Need Your Opinion On This - Brackets welded on Axle

i want to mount the upper trailing arms on this axle at an angle. As you can see, the brackets have to remain parallel to each other and the bolt must be perpendicular to the trailing arm. So, the brackets are seated kind of funny on the axle tube. Is this ok or should I make changes? They are only tack welded:

 

It should work ok like that, but it will look a lot better if the tabs are parallel to each other when viewed from the tab side as well as parallel for the pivot bolts.


I hope you're planning on rounding the tab corners and breaking the sharp edges of the tabs.
Nothin like working under the car and cutting hell out of yourself on a sharp edge you've left behind.

Besides, what you're doing by building this car is showing the world your skills and workmanship.
It doesn't take long to do it right.

 

If I was that close to just using the factory upper control arm mounts I'd sure as hell be trying to...

Why aren't you?
The pumpkin's gonna hit the bottom of the back seat anyway...

 

I think the mounts will work out, but it looks like the upper and lower arms are coming together pretty close to each other at the frame attachment point. That's gonna make for some pretty hokey geometry when you put power to it, not to mention the extreme change in pinoin angle as it goes thru travel.

If you added another crossmember, you could probably use the stock upper rear end mounts and maybe get the geometry a little closer to what it should be.

 

No offesnse here but your metal fits arent too good Work on those till they contour with the axle tub not a 1/8 inch of gap. Alos the tabs should be square and level across not staggered like that.

Also i would take some DOM tubbing and some heim joints and make new bars (links trailing arms whatever the hell you want to call them) THose factorys arent that strong to start with not only that you will save so much more room and ger much cleaner and much more functional results.

My 2 cents. anyway. Theres is book called Door Slammers the ch***is book that goes over 4 links, 3 links and everything else. ITs really good.

 

The connection point on the axle is much too low, a couple of inches lower than the stock position. Be prepared for m***ive wheel hop under hard acceleration.

You really should re-engineer the scheme to use the original mounts on the axle. If you're planning on putting some serious hard-launch horsepower in this car consider using Lakewood "hop stoppers" which raise the connection a couple of inches higher than stock and will eliminate wheel hop. Not HAMB traditional, but a very effective old musclecar trick. And while you're at it, box the control arms with a plate welded along the bottom. Another old musclecar trick direct from GM.

Mike

 

Thanks a lot fellas for all of your feedback (keep 'em coming!).

The reason I chose not to use the stock mounts on top of the pumpkin was because of the angle of the trailing arms - they will hit the body bolt mounting area as well as the lower trailing arm brackets. There would be a lot of interference.

You are right, I will make the tabs/brackets more flush than what I have there. The tops will also be rounded off and smoothed. I want to make sure the brackets will be flush on top of the axle tube.

I will look into that book you recommended. I went with the trailing arm idea because of cost and well, just trying to make it work. This is going on a ;47 Chevy Fleetline. Next time, I will go with a 4-link kit. More info welcomed please!

 

I'd try awfully hard to use the factory mounts, but I knwo sometimes things are easier said than done. If you do end up welding tabs on have you considered how you are going to deal with the warpage that localized welding stress will place on your axle tube??? One "trick" would be to use a O/A torch and heat up the remaining tube - immediately after welding - simulating a 360 degree weld bead. Just blasting a weld on may work for some, but you may find out that you "eat" wheel bearings after a while.

Just thinking out loud......

 

I think you should consider an un-equal 4 bar set up. Using short upper bars is not as complicated as it may seem. You will need to "plot out" travel and pinion angle changes but so be it. In reality rear axle travel really only ends up about 4-5 inches total, and you only use 1/2 that most of the time except in extreme driving conditions. The excess is what good snubbers are for. Think it through just a little more. You see something YOU don't like or you wouldn't be asking would you? I'm not wild about it...I'd build something boxed and stronger. And don't worry about pulling the tubes with the weld. You're covering an area there of what 2 inches? 3? A good hot clean weld will do you just fine. Bevel your edge and do a nice fillet weld and don't look back. Where do I get off with that statement? I've done litterally hundreds of welds on dozens of axles and never had one break, tweek, warp, wheel hop, or leave the line crooked, or drive dog-tracked. And my fellow drag racing bretheren beat the livin **** outta their race cars.


Look at it another time and you'll see what you got a little better. Trust me on the unequal deal. You obviously have the skills and knowledge. It's sometimes amazing what some conversation or a smoke and cup of coffee brings to a project.

 

Sorry for the double post...thought of this as well. Do I dare ***ume you don't want or have room for a panhard bar? That's why the angle on the uppers? You may indeed have room for one and it would make life easier and neat looking if you could run the 4 bars parallel to each other and use the panhard rod for tracking and adjustment. The longer the panhard rod used the better the control and ride.


Once again sorry for the double post.

 

Is that going to be enough surface area? I would think a wider piece of steel
with more depth in the pocket would allow that bracket to wrap around the tubing deeper.

 

Gaps are a good thing.... especially with 1/4" and heavier stock.

My only thing is thinking you want the bolt to run on the same parallel plane as the axle. Otherwise, I think it'll bind. You just need to make the inside plate longer (or the outside shorter... or both...)
Also, you have no adjustment, so nail it in there square, the first time, or you're gonna be crab crawlin'...


JOE

 

Looks like a barrel of trouble to me.
Compromised angles, relocated pivots, shortened arms...your really out on a limb if you don't know exactly what your doing considering EVERYTHING is modified.

I'd use 60's Chevy pickup style angled torque arms (think NASCAR) up to a fabbed crossmember and a panhard bar myself. Looks like you have the room and it would be safe, reliable and easy...plus the axle has nothing above it to contact your floor.

 

Whoa, a lot of good info.. Yeah, I think I should just get a 4-link kit. ANy reputable places I should look into?

I think the set-up I have may be too dangerous, not sure myself...

 

This is what he is talking about, these have been kicked up because the tires were 32" tall. but you get the idea.

 

Whoa, swee...this is the NASCAR that was talked about?

 

Nascar uses a similar design, its a long trailing arm, in the pic you can see the two arms that go up behind the cab and attach. Sorry the pics are bad, I just happen to have those on file.

 

IMHO, four bars with a panhard rod are trouble on a car with decent wheel travel. Reason being the axle ALWAYS goes sideways with any up-down travel.
Sure NASCAR racers use 'em, BUT, NASCAR tracks have fewer potholes, and the cars have less wheel travel as well. And, after all, you are not building a NASCAR racer.

Ride in an early 50's Olds, if you want to experience how bad rear bump steer can be.

The setup you have there IS the best, if set up properly. The longer arms, the better, longest on the bottom two, which are parallel to each other.
Roughly speaking, the bottom two should also be parallel to the ground, and the upper two angling down slightly from the pumpkin, viewed from the side, naturally.

Using the factory brackets on the pumpkin should be considered highly, even if you have to make changes on the body or frame or both.

Cosmo

 

Cosmo! NASCAR doesn't use a rear 4 bar!!!
We're talking just two long arms controlling location and torque, hard mounted to the axle and aimed towards the center of the car, about where the tailshaft of the trans is located. Rubber bushings and close mounting at the front allow easy articulation and NO self steering. Panhard bar controls the side to side shift. It's like a low profile P&J ladder bar setup.
You can even buy a kit if you don't want to fab it yourself, its that common.
(Can't remember the site though...)
It was just a thought...

I agree he should use the factory mounts if he stays with the triangulated 4 bar. Problem is...he needs to use frame mount locations that closely match the frame mount locations from the DONOR car to get his geometry right and he says he has interference.
Short factory 4 bar arms and relocated pivot points can mean funky handling...

 

I used this set-up in my 46 Chevy coupe, using all the factory mounts, and trailing arms. Works very well.
I didn't have any problems with body mounts, but did have to raise up the trunk floor to fit around the rear, arms, and crossmemeber to mount the uppers and springs (actually, bags).
It's a hell of a lot easier to move a body mount, or raise a floorpan, than to fool around with suspension mounting points, make brackets, and try to re-engineer a proven design! AND, it's only sheetmetal, so if your welding skills aren't the greatest, it really isn't as important as doing suspension modification!

 

Chop, you are the only person I have communicated that has done this set-up. Do you have pictures? Maybe take images?

As far as your crossmember for your upper trailing arms, was it square tubing? If so, dimensions? Any help or description would be GREATLY appreciated! Thanks...

 

I'll PM you pics tonight.

 

Great, thanks!

This is my next plan of attack before I toss the trailing arm idea and go with a 4-link kit (Crude drawing). Basically, I will extend the lower trailing arms and move the lower trailing arm brackets 3-4 inches forward. Then, I can run the upper trailing arms from the top of the pumpkin (as many of you suggested) to the frame rail (brackets will be made):

 

chopolds, would you mind posting some? I'm trying to come up with a triangulated 4 bar setup for my '50 chevy and need some pictures.
I don't think there's room for one, but I don't want a panhard bar, so I'm going to try and figure something out.

 

I think one design may be to extend your lower trailing arms to clear for the upper trailing arm bracket. I rather not have a crossmember running across the frame because of the interference between the yoke coming off the differential and the crossmember...

 

this was done on a 54 chevy.

 

OK, I'm back
Here in pic 1 is the start, locating the upper trailing arm brackets. I believe I used 1 x 2" tubing, 1/8" wall, mounted vertically. The reason for the smaller size, is that I put in another 1 x 2 farther forward, to act as a shock mount, and I used 1/4" plate to connect the 2 pieces, as the mount for the springs (or air bags, in my case). This combo is pretty strong!
Sorry for the lousy pics, I didn't intend to do a how-to with these, just for my own album.

 

Next I made the mounts for the lower arms. 2 x 3 this time, as they are stand alone. Here they are just tacked in. I welded fully, and added a large gusset on top, and toward the rear for extra strength.

 

Here is addind additional material to the top of the frame. Later I cut out the original frame underneath, so the rear can go higher up into it, so you can ride lower. Kinda like "C"ing the frame, just a bit different. 2 x 4" tubing, 1/8" wall. Heated it while applying pressure with the C clamps. Then weld.

 

another consideration is having the lower arms angled and the uppers parrallel (what I am doing) this gives more "seat room" as any notches are to the sides. although this does cut down on room for mufflers under the seat. the lower arms mount near the axle ends and converge near the centerline of the car. I am using some jonny joints from currie and plain poly bushes from suicidedoors.com.