Technical SUSPENSION, A-bone question

Does anyone have any pics or have a diagram or something on a rear suspension of a model A with a buggy spring with split wishbones? My thanks in advance. Btw, Happy 4th to everyone! p.s. Mine is a 29 5 window with mustang (I think) rear.

 

i can take some shots of how i did mine...gotta get my niegbors digi camera though...i did mine a little different but it works.

 

yeah kartbreaker lets see some more pics of your roadster...thanks

 

I have that set up on my T roadster. I just noticed yesterday, after 5000 miles, that there are cracks in the welds and a small amount of fluid leakage where the bones attach to the axle tubes. I'm runnning an 8"Ford rear end. The split bones cause alot of stress on the thin axle tubes. I know there have been previous discussions on the board about this issue and I'm now rethinking the whole thing. I'm not going to change the basic set up but I want to make sure when I fix it that it won't break again. Having the fixtures completely surround the axle tubes, I think,is critical to the success of this set up.

 

Think about running a rear wishbone, made up of long rear radius rods ('35-'36) connected together with a front wishbone yoke. I know of several high-mileage hot rods running this scheme with Ford 8-inch rearends without even a hint of trouble.

 

Thanks AV8, that's good advise. I'd have to give up on the split wishbone look but I'd end up with a more reliable set up. There isn't any stress on the axle tubes using what you suggest. I wonder if Frank Mack had the same problem but maybe he never side slipped the clutch. How one drives with split wishbones on the rear, I'm sure, will effect reliability. PS Sorry if I hijacked the post.

 

heres some bad drawings of what i got going down..

 

for some stupid reason i cant post the drawings...even though i srank them way down..stupid computer..sorry

well hot damn it works...

 

Kartbreaker. Do your drawings kind of small. I do all my Booze the Dog ones at about 4 inches square or so. Then I scan them in at that size and attach them. Dont know how big your drawing is but thats what works for me. Just trying to help out!

 

I wonder if having the spring in front of the rear axle takes some of the stress off the axle housing?

 

dirty dug....No, it doesn't.

 

Hello to Mike and John.
Well, once again tradition (mistaken design) gets in the way of good engineering.
I just looked back in my "archives" and this subject has been "hashed" quite a few times.

Split wishbones solidly attached to axles is an open invitation to something breaking.
Av8's advise to leave the wishbones attached to a single point like Ford designed them is the ONLY way to go unless you follow some of S.J.'s ideas that he came up with.
S.J. - time to repost the excellent Autocad drawings you shared back a while ago.

 

I remember a real good side on shot of a Magoo built A roadster from years ago. It had triangulated bars that all converged at a single point at the back of the rear trans crossmember. The bars were bolted through a big rose joint (heim joint) anchored to the crossmember.
We replicated the setup but used a rubber bush when we built the Clockwork Orange roadster, about 20 years ago. It's a great setup, simple, geometrically correct, and other than the rubber bush or heim joint, no moving parts.
Mart.
In response to Dave's note below, here's the best pics I have at short notice, you can see the bars coming forward from the axle, towards the middle of the car. (Pics are hosted on martsrods.com)
M.

 

Mart, your design works very well. Maybe you can post some pictures.
I seem to remember seeing the setup one time.

 

SJFast- No, I didn't think spring location would make a difference. Kartbreaker's drawing looks like it would snap right apart. I know there are better alternatives but I sure like the look of split bones not to mention the $ I spent to have the suckers chromed. Any suggestions as to how to keep the look and perhaps add unseen members and perhaps a flexable connection for the bones?

 

oh horseshit...driving an old hotrod is an open invatation to things breaking...lets see in the old day they melted coathangers and stickwelded shit and drove all over the damn place.if you build it up right and how i did it im not gonna have any problems with that.i see some what of a point ..but theres a reason i took my rearend to the best weld fab shop in town..so it would people have been running slit wish bones forever..and thats my two cents worth..

 

I had my rear end tig welded and straightened by one of the best. The axle tubes are very thin. The welds didn't fail it cracked the tube at the welds. Don't get me wrong, I'm not attacking you but rather looking for the best alternative. The set up I used is at least as good as your drawing but it failed. It's not a matter of too much horsepower either. My car might produce 125hp if I'm bragging.

 

Ok, kick this one about.
simple radius rod to each side of the axle, single point attachment to the axle, no attempt to control axle torque at this point. Use a rubber bush for comfort.
Make a single triangulated torque reaction bar, solidly mounted to the axle, positioned to the right of the diff, coming forward and mounted in a rubber bush to the X member or a crossmember. The forward mounting is approximately in line with the forward ends of the side radius rods.
Sideways location by transverse leaf or panhard rod.
The advantages of this is:
No twisting stresses in the axle as the car rolls.
Having the torque reaction member located to the right of the diff compensates for the imbalance caused by pinion torque and equalises the tyre bite during acceletration.
(Complex subject)
Mart.

 

Here's what I think Mart is describing. I agree !

 

With the above torque arm you can take oval tube wishbones and mount them split to the side but with pivots at BOTH ends as in this drawing. Ignore the torque tube on this drawing. Mount the spring ahead, over, or behind the axle. Above puts the least amount of stress on the torque arm.

 

Please explain the connection at the crossmember. That set up is similiar to what kept me awake last night.

 

That's it, SJ.
The side mounted radius rods on the green roadster are super cool. Early ford tapered tubing, chromed, would look great drilled too.

Dug, the mount to the crossmember only has to control torque. the side rods control fore and aft forces. The little link does away with having the pivots all in line.

In essence the rear suspension on my coupe was similar.

Mart.

 

Male and female rod ends screwed together. One connects to the arm and the other to the tranny crossmember. 3/4" min...maybe even 1". Lugs on both sides of rod ends to create a shear connection.

 

Thanks SJ, I'll have to give that some thought. As a side note: The old cars that had split bones probably had a torque tube making the set up OK. Would that be a correct assumption? The configuation you suggest would take it's place.

 

Nope....that would be the most "bound up" way it could be done.

 

OK, I get it. I'm still confused by the front connection. Some people call me slow.

 

The new Am.Rodder has a great article on Nelson Dupre's buildup of the frame for Lance Sorchik's B-400.Might not be what you're after,but I'm sure some here will find a little food for thought.

 

[ QUOTE ]
oh horseshit...driving an old hotrod is an open invatation to things breaking...lets see in the old day they melted coathangers and stickwelded shit and drove all over the damn place.if you build it up right and how i did it im not gonna have any problems with that.i see some what of a point ..but theres a reason i took my rearend to the best weld fab shop in town..so it would people have been running slit wish bones forever..and thats my two cents worth..

[/ QUOTE ]

Trouble is, it might might be me that you run into head on when that setup breaks off the axle.
The drawing you show (and I'll assume the ends of the wishbones are attached to the frame) in fact creates a torsion bar out of the rear axle. So driving on rough roads could fatigue the welds on the rear axle and cause them to break off.
Yeh, split bones have been used for years, (solidly attached to the axle) but that doesn't make them safe!

 

I don't think the car he's got that set up on has been driven yet. I think he'll find the same results I did once , or if, he gets it on the road.

 

That design is totally off-topic. This whole thread has been about side-mounted bones. What I see would work after a fashion because the ends all have poly bushings that offer some "give" as the rear axle works cancelling some of the bind.. Of course, they will deteriorate from use and fail eventually.

If the "bones" are connected solidly to the axle housings, I fail to see what the two top arms are even accomplishing....