Technical dead perch

Clem, maybe you find something in here that answers your question.

https://www.jalopyjournal.com/forum/threads/tranverse-springs-tech-info.1112840/

There are comments in there from HAMB guys who I hold in esteem who go to some lengths to explain stuff.

Personally, when the dead perch hit the commercial hot rod market, I thought they were the best thing since sliced bread.
However over the years I have done a full circle when it comes to my opinion regarding dead perches and can honestly say I would much prefer to have a Panhard rod every time.
A Panhard to me now is still a compromise as I'd much prefer something like a Watts link but they are not easily installed into hot rods, especially up front.
Pete & Jake used to market a very short Panhard rod setup that attached to the transverse spring retainer plate and reached out in one direction to the axle near to the spring perch bolt.
I also thought that they were a good idea, but it seems the bars length from center of spring to perch bolt was way too short to be any good and they lost popularity.
So when you look at a dead perch, it really mimics the same principle of the Pete & Jake Panhard rod, reaching from the spring chassis contact point at the center of the chassis and reaching out to the perch bolt position.
So if the short Panhard rod is not really satisfactory, then neither could the dead perch principle be...
From what I know the success of a Panhard rod depends on achieving the maximum length possible to reduce the arc difference during movement.
This being the main feature of a Panhard rod then if the length is too short or minimal, then it certainly can not be operating at its optimum design criteria.
There is also a degree of contention regarding which side a dead perch should be install on when combined with cross steering.
I have my own theory, but find it difficult counter the arguments of the opposition, since the facts are not supported by the reality of driving from what I can determine thru feedback.

 

Thanks,
I posted a few comments on that thread.
Post 39 is how I understand it to be, as regards preload.
A most interesting thread for sure !

 

I had a '41 Ford my first car more than 60 years ago and as best as I can remember it didn't have an anti sway bar. Back then we called a panhard bar an anti sway bar and what many now call an anti sway bar was called a stabilizer bar.

 

I agree with your observation about the popular name being ‘stabilizer’ but I think even that is also incorrect....I think more accurate to call it an ‘anti-roll’ bar as it does (or is intended to) minimize body/chassis roll in turns.

 

Anti-roll or anti-sway bar has a different function from a Panhard rod.

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Not sure for whom your comment was intended....but to be clear, my post above was NOT in regard to a Panhard bar....but referred to the various names for the 'sway' bar, 'stabilizer' bar, 'anti-roll' bar, etc. The Panhard bar is a separate animal.

Most words and nomenclature have 'official' recognized definitions. Unfortunately, in common usage, that is often lost and words mean whatever the person speaking or hearing them thinks they mean.

Sort of like the the old saw about "England and America are two Nations separated by a common language" .
(One might add 'OZ' to that saying)

 

Just a general clarification - not meant as a correction

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In the 70s Alfa Romeo's GTA racers used what they called a "sliding block" rear suspension.

https://www.alfaholics.com/articles/slotemaker-gta-octane-april-2016/

 

Not sure what I was looking for in that link and pic's and writing is pretty small.
Any chance that somebody could copy the pic in question and post it here for us all to see without trying to wear 2 pairs of glasses.

Thanks.

 

I 've been running dead perches on my Coupe for 31 years and love it. I have also built several other roadsters and sedans with them.

 

It’s a variation of the device mentioned in earlier posts where a ‘pin’ on the axle rides in a vertically slotted bracket, on the frame, to keep the axle centered during suspension movement. In the Alfa article the photo shows the sliding piece to be a rectangular block shape instead of a pin shape. Increases surface area of contact point, presumably to reduce the concentration of the load and wear on the moving parts.

 

In the 50s the DeDion rear suspension found favor with the Euro formula car set. Either a Watts linkage or center pin was the typical method of lateral control.

 

Wow Rootie, that top pic is cool! A Pat Warren quickchange, look at those inboard brakes, and notice the U-bolt upward travel stops. Lots to see there!!

 

1950s British HMW formula 1 car.

 

Sames as mine today...left side

 

I used a setup from the Deuce Factory years ago. It had a bearing mounted to the axle. It rode up and down in a channel mounted to the crossmember. It worked excellent until the channel wore, then you had bad wander. Shim stock took the play out, but didn't last long. Was a very clean setup (I had coilovers) for a straight axle car, just too much maintenance. And it never wore out close to home.LOL

 

was it noisy? could you feel the metal to metal contact as it went over bumps?

 

I have been watching and reading this conversation with interest because I am currently at this stage of modifying my roadster pickup. I had planed to install a panhard bar, but was having a hard time finding a way to mount it without it hitting something. I found the dead perch on the SoCal site and found an old thread here where someone welded their spring links to the perch (not what I am going to do). To sum up all the information I have read here and other places the dead perch works, only if there isn’t a lot of travel in the axle it is mounted on, panhard bar works well with a flat spring or an arched spring, and a sliding block is cool, but requires maintenance. I bought this truck finished when my kids went to college, and was working too many hours to build a car, what I learned was it better to build your own. I drive hard and fast in or on everything I own, and good looking car doesn’t alway drive well. Let me know if disagree with my summary.

 

No,never made any noise. My complaint was you had to work on it every 4-5,000 miles

 

Seen it done with a skate board wheel


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I wonder what the side-to-side force actually is?

 

On my first T, I had Vega cross steer, and it was squirrelly. I tried a number of solutions, and a dead perch finally fixed it. And it rode just fine.