Hello everyone, I'm looking for some help from the suspension guys. I hate to open up a can of worms, but after reading MANY posts in the tech section regarding split rear wishbones, I could still use a little direction. I'd really like to go with split wishbones for the look, but being new to this type of stuff, I don't want to kill myself or anyone else with my project car. It seems like many posts say there is a safe way to do this, but I want to make sure I am understanding the info correctly. It sounds like I could go with either a 3-link or 4-link type rear suspension as long as the low mount attaching the wishbone to the rear end is a single, flexible link, such as a bushed end, so it is a locator only, not a torque arm. The front attachment point (bone to frame) would be a heavy tie rod end. Is this correct? Also, it sounds like it doesn't matter if the upper link is in a 3-link configuration or a 4-link. Am I getting this right? Also, I don't think I am clear on whether there is a relation between the upper and lower links geometrically (angles intersecting, etc.) Does anyone know of a good book that discusses this stuff? I know I could just go buy a kit off the shelf, but that wouldn't be any fun at all. Any help would be great!!! Thanks much!!!
I'm sure you'll find a ton of stuff about split bones if you do a search. I'm using a set of '35 bones on my T Coupe project but modifying them to act as a ladder bar. I'm planning on using a regular urethane bushed 4 bar adjuster at he front and bringing them in as close to the driveshaft as possible. They've been shortened by at least a foot and I'm having a buddy with a Bridgeport make me some spuds to weld into the ends. This will be a very light car but with a pretty torquey motor (406)- skinny street tires but probably some fair sized slicks for the strip. I too would appreciate any comments on how much power these things can take.
I am building a '29 Coupster using a stock frame with a 5" step in the rear. It will have a stock transverse "A" spring. I have a set of wishbones from a '41 Ford that has been split with the rears cut off to install a typical bung kit. The front of the bars have been modified by cutting off the upper axle mount boss and filling the lower boss while leaving the spring perch intact for use with the transverse spring in the rear. I've also stretched the frame 3-1/2" to accommodate the new spring location behind the axle. If you have seen the article titled "Bones of Contention" in Rod Action, my wishbones are modified to be the same. The sad part is that the writer seems to be going down the wrong path based on what I've read here. He built a solid bracket mount to attach the rear end to the wishbones. Sounds like this is a no-no. Am I on the right track?
NOTE: I did not build this, I was just trying to point out some ideas. UPDATE: The pictures are from "ElPolacko's" shop Industrial Chassis in Phoenix. Here's a couple of pictures someone had previously posted of modified wishbones used with a torque arm and transverse spring. Don't personally know how it worked; but the OP said it did and it looks like it should. There are a couple of different chassis shown. The link on the front of the torque arm allows suspension movement without bind. The OP said it could point either up or down to best suit the installation.
Pics would help. If that writer is bring the bones out to the frame rails on each side, yet solid mounted at the axle, then yes, it will break something, at some point in time. Solid mount can work if they are mounted very close together up front, like Chevy truck arm system. Chevy had very flexible C channel, with very large flexible front rubber bushings. There have been some posts on making them like a 3 or 4 bar while using a transverse spring. There was talk of bind, if the added bars are not set up correctly.
Rich, the photos you included are exactly what I pictured in my mind when reading some of the posts. You mentioned that you didn't know if it worked or not, so how about opinions from the rest of the guys? This looks very simple and straightforward. how about it? Thanks!!
Thanks for catching that Striper. I also missed that the front mount of the third link has a "knuckle" in it. Not sure if that is what it is called, but this must be the link Rcih talks about that allows the axle to move without a bind. I think this is all starting to make sense now. F&J, yes the bones will be mounted on the outside of the rails, so I agree that this could cause a bind. Thanks much guys for the input......... I really appreciate it. Any other ideas from the crowd?
Good catch, I forgot to mention that the transverse spring version had the dead perch to eliminate the need for a panhard bar as used on the chassis with the coilovers.
Here is how I built the rear suspension for my 26 RPU project. I came up with a sort of modified triangluar 4 bar setup. I will be using coil overs and the design gives me great positive axle location and articulation up and down and from side to side without binding. On top of that my rear wishbones match the ones I built for the front.
I usually like to see a panhard bar with split bones or ladder bars running parallel to the frame since there is no triangulation.
I was thinking the builder maybe used the dead perch instead of a panhard bar because he wanted the car to look pretty traditional - banjo and buggy spring from the rear along with split Ford bones from the side. The torque arm and other stuff would be mostly hidden under the body.
Rich, does the dead perch create a wierd feel in the suspension? I've wondered about dead perches and whether the "live" side would lift a little more than the "dead" side while going over bumps in the road and result in a strange feel. And correct me if I'm wring, but doesn't the dead perch take the place of a panhard rod?
Hey Blue One, thanks for the photos or your project. Also very helpful as I have considered going with a "modified" 4-bar set-up similar to yours. I've read that you should hit between 30-35 degrees horizontal angle from the rear end to the frame rails relative to the bones, but don't know anything about vertical angle in relation to the wishbones (lower link). Should the front attachment point of the shorter upper link align with the front attachment point of the longer bones? Or be parallel to them? Thanks!
If you're talkin' early Ford banjo style, they used radius rods to support the perpendicular relationship of the rear axle housing to the centerline of the chassis. "Wishbones" were used to position the front axle on pre'49 Ford/Mercs. Rich B: nice work - simple in design and functional. D.I.R.T. Modifieds used something amazingly similar except for the lateral controlling device, a Jacob's Ladder to induce body roll. Blue One: coming along nicely, be ready for Red Deer 2012?
Yes, 30-35 degrees will work, 45 degrees will be better if you can get it, the angle of the upper bars forms the triangle and locates the rear end side to side without the need for a panhard bar. The front attachment point of the shorter upper bars in theory should be in line with the front pivot point of the lower wishbones if you extend a line along the upper bars. Think about standing on top and looking down using the top bars, and the rear end along with the lower wishbones and forming an independant triangle on both sides. Forgive my crude drawing
Thanks. No, unfortunately several factors will keep me from making the road now for several years. However I will endeavor to do what I can to continue
QUOTE Rich B: nice work - simple in design and functional. D.I.R.T. Modifieds used something amazingly similar except for the lateral controlling device, a Jacob's Ladder to induce body roll. As mentioned, the pictures I posted were copied from another builders earlier post on the HAMB.
Here's a shot of the rear end in my 29 roadster. The 40 rear bones use a tie rod end at the front and a Chevy upper control arm bushing in the rear. The torque arm is bolted directly to the banjo and a heim joint at the front right at the universal joint. I drove the car from London on to Victoria BC last summer with 4 friends. Works great and haven't had a single problem with it.
Rich B, In the first 2 pictures in your post, I wonder if the mount would not be a lot stronger if it attached to the bolts around the banjo axle tubes(where you could grab 3 or 4 on one common bracket) rather than the small front support. In the original torque tube everything pivoted at the front universal, once the lower arms are split and moved to the outer rails, some binding occurs during any twisting movement. (dropping one wheel into a pothole, stepping up into a driveway) All the brackets and fasteners must be strong enough to absorb this binding. John
Like I mentioned I didn't build the suspension shown, I was just pointing out an idea. I don't know how this worked out; but it looks OK to me. The original torque tube mounted to the same bolts on the front of the banjo, so if the bracket between the torque arm and the housing was built out of adequate materials, it should be strong enough. Again, I think the builder was also trying to keep it less visible from the rear. With the tie rod ends on the front and the urethane bushings on the rear of the radius rods along with the link on the forward end of the torque arm, it looks to me there would be very little, if any, bind with-in the limited suspension travel seen on the typical hot rod. The idea of doing this was to have the traditional look of the rear radius rods split and brought out to the side of the rails without the solid mount on the rear trying to turn the axle housing into an anti-roll bar and possibly leading to component failure in the future. IMO
Hello Rochie, thanks for the photo of your car. This looks clean and simple. The only question I have is if you have just a single link at the front attachment point of the torque arm. The design shown in Rich's photos had a double joint to allow for some forward movement of the rear end. Have you found this unnecessary due to the limited travel of the rear suspension? Or do the control arm bushings have enough give to allow eliminating the double link at the front? As a side note, can anyone here provide a minimum dimension for upward rear suspension travel? I have heard around 3-1/2" to 4". Thanks!
If you're going with a two trailing arm (a la '60s Chev pickup or Pete & Jakes) and want the early vintage flavor, the '36/'37 Ford has the strongest rods of the 1928 to 1948 era. These rods incorporate a beefy spring hanger to the rear, so they are adaptable to many rear axle housings provided the axle tubes are small enough to attach the brackets. The 8" Ford works well here. Weld in the bungs, thread in the tie-rod ends and and attach to brackets close to each other on the trans crossmember under the front U-joint. Works well on low center-of-gravity roadsters using the transverse spring. If the front pivot points are spread apart to attach to the frame, you get the equivalent effect of having a gigantic rear anti-roll bar, OK for driving on level, smooth pavement. On anything other, it is "bumpsville". Only one problem: finding '36/'37 Ford radius rods. I've done three in my time: got another on the go. They do handle the horsepower. Rochie: nice.....drool.
Since Steve hasn't seen or answered this yet, I'll go ahead. The first pictures posted on the first page are out of "ElPolacko's" shop Industrial Chassis here in Phoenix. The Model "A" frame that is shown is under a '29 truck that was sold to a local guy named John Gilbert a couple of years ago, and as far as I know has not been finished. The "T" shown belongs to local hot rodder Rick Dupont, and since being finished up at Steve's about four years ago, has done daily driver duties for Rick's twenty mile each way commute. Not cute, "when the weather is nice" daily driving, we're talking this is my only car kinda daily driving! I was I believe the first to drive it out of the shop and spin some donuts in the parking lot and it all works tits! The idea of the dead perch is exactly that of a front dead perch to limit side to side movement, similar to what a panhard bar does. Most times making sure your spring shackles are at a true forty five dgree angle will certainly suffice, the dead perch just makes it more "solid" feeling. Same is done on the left of the front on this car as well by turning solid perch side shackle bushings and welding the assembly together. No mention of problem of any sort from Rick, and I mostly see his wife driving the wheels off of it since he got married these days. The last chassis shown is either under Steve's personal twin turbo'ed '63 unibody truck, or one of many he has set up in a similar manner. He has broken and refined his personal truck a few times down the line each time improving his design, but bare in mind he's floating right foot on about 750 chassis dyno'ed horsies, too. Very few project vehicles come out of Industrial Chassis without the tourque arm suspension 'cause it just flat works. My avatar Plymouth is one of the few, and that will probably be rectified soon when repair of some accendent damage gets going. 'cause like most stuff coming off his chassis table, it get's driven... Hard!!!
Thanks! Now I know where the pictures were originally from and can give Steve the credit due for the torque arm set-up. Also, it's good to hear that time has proven it to work on the chassis shown in the pictures. I had lost the link and could not remember who had posted the pictures originally.
RK Hall, There is no bind in the rear. The heim joint at the front mounting point offers enough movement to allow the rear to move in all planes except forward and rearward. If you look at the pencil drawing you can see the the rear end can't move forward due to the arangement of the radius rods. Well I supose it could due to the crush factor of the rubber bushing, but it would be negligble. The car runs down the road straight and true and REALLY liked the twisties in the mountians. This picture is at 75 MPH somewhere in Montana
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