bilbo
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| posted on 13/1/07 at 11:33 AM |
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Rear Shock Orientation
Apologies if this topic has been covered before, but I’ve had a good search and not found anything.
Basically, I bought a De-dion axle which has mounting brackets for the shocks at 90 degrees from the ‘book’ brackets as welded to a live axle.
My question is, should I mount the top brackets to the chassis 90 degrees to the book design to match the axle? If so, I’m going to have to make some
modifications in that area to allow me to get the bolt through.
Alternatively, would there be excessive stress on the shocks if I keep the book design for the top bracket and have the two ends of the shocks at 90
degs to each other?
Hope that makes sense?
Thanks,
Bill
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Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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ecosse
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| posted on 13/1/07 at 12:52 PM |
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As long as the shock body sits vertically (at 90deg to each mounting) it should be fine, I can't see how it would cause a problem.
Cheers
Alex
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caber
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| posted on 13/1/07 at 01:33 PM |
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I think I disagree with Alex on this! The deDion axle will describe an arc as it moves because of the trailing arms constraining the movement if the
axis of both bushes are not parallel to the axis of the trailing arm pivots you will have problems, either bushes that need replacing very frequently
or worse the eye that is not parallel to the trailing arm will break off the shock absorber!
Both eyes should be parallel to each other and on axis with the axle and the trailing arm pivots IMHO
Caber
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ecosse
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| posted on 13/1/07 at 01:44 PM |
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I stand corrected  (damn, making a habit of this  )
But will the panhard not cause the same problem then, or is the effect reduced enough by its extra length?
Thinking about it I suppose it must be okay or someone would have noticed by now
Cheers
Alex
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gazza285
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| posted on 13/1/07 at 03:26 PM |
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Can't see it being a big problem. Tha axle moves in an arc in both planes and so shockers have either compliant bushes or rose joint which allow
for some sideways movement.
DO NOT PUT ON KNOB OR BOLLOCKS!
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bilbo
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| posted on 13/1/07 at 04:41 PM |
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Thanks for the replies.
Trouble is I can see both points of view on this
But as gazza285 says, the axle moves in an arc in both planes. Even if both ends of the shock are oriented the same way, they'll still have to
give in the oposite plane regardless of if they are parallel with, or at 90 degs to the axle?
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Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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caber
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| posted on 13/1/07 at 06:14 PM |
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Yes it does arc in both directions however reason for making the Panhard Rod as long as possible is to increase radius of arc to minimise sideways
displacement , trailing arms are a lot shorter therefore radius of arc is much shorter resulting in a lot more movement front to back than side to
side that is why my money is on having rotational axis of coilover bushes on same axis as majr movement.
Caber
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Peteff
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| posted on 13/1/07 at 06:27 PM |
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But there are two trailing arms and only one panhard rod  . I would decide which way round you are putting them and then have top and bottom the same
orientation. Whichever is easiest gets my vote.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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bilbo
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| posted on 13/1/07 at 06:31 PM |
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quote:
Originally posted by caber
Yes it does arc in both directions however reason for making the Panhard Rod as long as possible is to increase radius of arc to minimise sideways
displacement , trailing arms are a lot shorter therefore radius of arc is much shorter resulting in a lot more movement front to back than side to
side that is why my money is on having rotational axis of coilover bushes on same axis as majr movement.
Caber
This does make sense to me, hence the orientation of the shocks in the book design. Trouble is my bought in de-dion has them at 90 degs to that
Interestingly, I've just had a look at the Rorty Design De-Dion. This too is like mine in the orientation, so there must be some reason for
doing it like this?
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Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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DIY Si
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| posted on 13/1/07 at 07:16 PM |
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You could always use a Watts link to eliminate the side ways movement. Only have to worry about for-aft then, and can orientate the shocks
accordingly.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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3GEComponents
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| posted on 13/1/07 at 10:41 PM |
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So much easier to draw than to explain, but i'll have a go.
When mounted with the bolts of the shock facing front to rear, the shock bush will cope with the amount of movement that is generated from vertical
movement of the trailing arms.
If you were to mount them with the bolts facing left to right, the bush in the shock would have to allow for a situation where an extreme may occur,
4" compresion on one wheel and 4" drop on the other, for instance.
Where the most movement occurs is side to side, so the shock has to mounted to allow torsional twist to happen.
It would be the same as turning your wishbone bushes through 90 degrees, so the bolts were vertical and still expect the front end to have
suspension.
Does that make any sense at all?
It's late, and i've had a couple
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ecosse
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| posted on 13/1/07 at 10:59 PM |
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That is where i went wrong then, forgot to have a beer b4 thinking about it
Glad you explained that John as I've got my brackets on wrong!
Cheers
Alex
PS
Just tacked so no big problem, but never even thought about it
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MikeRJ
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| posted on 14/1/07 at 12:06 AM |
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I've always thought the book design was wrong, the arrangement used on the de-dion axles makes much more sense to me.
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gazza285
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| posted on 14/1/07 at 06:19 AM |
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quote:
Originally posted by DIY Si
You could always use a Watts link to eliminate the side ways movement. Only have to worry about for-aft then, and can orientate the shocks
accordingly.
The axle will still move in two planes though.
DO NOT PUT ON KNOB OR BOLLOCKS!
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bilbo
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| posted on 14/1/07 at 09:49 AM |
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quote:
Originally posted by jroberts
So much easier to draw than to explain, but i'll have a go.
When mounted with the bolts of the shock facing front to rear, the shock bush will cope with the amount of movement that is generated from vertical
movement of the trailing arms.
If you were to mount them with the bolts facing left to right, the bush in the shock would have to allow for a situation where an extreme may occur,
4" compresion on one wheel and 4" drop on the other, for instance.
Where the most movement occurs is side to side, so the shock has to mounted to allow torsional twist to happen.
It would be the same as turning your wishbone bushes through 90 degrees, so the bolts were vertical and still expect the front end to have
suspension.
Does that make any sense at all?
It's late, and i've had a couple
Thanks for this. It does make sense - I think
It does make things clearer for me. What I'm going to do is mount the top brackets to match the de-dion (i.e. bolt pointing front to back, 90
degs from the book design). If I make the brackets slightly longer/taller then I should be able to get the bolt on and off.
There is always going to be stress on the shocks in the oposite plane, but if I'd set it up like in my original idea of the top bracket 90 degs
to the bottom, I'd have had stress in every plane
Thanks again for everyones replies.
[Edited on 14/1/07 by bilbo]
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Build Diary: http://bills-locost.blogspot.com/
Web Site: http://locost.atspace.com
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