TA22 + rack and pinion

[stidnam]

refer to my previous post (2-3 days ago) in this thread on how I plan to shorten the ke70 rack to fit.

[79GT]

yeah yeah, i do understand that it needs to be shortened, was just saying that there has been lots of discussion, and limited definate conclusions. so hence my comment, sorry for being obtuse.

stidnam, when you do, or if you have alreeady shortened the rack be sure to take lots of photos and measurements as where you decide to cut. etc etc. good job mate. like what you have done with the collum.
Jamie

[PULSE]

I read over the entire thread the other night and maybe I missed something, but how does one shorten a rack? What is the actual method for doing it? Because if its not too hard, and just requires a little stuffing around to get it right, once someones done it and made it work properly, it wont be hard for everyone else to copy it because they know its going to work and they have something to go off.

[hsmidy]

so have we come to the conclustion that there isnt a rack out there that is able to be used without modifing it or sucrificing (sp) build bump steer etc into the system.

is that a fair comment?

["Z" UTE]

A gentleman I contacted, had used a KE70 rack in his TA22. 3 tries before he got it right, with negligible bump steer.

The rack needs to be shortened to position the rack end pivot point inline with the lower control arms. Effectively if one moves, the other moves the exact same amount.

Locating the rack involves running a string line between the tierod ends at the strut steering arms. That will give a position where there is least angle change when the car hits a bump. Effectively giving a little toe in, instead of the usual toe out associated with bump steer.

Ackerman angle is often bandied about, I suggest that if you are really interested in this "google" Ackerman. What we are doing has negligible affect on the Ackerman angle.

It has been said previously in this thread "We should aim for a parrallellogram, when setting the rack in place". What this means, is:

a, The lower control arm xmember pivot point, and the rack end pivot point should be in the same horizontal plane.

b, The strut ball joint, and the steering arm tie rod point should share the same horizontal plane.

c, The distance between the centre of the lower conrol arm (LCA) pivot point, and rack pivot point, should be identical to the distance between the ball joint and the tierod end.

If a,b, and c are correct, then the LCA and rack rods, will be of effective equal length.

Jump under your Celica, and have a look at how closely the angle of the tie rods match that of the lower control arm.

Disregard the fact that the current drag link ball ends are inboard of the LCA pivot point. The simple fact is that the drag link moves and the rack does not.

Of course if you are midifying the KE70, and TA22 steering columns to create a unified unit, be very warey of what your engineer will accept. You are effectively modifying a component which has strict ADR compliance rules.


Cheers Chuck.

[mynameisrodney]

what other options are there for the column? i hadn't really thought about this until stidnams post.

[stidnam]

I haven't talk to an engineer yet about this but I can't see why it wont be a problem as the only thing that I have cut and welded is the outer column tube not the actual column itself.

The factory TA22 and KE70 columns themselves identical in the way they fit together. The top half of the shaft slips into the lower half. It is not welded or anything the only thing that keeps it tightly fitted together is two pieces of plastic that are around the grooves on the upper part of the shaft. You can see these grooves in the pics that I've posted.

This plastic appears to have been hot injected inplace when the column is together as there are two small holes in the lower part of the shaft that correspond exactly to the areas of plastic and are filled with plastic also. I couldn't get the plastic to stay when I fitted the two pieces together which is why I was going to use a spring pin. I suppose you could inject new plastic into these holes but I thought the spring pin idea would be better.

I suppose I'd better talk to an engineer

[danielc]

The rack needs to be shortened to position the rack end pivot point inline with the lower control arms. Effectively if one moves, the other moves the exact same amount.

someone correct me if im wrong, but if the rack is the same length as the LCA pivot points then with the offset of the steering knuckles the tie rods will be shorter than the LCAs....
This will cause the LCA and tie rods to follow two different radiused arcs when suspension travels up and down.
If im correct it will push the steering knuckle out when suspension travels up or down, giving toe in either way which is good- to a point, you will just have to check how much toe in it will give

[TA22 GT]

Ed (Shelldrake) and I went and looked at a TA22 GTV (fake, but that's another story) with R&P Steering, and it looked very similar to the KE70 setup that I have in mine, but the dude (tool) didn't know what it was out of...

Ed took some photos of it also... I'll get him to post them up...

The R&P steering in that GTV on ebay is from a KE70. I know the history of the original car well and one thing is for sure, the guy selling looks only to have the engine from the original car which was a genuine GT. The original car had square lip gaurds, funny how the one for sale had rounded lip guards and a sunroof...

As for the steering I have tried for a long time to ge tthe exact detail from the original owner with no success. I believe it was shortened by 15mm on each end, but after taking measurements myself I don't know exactly what was done to make it work.

It seems that the KE70 and TA22 steering column can be matched together fairly easily. But to me the KE70 seems to wide. Maybe he shortened the actual column....

Cheers,
Simon

[takai]

Ok, after some trawling at U-Pull-It, i am now interested in the specs on an EP90 rack. They seem to be narrower than even the AE82 racks, and look bloody simple, and therefore easy to convert over.

Anyone have exact widths, i didnt take a tape measure.

[79GT]

the paseo may also have a similiar rack as the starlet. may be worth looking into.

"The 90 Series Starlet shared its platform with the Paseo including suspension, engines and many other components" wikipedia

just thought i would throw that out there.

[stidnam]

Got some dimensions of the AE71 / KE70 rack.

Rack dimension


Rack housing dimension




Now I'm thinking of cutting up the housing to see if the tube is press fitted into the alloy housing because it could mean that no welding is needed to shorten the housing if it can be removed and refitted together after shortening the tube.


For the actual shortening here is what I am thinking, I have to shorten the rack by say 70mm (not exact so don't use this figure) so if I shorten the inner by 70mm and then shorten the rack housing by 51.4mm which still keeps the ratio of the rack inner to the housing length the same as an uncut inner and housing. Calcs below

uncut 545:400 = 1:0.73394495
Cut 475:348.6 = 1:0.73389474

This should still give relatively the same amount of rack travel as the ae71/ke70 before the inner rack ends hit the housing from lock to lock. Might not be explaining this quite well as its clear in my mind but hard to describe in words. Ideally the rack would be mounted on the cross member and then the steering turned fully each way and see where the rack inners are just before the tires rub on the control arms and this is where the rack housing length should be so that the rack housing stops the rack travel and not the tires on the control arms.

Any flaws with any of my logic so far?

[mynameisrodney]

i think you meant to say shorten the housing by 51.4

EDIT: and that background makes it quite hard to find the dimensions haha

[twentyEight]

I didn't even notice the dimensions until you said that...

[stidnam]

lol yeah I was a bit tired last night so a few maths errors are to be expected, all fixed now.

I sort of thought that the background would be crap but I had to protect the living room carpet and a target catelogue was on hand