Triangulated four bar rear suspension

[Bucketman]

Meangreen,

I didn't forget you! Building 23 frames for yourself is pretty impressive. You named just about all the rear suspension designs commonly used but you left out one of my favorites and that would be the single lift torque arm. If it wasn't for the crowded packaging issues with a T-bucket it would be my first choice. As a dirt racer I know you're familiar with them. Those guys can stick tires to oil slicks with a T-arm car. I have put several in '32 Fords and later and they really work great. I'm not going to go into it now but they have a number of advantages in my opinion. Another subject for another time.

George

I'd like to see a picture of that suspension. I'll try Googleing it.

 

[Bucketman]

I've decided after hearing all the great input, to put a little more time into the rear suspension. I would hate to have a really cool T-bucket that was not fun to drive. In this case I believe building an arch to go over the differential, out of some 2" square 1/8", might be a better idea than switching location with long and short rods. I would like to post pictures but I'm having problems uploading.
Stan

 

[Hackerbilt]

Before you start making stuff do a full mockup to make sure you have all the necessary room you need for a bridge structure over the diff.
I really think you are making a load of work/complication for yourself, and the end result will handle no better than a simple parallel setup.
My car has race style ladder bars right under the body and while I could see me changing that for parallel 4 bars to enable a drop in ride height...I wouldn't even consider the change to triangulated.
I see nothing there that would be an advantage...and on top of that my frame height is already close to the axle AND my gas tank is at a height I like. Theres no real room to fudge these little cars around like you can with a later car.
You move one thing and a lot of other things in plain sight need to move too.
Try to plan at least 4 things ahead as you go...

 

[fluidfloyd]

I'd like to see a picture of that suspension. I'll try Googleing it.

Bucketman,

I'll see if I can post a few more later tonight.
George

 

[meangreen]

The single lift torque arm (pictured by George above) is what I was thinking of when I said 3-link and it's what I usually think of when I hear the term. I have built a couple of these; I put one under a '40 Ford coupe for a friend of mine and he loves it. However, I know it's only one type. The true 3-link has a short lower link on each side (similar to a four bar suspension), but has only one long link on the top, near the center of the rear axle housing, with an adjustable spring-loaded telescopic mount on one end. It supposedly reduces the sudden shock of acceleration and reduces tire spin off a corner. It is not practical for street use because of the constantly changing pinion angle.

For those readers out there who are not familiar with it, the single lift torque arm suspension is popular on dirt track cars because they can be tuned to induce "rear steer" into a chassis by changing the angle of the short links. Meanwhile, the loading/unloading due to acceleration/deceleration can be adjusted for track conditions by moving the pivot point of the center torque arm. The effects are usually less dramatic (and not adjustable) on a street driven car because we aren't in the habit of throwing our cars sideways on every turn while trying to put 500+ horsepower to the ground. The advantage IS, however, smooth no-bind operation which makes for a good riding suspension. Several GM cars have this type of suspension from the factory including '82 and later Camaros & Firebirds. The 3-link isn't really practical for a T-bucket because of the short distance between the rear axle and the transmission crossmember.

Triangulated four bars produce a good ride, but if you like to do "hole-shots" frequently you may be replacing upper bushings often. This is strictly my opinion, but I prefer either truck arms or beefy hairpins and panhard bar. Built properly (rubber mounted at the axle housing), they are bullet proof and reliable and provide good traction for "launch".

 

[Bucketman]

There we go. Now if I can upload the right picture.

 

[Bucketman]

My pictures are all too big. That one is a week old.

 

[Bucketman]

George, thanks for the picture of the suspension. I'm just trying to get rid of the pan hard bar. Looks like that T bar suspension still has one. I'll try to take a smaller picture so you can see what I did on my build.

 

[Bucketman]

Well, this is what I did with it. I only have it tacked on to axle, incase it doesn't clear. Should receive my radius rods today then I'll know if I wasted time n material.

 

[Bucketman]

Wasted time and material!

 

[James C]

Triangulated four bars produce a good ride, but if you like to do "hole-shots" frequently you may be replacing upper bushings often. This is strictly my opinion, but I prefer either truck arms or beefy hairpins and panhard bar. Built properly (rubber mounted at the axle housing), they are bullet proof and reliable and provide good traction for "launch".

Is there any room for a truck arm under a bucket? Any pictures of one? I've always liked that layout.

 

[AmericanGraffiti]

Well, you know we've all heard the phrase about keeping it simple "stupid." Not sure I like that phrase and and in no means imply that anyone is stupid. However, if we think about rear suspensions, it is all about making the pinion angle work and keeping the rear end axially located. How we do that really doesn't matter in my opinion, but these are the objectives at hand. I have really enjoyed this thread and the comments by experts in the field. I look forward to seeing how you figure this out for your cool ride!

 

[Hackerbilt]

How about something like this? It bolts between the cover and the housing...uses two gaskets of course.
http://thorbros.com/4-link-parts/s10-differential-bracket/s10-bolt-differential-bracket

 

[fluidfloyd]

How about something like this? It bolts between the cover and the housing...uses two gaskets of course.
http://thorbros.com/4-link-parts/s10-differential-bracket/s10-bolt-differential-bracket

Hackerbilt,

Here is a link

http://www.customclassictrucks.com/...classic_enterprises_trailing_arm_kit_install/

that details the Chevy truck trailing arm suspension system way better then I can describe it. I do like them and have installed several of them in past years. As you will see by using OEM arms, you will have a lot of arm hanging below the rear end housing. As T buckets are usually pretty low this will probably work against you. I have always put them in heavier cars and trucks that had a bit more ground clearance and longer drive shafts. This very system is mandated for NASCAR cars the last time I checked. The forward arm locations come together at the transmission cross member and ride in large rubber bushings allowing body roll/rear suspension twist to take place. They are really no different then a pair of Henry Ford's rear radius rods from the early days up through 1948 (I Think). You could just build the arms much like a hairpin or ladder bar and accomplish the same thing. I think the problem you will run into with a T bucket will be the normally short coupled drive line. Unusually short ladder bar style suspension usually don't ride that good. You would really need to lay it out in a side view and see how everything worked out. Pinion angle is fixed in relation to the two arms and will swing on that arc and that might be more then you want but I would have to plot it to really see what was going on. You would also have to run a watts linkage or a panard bar to center the housing. There is one other element that I should have mentioned earlier. When running a single lift torque arm, a true 3 link, or any other similar "free" linked system you will need to run an anti roll bar. If you don't you will have excessive body roll on hammering it at the stop light or when entering curves at speed. I personally think you should run them no matter what rear suspension you run. I like this system but not for use in these cars for whatever it's worth. Hope this will give you something to think about. Good luck.

George

 

[fluidfloyd]

How about something like this? It bolts between the cover and the housing...uses two gaskets of course.
http://thorbros.com/4-link-parts/s10-differential-bracket/s10-bolt-differential-bracket

That would sure be an easy and simple way to attach upper suspension tubes without having to weld a bridge in. I like this a lot.

George

 

[fluidfloyd]

George, thanks for the picture of the suspension. I'm just trying to get rid of the pan hard bar. Looks like that T bar suspension still has one. I'll try to take a smaller picture so you can see what I did on my build.

Bucketman,

Pretty much the only suspension you will find that doesn't need a centering devise is going to be a triangulated 4 bar, parallel leaf springs or an IRS unit. I'm sure someone will add another design but I'm just thinking of the commonly popular designs. If hanging the panard behind the housing is a problem there are other ways to get there. You can run the panard in front of and just above or below the pinion snout. Some people use a short bar and anchor it off of the pinion case bolt holes (8" & 9" differentials). Keep it long as possible. You can also lay a watts linkage flat and put it above the rear end housing. Google Images is your friend!

George

 

[Zandoz]

How about something like this? It bolts between the cover and the housing...uses two gaskets of course.
http://thorbros.com/4-link-parts/s10-differential-bracket/s10-bolt-differential-bracket

That would sure be an easy and simple way to attach upper suspension tubes without having to weld a bridge in. I like this a lot.

George

I'd forgotten about those S10 brackets. There are also Wishbones available that go with those. If you get one of the wishbones with a johnny/flex/super-pivot joint (not a bushing) on the frame end, you have the upper link(s) half of a nice variation of a triangulated 3/4 link set up. That design is what I had planned before I got my ford 8.8 with built in upper link mounts.

 

[Bucketman]

I'd forgotten about those S10 brackets. There are also Wishbones available that go with those. If you get one of the wishbones with a johnny/flex/super-pivot joint (not a bushing) on the frame end, you have the upper link(s) half of a nice variation of a triangulated 3/4 link set up. That design is what I had planned before I got my ford 8.8 with built in upper link mounts.

I thought of using the cover bolts to bolt on a bracket, but was afraid my rear end would be leaking all the grease out. That full ring might prevent leakage. I already changed my mind again. The bridge is gone and I'm going with reversing the rods. Didn't look real good and to difficult to weld brackets between housing and bridge.

 

[Bucketman]

Here's where I'm at now. I made a bracket out of frame material (2 x 3 x .188) and have it clamped on. Need to locate the bracket farther forward or shorten the rod. Easier to move the bracket forward. First I need to weld up my perimeter frame before I get to far ahead of myself. All comments are appreciated. I only just joined this site but it has given me many ideas and some really good information.

 

[Bucketman]

Sorry about the two same pictures. This is the one I meant to post.