Watts link position, and bushes
Trev Borg - 18/6/09 at 07:21 PM
The live axle I have has a panhard rod setup that I think will give problems.
The axle sits on top of a chassis rail, with the panhard rod axle bracket positioned lower so that the panard rod goes under the chassis.
This kinda restricts movement, butaslo puts the lower bracket very near the ground.
I'm thinking about replacing it with a watts link and wanted some info.
Am I better mounting the link on the diff, or on a chassis tube?
The diff is not cetral, but a chassis tube mount could be, so the links could be equal lengths.
Also, do I use rose joints or bushes. The rest of the car is bushed, and the original panhard rod is bushed.
Thickness of steel, size of theads?
If anyone has any nice pictures, or diagrams, this would be nice.
any comments welcome 
[Edited on 18/6/2009 by Trev Borg]
pewe - 18/6/09 at 07:56 PM
IIRC PPC magazine are putting a Watts linkage on one of their cars. In either the April or May issue they showed some pics as to how they were doing
it.
Also you could do worse than give them a bell as they are normally quite helpful with interesting mods.
HTH
Cheers, Pewe 
dmac - 18/6/09 at 08:13 PM
Its not clear from the pic but if your rod bracket is above the bottom of your wheel rim then you will probably have bigger problems than a bent
bracket if it ever gets hit.
Duncan
Trev Borg - 18/6/09 at 08:15 PM
I saw the car at the PPC birthday bash at Mallory, and will be at curbrough on the 3rd of July.
The links on the car they had did not appear to be level at rest. Don'y know if this correct or not ?
Minicooper - 18/6/09 at 09:16 PM
I copied the watts linkage from the PPC article and then realised the links need to be level not angled like this, as it is in the picture when I
lifted it up and down to check for any binding it was moving sideways
Cheers
David
Rescued attachment My Mini.jpg
MikeRJ - 18/6/09 at 10:16 PM
The mounting location of the Panhard rod determines the roll center height, and usually the lower the better.
You might want to look at the Mumford linkage, they can give a low roll centre without being
physically mounted low down.
blakep82 - 18/6/09 at 11:26 PM
here's a photo of mine. i think you'll find it easier (and cheaper, if you look at the price of watt link diff covers) to put the pivot on
the chassis, linking to 2 points on the axle
bigger photo here
as for rose joints/bushes, i'd go rose joints. they can be a bit funny to set up. 1/2" or M12 would be the minimum, but i went with
5/8" with 1/2" bolts
hope this helps 
[Edited on 18/6/09 by blakep82]
blakep82 - 18/6/09 at 11:28 PM
quote:
Originally posted by Minicooper
I copied the watts linkage from the PPC article and then realised the links need to be level not angled like this, as it is in the picture when I
lifted it up and down to check for any binding it was moving sideways
Cheers
David
is the centre joint free to swivel on yours? if it is, there still shouldn't be much sideways movement. its not 'ideal' but should
still be better than a panhard
if the axle moves up on yours the effective length of the top bar should 'shorten', and the bottom bar 'lengthen' by the same
amount
[Edited on 18/6/09 by blakep82]
MikeRJ - 18/6/09 at 11:59 PM
quote:
Originally posted by blakep82
is the centre joint free to swivel on yours? if it is, there still shouldn't be much sideways movement. its not 'ideal' but should
still be better than a panhard
With such short link it may well be worse than a panhard.
The people who were doing the space framed Escort project in PPC a while back made the exact same mistake, but they were worse since they came up with
some daft reason why people had been doing it wrong for years.
blakep82 - 19/6/09 at 12:06 AM
quote:
Originally posted by MikeRJ
With such short link it may well be worse than a panhard.
the swivel in the middle should take up that arc. difficult to explain, but the length shouldn't make a huge difference (shorter bars should just
mean the whole thing can only handle less suspension travel than long bars, but the side to side movement would be an S shape rather than an arc.)
the main point is, as long as the bars are the same length, it will be fine, but best get them as long as possible
this is quite good.
http://www.mekanizmalar.com/watts.shtml
i'd say the length of the bars is short on this. i was trying to find one with a way to type in the length of the bars, but i can't
[Edited on 19/6/09 by blakep82]
MikeRJ - 19/6/09 at 12:23 AM
quote:
Originally posted by blakep82
the swivel in the middle should take up that arc. difficult to explain, but the length shouldn't make a huge difference (shorter bars should just
mean the whole thing can only handle less suspension travel than long bars, but the side to side movement would be an S shape rather than an arc.)
the main point is, as long as the bars are the same length, it will be fine, but best get them as long as possible
I understand what you mean, the linkage in the middle effectively gives you the average of the error between top and bottom arms, so lateral movement
will be far less than a panhard of the same length as one of the arms in the Watts link.
What I meant was an appropriately sized panhard (i.e. one as long as possible) would probably give less total error. If you go to all the trouble of
using a Watts linkage, it's a bit pointless if you aren't getting it's advantages over a Panhard because it's not located
correctly.
blakep82 - 19/6/09 at 12:34 AM
i getcha! yeah, definitely worth doing all the calculations first to make sure its worth while.
i think with a panhard rod, you'll get sideways movement as soon as the axle moves. with a watts linkage, you will get an 'area' where
theres no sideways movement (even if its only 3"
but worth doing the calculations to show what the sideways movement will be beyond that. it
might be ok (less than the panhard) or it might be real bad.
personally, i would go watts linkage anyway. and i did, but mainly because my chassis was already link that...
Minicooper - 19/6/09 at 10:42 AM
quote:
Originally posted by blakep82
is the centre joint free to swivel on yours? if it is, there still shouldn't be much sideways movement. its not 'ideal' but should
still be better than a panhard
if the axle moves up on yours the effective length of the top bar should 'shorten', and the bottom bar 'lengthen' by the same
amount
Yes the centre moves freely
Looks ok doesn't it but when the axle goes down it moves to the left, when the axle goes up it moves to the right, I must admit the travel I was
testing it on was in total about 10 inches was a bit excessive, with that amount of travel I was getting about 3/4" of sideways movement so it
would be considerably less in the real world.
I just moved the right hand link chassis mounting point up the distance between the central link rose joint mounting, this completly sorted it
Cheers
David
Trev Borg - 22/6/09 at 09:14 PM
the panhard rod i have will only move the axle slightly, but the main reason I was thunking watts link is dur to the very low bracked.
I think I will mount a watts link on a cross chassis rail, and use the top of one axle bracket and the bottom of the othe axle bracket as the mounting
points.
Bushed at one end, rose jointed at the other
thanks for the replies
