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  #16 (permalink)  
Old 07-31-2006, 04:03 PM
 

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Quote:
Originally Posted by BillyShope
Only if you locate a third link above the axle.

If you're intent on fabricating something, I'd strongly recommend a 3link. If you follow the instructions at my blog, you have the opportunity to dynamically cancel driveshaft torque.
Would the Panhard bar constitute a 3rd link? If not, would the 3rd link be parallel to the lower trailing arms, or would it triangulate across the differential? If I use a 3rd link, will I still need a panhard bar?

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  #17 (permalink)  
Old 07-31-2006, 04:55 PM
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A third link will attach at the top and go forward. It controls axle wrap. The panhard bar is not a third link and it controls axle movement side to side. In you original idea sketch, you haven't a way to control axle wrap up. Using the lower links binds the rear axle.
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  #18 (permalink)  
Old 07-31-2006, 07:02 PM
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Quote:
Originally Posted by bigjoe
Would the Panhard bar constitute a 3rd link?
As johnsongrass has already pointed out, the answer is "No."

Quote:
Originally Posted by bigjoe
If not, would the 3rd link be parallel to the lower trailing arms, or would it triangulate across the differential?
If you center the upper (3rd) link and triangulate in both directions, you have what is called a "triangulated 4link" and a Panhard is not required. But, as you've said, you don't have room for this sort of thing. Commonly, the 3 links are parallel in plan view.

Quote:
Originally Posted by bigjoe
If I use a 3rd link, will I still need a panhard bar?
With a conventional 3link (as in a new Mustang), you definitely need a Panhard.
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Old 07-31-2006, 07:32 PM
 

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Does the upper (3rd) link need to be parallel to the ground or the lower links, or either? I think I may have this worked out.

If I use a triangulated 4 link at the top, I can dispose of the panhard bar, make the lower links attatch with a bushing at the rear-end and with the ball-joint at the frame, it should work, correct?
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Old 07-31-2006, 07:33 PM
 

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By the way, I REALLY appreciate all of you guys' input here! It has been invaluable, and informative!
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  #21 (permalink)  
Old 07-31-2006, 08:16 PM
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Quote:
Originally Posted by bigjoe
NO, I welcome the picking apart! That's how I'm gonna figure this all out. I decided to use the lower link setup because I already have a set of split wishbones on hand that are too short to be used as a frontend setup, and I want to: A) Keep cost down, B) Use as many old or OEM parts as possible, and 3) I have a hard time doing "what everyone else is doing". I like to be different.

As for wheel hop, this thing is NOT, NOT going to be a powerhouse, nor do I drive like a fool, so that shouldn't be an issue.
No problem...just build it safe. I'm not a "me too" rodder either. My '39 Chevy is Ford from the gas pedal to the road. SBF 289, 3-sp trans, 8" rear, MII front. It just irritates the hell out of a lot of people, and I wouldn't have it any other way...

George
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Old 07-31-2006, 08:34 PM
 

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Originally Posted by gdubstub
No problem...just build it safe. I'm not a "me too" rodder either. My '39 Chevy is Ford from the gas pedal to the road. SBF 289, 3-sp trans, 8" rear, MII front. It just irritates the hell out of a lot of people, and I wouldn't have it any other way...

George
Good for you! I think that hot rodding would be in a lot better place if people would not rely so much on aftermarket parts. If everyone would rely on what they know, instead of what they could buy, this hobby would be MUCH cooler than what it is. If you cant't build it, learn! That's my thought. I didn't know how to reverse a steering box until I tried tonight. Now I'm done, I have a great feeling of accomplishment, and I'm closer to my goal of " I built it ALL myself."
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  #23 (permalink)  
Old 07-31-2006, 09:06 PM
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That upper link will set you anti-squat so you can drive straight off without the rear hiking up or squatting. Do a search or look up Billy Shopes for further explanations.
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  #24 (permalink)  
Old 08-01-2006, 12:57 AM
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Here are some pictures of a 3-link I built, just fo ideas. It was made to fit in a tight space, and utilize all the room I had.


Cost was about $75 to build my own. With link ends and laser cut brackets.
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  #25 (permalink)  
Old 08-01-2006, 04:42 AM
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Joe, click on my blog address (in an earlier post in this thread) for more information, but, briefly, when viewed from the side, it would be best if the intersection of lines through the links was on a line which passes through the rear tire patch and the intersection of two other lines, one a horizontal line through the car's center of gravity and the other a vertical line through the front tire patch. Just take a reasonable guess at the center of gravity height. It's not all that critical.

Twisted, you have, for all practical purposes, a "triangulated 4link." Very nice work! You're certainly far, FAR ahead of myself when I was only 17 years old. I can only hope this crazy world will allow you to develop to your full potential. My only criticism would be that it would appear that the link line intersection, as described in the previous paragraph, would be behind the axle. This is certainly no disaster for a street rod and, if the car is completed, I wouldn't worry about it. But, if the car is still in process, you might consider changing the lower links.

Last edited by BillyShope; 08-01-2006 at 04:49 AM.
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  #26 (permalink)  
Old 08-01-2006, 08:09 AM
 

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Yeah, Twisted, when he mentioned 3 link, I was thinking back to your project journal, i think I have room for that, also, I think I can make them intersect just as explained.
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  #27 (permalink)  
Old 08-01-2006, 08:52 AM
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Quote:
Originally Posted by Twisted Minis
Here are some pictures of a 3-link I built, just fo ideas. It was made to fit in a tight space, and utilize all the room I had.

Cost was about $75 to build my own. With link ends and laser cut brackets.
Twisted,
Aside from its elegent simplicity and excellent use of space, what other benefits come from a 3-link vs. a 4-link setup? What kind of suspension do you run with this setup?

George
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  #28 (permalink)  
Old 08-01-2006, 09:47 AM
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Quote:
Originally Posted by gdubstub
Twisted,
Aside from its elegent simplicity and excellent use of space, what other benefits come from a 3-link vs. a 4-link setup? What kind of suspension do you run with this setup?

George
You addressed your question to Twisted, and I'm certain he's perfectly capable of answering it, but allow me to touch on some generalities. A chair usually has 4 legs, but 3 are all that's necessary and, with 3, you don't have to stick that matchbook under the 4th leg to keep the chair from shaking. Only 3 trailing links are necessary to locate the axle. The 4th is an unnecessary redundancy.

Now, someone might point out that you don't even need 3 links. You could locate the axle with 2 or...perish the thought...even 1 link! I suggested to Big Joe that he might eliminate the binding by using bushings at both ends of one of the links. So, that would be the 2 link arrangement. But, actually, you don't even need that link with the 2 bushings. That which remains would be the 1link suspension. But, it should be obvious that the 1link is simply not practical. Focusing all the forces at a single welded juncture between link and axle housing would mean certain disaster. You might get the 2link to work satisfactorily with a street rod. But, for a high torque application, you need at least 3 fully articulated links.

Why not a 4link? With 4 links, you run into the binding problem again. That is, there is a binding problem, while cornering, UNLESS the 2 links, on each side, are parallel. (That is, parallel to themselves, NOT parallel to the ground. Many 4link suppliers recommend the parallel setup while the car is in operation on the street.) But, someone might point out that a 4link can be preloaded and a 3link cannot. Yes, that is true, but the preloading provides equal rear tire loading for only one value of driveshaft torque, while the 3link can be arranged asymmetrically to provide equal rear tire loading for ANY value of driveshaft torque (dynamic cancellation). (See my blog for details.)

I assume, when you ask about "suspension," you're asking about the type of spring. You can run any kind of spring you like, from torsion bars to coils to air bags.
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  #29 (permalink)  
Old 08-01-2006, 09:56 AM
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Quote:
Originally Posted by BillyShope
You addressed your question to Twisted, and I'm certain he's perfectly capable of answering it, but allow me to touch on some generalities. A chair usually has 4 legs, but 3 are all that's necessary and, with 3, you don't have to stick that matchbook under the 4th leg to keep the chair from shaking. Only 3 trailing links are necessary to locate the axle. The 4th is an unnecessary redundancy.

Now, someone might point out that you don't even need 3 links. You could locate the axle with 2 or...perish the thought...even 1 link! I suggested to Big Joe that he might eliminate the binding by using bushings at both ends of one of the links. So, that would be the 2 link arrangement. But, actually, you don't even need that link with the 2 bushings. That which remains would be the 1link suspension. But, it should be obvious that the 1link is simply not practical. Focusing all the forces at a single welded juncture between link and axle housing would mean certain disaster. You might get the 2link to work satisfactorily with a street rod. But, for a high torque application, you need at least 3 fully articulated links.

Why not a 4link? With 4 links, you run into the binding problem again. That is, there is a binding problem, while cornering, UNLESS the 2 links, on each side, are parallel. (That is, parallel to themselves, NOT parallel to the ground. Many 4link suppliers recommend the parallel setup while the car is in operation on the street.) But, someone might point out that a 4link can be preloaded and a 3link cannot. Yes, that is true, but the preloading provides equal rear tire loading for only one value of driveshaft torque, while the 3link can be arranged asymmetrically to provide equal rear tire loading for ANY value of driveshaft torque (dynamic cancellation). (See my blog for details.)

I assume, when you ask about "suspension," you're asking about the type of spring. You can run any kind of spring you like, from torsion bars to coils to air bags.
Billy,

Nice write-up...even old dogs can learn new tricks. Referencing the pics that Twisted posted, the 3-point center link connection looks it removes the need for a panhard bar and positively locates the axle with respect to the framerails, with the other two links providing the necessary axle travel.

I'm building a '41 Dodge 3-window coupe this winter, and I think I just found my new setup. Twisted's frame mods look equally interesting. I'll bet it sits right down on the ground.

George
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  #30 (permalink)  
Old 08-01-2006, 10:30 AM
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Billy definitely covered it all there. Lol.

The 3 link does keep the axle centered. I think of the upper link as working like an A-arm.

And Billy, I couldnt move the lower links any farther forward, otherwise they would be in the ground. The setup should work fine, the bars are parrallel with eachother from 4" to 10" off the ground.

And my suspension is air.

It is set up to lay frame on a 27" tall tire, and it will lift over 10 inches off the ground, which is unneccessary, but the ability is there.

Last edited by Twisted Minis; 08-02-2006 at 02:13 AM.
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