look at this... I think you should rethink this setup... It may save your rear seat, but could endanger your life... http://www.jalopyjournal.com/forum/showthread.php?t=224871
Seems like it wouldn't take much to fix it. I would think you could just pie cut and plate the radius rods to bring them as far inboard as possible and add some sort of torque arm.
if you do as kevin says, and bring the font ends of the bones as close together as possible( and ideally meeting directly below the front driveshaft uni) then make a beefy bracket and run a link from the centre top of the diff down to the same mounting point as the front of the bones (slightly offset to clear the driveshaft), you will have a bind free system that i would trust up to maybe 200 rear wheel HP. ALSO do as Jimmy white did to his 36 bones..this strengthening is VITAL and looks fucking Kool too. Im building this setup later this week and will do a post on it, prob. a bit late for tech week, but watch for it.
I'm curious about the chains...? Are they stayin' in there? They will have no effect if that thing let's loose, just more shrapnel... Don't run it like that, you've asked because you have doubts, trust your better judgement. We don't want you to post from a hospital bed.
Look at using a set of '46-'48 axle tubes with the spring mounts on them and turn them 180 deg. so the spring mounts are on the front side. Lots of T-buckets do that. Just go with aftermarket ladder bars like the Pete and Jakes or make a set. That way you can use the stock crossmember to mount the spring (just not a Model a spring). With a good set of Ladder bars you should be fine and able to use your frame like you have it.
The chains are to lift the body on and off with my cherry picker... not for the suspension...DUH... In the original application of '35-'36 bones the spring is mounted behind axle- weight on the split end of the bones is forced up, the way I have it the weight at split end is forced down, SAME WEIGHT - just different direction. I've seen other cars run in this same fashion-without problems-
Why do you ask if you know better than everybody? Your MAIN problem is not the spring mount, it's the way you mounted the bones at the front......
After what happend to 5wbomber I would definitley rethink using rear bones, as mentioned above they aren't meant for that kinda abuse. Save your pennies or build a 3 link, 4 link, or ladder bars.
This statement clearly places the chains in the setup...DUH... I will retract my previous post statement, as you know it all. RUN IT!
Moving the spring reduces the effective length and puts more stress on the bars and less of it through the axle housing. A lot more, since the ends of the bars support the entire rearend. At least, it looks to me like the spring mounts to the bones and not the rearend housiing. De-triangulating the bars adds torsional stress on both as it's harder for them to let one side of the rearend move up and down idependent from the other side. At least that's what I gather from reading up various threads on this board. Also, that putting new stresses on 70 year old parts is usually asking for trouble. I've seen guys run paralell bars, but it seems like they let the rearend rotate where they connect, or there's some other way to keep them from trying to bend when one tire is going through a pothole 4" deep. I can't see where that happens with this setup. As far as trunk space goes, is this a hot rod, or a grocery cart? Now, back to the original question. Can you run that? Sure. You can do anything you want. But uh, get an AAA membership or make sure your insurance pays for a free tow. I hardly know anything about setting up a rearend on one of these, and I don't see myself being comfortable with it.
Man, I got a bad feeling about that setup. I don't think those bones will take the stress -- they weren't that strong to begin with.
Since you posted the pics after you had this all welded up, I gotta assume you're just fishing for compliments on your setup... That's too bad because I think if you had asked the question earlier you could have saved yourself some grief. Your setup is aesthetically ugly and convoluted at the very least. Moving the spring in front of the axle is goofy on anything but a modified. The reason the spring was behind the axle, attached to heavy cast mounts from Ford was to lengthen the sprung area (someone help me with the correct terms here) of the car so that the short wheelbase cars didn't ride like buckboards too much. That move alone is going to provide you with a much more 'active' ride that the stock 36 setup... The next issue is the untriangulated split bones situation in the rear... This is bad because as the axle goes up on one side, the bones have to flex to compensate for the lack of a flexible mount at the rear. That's why the bones were triangulated from Ford so that they could rotate around a single point in the front. The way your setup is now, you will eventually break a mount on the rear end. It's been happening for years and it will happen to you with this setup. To fix it, either cut the mounts off the rear and make new ones that angle the ends in as close as possible in front, or do like Kevin said and pie-cut the bones to bring them in at the front. This triangulation coupled with the use of a cross-spring should basically eliminate the need for a panhard bar as well. The closer together in the front the better and the closer to the tranny u-joint the better. That's the next issue... I can't tell from the pics but if the front of the bones don't line up with the u-joint on the tranny, you should try to run a slip joint in the drive shaft somewhere, or you're going to have bind as the rear articulates. This could cause a failure at some point too. Probably at the front bone mounts but it could be anywhere. These aren't huge fixes... You could probably turn it around in a weekend.
Off topic a bit but.....I know the Ford sales pitch about moving the springs off the axle centerline was about lengthening the 'spring base' and improving ride, but I think the real motivation was to allow the cars to ride lower and to increase interior space. If there's a ride improvement, I'd say it's from the longer springs rather than the location of them relative to the axle. On the subject at hand there's been some really good advice given. While I'm not against the spring in front idea in concept, I have observed over the years that the more you use parts as-is the easier (and safer) these things come together.
When I was building my A roadster (circa 2002) I was going to use Model A rear radius rods-- Talk about weak little spindly things! Then I saw a post from Buzzard how he twisted his rear end so bad the rear trailing arms snapped free and stood up on end! I went with 47 radius rods, gusseted and grade 8 bolted directly to rear axle brackets that were arc welded to the rear end housing!
As far as suspension goes....I have split bones on my T roadster. After about a year I noticed cracks in the welds where I attached the bones to the rear end axle tubes, 3/8" cold rolled plate. I hadn't surrounded the entire tube, also didn't have a panhard bar. When I repaired it I surrounded the axle tubes and added a panhard bar. There is side to side motion of the rear end with a transverse spring, not much but, enough to cause this type of failure. The panhard bar is very important with slit bones. But with unsplit bones this is not as critical considering the geometry ....The reinforcement to the '36 bones in a previous post is also critical if you're running them split or unsplit with an open drive car. Another thing to keep in mind is the thickness, or should I say thinness of the axle tubes you're welding to. I've seen some 8" Ford rear ends, Mavericks, that are only about an eighth of an inch thick but have also seen others out of early Mustangs that are a quarter of an inch. They may be a better candidate for this type of application...You should also buy and read some books about chassis building of find a good mentor in your area. New ideas aren't necessarily good ones.
The very core of the split bones setup (also ladder bar) is that it forces the rear axle (or front) to act as a sway bar. Mock it up - the radius rods are forced to move as a part of the axle, twisting either the axle or the frame, and something WILL break. Ladder bar setups are for the strip, where there aren't potholes. The further weakness of split bones is the concentrating of rotating torque forces into a very small area. A four bar eliminates this sway bar-like twist, but requires a fifth bar to locate the axle from side to side. Enough rear wheel travel to allow a decent ride and this setup will always have some bump steer. Doubt me?? Drive an early fifties Olds on a bumpy road. Note: transverse leaf with short shackles (as original) do not need the panhard rod. A Hotchkiss setup uses just four bars, with two of them triangulated to locate side to side and two parallel to take the torque. And no bump steer with this one. As an aside, I once knew a guy with a Harley and a trailer he pulled behind the bike. He used a swingarm-mounted hitch. Naturally, the trailer tongue broke repeatedly. Each and every time he had the tongue welded, trying to strengthen it each time. Finally, Success!!! The tongue no longer broke!! The hitch broke instead. Meaning: those with split bones and/or ladder bars will all tell you that the setup works, and it does, in a limited way, BUT, the engineering is unsound, and these will all break something eventually. Cosmo
Don't give up on your idea brotherman. Trunk space is golden when road-trippin'. Check this thread out (similar to what you're trying to accomplish): http://www.jalopyjournal.com/forum/showthread.php?t=222 Heed the warnings on tearing up your axle tube walls. A friend of mine welded his radius rods to the axle tubes (quarter elliptics/radius rod setup) and after about a month of shakedown driving the axle tube walls began to crack. You mentioned you're using urethane-bushed rod ends which will help absorb some axle wrap when you get on the gas so you're on the right track there. Seems like some triangulation of your split bones and a torque arm is all you need. Maybe you can work a panhard bar in there too to take a little lateral stress off your bones. Post your solution when you're done--would love to see it.
looks like a good ride. Keep at it, all the engineering problems eventually get solved. Always best when you put some thought into it, and you have done that here. Keep us posted with pics as you progress.
I think its interesting that more people have told you your problem can be solved by triangulating the weak part, than by replacing the weak part itself... non-triangulated ladder bar cars have, and continue to, live on the street. Its a tired subject, is it better to have them mounted inboard, toward the tail of the trans.? yes... will it fail disastrously? probably not, at least not anytime soon, provided you have welded everything well, and have a housing with no thin/weak spots. A model A with un-gusseted split bones in the rear...is not "sound" engineering! actually, an 80 year old model A frame, paper thin tin, chopped so that your visibility is near to nil, and banjo rear, with a 350+ horse motor is probably not "sound" engineering, but...by todays standards...a model A is not "sound". here's the thing... are you going to drive it across country? if the answer is no...you and the thousands of other guy's that have been doing this for years, will probably be fine with out them triangulated. The bones themselves? well...I'd lose 'em ha! I just read your last post...I see that you ARE intending to go across country in it! well...then...triangulated ladder bars? 4 link?, Coil-overs, panhard... what about "birdcages"? was this not the cure I read about regarding parallel Hairpins/ladder bars? anybody?
here's something to think about , engine torque say 350 ft./lbs X torque converter multiplaction 2.2 = 770 ft./lbs. X trans low gear say 2.43 =1871 ft./lbs X rear end gear ratio say 3.50/1 =6549 ft./lbs. of torque divided by 2 =3275 ft./lbs. per axle. since torque is in ft./lbs. take the tire radius say 15''/12'' =1.25 . now divide 3275 by 1.25 = 2620 lbs. of thrust acting on your rear axle not factoring in tire spin.
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