Gear rack on watt's link instead of pivoting arm - Suspension fabrication for SN95

CornerAddict98 said:

In reply to Racebrick :

So, you understand how not having any movement from a panhard bar at all will help to limit the overall movement? Perfect! So what do you suggest instead of a panhard bar?

Why are you so concerned with the tiny amount of movement from a panhard bar? Is the 9" lighter than the 8.8?

In reply to bumpsteer :

I had not considered the jacking moment that you very correctly point out! The Alfas in question rolled a whole lot too, all their roll resistance was in the front. The sliding block set up I referenced in the Taraschi was well enclosed from the elements, unlike the environment of the underside of a Mustang. Putting the track on the axle and the roller on the chassis solves both of those, but at a huge unsprung weight penalty. Another thing I have never seen, but solves the roll center movement would be to anchor the watts rocker to the chassis and the outer arms to the axle. A panhard rod works perfectly well and weighs the least, and would be my choice with a live axle for sure. 

TurnerX19 said:

In reply to bumpsteer :

I had not considered the jacking moment that you very correctly point out! The Alfas in question rolled a whole lot too, all their roll resistance was in the front. The sliding block set up I referenced in the Taraschi was well enclosed from the elements, unlike the environment of the underside of a Mustang. Putting the track on the axle and the roller on the chassis solves both of those, but at a huge unsprung weight penalty. Another thing I have never seen, but solves the roll center movement would be to anchor the watts rocker to the chassis and the outer arms to the axle. A panhard rod works perfectly well and weighs the least, and would be my choice with a live axle for sure. 

An exact such watts link exists for the SN95 

http://www.fays2.net/fays2_watts_link_17_.html

In reply to CornerAddict98 :

The lateral locating arm on a diDion is called a panhard rod, and I have installed such on a Bandini which was a failed design for many reasons, none of which were the panhard rod! Watts linkages are most common on diDion, such as Alfa , but absolutely any location geometry which works on a live axle works on a diDion, and vice-versa. Given the excess mass of any Mustang, and your target weight the only thing to do is a panhard rod. Your low overall target makes the unsprung component all the more important as well. I can feel the difference between a watts linkage and a panhard rod in large travel situations, like curb hopping, but the difference in feel made zero difference in lap times. Once the total travel is under about 3 inches there is zero difference in feel either. The best handling live axle car I ever drove had a panhard rod, and relative to your Mustang pretty similat unsprung mass %.

In reply to bumpsteer :

I have largely avoided the Mustang scene in spite of predating Mustang I myself by 10 years.....The only large V8car I raced was a former Kelly Girl Camaro when it was already 30 years old. It had a panhard rod and handled just fine for a giant car. So did my Turner 950, and that was a perfect handler. It made my driving look better than it was....

I'm still having a tough time visualizing this gear rack setup. Is the gear rack mounted to the axle?

I think we've all hammered home that the panhard is the most succinct solution but I'm curious how this rack plan would layout. It's obviously not the lightest, or easiest, or cheapest but could be interesting nonetheless.

I think we were being trolled.

Op only posted in this thread and the only answer for why he was making things difficult for himself was "because racecar".

ShawnG said:

I think we were being trolled.

Op only posted in this thread and the only answer for why he was making things difficult for himself was "because racecar".

I thought he was just on a crusade against any lateral movement, and wanted to understand why. I want to believe this is real, and want to see it built.

Racebrick said:

ShawnG said:

I think we were being trolled.

Op only posted in this thread and the only answer for why he was making things difficult for himself was "because racecar".

I thought he was just on a crusade against any lateral movement, and wanted to understand why. I want to believe this is real, and want to see it built.

Me too. It's frustrating to post something and predominantly get answers to questions you didn't ask.

In reply to Gimp (Forum Supporter) :

That sounds like a really good option. Do you have any technical specs for this? link bar length, pivot bar length, mounting hight difference, etc?

In reply to iansane :

It would be contained in a small steel box, welded to the rear axle. I was designing it so it could fit on top of the center section, to keep it as close to the chassis as possible.

In reply to Racebrick :

the 9" (I assume) is heaviuer than the 8.8, however, it's also a place holder for when I have the funds required to attach a Dana rear end. the 9" happens to be cheap and easy to use witha lot of parts and aftermarklet support. So mainly a convenience thing.

In reply to bumpsteer :

Do you know of anyone who has tried attaching a watt's link like that? It sounds like it wouild definitely work, but it doesn't seem incredibly beneficial.

In reply to Patientzero :

That's a very unrelated question. Not only is an 8.8 completely irrelevant, due to the fact that my car comes with a 7.5, but I've currently got an LS block that after boring and honing, is being assembled to output about 500hp. chevy drive train with a ford 9" is a combination that has been known to work and is relatively cheap, so I'm planning on using it until I have access to something better.

In reply to bumpsteer :

That would have the same issue I was originally trying to avoid. The only way to use a watt's link and not have it is to mount the rotational axis of the pivot perpendicular to the ground-which this one isn't. The movement pattern that I take so much issue with is due to the arc inscribed by the ends of the pivot arm, which, when its not moving parallel to the ground changes the vertical distance between the two ends of the pivot as it changes the horizontal distance. That's why I originally didn't want to use a watt's link. The "no cutting, no welding" bit in their sales pitch is made almost entirely irrlevant by that fact, beacues to get it how I want it to be, I would need to both cut, and weld. I'd imagine the price point isn't amazing either.

In reply to Racebrick :

I'm planning on ordering parts soon, so ideally the prototype will be done and tested in less than a month. I'll post it if it passes.

In reply to ShawnG :

What other threads should I post in then? I looked for similar threads before starting a new one, so please, tell me, if you're so smart.

CornerAddict98 said:

In reply to bumpsteer :

That would have the same issue I was originally trying to avoid. The only way to use a watt's link and not have it is to mount the rotational axis of the pivot perpendicular to the ground-which this one isn't. The movement pattern that I take so much issue with is due to the arc inscribed by the ends of the pivot arm, which, when its not moving parallel to the ground changes the vertical distance between the two ends of the pivot as it changes the horizontal distance. That's why I originally didn't want to use a watt's link. The "no cutting, no welding" bit in their sales pitch is made almost entirely irrlevant by that fact, beacues to get it how I want it to be, I would need to both cut, and weld. I'd imagine the price point isn't amazing either.

I cannot conceive a suspension lateral position control device which would have more ideal behavior than a watts link at travels less than 3-4" and which allows for good roll center positioning as well as reasonable durability. 

If you draw out your gear rack concept in multiple suspension positions from both the rear and side view you will quickly learn that it is neither capable of allowing for necessary fore-aft displacement of the axle or that it actually keeps the axle in the center due to the intersection point of the rack pitch lines and spur gear pitch circle as the suspension travels, offsetting to one side of the spur gear. 

Someone should build this in Lego first. 

In reply to CornerAddict98 :

I mentioned the fact that this is the only thing you've commented on because we get a lot of spam posts here that do the exact same thing. Not to say that you should have posted somewhere else.

Considering how many competition vehicles have been built and driven over the years by people far smarter and more talented than any of us, there has to be a reason that a panhard bar or watts link has been more than adequate for most of them. 

Not saying your design won't work, just that the cost / benefit may not be worth it. There's probably another area that needs improvement where your time and effort would be better spent.

In reply to bumpsteer :

Not to mention that the axle rotates in pitch slightly as it moves through its travel, and also changes in thrust angle. Whatever the lateral location solution, it has to articulate in all 3 axes.

I understand the Watt's Link isn't exactly what you want. But it's the superior choice for the lame SN95 rear suspension setup. It's heavier than a panhard, but use an aluminum center section and you'll equal out.

My last car with a Watt's Link was a '63 Comet. With 275 horsepower I still ran out of tire and talent before I could fully compress the rear suspension. And that was with lowering leafs and lowering blocks (taking nigh 2" of travel out of the back end).

Far more critical to your on track success in an SN95 will be setting up the front suspension for proper camber gain. I have no idea why any one would swap a 9" for a Dana. A 9" with a full float conversion, Auburn diff, and 35-spline axles will be bullet proof behind any naturally aspirated LS. 

This seems to be going well.

In reply to CornerAddict98 :

So this is how you like to exchange ideas? I can oblige you. Your rear suspension "design" won't work, and focusing on this instead of fixing all the other things wrong with a sn95 makes people wonder if you know what you are doing. There is a reason people build race cars they way they do.  Smart racecar builders use a watts link, or panhard on a live axle car. Exceptions to this include space factors, or class rules. What class are you building for anyway? You never even mentioned that detail, even though it is critical.  If you were a smart racecar builder you would take the good ideas and use them, even if they aren't your own.
 

In reply to CornerAddict98 :

Have a nice day man...