Lew The Machine
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| posted on 4/4/12 at 08:34 AM |
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Rear Suspension Mounting Positions and an Inventor model shopping list...
OK first dumb question (its been coming)
In "the haynes book" the rear shock mounts are ABOVE the rear upright inline with the bearing CL, but im sure ive seen other designs where
the shock mounts down at low level infront/behind the rear upright??? (id prefer this)
Does anyone have any info on this setup? (ive searched and searched!)
Im modeling my suspension in inventor so i can make any changes and check geo as i go!
got most of the fabricated parts done in 3D now but still looking around the web for:
Rose Joints (any size available)... or drgs to model them from.
Rose joint adapter pins to suit cortina uprights (upper, lower and steering)
Ball joints (maxi)
track rod ends (escort)
Drag links (transit)
Everything and anything Sierra LSD rear end based. (diff, shafts, hubs, calipers, discs, etc)
Basically anything id have to buy and manually measure from!
Kind Regards
Lewis
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Neville Jones
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| posted on 4/4/12 at 09:48 AM |
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Mounting the shocks to the front or rear of the centreline, on the lower wishbone, is flawed thinking.
It can be made to work (I've done it myself in the past, out of necessity), but the wishbones need to be heavy, and the resulting torsional
loads accounted for in the design.
Every time the car hits a bump, the wishbone is twisting, and early end of life is inevitable. Even it the top wishbone mount doesn't move, the
bottom mounts are moving unevenly due to load.
That one or two well known builders do this, is no confirmation of the practice being safe and useable, if not properly designed for.
Cheers,
Nev.
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Lew The Machine
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| posted on 4/4/12 at 10:05 AM |
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quote:
Originally posted by Neville Jones
Mounting the shocks to the front or rear of the centreline, on the lower wishbone, is flawed thinking.
It can be made to work (I've done it myself in the past, out of necessity), but the wishbones need to be heavy, and the resulting torsional
loads accounted for in the design.
Every time the car hits a bump, the wishbone is twisting, and early end of life is inevitable. Even it the top wishbone mount doesn't move, the
bottom mounts are moving unevenly due to load.
That one or two well known builders do this, is no confirmation of the practice being safe and useable, if not properly designed for.
Cheers,
Nev.
Yeah that’s a pretty comprehensive answer lol tbh I’ve only seen the odd picture of the "offset shock" setup (and that was a while ago) I
just wondered if it was an acceptable alternative?
the "inline shock" approach is definitely favorable but makes the whole rear suspension setup a lot taller, I was hoping to keep it all
quite low and compact (without using rockers and pushrods) but I admit I hadn’t really considered the amount of torsional load on the wishbones.
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40inches
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| posted on 4/4/12 at 10:20 AM |
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You might get away with a damper each side of the upright, ala
Jaguar, using motorcycle dampers? Possibly?
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Slimy38
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| posted on 4/4/12 at 10:57 AM |
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I'm probably going to be committing some cardinal sin of suspension, but could you rotate the lower arm and mount it at an angle? So it's
closer to 45 degrees to the chassis rather than 90? At least then you could mount the damper on the centre of the lower arm (due to it no longer being
underneath the driveshaft) and it would be no higher than the front suspension? The damper would still be inline with the suspension so there
wouldn't be any twisting forces (I think?). The only thing might be that if the bottom one works in a different plane to the top, it would
change the wheel camber under compression.
I'm not a suspension engineer in any form so I have no idea whether it's safe or even physically possible.
[Edited on 4/4/12 by Slimy38]
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Lew The Machine
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| posted on 4/4/12 at 11:08 AM |
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quote:
Originally posted by Slimy38
I'm probably going to be committing some cardinal sin of suspension, but could you rotate the lower arm and mount it at an angle? So it's
closer to 45 degrees to the chassis rather than 90? At least then you could mount the damper on the centre of the lower arm (due to it no longer being
underneath the driveshaft) and it would be no higher than the front suspension? The damper would still be inline with the suspension so there
wouldn't be any twisting forces (I think?). The only thing might be that if the bottom one works in a different plane to the top, it would
change the wheel camber under compression.
I'm not a suspension engineer in any form so I have no idea whether it's safe or even physically possible.
[Edited on 4/4/12 by Slimy38]
its possible, but would require a complete re-think of the rear end and probably result in a setup as wierd as the original sierra geometry was?!
AND THATS BAD... VERY BAD! there are some seriously wierd and wonderful geometry changes throuought the suspension travel on sierra's!
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