Echidna
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| posted on 12/4/08 at 03:48 PM |
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Mushroom plugs (off-center)
Where can i find the off-center mushroom plugs for Sierra front uprights?
I guess that i will be able to adjust caster with these but is there any easier method for incorporating adjustable caster in a front suspension
design?
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[Edited on 12/4/08 by Echidna]
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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IDONTBELEIVEIT
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| posted on 12/4/08 at 04:00 PM |
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castor can be adjusted by using a wider suspension brkt shimmed either side until desired castor angle achieved for self centering or not,when happy,
the shims can be replaced by one machined washer to the correct thickness
wayno!!
Are We There Yet, Are We There Yet!!!!
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britishtrident
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| posted on 12/4/08 at 04:04 PM |
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Offset mushroom have no effect on caster.
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Echidna
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| posted on 12/4/08 at 04:06 PM |
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Doesn't it affect the outer hardpoint of the upper wishbone fore-aft?
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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britishtrident
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| posted on 12/4/08 at 04:22 PM |
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quote:
Originally posted by Echidna
Doesn't it affect the outer hardpoint of the upper wishbone fore-aft?
No because it isn't fitted to the wishbone.
[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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MikeRJ
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| posted on 12/4/08 at 04:38 PM |
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quote:
Originally posted by Echidna
Doesn't it affect the outer hardpoint of the upper wishbone fore-aft?
Castor is the angle formed by the upper and lower pivots (ball joints) from the vertical plane. The mushrooms can have no effect on that angle.
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bilbo
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| posted on 12/4/08 at 04:56 PM |
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quote:
Originally posted by MikeRJ
quote:
Originally posted by Echidna
Doesn't it affect the outer hardpoint of the upper wishbone fore-aft?
Castor is the angle formed by the upper and lower pivots (ball joints) from the vertical plane. The mushrooms can have no effect on that angle.
Hang on a minute though. If you have off-centre holes in the mushrooms, and position the hole towards the front of the car, this would have the
effect of moving the upper ball joint position backwards relative to the bottom ball joint - therefore increasing the castor angle?
Or am I missing something?
[Edited on 12/4/08 by bilbo]
Editied to say - Yes I am missing something
The ball joint doesn't move, only the upright.
I'll get my coat
[Edited on 12/4/08 by bilbo]
---------------------------------------
Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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AdrianH
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| posted on 12/4/08 at 06:25 PM |
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The upper and lower ball joints are fixed points at the ends of the wishbones and there is no adjustment fore and aft to move these, therefore the
povit points do not move.
What I think you do with the offset mushrooms is move the pivot line of the upright closer or further away from the centre of the hub.
Putting the offset to the front, of the upright is the closest to centre of hub you can make it, Still not in line but a reasonable compromise. Are
you building the Gibbs or the Chapman?
Cheers
Adrian
p.s.
someone let me know if I am on the right idea!
Why do I have to make the tools to finish the job? More time then money.
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caber
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| posted on 12/4/08 at 06:50 PM |
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The off centre bushes change King-Pin Inclination not caster angle IIRC
Caber
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Liam
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| posted on 15/4/08 at 06:03 PM |
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They dont adjust KPI either! That's another parameter defined by the pivot points which are not moving here.
The offset mushrooms primarily adjust camber. There will also be small changes in trail and scrub radius that will be arguably unnoticable in terms
of car handling.
Liam
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chrisg
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| posted on 15/4/08 at 06:40 PM |
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The ofset is toward the front of the upright, not to adust caster. camber or KPI it increases trail to help with self centring.
It could theoretically change camber but it shouldn't be used in the in/out plane, just to change the angle of the upright.
Cheers
Chris
Oh and 3GEcomponents sell the offset ones.
[Edited on 15/4/08 by chrisg]
Note to all: I really don't know when to leave well alone. I tried to get clever with the mods, then when they gave me a lifeline to see the
error of my ways, I tried to incite more trouble via u2u. So now I'm banned, never to return again. They should have done it years ago!
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Liam
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| posted on 17/4/08 at 10:48 PM |
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Yeah but your trail is primarily determined by your castor angle which you should get right at the design stage. For example a castor angle of 7
degrees gives approx 37mm of trail. Adjusting the mushroom all the way round from front to back only represents a perturbation of approx +/- 3mm on
this nominal trail. Adjusting from left to right, however gives a camber adjustment range of approx 3 degrees, which is a significant amount.
In other words I am using my mushrooms to give me a 3 degree camber adjustment range, and I'll live with the 3mm or so variation on my trail
throughout this range, which I dont expect to notice. So i stand by my claim they primarily adjust camber!
Note i'm doing it this way because the load bearing nature of my top wishbones prevents me using the conventional camber adjustment method of
threading in/out a transit ball joint with an acceptable factor of safety. I wasn't reccommending it as the ideal camber adjustment solution
for everybody, just trying to clear up the confusion often surrounding what these mushrooms actually adjust and what they dont!
Liam
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chrisg
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| posted on 18/4/08 at 11:20 AM |
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This is difficult to describe but trail and caster although related aren't the same thing.
Adjusting caster involves moving the wishbone pivots, trail can only be adjusted by moving the upright pivots.
Imagine a line going through the upper wishbone pivot and the axle centre line. call this the upright centre line. If you move the wishbone
pivot back you increase the caster but if you move the top upright pivot forward you increase the trail.
I'll try to scan some drawings that explain it better.
Cheers
Chris
Note to all: I really don't know when to leave well alone. I tried to get clever with the mods, then when they gave me a lifeline to see the
error of my ways, I tried to incite more trouble via u2u. So now I'm banned, never to return again. They should have done it years ago!
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charlierevell
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| posted on 18/4/08 at 12:29 PM |
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Mushroom Insert
I think thats what you were after....
Tango orange is an 'IN' colour!!
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quattromike
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| posted on 5/5/08 at 11:14 AM |
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I machined up my own insert with lots of offset. Not that it helps this arguement but I like to mention it now and again
linky
[Edited on 5/5/08 by quattromike]
"At the end of the day, I think it's going to get very dark"
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