blueshift
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| posted on 3/9/03 at 04:36 AM |
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Panhard rod vs Watts linkage
Been pondering both of the above for our dedion setup, which we may be making up as we go along if GTS tuning don't bring out their kit soon.
I have the impression that panhard rod is simpler and lighter, but watts linkage perhaps offers better location of the axle.
If there's no real mechanical or suspension geometry disadvantage though, I think I'm tending towards panhard rod.
Any comments? alternatives?
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pbura
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| posted on 3/9/03 at 05:14 AM |
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I really liked this page about rear suspension linkages:
http://www.geocities.com/markianfox/
BTW, the fellow who published this says that he is "that" Mark Fox, which doesn't register with me but maybe someone in the UK can
explain. 
I'm thinking about building a Mumford linkage, if it turns out that putting the rear roll center below the rear axle would be desirable. There
was some discussion about the Mumford a little while back in Locost Theory. Below is the linkage from a Mallock race car.
A Locost builder, Jeff Underwood, has built one, and here is a link to his photos:
http://www.project-seven.goof.com/gallery.htm
To me, it looks easier to make than a Watts link.
Enjoy!
Pete
Mumford link (http://www.billzilla.org/mallock11.jpg):
[Edited on 3/9/03 by pbura]
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kiwirex
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| posted on 3/9/03 at 08:19 AM |
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Personally, I'd not feel comfortable making a watts unless the donor axle had it built in.
I'd be quite comfortable about the strength of the bracket that I could build for a panhard, because it's easy enough to get around the
axle at that end, and you get quite a bit of weld surface.
But for some reason I'm not happy about welding directly onto the back of the diff.
I'd say the difference in location would be minimal, given the figures we're talking about:
The length of your panhard rod is going to be ballpark 32 inches. Call it 30 for the sake of the maths.
If you say 3 inch bounce, 2 inch droop in your suspension. 3 inches will be what we work from.
Given pythagoras, we get 900 = 9 + x^2
therefore, you're going to get a very small number of movement. Hang on.
sqrt (891) = 29.8496231
(did everyone know you can now type maths into googles search window?? How cool is that??)
-> you'll get approx 0.15 of an inch lateral movement on 3 inches of bounce.
OTY.
cheers,
Greg H
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blueshift
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| posted on 3/9/03 at 05:09 PM |
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Interesting, syd. I didn't know you could do it that way round.
mounting the centre to our sprung parts would not be a problem, though; with de dion (de-dion? dedion?) it would be mounted onto the tube, not the
diff (the diff's bolted to the chassis)
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sgraber
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| posted on 4/9/03 at 02:04 AM |
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IMHO - If you have room for a panhard bar and are looking for easy and lightweight with little performance loss, then Panhard is definitely the way to
go.
I ended up building a watts link because of my mid-engine exhaust routing, and it's at least 4 times the weight. (I may have over-built...)
See my results here - deDion with Watts link: http://www.newtier.com/graber/mid-engine/Images/Rear_Drive_Cradle/07-07-03/index.html
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
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blueshift
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| posted on 4/9/03 at 03:42 AM |
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Ah, right. I think there should be room for a panhard rod. I should get back to the CAD, see if I can fit it all in.
Alarming cut&shut job on that fuel tank.. I hope you know what you're doing, I've heard scary warnings about welding/cutting on fuel
tanks, oil drums etc. Mostly with the moral "don't ever".
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kiwirex
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| posted on 4/9/03 at 09:00 AM |
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Syd Bridges:
> The central pivot of the Watts Link does not have to be welded to the axle!
> It can be attached to an additional member on the chassis, and the outer
> linkage ends attached to the axle ends.
Clever!
nice one.
:-)
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blueshift
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| posted on 5/9/03 at 08:51 PM |
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Hmm, better location, but am I actually going to notice any difference? Or would I be better off saving the weight of the central arm assembly and a
couple of jointy things?
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pbura
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| posted on 5/9/03 at 10:24 PM |
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quote:
Originally posted by blueshift
Hmm, better location, but am I actually going to notice any difference? Or would I be better off saving the weight of the central arm assembly and a
couple of jointy things?
Kiwirex had an excellent point in that you'll get only about .15" lateral movement in 3" of bump.
Also, with the Panhard rod, you can get your roll center slightly below your axle, probably a good thing for you, where with the Watts it will be
right in the middle. If you wanted it a lot lower, I'd go with a Mumford.
I'd use a Panhard with a book build, hands down, FWIW
Pete
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