Watts linkage question
03-25-2010, 05:14 PM
#1
5th Gear Member
Thread Starter
Join Date: Sep 2006
Posts: 3,401
Watts linkage question
Ok, so I'm trying to work out something here and my brain keeps farting on me.
Right, the lateral links on a watts linkage have to be the same length, installation procedures stress that very highly.
Well that's all fine, mine are, at least to 1mm.
But what I find myself wondering is what would happen if they were different lengths, say 1/2" or so.
Would the rear end move side to side under suspension movement, like the panhard system, or would the linkage simply bind up?
My head hurts..................
Right, the lateral links on a watts linkage have to be the same length, installation procedures stress that very highly.
Well that's all fine, mine are, at least to 1mm.
But what I find myself wondering is what would happen if they were different lengths, say 1/2" or so.
Would the rear end move side to side under suspension movement, like the panhard system, or would the linkage simply bind up?
My head hurts..................
03-25-2010, 05:35 PM
#2
4th Gear Member
Join Date: Dec 2007
Location: Ontario, Canada
Posts: 1,692
Marcus
I thik you are correct and what would happen is that the propeller center point would try to move sideways and in a car that means that the LCA and UCA bushings would bind.
How about if you made up a model using cardboard and pins and tested it?
http://en.wikipedia.org/wiki/Watt%27s_linkage
I'm too busy working to try it out
I thik you are correct and what would happen is that the propeller center point would try to move sideways and in a car that means that the LCA and UCA bushings would bind.
How about if you made up a model using cardboard and pins and tested it?
http://en.wikipedia.org/wiki/Watt%27s_linkage
I'm too busy working to try it out
03-25-2010, 07:05 PM
#3
5th Gear Member
Thread Starter
Join Date: Sep 2006
Posts: 3,401
Marcus
I thik you are correct and what would happen is that the propeller center point would try to move sideways and in a car that means that the LCA and UCA bushings would bind.
How about if you made up a model using cardboard and pins and tested it?
http://en.wikipedia.org/wiki/Watt%27s_linkage
I thik you are correct and what would happen is that the propeller center point would try to move sideways and in a car that means that the LCA and UCA bushings would bind.
How about if you made up a model using cardboard and pins and tested it?
http://en.wikipedia.org/wiki/Watt%27s_linkage
Yes, I think making a cardboard mock-up is the only way I can unlock this log jam in my brain....
Last edited by marcuskeeler; 03-25-2010 at 07:08 PM.
03-26-2010, 06:35 AM
#5
6th Gear Member
Join Date: Feb 2007
Location: state of confusion
Posts: 7,635
Unequal Watts link lateral links will cause the axle to walk back and forth slightly. But probably less than you might imagine, and maybe not enough to notice if the length difference isn't all that much. Normal OE LCA bushings or rod ended LCAs should be able to cope with small amounts of lateral movement - the PHB walks the axle laterally a little as it is. Poly bushings, maybe not so well.
I'd worry a lot more about getting the lateral links to be parallel at some ride height than getting the laterals to match lengths to within any closer than about 1/16". Note that parallelism does not have to happen when the car is at its static ride height, though it's generally easier to get the installation done if it does.
Actually, it's at least possible to get away with significantly different WL lateral links - but then you need to use unequal offsets from the main pivot of the "propellor" for the different length laterals. I don't think the longer lateral link would go to the longer offset on the propellor.
Norm
I'd worry a lot more about getting the lateral links to be parallel at some ride height than getting the laterals to match lengths to within any closer than about 1/16". Note that parallelism does not have to happen when the car is at its static ride height, though it's generally easier to get the installation done if it does.
Actually, it's at least possible to get away with significantly different WL lateral links - but then you need to use unequal offsets from the main pivot of the "propellor" for the different length laterals. I don't think the longer lateral link would go to the longer offset on the propellor.
Norm
03-26-2010, 07:49 AM
#6
5th Gear Member
Thread Starter
Join Date: Sep 2006
Posts: 3,401
Yea Norm, all my 'lengths' are as equal as I can get them, it was more of a "what if" question. Your answer certainly makes sense although when you say walk back and forth slightly I take it you mean laterally of course [?].
FAYS instructions call for parallel rods at normal loaded ride height with a clockwise position of the propeller which is what i shot for.
Being that the main function of the Watts is to remove lateral rear end movement, and that poly bushings work within tolerance with a PHB, then any minor lateral movement sneaking under the wire will be of no consequence to them.
Colin, I have taken her up the road for a short run but only a mile or so to check for oil leaks following the off season valve cover refit. No noises at all from the rear end and very smooth. Previously when I pulled into my driveway which is sloped (I always have to go up it at an angle to avoid scuffing the spoiler) I used to get a rear end 'bonk' which I was never able to isolate. Now it's silent as night itself during the same maneuver, so that's a bonus
FAYS instructions call for parallel rods at normal loaded ride height with a clockwise position of the propeller which is what i shot for.
Being that the main function of the Watts is to remove lateral rear end movement, and that poly bushings work within tolerance with a PHB, then any minor lateral movement sneaking under the wire will be of no consequence to them.
Colin, I have taken her up the road for a short run but only a mile or so to check for oil leaks following the off season valve cover refit. No noises at all from the rear end and very smooth. Previously when I pulled into my driveway which is sloped (I always have to go up it at an angle to avoid scuffing the spoiler) I used to get a rear end 'bonk' which I was never able to isolate. Now it's silent as night itself during the same maneuver, so that's a bonus
03-26-2010, 08:08 AM
#7
4th Gear Member
Join Date: Dec 2007
Location: Ontario, Canada
Posts: 1,692
Colin, I have taken her up the road for a short run but only a mile or so to check for oil leaks following the off season valve cover refit. No noises at all from the rear end and very smooth. Previously when I pulled into my driveway which is sloped (I always have to go up it at an angle to avoid scuffing the spoiler) I used to get a rear end 'bonk' which I was never able to isolate. Now it's silent as night itself during the same maneuver, so that's a bonus
I'm not sure where my noises are coming from but will check everything out next month before my first track day.
Thanks.
03-26-2010, 08:59 AM
#9
5th Gear Member
Thread Starter
Join Date: Sep 2006
Posts: 3,401
My sway bar is very close to the watts frame as we mentioned before but they don't actually touch and given the way the sway bar moves I don't think it'll be a problem.
Maybe you have a loose heim joint or lock nut?
Last edited by marcuskeeler; 03-26-2010 at 09:01 AM.
03-26-2010, 10:57 AM
#10
4th Gear Member
Join Date: Dec 2007
Location: Ontario, Canada
Posts: 1,692
What noises do you have Colin? Are you getting them from normal road driving or on the track only?
My sway bar is very close to the watts frame as we mentioned before but they don't actually touch and given the way the sway bar moves I don't think it'll be a problem.
Maybe you have a loose heim joint or lock nut?
My sway bar is very close to the watts frame as we mentioned before but they don't actually touch and given the way the sway bar moves I don't think it'll be a problem.
Maybe you have a loose heim joint or lock nut?
On the track last year everything was quiet but as you know both Mosport and TMP are pretty smooth.