Technical Another Dead Perch Thread

I've read every thread here on the topic of Dead Perch. I know it's origin, it's positives and negatives so this is not why I'm bringing this topic up . I'd like to talk about why it makes sense that a dead perch with cross steer would be mounted on the driver's side vs the passenger side as so many "think". Maybe they think this because this is where the other end of the panhard arm attaches, at the axle. I'll start in the form of 2 questions then a think about it question. Which side of a vehicle frame is a panhard arm mounted to ? Isn't that the same side the steering box is ? Does this not keep the axle located like a panhard arm in respect to geometry especially to the tie rod it's self ? Let the theories begin, now !

 

Was taskin to a guy at a car lot the other day ... He has a panhard bar on the front of a hot rod . he said it was scary as hell, when he got on it the car would shoot left and when he stepped on the brakes it would pull weird also. I think he was saving issue cause of that front panhard bar but im no expert. I should stop in and see if he ever figured it out.

 

^you might want another opinion than that guy above! Panhard bars are very common and work well. Open up any chassis catalog or web site (P&J, TCI, etc.) and you'll learn / see them properly installed. Gary

 

This sounds like a problem BEFORE a panhard was added,not after. HRP

 

or the panhard is too short, you want it as long as possible

 

How about how much suspension travel play's into how a dead perch will affect thing's. Stock height lot's of suspension travel ? Not so good. Lowered with very little suspension ? This is where I believe the issue or debate is for the street and how it doesn't mess things up. Agree or disagree ?

 

Hey i said i was no expert lol

 

I too read through every post for similar reason. RHD car. Built frame with rear panhard welded on left side.
Thinking at the time it didn't really matter. Now would like a front installed to cure wheel shimmy at 65.
Problem…Front needs to weld to right side. Think I'll try new tires 1st, then consider dead perch left side.
Your thoughts.

 

If a panhard needs to be as long as possible to work properly, a dead perch is basically asking for disaster. The common front spring is about 32" long, so half of that is your new 17" dead-perch/panhard. I'd hardly call that "long".

My Dad had a '32 with cross steer and no panhard or dead perch, and he felt some uneasy jerks on bumps. He installed a dead perch and it worked for him. I've never used one though, so I can't give a first-person account.

 

The length of the bar is the most import element affecting the sway of the body. Making the bar as long as possible is the key. If one cannot make a pan hard bar long enough to keep the radius it travels is too big one can use a Watts link which allows for a much shorter bar but in effect makes a larger radius of travel. Watts link effect pictured below.

 

I put a dead perch on my '32 coupe, on the driver's side, about 12 years ago. It has never had any issues with darting, bump steer, or any other unusual handling characteristics. It has a 525 cross steer steering box set up

 

"Shimmy at 65" maybe try a steering damper

 

When I had my deuce roadster there was no panhard bar or a dead perch and sailing into a curve it was Ok but just as the spring unloaded when you turned the steering the opposite way it would scare the crap out of me.

I had a perch on my 4 door and it was ok but I have used nothing but panhards on every thing since,I prefer the fell, almost like a sports car steering. HRP

 

From what I see I'd think that some of the guys having trouble with a Panhard bar setup have mounted the end that goes to the frame too high for visual ecstatics and that creates too much of an angle on the bar causing excessive side movement on the axle. The old "I think I need one but don't want it to show" thing.

 

I always wondered where the line was. What magic voodoo curse is calling for a bar or perch to fix it? I don't doubt there are issues, too many people have solved their woes with a bar or dead perch. I have a dropped model a axle, Spring-over, '40 cross-steer. No Dead Perch. No panhard bar. No stabilizer. Turns like a Porsche and goes straight. Why are there no issues with mine or am I just blind and not caring about it? Just semi-rhetorical thought-blabbing.

 

The angle of your shackles will make a lot of difference. If the shackles hang straight down you will have more side-to-side sway. If they are at a 45 or less the sway will be much less.

 

I don't have your car to make any accurate determination as to what is going on. The purpose for my post is to get hard fact's about what work's. As you can see, there are those that have no issue using a dead perch. What did they do right as opposed to what went wrong and blaming it all on a dead perch.

See guy's, it works. It's voodoo I know, or is it ?

Dead perch, not watt's.

This is why I started this post to try and sort things out. But........ ?

This I agree is one key element to the darting around affect.

 

I have no issue with a dead perch... I do have issue with a panhard bar that is short enough that the radii of the arc traveled is to short which is caused by a short panhard bar... is all Im am saying

 

Back in the late '70's "Jake" did illustrations and explanations of all of this & it has been in every Pete & Jake's catalog ever since.

I wish everybody would get a copy & read it !!!!!

It's basic geometry, but you have to consider all the factors. (You all took geometry, right ?)
Sprint cars have the dead perch on the left side, they only go left & are pulling on the dead perch side. But they have side steering and are just trying to limit axle movement on the shackles. Not much impact on steering.

Now on to hot rods.
Cross steer with a transverse spring, should have a panhard bar or dead perch. Dead perch is the easy way out, a proper panhard bar is better.
Ideally the panhard bar should be the same length as the drag link.
The steering box & the panhard bar should both be mounted on the same side of the chassis.
The opposite end of the panhard bar will attach to the front axle/wishbone/hairpin(what ever works best).
Picture looking at the front of the chassis, head on at ground level. The panhard bar & the draglink should be parallel ( at the same angle). The goal is for the draglink & the panhard bar to work together & not fight each other. If you do these things, you will have no bump steer.
A dead perch simply turns 1/2 of the spring into a panhard bar, therefore, the dead perch should be on the right side of the car.

Go read your Pete & Jake's catalog !!!!!

 

^^^^^ Thanks Pete for that bit of information. That is the exact fact's vs opinion I've been looking for. But much more than that, it confirm's thoughts from being gray to black and white.

 

Thanks Pete, great explanation. Guess I will dig out my P&J catalog and do a little self study.
Phil

Sent from my Nexus 7 using The H.A.M.B. mobile app

 

Yes - Thank you.
I've had several straight axle cars. P&J chassis, Cornhusker, Creative Metal Works, all with Panhard as noted below (fixed under the left rail to the opposite suspension member) and all worked really well. Also had Metal Fab - Jim P car with a reverse wishbone from the rear of lower four bar mount to a center pivot on the axle that worked well.

On the other hand had a really low spring (so the shackle angle was getting closer to upright) heavier 39 deluxe coupe with a straight axle split bones, 525 cross steering, no panhard, parallel leaf rear, and when you leaned into a corner the axle would move on the shackles and required an immediate quarter turn of steering input for an oh-shit moment. Car needed panhard and main leaf.

 

Here is the illustrations and explanations Guy's and Gal's. https://www.peteandjakes.com/wp-content/uploads/2016/10/facts-about-cross-steer.pdf Just a side note. Pete and Jakes didn't show a dead perch available (today) nor any info about proper instillation.

 

Agree on half a panhard bar. However wouldn't a dead perch mounted on the right (passenger) have shackle movement being only on the left (drivers) side make for more bump steer ? Think about it. The drag link and axle will always be moving left and right of each other. Agree or disagree.

 

NOPE - Think about it, the Center of the leaf becomes the stationary mount to the chassis, just like the left side of the panhard, and the dead perch becomes the suspension mount, just like the right side of the panhard.
Even though mine was on the Left side, and was incorrect, it did work fine due to limited travel.

 

I've always used a dead perch on the right (passenger side)
If Pwood talks, just listen.

 

Are you saying that HiHelix's animation is showing a dead perch and not a Watts linkage?
If you are, then you're wrong, because that illustration is absolutely a Watts link.

If you are not, then I'm not understanding your comment.

 

Lol. I'll classify this under "juxtaposition". It won't work but it did.

 

I'll make it more clear. The topic is Dead Perch so why was the Watt's system mentioned ? Totally two different application.