Ivan
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| posted on 8/6/13 at 05:11 PM |
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Advice please on Watts linkage
I am wanting to fit fore and aft watts linkages on my Cobra's Jag rear suspension to stop the power on power off toe changes that unsettle the
rear end quit badly especially if you are turning at the time  , however without making outriggers for the chassis I cannot mount the chassis ends
of the arms in line with the rocker but would have to go inboard some 4" - provided I allow for side thrust on the rocker and the outer mounts
of the arms are the same distance from the center line will this affect the effectiveness of the linkage?
Here's a picture of another Cobra but with the mountings aligned.
[Edited on 8/6/13 by Ivan]
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DIY Si
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| posted on 9/6/13 at 02:41 PM |
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I hope not, as this is how my Sprite's rear end is aligned:
The only difference I can see is that the linkages will have less relative movement from being inboard but other than that I couldn't foresee
any issues.
“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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DIY Si
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| posted on 9/6/13 at 07:50 PM |
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Having said that earlier, did you mean that just the front arm will point in towards the centreline of the car, and not run parallel with the rear
arm? That will reduce the effectiveness of the linkage as the arcs won't quite combine the same, but I can't see it causing any real issue
on a road car as long as the joints will take the changing misalignment.
“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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britishtrident
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| posted on 9/6/13 at 08:37 PM |
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quote:
Originally posted by DIY Si
I hope not, as this is how my Sprite's rear end is aligned:
The only difference I can see is that the linkages will have less relative movement from being inboard but other than that I couldn't foresee
any issues.
This one has me scratching my head wondering what it achieves over a normal Watts linkage for a dead axle or de dion such as on the Volvo
480, Rover 213, Rover P6 ?
[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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Ivan
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| posted on 10/6/13 at 04:34 PM |
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quote:
Originally posted by DIY Si
Having said that earlier, did you mean that just the front arm will point in towards the centreline of the car, and not run parallel with the rear
arm? That will reduce the effectiveness of the linkage as the arcs won't quite combine the same, but I can't see it causing any real issue
on a road car as long as the joints will take the changing misalignment.
Both ends will point inwards towards the center line - almost like a mini A arm.
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DIY Si
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| posted on 12/6/13 at 08:45 AM |
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BT,
That's the back end of a Caterham but narrowed a bit to fit under the Sprite shell. The normal set up using trailing arms rather than the
Watt's linkages, but this way reduces the toe changes in roll. Unless I've missed your point as I know little about the set up the other
cars use.
Ivan,
Does the mount on the axle have to be offset to the arms? Could it be moved inboard to match them? Although, as long as the design allows for the side
forces and the bushes are compliant enough to handle the mismatched arcs it should be ok. The thing to watch will be the arcs on both sides acting
away from each other, especially in roll, as they'll be trying to swivel the mounts off the axle.
“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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nick205
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| posted on 12/6/13 at 10:39 AM |
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Ivan,
Isn't your set up different in that the Jag axle is IRS?
Certainly on the E-Type, the lower arm has a trailing radius arm to limit fore/aft movement. Is this not fitted in your application? Would a single
poly bushed trailing arm be easier to install and give the same improvement?
Also, not by a huge amount, but the Watts linkage pivot point will travel in an arc as as the lower suspension arm moves through its travel. Coupled
with moving the linkage rods chassis pickup points inboard does this give any issues?
E-Type rear axle for reference...
[img] [/img]
[Edited on 12/6/13 by nick205]
[Edited on 12/6/13 by nick205]
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mark chandler
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| posted on 12/6/13 at 11:05 AM |
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Jag trailing arm is only required as the subframe is mounted on rubber bushes, the lower bone has bearings both ends so should not wiggle.
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nick205
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| posted on 12/6/13 at 11:09 AM |
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quote:
Originally posted by mark chandler
Jag trailing arm is only required as the subframe is mounted on rubber bushes, the lower bone has bearings both ends so should not wiggle.
Makes sense, assuming Ivan has his hard mounted I guess?
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MikeRJ
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| posted on 12/6/13 at 11:19 AM |
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I think this is one of those cases where a simple diagram would be worth a good thousand words.
It sounds to me as though, looking down from the top of the car, the front arm would be sitting at an angle, with it's front end further inboard
than the axle end?
If so this would effectively reduce the geometrical length of the arm, so you would need to compensate for this, either by making the arm longer or by
moving the pivot on the axle bracket. The angled arm will also translate any thrust from the axle to a side thrust which will have to be constrained
by your Panhard rod and the watts linkage brackets themselves.
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Ivan
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| posted on 13/6/13 at 07:01 AM |
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Yes my jag suspension is hard mounted and I still retained the trailing arms but they do nothing because of the large flexible rubber bush in them.
I would as first choice fit a trailing arm with the front mount aligned with the inner lower arm pivot but chassis members in the way and ground
clearance constraints mitigate against that option.
With the watts linkage option the front member could be aligned with the rocker but there is no chassis near the back linkage hence I must either
extend a mount outwards or move both outer pivot points on the linkages inwards.
Another option at the back is to mount it to the glass fiber body suitably reinforced but I am loath to do that.
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MikeRJ
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| posted on 13/6/13 at 09:24 AM |
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Of course it's IRS, so no panhard rod, was obviously not paying attention last night! I think your proposed solution should work ok provided
you get the length of the angled arm and/or axle bracket hole position correct to minimise movement at the watts linkage pivot.
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