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Watts Link
- Thread starter ChrisS
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Steve_Lawrence
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I've been noodling on the Watts link idea for a few days now also. I'm wodering if I could get away with using a double-ended stud (with a hex in the middle) to mount a bracket on the three top differential bolts?
Any thoughts?
Any thoughts?
aeronca65t
Great Pumpkin
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Hello Steve,
I'm not sure what you mean, are you planning to bolt a mounting for the single central pivot of a Watt linkage?
If so I supect that it will not be strong enough as it has to carry the sideways load of the car when cornering.
It would probably be better to weld the pivot, with some gussets to spread the load across the diff cover. Also bear in mind that the pivot point then determines your roll centre, so you may want to decide where that should be.
Alec
I'm not sure what you mean, are you planning to bolt a mounting for the single central pivot of a Watt linkage?
If so I supect that it will not be strong enough as it has to carry the sideways load of the car when cornering.
It would probably be better to weld the pivot, with some gussets to spread the load across the diff cover. Also bear in mind that the pivot point then determines your roll centre, so you may want to decide where that should be.
Alec
Hello Aeronca,
some of the pictures you linked to seem very complicated and one claims that it reduces body roll (Mustang), which I don't believe it does.
It is a relatively simple and easily fabricated unit given sufficient space, but can be required carry a significant load. As I said the roll centre of the rear axle is whatever the central link pivot point is. Some of those designs were above the axle centre line (normal roll centre for a live axle), which may not be desirable.
Incidentally it is a Watt linkage not Watts linkage, after the engineer James Watt.
Alec
some of the pictures you linked to seem very complicated and one claims that it reduces body roll (Mustang), which I don't believe it does.
It is a relatively simple and easily fabricated unit given sufficient space, but can be required carry a significant load. As I said the roll centre of the rear axle is whatever the central link pivot point is. Some of those designs were above the axle centre line (normal roll centre for a live axle), which may not be desirable.
Incidentally it is a Watt linkage not Watts linkage, after the engineer James Watt.
Alec
G
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We fabbed up a Watt's Link on a Spriget of a friend years ago. Made a bracket to bolt it to the lower bolts on the diff. It made ~some~ difference, but IIRC the conclusion was that it was more of a pain than it was worth. This was a street driven car with a well "tweaked" 1275, BTW.
Trevor Jessie
Yoda
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So... Panhard and sway light sway bar?
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[ QUOTE ]
but IIRC the conclusion was that it was more of a pain than it was worth. This was a street driven car with a well "tweaked" 1275, BTW.
[/ QUOTE ]
I tend to agree. The Watt's linkage is a pretty complex way to obtain positive lateral axle location. The center requires a very sturdy pivot point at the axle center, rigid bar end mountings, & bars, all located in the correct positions. Vertical positioning of the linkage will determine the rear roll center & must be carefully considered. There are five pivot points to maintain - keep tight & lubricated. It's hard to find room for all the parts.
To compare, a Panhard rod 45" long will keep the axle centered within plus or minus 0.2" for six inches of vertical axle travel. Pretty good for all but the most precise handling requirements. There are no pivots to worry about, just two sturdy brackets, one on the axle, one one the frame. Good Poly bushings on the ends will require practically no maintenance. Much easier to find room for.
If vertical axle travel is only five inches, the lateral movement with the Panhard rod would be plus or minus 0.14".
D
but IIRC the conclusion was that it was more of a pain than it was worth. This was a street driven car with a well "tweaked" 1275, BTW.
[/ QUOTE ]
I tend to agree. The Watt's linkage is a pretty complex way to obtain positive lateral axle location. The center requires a very sturdy pivot point at the axle center, rigid bar end mountings, & bars, all located in the correct positions. Vertical positioning of the linkage will determine the rear roll center & must be carefully considered. There are five pivot points to maintain - keep tight & lubricated. It's hard to find room for all the parts.
To compare, a Panhard rod 45" long will keep the axle centered within plus or minus 0.2" for six inches of vertical axle travel. Pretty good for all but the most precise handling requirements. There are no pivots to worry about, just two sturdy brackets, one on the axle, one one the frame. Good Poly bushings on the ends will require practically no maintenance. Much easier to find room for.
If vertical axle travel is only five inches, the lateral movement with the Panhard rod would be plus or minus 0.14".
D
aeronca65t
Great Pumpkin
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Alec:
I agree...some of the pictures in the Google Image link I posted are not as good as others.
As always, information on the internet can have mixed value.
Trevor:
I fitted a 5/8" rear sway bar on my racer a few years ago. It really made the car too tail-happy and "sudden". I disconnected it in the middle of an event rather than continue. Others may have different opinions on this, but none of the amateur-level Spridgets I race with use a rear sway bar. We all use panhard rods (as well as tube shocks).
~HERE IS A LINK~ to the famous Mumford link used on some Mallock cars....sort of a super-Watt's linkage.
I agree...some of the pictures in the Google Image link I posted are not as good as others.
As always, information on the internet can have mixed value.
Trevor:
I fitted a 5/8" rear sway bar on my racer a few years ago. It really made the car too tail-happy and "sudden". I disconnected it in the middle of an event rather than continue. Others may have different opinions on this, but none of the amateur-level Spridgets I race with use a rear sway bar. We all use panhard rods (as well as tube shocks).
~HERE IS A LINK~ to the famous Mumford link used on some Mallock cars....sort of a super-Watt's linkage.
G
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We "over engineered" it. Shoulda just done a Panhard setup and walked away. I remember it being a real bugger to find a way to mount the ends and have it NOT interfere with all the "other bits" so close together in there. I seem to recall it broke itself or the diff housing... he did up a Panhard after that.
Lessons learned in youth. That's been over 30 years ago now.
Lessons learned in youth. That's been over 30 years ago now.
Chris;
There are quite a few permutations of horizontal Watts links and a lot of them are shown on Aero's link above.
Simple Panhard bars properly installed work well also.
IT ALL DEPENDS on what your going to use the car for and what your level of prep is and what the car wants to see.
you might post what you want to do with the car....
There are quite a few permutations of horizontal Watts links and a lot of them are shown on Aero's link above.
Simple Panhard bars properly installed work well also.
IT ALL DEPENDS on what your going to use the car for and what your level of prep is and what the car wants to see.
you might post what you want to do with the car....
Hello Dave,
I haven't done any geometrical evaluation but I suspect that the lateral movement will be greater than you say when the roll angle is taken into account. Still I do take the point that there is probably not much discernible difference between the two systems.
What about the Jaguar MK 2 which has a half distance panhard rod, it runs from one (quarter elliptic) spring mount to the differential, probably no longer than 15". I have often felt that that would give quite a lot of lateral movement.
I think it was the Aston Martin DB3 racing car that located the rear axle by having a bearing on the differential case running within a vertical channel on the chassis as a guide.
That seems a simple and elegant engineering solution to the problem and one which I've never seen on any other car?
Alec
I haven't done any geometrical evaluation but I suspect that the lateral movement will be greater than you say when the roll angle is taken into account. Still I do take the point that there is probably not much discernible difference between the two systems.
What about the Jaguar MK 2 which has a half distance panhard rod, it runs from one (quarter elliptic) spring mount to the differential, probably no longer than 15". I have often felt that that would give quite a lot of lateral movement.
I think it was the Aston Martin DB3 racing car that located the rear axle by having a bearing on the differential case running within a vertical channel on the chassis as a guide.
That seems a simple and elegant engineering solution to the problem and one which I've never seen on any other car?
Alec
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Hi Alec,
You are of course correct, IF the suspension were fully topped out on one side & bottomed on the opposite side. It's likely, however, that the other suspension parts, by design, would limit the roll angle to somewhat less than this extreme. Also, cars where this might be a problem are usually limited to something less than 5 inches of axle travel. At the limits of handling there would likely be more pressing problems than slight axle lateral movement.
I am not familiar with the DB3 solution but suspect it would end up being somewhat fussy to keep working well.
As you can tell, I'm in favor of keeping it simple.
D
You are of course correct, IF the suspension were fully topped out on one side & bottomed on the opposite side. It's likely, however, that the other suspension parts, by design, would limit the roll angle to somewhat less than this extreme. Also, cars where this might be a problem are usually limited to something less than 5 inches of axle travel. At the limits of handling there would likely be more pressing problems than slight axle lateral movement.
I am not familiar with the DB3 solution but suspect it would end up being somewhat fussy to keep working well.
As you can tell, I'm in favor of keeping it simple.
D
Hap Waldrop
Yoda
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The Huffaker Bugeye in my avatar photo has a horizontal watts link, it took a far amount of structure to mount it. I like panhard bars and wishbone for thier simplicity and they do the same thing, lateral support.
Hello Dave,
The DB3 was designed as a racing car so the practicalities of keeping it maintained was not the main criteria.
However I suspect with modern bearings and materials that it could be made more durable. I would imagine that dirt would be the biggest problem to making this work.
For those who are modifying cars to race this could be a solution to the location of the rear axle given that the frame has to be close to the rear of the differential for it to be practical.
Alec
The DB3 was designed as a racing car so the practicalities of keeping it maintained was not the main criteria.
However I suspect with modern bearings and materials that it could be made more durable. I would imagine that dirt would be the biggest problem to making this work.
For those who are modifying cars to race this could be a solution to the location of the rear axle given that the frame has to be close to the rear of the differential for it to be practical.
Alec
aeronca65t
Great Pumpkin
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Since some of this discussion has moved to panhard rods, here's my simple unit (below). I built it for about $35 and it is as long and horizontal (statically) as possible. Made a useful difference.
A friend of mine has a Lotus Seven with a half-length panhard rod fixed to the diff. Seems too short to me, but maybe with limited axle travel, it's OK.
tripod chassis-mount end
axle-mount end
A friend of mine has a Lotus Seven with a half-length panhard rod fixed to the diff. Seems too short to me, but maybe with limited axle travel, it's OK.
tripod chassis-mount end
axle-mount end
Hap Waldrop
Yoda
Offline
[ QUOTE ]
Hap, is that Bugeye Steve Hussey's old ride?
Huffaker built my setup too.
Jeff
[/ QUOTE ]
Yes, Kinda, this was the second car that was built by Huffaker for the Husseys for the brother Rob, it's a bit tricker than the first car Steve drove, that car is owned by Andrew Wright now, Rob didn't like driving as much as Steve, so the first car was sold to Andrew, then Steve and Gary kept the second car, a few years later Steve and Gary got out of HP raicng and sold the second car to Kenny Pergason ( past HP national champ), after owning the car for only one year, Kenny then got out of racing and sold the car to friend of mine, who found out after spending a buttload of money he didn't like driving, so I drove the car during 2005 season to qualify for the runoffs. At the Roebling double national, the car spun and got hit, not too bad, but enough to make the owner wonder if putting in harm's way was what he wanted to do and decided he did not want to race it at the runoffs, so thats why we built Speedracer (LP Midget).
The car's supension has been messed with alot during Kenny's ownership and when we got the car it was almost impossible to drive, over the course of the season we started getting the car better. During the off season I decided I didn't really want to drive a 948 car, so the owner now has plans to let another driver race it, it been repainted and alot of work done to it to bring it back to it's former glory and should see action next year in SEDIV. I'm sure that when the car is fully sorted it will be a blast to drive, but I can't say that my time in the car was that enjoyable and that I cared much for the 948s.
Hap, is that Bugeye Steve Hussey's old ride?
Huffaker built my setup too.
Jeff
[/ QUOTE ]
Yes, Kinda, this was the second car that was built by Huffaker for the Husseys for the brother Rob, it's a bit tricker than the first car Steve drove, that car is owned by Andrew Wright now, Rob didn't like driving as much as Steve, so the first car was sold to Andrew, then Steve and Gary kept the second car, a few years later Steve and Gary got out of HP raicng and sold the second car to Kenny Pergason ( past HP national champ), after owning the car for only one year, Kenny then got out of racing and sold the car to friend of mine, who found out after spending a buttload of money he didn't like driving, so I drove the car during 2005 season to qualify for the runoffs. At the Roebling double national, the car spun and got hit, not too bad, but enough to make the owner wonder if putting in harm's way was what he wanted to do and decided he did not want to race it at the runoffs, so thats why we built Speedracer (LP Midget).
The car's supension has been messed with alot during Kenny's ownership and when we got the car it was almost impossible to drive, over the course of the season we started getting the car better. During the off season I decided I didn't really want to drive a 948 car, so the owner now has plans to let another driver race it, it been repainted and alot of work done to it to bring it back to it's former glory and should see action next year in SEDIV. I'm sure that when the car is fully sorted it will be a blast to drive, but I can't say that my time in the car was that enjoyable and that I cared much for the 948s.
Hap Waldrop
Yoda
Offline
Getting back to the Watts link/lateral support subject, the trianglated three link or as I've heard it called "the wishbone" is now becomning a popular choice because it take hardly any substructure to mount, thus keepng weight down. Imagine a big trianglated A-arm if you will, that attaches to the chassis at the same plane as the pivot point of the trailing arms, or leaf springs in our case, and then goes back and attaches on the rear end housing. I've started to see more and more of these pop up. The biggest thing you would have to do is find the attachment point on the rear end for the best roll center, but since I've seen this application on several Spridgets that has already been determined and it is too easy, it's the drain plug on the rear end housing. Now mind you this area was beefed up with a piece of round stock drilled and tapped to accept a rod end and you have to relocate the drain plug to the side, but still easier and simplier and lighter than any Watts or Panhard bar I've seen. Anyway food for thought, one of the benefits of being at the race track and looking at other's cars.
