A Halloween question: Are my bones too short?

Hey suspension gurus. I have been racking my brain designing my rear suspension for my lakes modified style car. Can you take a look at this image and tell me what you think?

I will be running a Model A rear spring behind a 9” axle with a fabricated Model A rear cross member. The spring perches will be adjustable in both height and width.

I want to run a three link rear with a pan-hard bar. Are the linkages positioned correctly and are they OK length wise? I do realize they are not the optimum length, they are on the short side, but will it work?

Comments and suggestions please!

Thanks,
Motor

 

Nice layout, but I think your rear links are too short. I would be afraid of the rear steering itself over one-wheel bumps.... Recently I read the upper links should be aroung 17" long when designing a tri 4-link. You might be able to bring this length down a bit for a parrallel 4-bar.

my 2 cents

 

You're gonna want the links to be around 18" (or more).
They should be somewhere close to the same length.

Looks like you aren't haveing a problem getting length on the top, you might try running your lower links outside the chassis to get length on them.

 

Actually, the top is whats creating the problem. The frame uprights represent the back of the body and are limiting the length of top link. The lower ones I can make longer by fitting inside the frame rails.

Any more ideas?

Motor

 

I built my own triangulated four bar, and had a similar length problem, all i can say is make em as long as you possibly can, maybe run the axle brackets further behind tha axle centreline?
My car rides pretty choppy in the rear, going to swap in rubber bushes to replace the urethane ones, and have the A spring reset with two less leaves. It sure hooks up good though, and sits flat thru twisty stuff, you can really feel how well located it all is with this setup. the ride quality on shitty roads is my only drama.Fairly sure longer rods would help...but no room.
good luck!

 

G.M. G-Body Short and long 4-link?

T.OUT

 

Is it a 4-bar? or a Tri-bar(triangulated 4 bar) or is it a 3-Link?

 

I was thinking parallel three bar with pan hard or maybe triangulated four.

How about using a ladder bar set up like a SoCal unit but dropping them realy low under the axle? Issue with this design would be it hitting the floor which site on top of the frame rails.

What is a: G.M. G-Body Short and long 4-link?

Motor

 

NO! I just drew it and CAD and it hit the floor, NO ROOM!



How about using a ladder bar set up like a SoCal unit but dropping them realy low under the axle? Issue with this design would be it hitting the floor which site on top of the frame rails.

 

bttt

Come on guys, keep the ideas coming, Please!

Motor

 

What is a: G.M. G-Body Short and long 4-link?
Most G.M. cars from 66 thru 70 odd use 2 long lower arms and 2 short uppers pointed from center out and coil springs.
Urethane bushing kits are readily available and with adjustable uppers are very tunable.
I've been kickin' around puttin' one of these set ups in my coupe for the reasons you mentioned earlier,Ie. My ladder bars (when the car is low enough to look respectable) bang on the bottom of the body on these old Okiehoma roads( I have about an inch and a half of travel before the afformentioned interferance takes place).Although I gotta admit the old turd sticks like glue in a turn due to the torsion bar effect they have.LOL
The g-body set up although a pain in the ass to begin with would allow the upper to mount at about kidney height(sittin' in the car) and the lowers to be parralell to the ground with loads of adjustability.
T.OUT

 

Like this:

 

That's the general idea but with the 2 uppers independent from one another.
There is a guy with a 3650lb 66 Chev. that uses a Sonny Leonard motor and a butload of nitrous to run in the low 8's on 10.5 slicks in a 66 Chev. with a modified upper factory style uneven 4 link.
Also AMC had a version of it with factory adjustable uppers in the 4 spd AMX's of the late 60's.
T.OUT

 

Can't tell 100% from the CAD drawing, but looks like the top bar might come into contact with the axle tube at full upward suspension travel (i.e., hitting a big frickin' bump). Other than that, same comments as above -- make the bars as long as you can.

What CAD program are you using?

 

Those illustrations show what I'll be building for my modified. Substitute the coils and tube shocks for torsion bars and lever-arm shocks (thanks, Metalshapes ).

 

Thanks for all the posts everyone.

Yo Baby, Do you have any images or sketches of what your talking about? I would like to see exactly where things need to mount.

I'm using AutoCad 2005 and Rhino for the complicated 3D stuff.

I have thrown the axle through it's travel and it will hit frame snubbers before it hits anything important.

Johnny Fast, How many links are you using there?

Motor

 

Two lower arms and a single triangular upper. I was under a '58 Bonneville the other day....same design.

I'll build a simple bracket that bridges the banjo center section and provides a mounting point for the single rubber bushing or spherical rod end bearing....whichever I decide to use.

 

Do you think having uneven arm length and altering pinion angle will be an issue?

How deep, front to back, as in total swing will that triangular link be?

Motor

 

I dont't have any pics but speedway motors has the 9" Ford housing set up for this deal or you can buy just the brackets and install 'em on your housing. Get your arms at the salvage orjust get a junk car nd raid 'em. I think Hotchkiss makes the adjustable uppers. Here is a link.
http://www.speedwaymotors.com/xq/aspx/parent_id.90/dept_id.92/qx/DisplayGroup.htm

T.OUT

 

Total swing on the upper (triangle) is 13".

I haven't plotted the arcs yet but the lowers I can make to any length or angle that works. I'm not afraid of minor pinion angle change...I have a fairly long driveshaft. Also....most of the suspension travel occurs at the ends...not as much in the center.

 

Johnny,

That design fits great in my design. Do you think it matters if I reverse the the direction of the triangle? I want to keep the pivots off the pumkin and flank it with two RATHER THAN HAVE THE ONE ON TOP.

Motor

 

i did a similiar setup on my track nose t....it had 2 bottom links that were around 14" long and a top a frame style link...it had 2 bushings on the frame end and a rod end at the rearend.....kept the pinion angle consistant thru out the arc.....was going to run with coil overs.....but went a little bit more track like and went with hair pins instead......sort regret changing it now.....but....i like the track look better.....haha brandon

 

How does it ride?

 

Reversing the triangle would probably work O.K. but it would add unsprung weight and might look a little funny. If it's under the bodywork....no sweat. Mine will be hanging out there in front of God and everybody.....

 

I know what your sayong, I just don't have room on top of the pumpkin. I think it may hit the gas tank.


Motor

 

Here is a quick drawing of what I'm thinking. Granted elements are not drawn as beefy as they need and connecting tabs are missing. The lower links will be split 1936 bones.

Motor

 

Will having links of such different length be an issue with this design?

Motor

 

It might. Do a CAD sketch and plot the arcs to determine how much pinion angle change you get in (maybe) 4" of axle travel...2" each way.

 

I did a little one the other day with (Illustrator, I'm a simple graphic artist), and it changes less than 2.5 degrees. I think I used 27" on the 36 radius rods, and 18" for the top arms.

 

I just did the CAD swing thing and I only end up with .65 degrees of pinion angle movement over 3.5" of travel. I also calculated that the axle will only move forward and back a grand total of 1/8" over 3.5" of travel.

I think this will work???

Motor