Fred W B
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 posted on 5/1/05 at 10:17 AM |
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Rear Uprights - Top pivot position?
Are there any geometrical or other reasons to position the top pivot on a rear upright further inboard then the lower pivot point.
This is done on a front upright, in order to get the desired king pin inclination.
If any inclination is desirable on the rear, any rule of thumb as to how far inset the top pivot should be?
I have plenty of space, as the rear discs are mounted inboard, on the transaxle.
Regards
Fred WB
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britishtrident
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| posted on 5/1/05 at 12:04 PM |
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For space reasons some Honda & Rover rear suspensiosn use very short upper links with the outer pivot way outboard over the centre of tyre
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smart51
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| posted on 5/1/05 at 12:10 PM |
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the top link is shorter than the bottom to control the camber angle of the wheel through out the suspension's travel (ie in a roll and when
going over a bump)
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Rorty
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| posted on 6/1/05 at 03:21 AM |
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quote:
Originally posted by Fred W B
Are there any geometrical or other reasons to position the top pivot on a rear upright further inboard then the lower pivot point.
This is done on a front upright, in order to get the desired king pin inclination.
The positions of the front balljoints do dictate the KPI, but as smart51 points out, if you mess with the position of the top balljoint, you'll
alter the wheels' camber which is something you probably shouldn't be doing if you don't understand the principal.
Winding in a male-threaded upper rod end (or similar) to alter camber by less than one degree is about all you should be considering at the rear.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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Fred W B
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| posted on 6/1/05 at 06:43 AM |
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Thank for replies guys.
What I am doing is designing and making rear uprights from scratch. I am aware of the theory of suspension geometry, and was just looking for input
before I start with the final layout.
I asked the question, as it seems a lot of rear uprights I have seen do have the top pivot inset, while it seems to me that it would make the uprights
much simplier if they were vertically above the bottom pivot point. The lenght of the top wishbone can be adjusted (in my case) by moving the inboard
mounting point and relevant bit of chassis.
Cheers
Fred WB
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Rorty
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| posted on 6/1/05 at 07:12 AM |
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In theory, you could place the top pivot wherever you want, as long as the wheel behaves properly in bump, droop and roll.
In reality, the upper pivot usually falls inboard of the lower one. There are so many influences on the suspension that you'll find you're
relatively quite limited for choice of pivot locations.
Having said that, as you'll be designing the uprights from scratch, you'll have a free hand with three of the pivot axes (lower outer,
upper outer and upper inner).
I would either draw it in a CAD programme or make a two-dimensional half scale model to explore the possibilities.
Cheers, Rorty.
"Faster than a speeding Pullet".
PLEASE DON'T U2U ME IF YOU WANT A QUICK RESPONSE. TRY EMAILING ME INSTEAD!
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