and Pinion conversion below:

http://www.toymods.net/forums/showthread.php?t=57054

Rob J

[jb_22]

Hi all, I read through this thread as I want to improve the vague steering in my TA22 and woah... confusing much! So, I decided to draw my own diagrams to try and explain it all to myself a little better. Thought I'd post them



NB: Above holds true whilst the LCA, tie-rod and steering arm are all in the same plane. (a simplified example: the LCA bush, balljoint, outer tie-rod end and inner tie-rod end are all the same height above the ground when the vehicle is sitting on a level surface).

Altering the height of the rack relative to the inner LCA bush affects bump-steer as well. From what I figured in my head, mounting the rack too high will result in toe-in on bump and mounting the rack too low will result in toe-out on bump.

My opinion so far is that a little toe-out on bump would be beneficial to cancel out static toe-in and improve steering response during corners (thanks Rob KE25). However, I don't know whether this small amount of toe-out should be generated from having the tie-rods slightly shorter than the LCAs (involves shortening a rack less), or by having the rack mounted a little lower relative to the LCA/steering arm/tie-rod plane.

[Radar]

SamQ are you making these to sell yet? Also could this be modded so you could add a power steering pump?

[Sam_Q]

well sorta, heres my update







thanks to eddie/Shelldrake for the pics. Now as you would be able see the ends are seriously reinforced, even more than the pics show. Fits straight in without big oversized holes or anything unproffesional like that.


Now I have found some complications;

crossmember #1: stock A mounts, fits a 16V engine but won't clear the dizzy base on a 20V.

crossmember #2: engine mounts moved forward 20mm, fits the 20V nice but the A to W adapting bellhousing lightly touches the tunnel.

crossmember #3: engine mounts forward 20mm and down 20mm, fits nice all over but the sump is under the crossmember, no way around this.

So yeah I am ready to start some mass production as soon as I go to the wrecker and buy a pile of parts, something I am not looking forward to.

Comments welcome

[Radar]

If you can make one with T series mounts I'm keen as for one