Ok I am working on my 29 AV8 and I am making progress. You guys answered my F1 box question already. My next step is to mount the rear trailing arms. I have a 1940 Ford banjo and it is open drive. The trailing arms are too long. They come just past the F1 trans crossmember. I was thinking I could shorten the trailing arms and make a mount with a spacer in the center to mount the arms to like they were on the torque tube. I would also triangulate the mount to the to the frame which would also triangulate the crossmember. Is this ok to do or should I pie cut the trailing arms and make a mount hanging down from the outer frame to attach them to with a tie rod end?
What are you using for trailing arms and don't even think about the stock radius rods because they are not made of a sufficient thickness material to work. Make or purchase a good set of ladder bars. Good location is on center near the rear mount of the transmission with about a 6-8" spread.
i second that. do not use the stock radius rods. will not work with open drive. they will snap off at the cast part on the rear where it bolts to the backing plate. had it happen to my dad in his roadster.
If you do a search there have been some tech articles where guys have used the stock radius rods for lowers and mounted modern upper control arms for a four link type suspension.
Ok that does make sense. What if I use the torque tube? Right now it is way to long and I don't have a 33-34 like Vern Tardell says to use. Is there another way to modify a 40 torque tube to work?
Never done it but you can shorten the torque tube and drive shaft. Dick can probably provide some good advice on that. But you said you already have an open drive rear. You don't mind changing to closed drive?
I can change, the project is in that stage where anything goes. The open conversion is not finished yet anyhow.
Heres how you do it. This is a pic of mockup and the misalignment bushings aren't in the 1/2" heim that the radius rods bolt to. The rods come together at the heim screwed up into a threaded socket in the bottom of the crossmember. This triangulates the radius rods and allows full movement of the rear housing so it can work with an open driveshaft. The arraingement is kinda dainty but it is held with the same size fasteners as ford used, i would do smoething different if i had anything other than a flattie. Shoot me a PM if you need an explanaition or different angle pics. Hope this helps, oj Happy Thanksgiving!
Oj you are going to have some issues with your design, I maintain that even with a small Hp engine the axle and brake torque is greater than the strength of original tubular sheet metal radius rod braces when used with an open drive line. Quick accleration or more important a panic stop will bow the braces right up. Also point out that the front anchor point should be fixed, the use of a heim end allows the axle to rotate and produces a rear steer effect as the spring flexes or the chassis rolls. You may get away with it but it is a question. If you want to check it out, put your frame on jack stands in the front and 3/4 to the rear, hang your rear axle at ride height by heavy string or fishing line and plumb bob each end of the axle housing and mark a reference point on the floor, insert a bar in the axle tube end and lift up slowly and watch the relationship of the plumb bob point to the original dot. Now you might laugh at this back yard mechanics but it will indicate the action of your design.
Hi Dick, wouldn`t it be the same rear steer effect with ladder bars if they are close together at the front pivot? The advantage of the heim joint solution is that it is bind free.If its fixed it would only cause a bind , but doesn`t help to avoid rear steer?!? Michael
Good suggestion Dick, i'll mess with rearend movement before i go further. When you say 'allows the axle to rotate' are you speaking as like a propellar would rotate where the rearend wants to turn along with the driveshaft? Can you elaborate further on how the brake can have an effect on the radius rods, seems like they'd be under tension during braking. I can see a problem under heavy acceleration when they'd be under compression and prone to deflect. Help me out here, thanks oj
To answer your questions about the front locating point. The front locating point moved to two fixed points establishes better longitudinal and lateral positioning. By splitting it from a triangle to a trapezoid it locates the axle centerline to prevent the lateral rear steer tendency when the link would have just a central pivot. But both a split and a tri-axis pivot may also require the use of a panard rod for lateral location in some applications. Normal road use does not require that degree of freedom because of the small axle travel, where the tri- axis central piviot might be better for large axle deviations like a rock crawler because of its larger operating range. In regard to the brake issue bowing the rod. Even the rod being under tension will be subject to bend because the braking force might not be even side to side.
I talked it over with several guys and I think it is easiest to use the torque tube. I only need to shorten it a bit. Thanks for the info. That's what I love about the hamb.
Now my next question is: can I shorten a 40 torque tube? It looks easy enough. I need to remove 20" As long as I do it so the bearing still is located correctly, it should not be a problem?
This is why we should listen to Dick. I thought it was a clever idea using the ball from a front wishbone on the rear because it eliminated bind. I couldn't imagine a negative of this set up until now Having said that, I have been driving my hot rod with this set up for a year and can't say I have noticed any rear steer. It drives very nicely actually. But I see the issue. Pete
Hi Pete, i built four Hot Rods using the same set up as you. I haven`t noticed any rear steer ,too. I still think it is a better design than mounting the bones far apart. Then you will always have bind problems. Like Dick wrote, with little suspension travel you won`t notice it anyways....
Hi Dick how far would you mount the front locating points apart? I think we agree that mounting them to the frame rail is too far..... But is the only point where you will have zero rear steer . Michael
I would atleast use modified front wishbones with a piece of tube comming from the top of the rearend down to them to make them into hairpins or go like striper That is what im doing, makin hairpins, but i'm mounting my ends about 12" apart to create less roll Now for what dick said, I understand the concept, an old racer friend of mine split the wishbones on his restored cars for that reason, but basicly couldnt that be conqured by a sway bar also?
The rear axle still pivots around that same point, even with a sway bar. I have to say if it is a problem it is very minor compared to some of the alternatives. Pete
Dick is 110% correct......been there done that. Back in the day we use to bow the rods when and if the car would hook...after the good hook and going down the street the car would vibrate like hell....we found out if you backed up hard the rods would unbow and you could drive with no vibration....which worked great a few times untill the rods would actually break in half......also remember a tri-angle is a very strong ...
yep. no problem there. it's been done for 60 years. couple ways to cut it. I've heard of people using a very big pipe cutter to make a nice clean cut. last time I did it, we used an abrasive wheel in a chop saw. line it up straight, tack it then put a good hot bead around it. the driveshaft tends to be a bit harder. we cut the splines off the back and bored the coupler to a press fit then welded it together. got 15 years or so on the current driveshaft in that configuration.
I just got done cranking my rear around - i did it when i built it too - i still don't see rear steer. The rear end cannot get closer to the front because of the length of the radius rods. I move it up and down simulating turning into a parking lot, there is barely perceptable movement - no more than any other vehicle with rear axle. I see Dicks' (an others') point about the radius rods being week under compression, if the car had any horse power the radius rods would have to made from heavy wall xmoly. As far as problems when braking, the rods are under tension (they are trying to be pulled apart, a very desireable stress) and if the brakes are uneven then you best resolve your braking issue. I have a ton of respect for Dick and his opinions are invaluable. I am not discounting what he sees as a possible problem, he is giving advice on the cautious side. He didn't say absolutely there is a problem, he said there might or can or may be a problem. Heres' the whole thing, what is there about the radius arms going to a torque tube as opposed to a fixed chassis point with an open drive that you see more stability? The whole rear is still going to rotate about the same attachment point at the tranny (be it either attached direct via the torque tube bell or the radius rod attachment). The actual rear has no clue what is holding it to the car, it is going to move in the path of least resistance. I like the trapazoid analogy and i can see where spreading the distance between attachment points would give greater surface area and strength. I chose to go to the single heim because it is bindfree and the radius rods don't need piecutting, they just bolt right up. I am adding a safety plate under the front and rear attachment points in case something brakes they'll be held secure. Happy Thanksgiving! oj
Hi Mike, The reverse wishbone idea is ok but just like anything else it generates an issue with some types of mounting. If you have a transverse spring on the rear, the spring locates the rear axle and controls the lateral shift of the rear axle as the vehicle rolls. If you were to plot the rear axle you would see a degree of rear steer but because the travel is only around 2", this steer is hardly noticeble at lower speeds. However mounting the rear on independent coil over shocks requires a locating rod and the position of this rod become important as its arc determines the lateral offset as the vehicle rides and rolls. I feel that splitting the rear wish bones the span should be no more than 8" - 10". If you want to get a good idea of the difference between the two designs and the movement potential just get a compass and a sheet of paper. Place a point on the paper and say draw a line parallel to that point about 4" rearward. Draw a line perpendicular connecting that point to the line. Now just measure 1" l and r and place a point to represent your control arm axle location and connect these points to the upper central point. This would represent your axle setup. Take you compass and swing an arc using the distance of the axle mounts to the center as a radius. Now to compare from the central upper point measure place a point about 1/2" off the central pivot to the right side and one to the left parallel to the axle line. With these points and using the previous axle mount use your compass and swing an arc from each radius rod. If you compare the arcs you can interpret the potential axle shift. Shaggy a sway bar will not locate an axle because it usually has a flexible link to hook up and compensate for the shortening of the bar as it twists. I corrected some spelling so I might as well address the issue of using stock ford radius rods as real radius rods. The only radius rods that come close to being strong enough for use as a radius control rod are 35/6 units but even these have issues with rust out. The item that we call a radius rod from an old torque tube rear is nothing more than a triangulation tube to keep the torque tube from bending during rough road travel or during an accident. They are not designed to be used as control links.
For what it's worth, the Hot Rod Works has already re-engineered the Ford Banjo rear end to make it a suitable alternative for today's modern drivelines... Modified radius rod mounts for converting to open driveshaft... You could get a rod end and make your own crossmember... and a torque arm to handle the horsepower... During acceleration the torque arm is in tension so the bending moment on the radius rods is negligible... Plus they have a kit to convert the early banjo's to late model axles... I think anyone running a banjo with open drive and trying to maintain a traditional appearance should look at this as a possible option...
There are some compression/tension forces acting on the radius rods, but the main forces that apply are rotational forces, and this applies to both braking and acceleration. Under accelleration, the rotation of the pinion is trying to rotate the front of the radius rod up. Under braking the brakes are trying to stop the wheel's rotation which tries to rotate the front of the radius rods down. The braking rotation is why Ford front wishbones are made of thicker material than the rear ones as they have to absorb all of the braking forces. This is why they are sometimes used on the rear in open drive setups.
One thing is 100% for sure .... unless you have 35/36 rear bones you NEED additional support for the bones. One bar like HRW does the job. Michael
Hi Dick, i try to read/understand what you write , but it`s not easy for me as it`s not my native language... Your drawing only describes side movement.and doesn`t adress suspension travel,correct? So the same side movement would apply to a stock closed driveshaft mounting like the "mounting ponits together with a heim joint" soloution.... So i see no disadvantage over a closed driveshaft Or in other words there has to be rear steer in a stock closed driveshaft suspension... ?!?!?!?!? The HAMB is sooooo cool , talk about Hot Rods and lern something every day. Michael
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