The Baron
|
| posted on 28/4/08 at 07:43 PM |
|
|
Self Centring
Any one know any tricks to ensure that a kit car will pass the self centring test,
Cheers
|
|
|
|
|
richard
|
| posted on 28/4/08 at 07:53 PM |
|
|
There were a few posts a couple of weeks ago about this and some suggested using valve srpings under the gators.what stage are you at as it only has
to have a tendency to self centre, not fully self centre. I believe what the tester is looking for is that it does not carry on turning in the
direction as he goes forward.Have you tried a search yet.
|
|
|
IDONTBELEIVEIT
|
| posted on 28/4/08 at 08:02 PM |
|
|
slightly overinflated tyres helps
wayno!!!
Are We There Yet, Are We There Yet!!!!
|
|
|
NeilP
|
| posted on 28/4/08 at 08:08 PM |
|
|
As does a bit of toe-out and if using mushroom adaptors, a bit of trailing hub and not too much camber...
If you pay peanuts...
Mentale, yar? Yar, mentale!
Drive it like you stole it!
|
|
|
Danozeman
|
| posted on 28/4/08 at 08:20 PM |
|
|
I have been a lucky git, mine self centres from when i put it together so its staying exactly as it is until after the test!1
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
|
|
|
JeffHs
|
| posted on 28/4/08 at 08:31 PM |
|
|
I built my chassis by the book years ago and have just failed SVA on self centre, but more to the point it's nasty to drive, so I spent to-day
grinding off the top wishbone brackets, making new ones and welding them on 25 mm further back. I've now got 6 degrees of caster and nowhere to
put my coilover. So I need to make different top wishbones.
Bugger
FU2 Ron Champion!
|
|
|
BenB
|
| posted on 28/4/08 at 09:21 PM |
|
|
My SVA examiner said "you know you should really do something about the KPI because you've got didly squat self-centering".
To which I said "yes, of course, it's on my list of jobs to do"
To which he said "if would be a shame to drag you back here just to see that you've re-welded the wishbones"
Jammy or what!!!
|
|
|
les g
|
| posted on 28/4/08 at 09:38 PM |
|
|
i think hes called steve the guy who does the aries 7 is a bit of a guru on the front end setup i,m sure he would help if you asked him
les g
|
|
|
matt_claydon
|
| posted on 29/4/08 at 04:14 AM |
|
|
FFS don't put valve springs in your rack! It's the biggest bodge of all time 
|
|
|
Syd Bridge
|
| posted on 29/4/08 at 09:31 AM |
|
|
quote:
Originally posted by BenB
My SVA examiner said "you know you should really do something about the KPI because you've got didly squat
self-centering"........
KPI has little to do with self centreing, whereas CASTOR has everything to do with it.
|
|
|
britishtrident
|
| posted on 29/4/08 at 12:55 PM |
|
|
KPI has an effect on self-centering not as large as the effect of caster but useful.
Trouble kpi isn't easy to alter.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
MustangSix
|
| posted on 29/4/08 at 02:04 PM |
|
|
Caster is a dynamic effect which relies on roadforce, but KPI and Camber cause the steering to move under the force of gravity.
Often, if you dial in more camber, the car will tend to self center more effectively because the effect is for the tire to "jack" the car
a bit more than just the KPI will do as it turns thru an arc.
Many (American, at least) cars from the fifties and early sixties had factory alignment specs which called out negative caster, relying entirely on
KPI to center the steering.
[Edited on 29/4/08 by MustangSix]
|
|
|
britishtrident
|
| posted on 29/4/08 at 03:09 PM |
|
|
quote:
Originally posted by MustangSix
Caster is a dynamic effect which relies on roadforce, but KPI and Camber cause the steering to move under the force of gravity.
Often, if you dial in more camber, the car will tend to self center more effectively because the effect is for the tire to "jack" the car
a bit more than just the KPI will do as it turns thru an arc.
Many (American, at least) cars from the fifties and early sixties had factory alignment specs which called out negative caster, relying entirely on
KPI to center the steering.
[Edited on 29/4/08 by MustangSix]
Vauxhall in the UK used exactly that setup on the Cresta -- it gave light steering without the need for PAS.
|
|
|
Liam
|
| posted on 29/4/08 at 04:22 PM |
|
|
My view, for what it's worth, on all these 'tricks' to fool the SVA man into thinking your car self-centres is that it's
really missing the point. The rule isn't there to annoy us - there are strong and compelling reasons why your steering should exhibit
self-centring, continued life probably being one of them
If my car didn't self-centre I'd consider it improperly designed/built and fix it. And fix it properly.
Liam
|
|
|
britishtrident
|
| posted on 29/4/08 at 05:50 PM |
|
|
quote:
Originally posted by Liam
My view, for what it's worth, on all these 'tricks' to fool the SVA man into thinking your car self-centres is that it's
really missing the point. The rule isn't there to annoy us - there are strong and compelling reasons why your steering should exhibit
self-centring, continued life probably being one of them
If my car didn't self-centre I'd consider it improperly designed/built and fix it. And fix it properly.
Liam
Key phrase is sneeze factor
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
|
|
|
MustangSix
|
| posted on 29/4/08 at 06:20 PM |
|
|
quote:
Originally posted by Liam
My view, for what it's worth, on all these 'tricks' to fool the SVA man into thinking your car self-centres is that it's
really missing the point. The rule isn't there to annoy us - there are strong and compelling reasons why your steering should exhibit
self-centring, continued life probably being one of them
If my car didn't self-centre I'd consider it improperly designed/built and fix it. And fix it properly.
Liam
I suspect that if the friction in the ball joints and tie rods isn't excessive that the KPI in most doner spindles would be adequate to pull the
steering back toward center. In fact, it would seem to be difficult to engineer self-centering out of the car given the origin of most of our
spindles.
|
|
|
MikeRJ
|
| posted on 29/4/08 at 08:54 PM |
|
|
quote:
Originally posted by MustangSix
I suspect that if the friction in the ball joints and tie rods isn't excessive that the KPI in most doner spindles would be adequate to pull the
steering back toward center.
I wonder how many self centering problems are caused by people using "reconditioned" steering racks? Many of the monkeys in this business
just slap new gaiters on and crank up the rack preload, before dunking it in a vat of black paint. This makes the rack very stiff, and it takes a
long time to loosen up, if indeed it ever does.
|
|
|
Syd Bridge
|
| posted on 29/4/08 at 09:42 PM |
|
|
You can have all the kpi you can fit in. But, with zero castor, it won't self centre in a million years.
It's CASTOR that causes self centreing, due to dynamic geometry shifts and weight(gravity). KPI gives centrepoint and dictates scrub, which
dictates kickback.
Well, that is unless all the texts and engineers I work alongside are wrong!!
Walk down the pitlane at a Sports Proto meeting. You'll see cars with ZERO kpi, ZERO scrub, but CASTOR to the amount dictated by the driver for
feel. That's how it was yesterday, anyway.
Cheers,
Syd.
[Edited on 29/4/08 by Syd Bridge]
|
|
|
.jpg)
