Chassis Fixture

[Coyote187]

Hey,
Soon I will be starting to rework and modify my 69, one of the things I'll be doing is changing the multi leaf over to a tri-four bar setup. Now you might be asking why, well I decided on that because it’s just something you don't see every day, also from what I've read it is a very lets say tunable setup. I have never done anything like this before, but I am a welder/metal fabricator and have been for the last eleven years and I have a good Idea on what I can do.
Now my question is when I build my chassis fixture, what should the mounting points be and what dimensions do I need to concern myself with? I understand that the frame rails have got to be square and the placement of the rear-end is very important. But does the body need support any where in particular?
If anyone has drawings or pictures that would be a big help.

[wally8]

Just so we can get the terms straight, what exactly is a "tri-four bar" in your mind? 3 link? 4 link? satchell? A-body style? I haven't heard this exact term before so I could use some more description.

Thanks.


Wally

[Coyote187]

The tri fuor bar is like the one used on "Novacane" on the Lateral-g homepage. Art Morrison makes some, I'ts kinda like a chevelles.

[awr68]

I beleive he is refering to AME's triangulated 4-bar...no need for a panhard bar with this setup....

I hope you are planning on using new 2x4" tubular frame rails, the stock sheet metal 'top hat designed' rails will absolutly not handle the lateral force of the triangulated bars...if you are using new frame rails (back halfing) then you have nothing to worry about.

This setup actually isn't as adjustable as you may think since the only thing you can fully adjust is the coil spring rate...all other points are fixed, well you may be able to do minor pinion angle adjustment, but nothing like a 4-link. My 4-bar on the other hand has an adjustable panhard bar which will help add in the final tweeking, along with changing spring rates and shock dampining...

[wally8]

Hhmmmmm. Looks like a cross between a chevelle style four link and an inverted Satchell.

I agree with awr68. This setup won't be very adjustable. I'm wondering how this would be better than a chevelle setup which is generally considered to be one of the worst choices if you were going to fab something from scratch.

Just a guess but I assume by lowering the upper links from what would have been a chevelle location you decrease the tendency to move the roll center laterally and lower it as well. The added lateral angle and length of the uppers compared to a chevelle probably help this too. Maybe even moreso than lowering the links.

Granted, you want something different but different isn't always better. What do you want the car to do ultimately?

I'm going to try to get some more info on this setup since I'm not familiar with it in that form. I like it from a packaging standpoint but I don't understand the kinematics enough to really see how it works.

Should be interesting to see how it works.


Wally

[awr68]

Well, Katz did get Art's '55 to out perform the stock C4 using this rear suspension and C4 front suspension....but I don't know how he had it setup compared to their off the shelf kit, I guess there's proof it can work though!!

[wally8]

Yeah, that's who I was going to talk to of course :)

I guessed that was what the 55 was running but didn't know for sure. I'd be pretty happy with that sort of performance.

I'm interested to hear his thoughts on it. He doesn't hang around here though.


Wally

[Coyote187]

[QUOTE=wally8]Hhmmmmm.
I agree with awr68. This setup won't be very adjustable. I'm wondering how this would be better than a chevelle setup which is generally considered to be one of the worst choices if you were going to fab something from scratch.

If this is what I end up doing I will order a premade kit (unwelded) and fit it myself,
And whats with this 55 your talking about? I would like to see it.

[Coyote187]

never mind I found the 55
:eek:

[PhaseShift]

Coyote- To answer your question about the chassis fixturing / assembly fixture....

Yes, the better the surface you have to work with, the better your chances of coming out on track when you complete the thing. There are many ways to do this, but the important thing is to have a surface that you know is flat and true in all 3 dimensions. You also need to be able to clamp your tubing / widgets in a way that they will stay in place while welding and cooling. This is especially important and I have seen a lot of times where people did not do this and regretted it later.

In our shop, we use a surface stone quite a bit for weld up operations. It is flat, solid and very resistant to flex. That may not be the ideal thing for your shop, but you can get the same results out of very heavy steel tubing. Maybe consider getting a shop who can weld that up for you and guarantee that it is "right" in 3D and get that into your shop to use as the frame fixture.

The next car I do will be here at our shop in ShenZhen. I plan to get a new stone just for that and do all the design work based on the widgets and hard points bolting on to machined, exact fit mounting locations which are tied to the stone. In essence, that gives me a manufacturing fixture so that we could make more chassis or replacement parts in case I crack the thing up. Who knows, maybe we will make pro touring chassis in China and ship them to the USA. How many will fit on a shipping container?

[CraigMorrison]

Well, Katz did get Art's '55 to out perform the stock C4 using this rear suspension and C4 front suspension....but I don't know how he had it setup compared to their off the shelf kit, I guess there's proof it can work though!!

The tri 4-bar that we used on the GT55 project build is the same thing that we use on our chassis. There were no "tricks" that we used to get this to work. Katz lowered the upper bars down to the C/L of the housing to reduce the roll center. Packaging wise, the tri 4-bar works great on the 55 chassis and no mods are required to the floor!

The front was our own IFS design and not C4......

Hope this helps!