Dunc
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 posted on 25/10/01 at 11:12 PM |
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Modifying Sierra steering rack
I've done the sums and I'm going to have shorten the steering rack and extend the track rods, have any of you guys had to do this or know someone
who has? Is it just a case of cutting right down the middle and welding back together or is there something more subtle?
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Dunc
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 posted on 6/11/01 at 11:43 AM |
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Managed to modify the steering rack quite easily. Dismantled the rack as per Haynes manual, removed the track rods and placed the rack in a lathe and
used it to turn off 120mm from it's length at the opposite end from the rack. Drilled a 12mm dia x 20mm hole and tapped it with a M14 fine. Made 2
60mm extensions to go between the track rods and the track rod ends at either end, M14 standard thread. Cut the Aluminium rack housing in the middle
and cut and welded in back together 120mm shorter. Sorted. Just in case any of you guys feel like doing the same. Total cost- 0p, Ron would be
proud.
Dunc.
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EA82T
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| posted on 13/11/01 at 03:33 PM |
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Well done that man......
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ChrisW
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| posted on 14/11/01 at 05:31 PM |
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Just out of interest guys - is the Sierra rack the same way around as the mk2 Escort (ie it sits in front of the wishbones?)
Ppl have said that I can't use my mk4 escort rack because it'll turn the wrong way if put in the place shown in the book but I can't see why (space
permitting) I can't have it behind the wishbones and swap the hubs left-right.
Hope that makes sense! Any comments?
Chris
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Alan B
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| posted on 14/11/01 at 09:20 PM |
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Chris,
In theory you could. If a rack was used "rear-steer" (behind the wishbones) in its donor then it can be used "rear-steer" again" whatever the
uprights. The only difference between a "front-steer" rack and "rear-steer" rack is whether the pinion is below, or above the rack. The only way a
rack can be used opposite to its design position (front or rear) is by flipping it over, but then it becomes LHD or RHD depending what you started
with. However, just because you could use a Mk.4 Escort rack, rear-steering a pair of swapped Cortina (or whatever) uprights, doesn't mean it's a
good idea, there may be other considerations to think through.
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Dunc
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| posted on 15/11/01 at 11:24 AM |
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Chris,
The sierra rack sits in front of the wishbones. I did think about swapping the left and right hubs around and making the steering rack behind the
wishbones, the benefits I could see would be a shorter steering column with little or no modifications to the standard sierra column and the castor
angle would be positive. Major problems with this however was the resulting steering geometry would've been anti-ackermann ie the inner wheel would
turn less than the outer wheel giving severe tyre wear at any steering angle to name one, another problem is the thread of the hub would be reversed
and could lead to the nut tending to loosen rather than tighten but could be solved by just swapping the uprights and not the hubs.
In the end I've opted to keep hubs and steering rack in roughly the same positions as original but I've rotated the upright 10 degrees to adjust the
camber angle to positive 5 degrees.
You could use any rack in any car as long as it was like alan says in roughly the same position as original, ie, forward or rear of the axle centre,
but careful consideration needs to be done on the actual position of the rack and effects of bump steer and turning has on the steering angle of each
wheel.
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ChrisW
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| posted on 17/11/01 at 01:12 AM |
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Hmmm... this all sounds far more complicated than I thought! Best just get a 'front steer' rack!
Chris
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Dunc
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| posted on 18/11/01 at 11:54 PM |
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Chris,
You should be able to use almost any rack but if you want it to be rear steer then you need to choose a rear steer set of uprights. If my memory if
correct, the escort mk vi uprights are rear steer but you then might have the problem of what to do with what to do about the end of the drive shafts.
Nothing a hacksaw and a pretty metal cap won't sort.
Dunc.
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ChrisW
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| posted on 19/11/01 at 12:44 PM |
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That would be an idea except... the Escort uprights went with the rest of the car to the big car park in the sky! Might be worth seeing if I can get
some others though - Mk4's are common as muck!
Also, can someone please tell me if Sierra uprights are front or rear steer? Oh, and while I'm posting, what's a good price for a set of Cortina
uprights?
Chris
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Dunc
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 posted on 20/11/01 at 01:08 AM |
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Sierra uprights are front steer.
Dunc.
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Metal Hippy™
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| posted on 11/12/01 at 07:23 PM |
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On the subject of steering racks, we're using a Y reg Capri 1600.
Useful rack or a bin men job?
If not that, then what would you suggest.
We already have Cortina hubs and discs at the ready. Apart from that, no wishbones or anything as yet...
Cheers.
Richard.
President of the Non-conformist Locost Builders Club. E-mail for details...
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Dunc
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| posted on 11/12/01 at 11:19 PM |
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I've heard of capri's, nope it's gone. Only joking, you could probably use any rack with any upright as long as the track rod ends fit, if they
don't then you could try cortina track rod ends at the end of the track rods of the capri rack. The cars are of similar era but that does not mean
they'll fit together. Check out the threads on both if you find capri track rod ends dont fit onto cortina uprights.
Also, have a think about where to locate the rack on the chassis with regard to the motions of the suspension and not just the most convenient place
to bolt it. You want to reduce the effects of track and toe changes during bumps and body roll conditions.
Dunc
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Metal Hippy™
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| posted on 12/12/01 at 06:46 PM |
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Ok, thanks.
Rich.
President of the Non-conformist Locost Builders Club. E-mail for details...
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davimora
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| posted on 8/1/03 at 08:59 AM |
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For Dunc
Hi Dunc,
can you post a sketch of how to modify the steering rack? I think can be useful for me (first!  ) and also for others.
Davide
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Dunc
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| posted on 9/1/03 at 03:55 PM |
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Davide,
I've done a quick sketch, ie poor quality in a rush type job, but hopefully you'll get the idea. I've left out my dimensions as it up to yourself
to modify the suspension & steering geometry to suit your needs.
I cut 120mm (X value) from the rack and housing and added a spacer each side of 60mm to keep the same front track.
Dunc.
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davimora
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| posted on 10/1/03 at 07:40 AM |
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Hi Dunc,
thank you veeeeeeeeeeery much! 
English is not my language, and often a sketch it's more useful than 10,000 words.
Davide
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Barker
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| posted on 15/1/03 at 01:13 PM |
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Maxi ball joints
Dear Dunc
You mentioned b4 using maxi bottom ball joints on your CAD drawing it mentions "needs taper"
Do you need to modify ball joint to fit sierra hub or did you mean the steering rod ends
Also -I am going to shorten my top front wishbone by 30mm from Rons book - did you shorten by simlar amount??????
cheers
pete
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Dunc
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| posted on 17/1/03 at 09:58 AM |
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The maxi ball joint sort of fits in the sierra hub, the threaded part fits in the hole and the taper engages in about 2mm. Not good in my opinion but
some manufactures seemed to think it was ok as long as you tightened it properly.
I reamed the taper in the upright out a bit until the maxi ball joint fitted properly, would make me feel safer when driving.
As for the wishbones I think I went long top and bottom and also moved the mounting points to try and optimise the suspension geometry as the position
of the upright upper and lower ball joints are pretty much fixed.
Dunc
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