desyboy
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| posted on 30/1/07 at 11:16 PM |
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self centering
I know this has been covered before but does anybody have an easy method to get the car to self centre easily.
Also once this is done what should it actually do?
Cheers Des
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MattCraneCustoms
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| posted on 30/1/07 at 11:23 PM |
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self centering is all about castor angle of the front uprights, which means setting your top wishbone offset to the bottom one. on the locost I think
its 5.8 degrees forward of the bottom wishbone. Self centering means with your steering wheel turned, it should go back to straight on its own. Like
when you turn at a junction and let the wheel slide between your hands . . .
Regards
Matt
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nitram38
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| posted on 31/1/07 at 12:20 AM |
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It should be between 5-7 degrees backward on the top bones.
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phoenix70
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| posted on 31/1/07 at 12:29 AM |
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Well this is a big can of worms, if your are just looking to pass the SVA and can live with no self centering, then a common trick is to put some old
valve springs in the steering rack. If you want the correct solution, I think you will need to get your welder out and move one of the wishbones.
Cheers
Scott
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PAUL FISHER
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| posted on 31/1/07 at 12:33 AM |
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I take it Des your looking at getting it to self centre to pass sva,what I did was ajusted the tracking out a few degree's,and lower the tyre
pressures down to 12psi,mine would then self centre just enough to pass sva,this is when after putting lock on the steering, the steering wheel turns
in your hands by itself, until the wheels are in the straight ahead position,it will need to be corrected again before you take it back on the road,I
adjusted mine outside the Beveley test station on my way in,and again on my way out
[Edited on 19/05/04 by PAUL FISHER]
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PAUL FISHER
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| posted on 31/1/07 at 12:45 AM |
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And before everyone starts saying the old MK chassis does not have any castor,and thats why they don't self centre,they do,7 degree's
see attached picture,I think to be fair most locost type 7's Ive come across don't self centre that well too,compared to modern designed
vehicles
Just to add as well,the original MK castor debate,was not for the Indy chassis anyway,it was for the MK LOCOST chassis.
Which also for the record also has caster,the MK Indy is one of the most stable cars at speed I have driven,you can confidently remove your hands off
the steering wheel at over 120mph.
[Edited on 19/05/04 by PAUL FISHER]
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PAUL FISHER
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| posted on 31/1/07 at 12:49 AM |
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MK Indy castor
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nitram38
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| posted on 31/1/07 at 08:34 AM |
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Do it properly !!!!!!!!!!!!
You might get used to driving the car once sva is over, but unless you introduce castor, your car will be unstable at speed.
I drove my car with and without the correct castor and I can tell you that without, it was an accident waiting to happen.
There should be a sticky thread on here which states that before you build a book built car, adjust wishbones for the castor !!!!!!!!
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macnab
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| posted on 31/1/07 at 09:29 AM |
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Just another point, insure that the rack is not too tight. I have put a bead of silicone on the underside of the pretension cover instead of the metal
shims. This allows me to easily vary the pressure on the slider. I have set it so the play just goes away and it feels very free. This will help any
castor take effect.
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PAUL FISHER
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| posted on 31/1/07 at 10:02 AM |
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Good point Mr macnab,your not as mad as you look,I have known a lot of MK owners past sva without any ajustments to the steering,I had a brand new
quick rack on mine,which may have not helped my self centering,it may be a case of trying your particular cars self centering prior to sva,and if it
does not make the ajustments as previously mentioned
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macnab
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| posted on 31/1/07 at 12:16 PM |
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I have my moments, when the medicine takes effect…
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DavidM
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| posted on 31/1/07 at 01:03 PM |
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For the SVA it only needs to "attempt" to self centre.
David
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chockymonster
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| posted on 31/1/07 at 02:31 PM |
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quote:
Originally posted by DavidM
For the SVA it only needs to "attempt" to self centre.
David
Mine didn't attempt to at the centre, mainly because the examiner didn't drive it
PLEASE NOTE - Responses on Forum Threads may contain Sarcasm and may not be suitable for the hard of Thinking.
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macnab
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| posted on 31/1/07 at 03:23 PM |
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he will though have put it on the rolling road for the brake test and would have checked it then, only takes 2 seconds.
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chockymonster
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| posted on 31/1/07 at 03:56 PM |
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quote:
Originally posted by macnab
he will though have put it on the rolling road for the brake test and would have checked it then, only takes 2 seconds.
Nope, we pushed it everywhere 
PLEASE NOTE - Responses on Forum Threads may contain Sarcasm and may not be suitable for the hard of Thinking.
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David Jenkins
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| posted on 31/1/07 at 04:03 PM |
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All the tester is supposed to do is stop the car, wind the steering to full lock, let go the wheel and pull forward slowly. There should be a clear
tendency to 'unwind' the steering.
During my car's SVA the tester drove the car out of the testing bay, round the building and out to the 'visibility and noise test'
area, so I guess that he did all these tests while I was walking round to meet him.
I find a positive self-centering action to be very reassuring when I'm driving along - it just feels 'right'.
David
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shortie
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| posted on 31/1/07 at 05:53 PM |
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Seems to differ, my tester at Mitcham (Michael) jumped in the car, went slowly to put it on full lock and then booted it to see if it attempted to
centre, it passed so it must have been ok, he then proceeded to blast full pelt around the testing centre It seemed to make him smile and after a
couple of goes he jumped out and ticked his little box!
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Stu16v
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| posted on 31/1/07 at 08:28 PM |
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quote:
Originally posted by David Jenkins
All the tester is supposed to do is stop the car, wind the steering to full lock, let go the wheel and pull forward slowly. There should be a clear
tendency to 'unwind' the steering.
If the tester does that, he isn't doing what the manual asks him to do.
The Procedures and Standards, as quoted from Section 15 of the SVA manual:
If driven at a constant speed in excess of ten mph a degree of self centring should be provided by the characteristics of the vehicle design...
[Edited on 31/1/07 by Stu16v]
Dont just build it.....make it!
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David Jenkins
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| posted on 31/1/07 at 08:49 PM |
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Perhaps that's what he was doing behind the testing shed, while I wasn't looking!
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bob
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| posted on 1/2/07 at 10:57 AM |
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I had the same tester as shortie,he did exactly the same with my car as well and all was well.
No toe out and 16lb tyre pressure.
As DavidM quoted earlier my tester said to me that it attempted to centre which was good enough for him and even the area examiner who just happened
to drop into my test that morning 
Any way Des, have you got the SVA box ?
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desyboy
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| posted on 1/2/07 at 11:14 PM |
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hello bob
No i havent got the sva box what is it?
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desyboy
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| posted on 1/2/07 at 11:18 PM |
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cheers paul
I gave it 1/2" toe out each side and 15psi in the tyres and the steering wheel straightened by 3/4s of revolution is that enough?
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