So I'm building a 46 mercury coupe right now, and the customer wants to keep the original rear end, however convert it to open drive. Well as many of you know once the torque tube is removed the wishbones have to be split and a torque arm installed to stop the rear end from twisting backwards and breaking the wishbones. Here is the stock set up. So the first thing I did was cut both ends off the bones right at the weld. The one end received the typical tie rod end. For the other side I decided to use the bottom bars from a 4 Link set up and slide them in the wishbone. I built a cap for the end with a 1" hole in it so the 4 link bar would be centered and have something to weld to, and then I drilled the wishbone as far as the 4 link bar slides in so I could plug weld it after for more strength. The front part of the wishbones I mounted to the X member. The bracket I made still needs to be cleaned up, these pictures are still in the mock up stage. Then I ran the wishbone parallel to the X member and built little brackets to hold it to the rear end . That takes care of the bottom links, now for the top. I built a little hat that bolts to the top of the rear end so that I could mount the 3rd link. After that I built a K member that bolts to the X member. this is where the other end of the 3rd link will mount. I built it far enough back that it will clear the floor pan. Next I just took another piece of tubing, tapped both ends for the bushings and that completed my third link. And here is what it looks like all together. Now when the torque tube is removed and a regular drive shaft installed the rear end shouldn't twist or break anything and with the tie rod ends being adjustable as well as the third link I can set my pinion angle and tracking.
Never thought of that. The car does have a factory panhard bar though so side to side travel shouldnt be an issue
Your work looks great....however, the upper torque arm looks like its going to be too short. You may run into significant pinion angle changes during suspension travel which will cause binding - especially when working against the transverse spring (they don't like to twist well). The arc of your lower arms is larger and more subtle whereas the arc for the upper arm is small and more abrupt this will cause the axle housing to rotate during suspension travel. You could run a long upper torque arm that is offset to one side of the pinion (ala some older Jaguars and late Camaros) that attaches near the trans or at least at the same plane as the lower arm pick-up points eleviating these issues. -Bigchief.
Man it looks cool but you just placed alot of extra stress on the spring mounts once the torque tube is gone. Now nothing else is keeping the rear from rotating. A standard 4 link bracket prevents this by supporting the housing above and below the tube. I hope you get it worked out but this does not look safe in anyway.
The top link does the same in this set up as it does in a 4 link. The problem as noted by big chief could be the change in pinion angles.
NO, NO it does not. Unbolt that spring once and you'll get it. It is a matter of where the pivot points are.
Yeah, your right. All he'd need to do though is drop the pick up points for the lower arms down about 3-4 inches off the axle centerline (where it looks like he placed the current lower arm pick-up points) to fix that problem.....along with re-engineering the upper arm/torque arm set-up.
Thanks for pointing that out, I never though of that. What do you think would happen if the 3rd link was on the same angle as the wishbones?
Now we are talking... Might suggest some thicker steel for the brackets aswell. The tubing looks well thought out but I'd also add some thickness to those bracket when you remount them unless that is moly. Boxing them wouldn't hurt either.
With the simple set-ups you want all three bars parellel with each other and all three bars picking up the front and rear locations in the same plane. ..........which means your cool looking upper control arm bracket would need to be shortened up and moved forward and your upper arm lengthened and off-set to one side. I like three links and I'm probably going that way with my pop's '29 A coupe. With cars that can tolerate some pinion angle change raising the front of the lower bar helps with off the line bite.....but because you've got the transverse spring out back it doesn't want to rotate or get pulled front or back....hence the need to keep the axle rotation (and resulting pinion agle changes) to a minimum during suspension travel. Luckily most rods have very little suspension travel.
I really like the way the Rolling Bones do it. And the Hot Rod Works solution is simple and effective. But my personal preference is ladder bars. Easy to set up with the torque tube in place.
Doesn't the lower arm rear bracket placed on center of the axle tube multiply the forces involved? A bracket on top or bottom of the axle tubing is getting a direct pull or push - depending on the direction the car is going - and receives only the torque the engine can develop. The axle trying to rotate due to the same amount of torque on the centered bracket is pulling up or down so there's considerable force there as well as the pushng-pulling torque from the arm.
YEP!!! And it may have some drivability issues under acceleration due to the instant center being behind the car instead of being near the front u-joint. I am also concerned about the hump that the upper arm mounts to in the front. If those 90 degree bends are **** welded together they will more than likely fail. But then again, what do I know anyway...
I have the same setup on my Track T, and it works extremely well, except that my upper link is extremely short due to space limitations. I was told that there would be drivability issues, pinion angle changes etc., but in a year of driving, I have experienced no such issues. Sometimes you just have to build something instead of nitpicking angles, geometry etc. to death.
Sometimes a little nitpicking will stop a death. So you've been running tha EXACT same setup, lower bars mounted to the center of the axle where they have no leverage and place all the torque on the single upper arm?
As noted there are a few issues. 1, Torque arm is awefull short. Look at Hot Rod Works arm, same length as bones 2, bones mounted too high on rear axle 3, all brackets look to be made of very thin metal? 4, Divergent angles of the bones and torque arm will do funky things di to "fighting" each other
The 90 degree pieces are beveled and tig welded so I'm pretty confident they ill be okay Space was an issue with this car, I originally planned on making the torque arm longer, however it would have clearance issues with the floor pan. I considered running it along side the driveshaft, however there would not be enough room in the driveshaft tunnel for a torque arm and a driveshaft. So thats why it is where it is. The hump in the center of the K member sits right where the rear floor pan rises up to start the trunk floor.
yes but the shear forces are 90 degrees to the weld.. I'd add some gussets. Not trying to be a douchetard but you really need to re-think this design. This is my Professional Drag Race Ch***is Builder's opinion.
man, i know who im gonna call: LG Kustomzzzzz & Hotrodzzzzz 16718F-111 Ave Edmonton AB Canada ehh (780)-886-1409 if this is for a customer.....then cut it all out and start over. if it was YOUR car with YOUR *** driving it, then cool. go ahead learn the hard way. this reminders me of some minitrucking ****. go to http://www.suicidedoors.com/. they sell 3-links kits there. look at some pics...then maybe you can learn how to build a 3-link correctly. your little multi-piece crossmember, kinda looks like a header donut. you can get crossmembers that are already bent like that, but in 1 piece, or you can bend one up like moi. i suggest you invest in a tubing bender and a basic ch***is principal book . go talk to honky herb http://search.barnesandnoble.com/bo...557880550&ourl=Ch***is-Engineering/Herb-Adams
Big chief nailed it . Just because you haven't noticed a problem and it has not broken yet does not mean that it works well . This will not work well . The good news is, the guy is obviously talented enough to do it correctly once he figures out what that is. My suggestion as always ...Build a simple , full size working model first .
I can save him the trouble. When I built my Torque arm setup I mocked up a full scale version just like he is showing. The pinion angle moved probably 10-20 degrees through the axle travel.
Think ladder bars . They're simple and will fix all your problems , the rear will travel on one arc like it's supposed to and they work great with transverse leaf springs .I know it's a bummer to hear all this , but better now than later when things bend or break. We're just looking out for you and your customer .
All he needs to do is get a couple of floor jacks under the axle, pull the spring and then use the jacks to move the the axle through its normal travel range with a magnetic protractor attached to its front face. The issue will become very obvious. -Bigchief.
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