johnemms
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| posted on 22/2/12 at 04:39 PM |
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Bump Steer
Standard cortina hub & escort rack.
With the track rod end properly fitted (ball joint bottom - nut on top)
I got bump steer..
playing around - putting the track rod end upside down (ball joint top - nut bottom)
I significanly reduce bump steer however the taper is wrong...
Question:
Has anybody opened up the hole & fitted their track rod end steering arm ball joint the opposite way?
Or is this a case of whatever works - locost style?
cheers
jon
[img] [/img]
[Edited on 22/2/12 by johnemms]
[Edited on 22/2/12 by johnemms]
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rodgling
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| posted on 22/2/12 at 04:45 PM |
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I have mine fitted this way (as per the GKD kit design). Don't see a problem with this arrangement if it gives the right results, but if
you've built yours to a design that specifies the other way up then I'd try to find the root of the problem as something must be causing
this.
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tomgregory2000
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| posted on 22/2/12 at 04:55 PM |
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mine were fitted from above, but the car was designed to have them this way
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britishtrident
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| posted on 22/2/12 at 04:58 PM |
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Easiest way is to convert to rod ends (Rose joints) and get adaptors made up and the uprights machined. if you look up McGill Motorsport on
eBay you will find loads and suitable dust boots.
Problem is your rack has M14x2 threads the solution is to find an Escort Mk1 rack with 1/2" unf threads
or Lower the rack.
[Edited on 22/2/12 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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daviep
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| posted on 22/2/12 at 04:59 PM |
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I don't mean to offend, did you check bump steer over the full range of movement with the spring removed?
I can't help with turning the track rods, however I would have thought if you were to try and open the hole up you will probably end up with a
parallel hole. I wouldn't be my chosen way of fixing the problem.
If your chassis is as per the book then the bump steer problems are caused by the steering rack being too long for the chassis. Shortening the rack
and lengthing the track rods cures the problem.
Cheers
Davie
“A truly great library contains something in it to offend everyone.”
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blakep82
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| posted on 22/2/12 at 05:09 PM |
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agree with BT, the steering rack is too high, lower it so its parallel with the bottom wishbones (or as new as) and the problem should be reduced til
its not noticable.
the rack looks about the right length to me, so start with lowering the rack
[Edited on 22/2/12 by blakep82]
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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johnemms
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| posted on 22/2/12 at 05:17 PM |
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Am getting ready to take the lot apart and lower the rack etc.... laser usual stuff..
But on a whim I turned the track rod end to the top and it looks to have cured it..
I have see some images of super sevens with the steering arms quite central and high..
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procomp
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| posted on 22/2/12 at 05:27 PM |
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Hi
As mentioned it's the rack that needs moving to get the right geometry. Also the rack does not need shortening. The LOCOST championship cars
with the rack moved get the bump steer down to 16 tho.
But why do people keep trying to eliminate bump steer when in actual fact you want bump steer to aid geometry change during cornering to gain an
advantage in grip levels.
Cheers Matt
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Dusty
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| posted on 22/2/12 at 05:54 PM |
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I think it depends how much bump steer you have. When I had built to rolling chassis stage I set the front wheels parallel by eye and could easily
push the car. I then dropped in the pinto engine. The car could not be pushed back into the garage by two of us as the front wheels had turned in by
about 20 degrees. The rack had to be raised about two inches and the wheels re-aligned before it was halfway reasonable.
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blakep82
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| posted on 22/2/12 at 06:22 PM |
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quote:
Originally posted by johnemms
Am getting ready to take the lot apart and lower the rack etc.... laser usual stuff..
But on a whim I turned the track rod end to the top and it looks to have cured it..
I have see some images of super sevens with the steering arms quite central and high..
it won't have cured it as such, because you'll have moved a problem, the taper in the steering arms on the hubs won't match the
taper on the ball joints now. what you will have done though is improved the angle of the track rods, which proves that lowering the steering rack is
the answer
________________________
IVA manual link http://www.businesslink.gov.uk/bdotg/action/detail?type=RESOURCES&itemId=1081997083
don't write OT on a new thread title, you're creating the topic, everything you write is very much ON topic!
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britishtrident
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| posted on 22/2/12 at 08:36 PM |
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quote:
Originally posted by johnemms
Am getting ready to take the lot apart and lower the rack etc.... laser usual stuff..
But on a whim I turned the track rod end to the top and it looks to have cured it..
I have see some images of super sevens with the steering arms quite central and high..
That is because Ron completely skimmed over the issue of mounting the steering rack in the book --- just look at the original design for the
rack mounting brackets.
The fact that Escort (or Sierra) rack is much too wide doesn't help the bump steer problem, bump steer completely robs the steering of
precision particularly at turn-in.
These days narrowing racks is the usual route I have heard of MG Midget/AH Sprite racks being used because they are narrower but that creates
the problem of mating 1/2" UNF track rods to Cortina or Sierra .
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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40inches
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| posted on 23/2/12 at 08:46 AM |
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quote:
Originally posted by britishtrident
quote:
Originally posted by johnemms
Am getting ready to take the lot apart and lower the rack etc.... laser usual stuff..
But on a whim I turned the track rod end to the top and it looks to have cured it..
I have see some images of super sevens with the steering arms quite central and high..
That is because Ron completely skimmed over the issue of mounting the steering rack in the book --- just look at the original design for the
rack mounting brackets.
The fact that Escort (or Sierra) rack is much too wide doesn't help the bump steer problem, bump steer completely robs the steering of
precision particularly at turn-in.
These days narrowing racks is the usual route I have heard of MG Midget/AH Sprite racks being used because they are narrower but that creates
the problem of mating 1/2" UNF track rods to Cortina or Sierra .
So MK got it right by shortening the rack.
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johnemms
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| posted on 23/2/12 at 12:08 PM |
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Steerin rack is quite low.. fitting the ball joint the other way round has given the best travel.
[img] [/img]
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MikeRJ
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| posted on 23/2/12 at 12:44 PM |
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quote:
Originally posted by johnemms
Question:
Has anybody opened up the hole & fitted their track rod end steering arm ball joint the opposite way?
To invert the taper in the steering arm by reaming it out means the overall diameter will increase significantly (the smaller end would have the same
diameter of the original larger end), so the standard T.R.E.s would no longer fit. You could perhaps fix this with a tapered sleeve, or an
alternative ball joint, or a rose joint conversion.
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