Technical SUSPENSION, A-bone question

I was refering to kartbreakers sketch. That other deal doesn't make any sense to me at all. Ignorance is trying something you're not sure will work, stupidity is trying it again after it fails. I try only to be ignorant.

 

well i dont plan on being in canada anytime...so as long as you dont come to texas you'll be alright.
i think the mighty 215 six im running is not goona pop anything up..the post was about spitwishbone ways to set up on a model a frame..i showed a way i did mine.and again plenty of people drive with split wishbones...some even drill them out... oh my and have zip for problems.
i dont have airbags in my t either.

 

I'll stick my oar in again, here's a couple of observations.
I once ran a sort of pro street Thames 3ooE van with Alston non-parallel 4 bars, and with the narrow axle, I didn't have a problem with axle twist or fatigue, the problem was that the inside wheel would want to lift as the body rolled.
Re the photo from the magazine: I afree with sj, the radius rods should not be solidly attached to the axle. The bars would tend to bend before the axle twisted or fatigued though. BUT I don't like that design, my coupe had a very similar setup, and without a pabhard rod, the slight sway in the shackles lets the axle steer, rotating around the forward attachment points (or the theoretical convergence point) of the radius rods. This can effect high speed stability. My coupe had a problem with this, and I reckon it was the rear suspension that was causing it.
I would modify the design shown by running the lower rods parallel, either outside or inside the frame. The car could still swing slightly on the shackles, but at least the axle would remain straight across the frame.
In SJ's diagram showing the triangular single torque reaction bar, it is feasible to run just the top part, as a single bar, as in the magazine photo, as long as the side rods are mounted kinda low. There is a slight bending force applied to the axle, but it's pretty strong, and would be ok.
All my observations assume mild motors and street usage, wild horsepower lumps and dragstrip usage require specialised approaches.
Mart. (Mr bloody Limey know-it-all)

 

Kartbreaker, Please let us know how your split wishbones hold up once you get on the road.

 

Why don't you use heay-duty Tie rod end as on a split front wishbone.Add one "Torsin Bar as Mart described wiht ruber mount at one side and a heim joint on the other and you are fine.
Michael

 

So, what I can distill off of this conversation is:

The best rear suspension is a 4-bar setup, but the better you hide the fact that it really is a 4-bar, the cooler it becomes ? Or just stick with stock...

Is that what I'm hearin?

Later,
J

 

That's what I gather. I think I'm just going to scrap the split bones this fall and fab up a four bar, won't be able to see it anyway plus it kinda goes with the vega box. Just hoping I can limp through the summer but I won't be driving to Bonneville.

 

Burnedup:
4 bar best?
I dunno.
My guess is that potentially 3 bars is better, you just have to overcome the idea that something is missing. If the two lower arms are parallel to the sides of the chassis, and fixed to the axle below the axle tube, and kinda level with the road, and the single top bar is mounted to the right of the diff, attached high up on the casing, and slopes down so the front is lower, then some benefit is gained.
It doesn't have to be complicated.
Mart.
PS: Gowjob29, you getting all this???
PPS: Just so there's no misunderstanding, "fixed to the axle" does not mean solidly, it means via a bush or spherical joint. In fact all three bars described above have bushes at each end.
M.

 

I think it's time to review whats been discussed here.
Ford used "bones" originally to keep the front and rear axles in their proper positions.
When "rodders" started to modify the frames and drop the bodies, the bones got in the way.
So the "quick and dirty solution" was to "split" them and move the ends of the wishbones out to the frame.

The technical problem was, now there was two "levers" that tried to twist the axle when the frame twisted.

The origin of 4 bars allowed up and down movement of the axle on either side without creating a binding action on the axle. But not everyone likes "the look."

If you examine S.J.'s drawings closely you'll see that the out side "bones" can pivot BOTH at the frame AND the axle. The centre "tourque" arm keeps the axle from "rotating." (thats what the original tourque tube was for on early Fords)

I'm not trying to say that split wishbones are WRONG; just that if you keep the original bones SOLIDLY attached to the axle
you set up some serious strain at the axle and the frame.

 

"The centre "tourque" arm keeps the axle from "rotating." (thats what the original tourque tube was for on early Fords)


"I'm not trying to say that split wishbones are WRONG; just that if you keep the original bones SOLIDLY attached to the axle
you set up some serious strain at the axle and the frame."



AHHHH YES... I fully understand and have mental tranquility of the "3 bar." Badass and simple.

 

Drag race ladder bar theory doesn't relate to splitting wishbones very well...
Ladders are usually only around 32-34 inches long, attached to the housing by full 360 degree double shear plates and use large, low pressure drag slicks which conform to the surface thus limiting the binding forces to the axle.
A ladder bar is designed like a truss...it will not fail due to any sensible load a car will see due to the triangle shape it has.

Wishbones, on the other hand, are much longer...the attachment point does not surround the axle housing and there is no upper bar to handle the torque from acceleration or braking forces.
This allows the tabs that the bones are bolted to on the housing, to fatigue at the weld and also stresses the joint at the rear of the bones, sometimes allowing that to break off as well.

A stock Ford absorbed the braking and acceleration forces thru the torque tube (notice name) and the bones just handled the impacts of the individual tires against road hazards...nothing compared to what they experience in a Hot Rod as the primary axle location device.

I would use 36 type bones, angled to the center or mounted to a front wishbone yoke (AV8) or rubber bushed like a P&J ladderbar setup. The tabs for the axle could be made to completely surround the housing for fatigue strength or a torque arm could be attached to the top of the diff housing and run forward to attach to the forward end of one of the wishbones. That would take most of the strain off of the axle/wishbone attachment points and allow more actual torque control.

Making wishbone style 4 links would be easy, as previously stated...

I've noticed some people using the fragile later (48ish) bones, complete with stock rear forged ends (!), as the only attachment for the rear axle...with no additional torque control.
My opinion...SUICIDE.
With the possibility of taking a few others with you...

Bill

 

Im planning on running split rear bones,will now design a mount that encircles the axle shaft,thanks to this thread,
my question is,does the torque control arm have to run forward to an imaginary line between the wishbone front mounts on the frame?that would put it somewhere in my left hip,which might hurt.
So will running a shorter torque arm cause it to bind?considering it will be rubber bushed at the chassis end.dont plan on having a lot of suspension travel,maybe four inches.its in an A chassis modified roadster(buggy sprung).
I cant quite get it all visualised in my head due to a hangover.

 

http://cgi.ebay.com/ebaymotors/ws/eBayISAPI.dll?ViewItem&item=2422373393

 

i am using 36 split bones on my roadster its on the road for about 2 yaers now , no problems yet . kept them as long as possible , tie rod in front is in line with A pillar . a guy at the L A roadster show tried to tell me how wrong that is and it would break , but he could not tell me where it would break .all parts are still unpainted so i can check for cracks , like i have been since i started driving it .

 

lowsquire...the length of the torque arm isn't critical as all components (torque arm, split bones, springs, etc.) work independently of each other. The rubber bushing at the front of that arm will be better than a rigid connection but I'd still recommend a double rod-end. That allows the arm to work side to side as well as forward and rearward while cancelling axle torque reactions.

 

S.J., I dug out the article from American Rodder. (the picture posted earlier)
The lower arms do have pivot (hinge) points on either side of the axle underneath.
So what was created is in fact a triangulated "four bar." The use of TWO top bars probably
was personal preference.

Still like your design the best.

 

Ahh man! I want to thank all you guys again. Hey Mart, I love your site and thanks for the input too. I'm trying to get all of it,lol. This is my biggest turn out on a post. Most of mine some how end up on page two before I have the time to check it,hehe. Thanks again everyone!

 

Question for av8: Is any additional bracing required, ie from the top of the dif housing to the front of the wishbones to handle the torque of a mild SBC, when connecting some 35-36 radius rods in this fashion? Like the idea and have a yoke off a 41 Merc. Was planning on using a couple of HD 4 bar ends spaced as close as possible.

 

So, why not use your split wishbones as the lower bars of a triangulated 4 bar setup. Make 2 upper bars that come from above and either side of the center section and out to the upper part of the frame (boxed of course) on the inside where it won't show. The (say 36) radius rods would show as they do on that green car above. The upper bars wouldn't be seen from the side as they'd connect on the inside of the frame. There must be a reason it won't work. I can't believe I'm the first to think of it, but I've never seen it done. Use the transverse A spring above the axle and fab up some shock mounts ala A-V8's book and call it done. Frame guys please tell me what I'm missing here. I was planning on doing this on a stock model-A frame kicked up frame hight in the rear. Only problem I see is raising the trunk floor so it clears the upper bars during suspension travel.

 

Well Joe, you'd have to destroy the 36 bones to make a proper 4 bar setup. I wouldn't do it to 36's...too valuable and strong as they sit. Use later bones with a bushing added to the rear to give proper freedom of movement to the suspension for a four link or brace the 36 bones at the rear with a gusset or a torque link and use them alone with the front pivots mounted close to the forward U-joint or, like AV8 mentioned, run a stock Ford front axle pivot ball setup, welded securely to the front of the rear bones, close to the U-joint to replicate the stock Ford geometry. That sounds like a really good idea and I'm going to use it as part of my system IF I have room. I have an axle locating idea that seems very workable AND I don't think its been done before! Naturally, once I do it this fall, it WILL be proven that EVERYBODY did it back in the Fifties!
Thats OK....
Not much left you can be first at! LOL

Bill

 

Smokin Joe....That will work fine as long as the wishbones and the two top links can all pivot at both ends. It's similar to a Chevelle 4-link. For quiet and comfort you might want to consider using rubber or urethane bushings at the forward ends of the four arms. Mounting the Model A spring over the axle will eliminate extra loading on those arms too.

 

smokin , if my setup would fail or start to crack , than this is my plan B : weld a machined collar to the axle where the mounting flange for the 36 whishbone is now . machine another ( 2 piece ) collar that grabs the 1st one and also bolts to the 36 whishbone , same for both sides of the axle .that would locate the axle the same in every way but rotation . and to take up rotation i would put in a torque arm like whats in a late model camaro . but before i start to redesign my car i would like to talk to someone that actually seen one fail , not some guy thats repeating what he has heard from another guy who was working with 2nd hand information himself .

 

Actually...you just need to go back to the fourth post on this thread, Metalshapes!
His welds are tearing clear of the housing!

Bill

 

hacker , i know , i read that too , but it sounded to me like he cracked the axle , not the whishbone .

 

This may be off the beaten path some but, what's everyones take on a tri-angulated 4-bar set-up? was looking at a C.E. chassis yesterday with that setup on rear and a 4-bar on front. is this a good setup, bad? or just too modern? thanks for clearing this up for me

 

Well...yeah, I guess your right...
But its still failure caused by fully split wishbones putting too much stress on the welds/housing...

Somebody here was having or had an issue with 36 bones cracking at the joint. Can't remember who...

Cool little roadster you have!
Would you be willing to give out a few secrets on your handling setup?
ALWAYS interested in hearing about hard cornering buggy spring setups!!!
I want to dust a few late models with my coupe and the chassis starts going together in the fall... In fact, I just ordered the replacement front rail sections from the local metal fab today.
I was gonna use tube but some HAMBers suggested this route...I'm always ready to listen to good advice!

Bill

 

thanks for the kind words bill . no real secrets on the 28 and ill tell you anything you would like to know .

 

well maybe one secret , its a unibody car

 

Can anyone tell me what the story is with this rear end set up ( I' cant remember where I got the picture from).
It looks like 36 type bones with a bar joining the two?
Anyone have any clues on its purpose?

Adam F

 

Unibody! Hmmm...thats interesting!
Thought about doing that too as the coupe is to be sectioned and MAY need to have the floor dropped into the rails. I'm leaning away from that at the moment...hoping the floor drop won't be necessary. I might need that extra bit of room for the suspension I want to run. The mock up in the fall will tell the tale.
What did you do? Make a welded tube framework and add the panels later?
At the very least, my coupe will have a braced roll bar setup...for stiffness and safety. I want a front hoop as well...but again, mockup needed!

Adam...Thats different isn't it? Seems like it was done to absorb some of the torque reaction and spread it into the bones AHEAD of the wishbones welded joint and axle mounting lugs.
Is it a good idea? Could be... I think it might be best to just weld the top and bottom of the square tube and leave the verticals alone. Good place for cracks to start if it were welded completely. Still a fair bit of strain being passed on... Kinda hard to visualize where strain is being placed with that setup in various road conditions.
JYD 32 is a welder up on that stuff...hope he adds a comment.
Hope EVERYONE adds a comment!

A very interesting thread!

Bill