LocostUSA.com

Tried a search but it seems all the Watts link post here relate to centering a solid axle.

I'm going with IRS on a couple of projects.

Browsing links posted at another forum I found a mention that a Watts link to the top of the upright serves to eliminate wheel hop, and that a Watts link to the bottom of the upright acts as a trailing arm.
Is this correct?
Doing both might be possible but seems overly complex and likely to create a binding situation.

I really want to use a Watts link for my Jag IRS project but am dismayed at the limited ground clearance I will have if I mount it to the lower arm near the hub.
"Wheel hop" is not a significant concern for me.

Could compromise with properly set up trailing arms but that has it's own issues.

_________________
If I must be a one-man PC free zone, so be it!

Richard
What suspension problem are you trying to solve?
If a Viper can plant the power of a V-10 using anti-squat, you probably can too.
Dave W

If I understand, you want to use a longitudinal Watts set up with the upper link acting as a trailing arm to the top of your upright and the bottom link acting as a leading arm to the bottom of your upright? You are correct, the Watts linkage will rotate your upright which will I believe will bind the Jag lower control arm setup.

Here's a sketch of a pair of Watts linkages used to locate a solid axle. The links are shown shaded; the diamond shaped frame is to support the links. I used a pair to counteract the link rotation. This is too complex but I had to try it out.

The easiest way to get the equivalent of trailing arm on jag irs suspension is to run helm jointed arm ( fore or aft ) from the inner arm fulcrum points anywhere up or down the chassis to the lower arm as close as you can get to the hub. The longer the arm the better, like the picture below or run it backwards.

Bob

_________________
Build Log viewtopic.php?f=35&t=16640&p=187700#p187700

Mancave http://s1116.photobucket.com/user/mypic ... ow/mancave

I know I cannot put one arm above and one below the axle, they have to share a common bell-crank pivot point.

The question was to confirm that only a Watts link to the lower Upright/Knuckle will function as a trailing arm?
A link to the top of the upright would be a cleaner install if it would still serve as a trailing arm.

Trailing arms as show above would be simpler, if the car did not use a perimeter frame leaving nothing near the center to attach the arms to.
Sure I can create another cross-member to a add but that also adds weight and complexity to clear the drive-shaft, may interfere with the exhaust routing, and might become an issue with our local too #@%! tall speed bumps.
At least a low mounted Watts Link would have the low point right at the wheel so as long as I do not get a flat tire it should be fine.
Lower link forward of the axle and upper link behind like this.

I suspect this Cobra guy has at least 16" wheels, I have 15".

Another point that occurs to me regards a Watts link is that it would seem the links must have parallel angles as different angles would have divergent arcs so would compromise the vertical path.
Yet I see lots of pics with clearly differing angles, do they still work or are they binding/moving the axle fore-aft?


Vipers and anti-squat, what does that look like, and can it be incorporated into the Jag IRS without major alteration?

_________________
If I must be a one-man PC free zone, so be it!

Fore - aft wheel movement under power and braking.
Jag had a trailing arm mounted forward that only "Worked" due to having a big soft rubber mount.
Not particularly precise and not good enough for what I am doing.

_________________
If I must be a one-man PC free zone, so be it!

The whole of the jag cage was hung from the top with four rubber mounts, the two forward facing lower radius arms were the only thing stopping the cage rolling out from under the car and tearing the top mounts off under braking and acceleration . The cage top mounts were in effect the top suspension links. One could mount the top of the diff with two large rose joints and use rose jointed conventional radius arms too the same effect. Just thoughts

Bob

_________________
Build Log viewtopic.php?f=35&t=16640&p=187700#p187700

Mancave http://s1116.photobucket.com/user/mypic ... ow/mancave

Looks like I will be doing a low mounted Watts Link as pictured above.
I can see that a high mount would still allow the lower arm to try to rotate.
Trailing arms and mount gets in the way of too many other components.

We start will an ideal, then deal with reality.

_________________
If I must be a one-man PC free zone, so be it!

Took me awhile to figure what you guys were talking about.

One thing to keep in mind is that if you use a Watt's link or trailing arm of some kind you no longer need that Jag lower arm with it's 2 inner mounting points. Cars with a trailing arm can use a reverse wishbone with a single inner mounting point.

It also looks like you could built a new lower arm that did not require a trailing link, it would have 2 tubes going fromt he upright to the frame with a diagonal between them. These are both common setups on race cars.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.