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Self centering
My car does not self-center at all. The mushroom inserts are with their hole forward, Toyo R888 tyres inflated to 1.5 bar (tried 1.8, too, no effect), 1 degree toe in, -2 degrees camber. The wishbones are built to book dimensions, there is a visible caster angle in the kingpin axis. It does seem to self-center in reverse, though. Any pointers, ideas?
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Albert Haynes Roadster FAQ | Haynes Builder Locations Gallery, build thread in Lithuanian / via Google Translate. |
#2
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Bit of toe out for IVA sorted out self centre issue
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#3
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*sigh* Thanks, I'll try that. But there's a reason why self-centering is a required for IVA, it's a safety feature.
I'm considering several ways to increase the caster angle. One is slotting out the holes on one of the front suspension brackets and fitting some eccentric washers, much like this: http://www.jegs.com/i/Specialty-Prod...23765/10002/-1 Another idea is shortening the four bushes on the top wishbones by some 2.5 mm (bush tube and crush tube) and packing with washers to increase the caster angle by about 1 degree.
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Albert Haynes Roadster FAQ | Haynes Builder Locations Gallery, build thread in Lithuanian / via Google Translate. |
#4
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Quote:
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#5
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If you have a dig about on here someone did an explanation of all this. The mushrooms dont add caster they give you trail. Its this trail that helps with the self centering, a bodge is a better word for it. There is not enough caster in the front suspension set up and no way to alter it.Thats why I am making my upper bones with adjusters on the inner joints. When they are on the car I will take some measurements of them in the corrected adjusted position then perhaps someone can do an ammended top wishbone drawing so they are built to include the caster without the need for adjusters. Caster is an important must have for straight line stability not just self centering. I am no expert on trig but i bet its only a few mm added to the front top wishbone tubes to sort it.
================... KPI ......... caster Lotus Elise........................ 12° ......... 3.8° caster Corvette C5, C6................. 8.8° ...... 6.5° caster Pinto/MustangII/Wilwood... 11° Ferrari 512BB............... 9 or 13° ATS AFX Tall..................... 8° Triumph Spitfire................ 7° ..........4.7° caster Lotus Seven..................... 9° .......... 5° caster Mazda Miata................... 11.3° ........ 5° caster Ferrari F355................... 13.16° McLaren F1...................... 9° ........... 6° caster ...... 16.25mm scrub Bob
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When The Results Disagree With The Theory: Believe The Results And Invent A New Theory If I had two brains I,d still be a halfwit The cave http://s1116.photobucket.com/user/my...deshow/mancave The build http://www.haynes.co.uk/forums/showthread.php?t=12669 Last edited by robo : 12th September 2012 at 09:24 AM. |
#6
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I would suggest that you lower the tyre pressures to 1.1 bar as a starting point,
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Be Lucky, Mike. |
#7
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set the toe to 0deg and try it. if that fails then 0.5deg toe out will get it self centering but it will feel twitchy at high speed.
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My Roadster Is Finished NerNer....... Pigs can fly, you just have to carry them onto the plane. My Pictures http://s707.photobucket.com/user/ashgardiner/profile/ |
#8
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Quote:
Fixing the Sierra's trail inceases positive caster distance, too. It's the distance between the kingpin axis' projection intersection with ground and the centre of the contact patch, and it is precisely the lever that does self-centering.
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Albert Haynes Roadster FAQ | Haynes Builder Locations Gallery, build thread in Lithuanian / via Google Translate. |
#9
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I thought so. But now I have 1.5 bar in the rear tyres, zero camber, and the marks left on the asphalt when spinning wheels are just narrow stripes along the edges.
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Albert Haynes Roadster FAQ | Haynes Builder Locations Gallery, build thread in Lithuanian / via Google Translate. |
#10
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Not quite the same thing because the trail wont become effictive untill you move where as the caster will be effiective at all times. Hence the lack of self centering when stationary. That castor like on a shopping trolley could be kicked arround 360 degrees and it will only straighten if you move forward. Also the inside wheel on turn in on the proper set up is forced downwards whereas the trail set up remains static. That in turn makes the steering feel vague, thats the reason all decent suspesion systems have caster built in. The mushrooms help but its only a patch up fix for an inherent problem, they do infact make the set up act as scrub which most would regard as undesirable.
Bob
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When The Results Disagree With The Theory: Believe The Results And Invent A New Theory If I had two brains I,d still be a halfwit The cave http://s1116.photobucket.com/user/my...deshow/mancave The build http://www.haynes.co.uk/forums/showthread.php?t=12669 Last edited by robo : 12th September 2012 at 06:18 PM. |
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