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Hot Rods Banjo rear bracing

Discussion in 'The Hokey Ass Message Board' started by Koz, Jul 29, 2018.

  1. Koz
    Joined: May 5, 2008
    Posts: 2,180

    Koz
    Member

    007.JPG 008.JPG 009.JPG In my endless T roadster project my banjo rear sets incredibly close to the chassis and I can't use the traditional radius rods to stabilize the rear off the torque tube as is typical, (and the way Henry did it). I've ended up fabbing some simple angle braces that I think will do the job. They are .250 mild steel with grade 8 bolts. All holes were reamed in place to near zero tolerance so there is no slop in this setup. With the very short torque tube, about 34", I think this will lock the rear in pretty nice. Obviously the welding is not finished.

    My question is, Has anyone done something like this before and how did it work? I'm definitely more comfortable with this setup than the 6" or so drops I would need to run a pair of radius rods under the frame, not to mention the related road clearance issues.
     
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  2. Koz
    Joined: May 5, 2008
    Posts: 2,180

    Koz
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    Pics of the car on the table for reference.
    002.JPG 007.JPG
     
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  3. oj
    Joined: Jul 27, 2008
    Posts: 6,138

    oj
    Member

    Hmm, Can't you run radius rods even outside the chassis? If all you have is torquetube and gussets if you hit a pot hole with 1 rear wheel it'll jerk you into the next lane or ditch.
     
  4. oj, I don't think there's an issue with having a Bump stuff him into a ditch. The factory radius rods did nothing related to keeping the rear Axle in a Fixed location. I'd be a bit more concerned with the length of the Torque tube unsupported and a big Pot Hole. If it's real short maybe not an issue at all.
    The Wizzard
     
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  5. Koz
    Joined: May 5, 2008
    Posts: 2,180

    Koz
    Member

    Stock Ford torque tube is around 68" on this rear. The stock radius rods hold the rear from breaking the torque tube flange where the rear goes on which is what these pieces do. If you put the radius rods on the outside they would need to rotate around the same axis point as the front universal. As soon as the car leaned, games over. This car uses a '46 rear and a '39 trans with a closed driveline. I'm just worried, not being an engineer, that the braces are up to the task. I know the geometry I spot on. These things drive like a go kart. These pics were taken some time ago. The car is almost ready for paint and I second guess myself way too much. The nice thing is they are virtually invisible under the tank when the car is on the wheels. I see radius rods hanging under rears on very low cars that do virtually nothing. I'm hoping these will do what I think they will.
     
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  6. I don't think I'd loose a lot of sleep over it. The other thing the Rods did was take the load off the 3/8" bolts holding the end housings to the center. You've taken care of that.
    The Wizzard
     
  7. oj
    Joined: Jul 27, 2008
    Posts: 6,138

    oj
    Member

    If a transverse spring located the rear a parallel leaf spring would never have been invented. Since its a 'one legger' I'll bet going down the road you'll be steering to the right all the time, that one tire will be way ahead of the other. If that gusset was that was needed Henry Ford would never have developed a radius rod, esp different ones for different cars. There lost of lakes style cars with the radius rods on the outside and I know for a fact they aren't ideal but they seem to be good enough, thye have to be able to flex.
     
  8. Fabber McGee
    Joined: Nov 22, 2013
    Posts: 750

    Fabber McGee
    Member

    OJ, how the hell could one tire get way ahead of the other? These gussets will do the same thing as the original radius rods as far as fore and aft location of the tires. The spring shackles will hold the axle laterally in the place Henry intended.
    Nice job Koz, run it and enjoy it.
     
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  9. pitman
    Joined: May 14, 2006
    Posts: 4,690

    pitman
    Member
    from Hampsha

    When the brakes grip, or the engine torques, the housing tries to rotate. Unless you employ the ctr section flange/torgue tube AND radius rod mount/rod as Henry did. From here it looks like the center section flange/TT will have the entire job. The bracket location may tear out, or flex due to torsion loads.
     
  10. Koz
    Joined: May 5, 2008
    Posts: 2,180

    Koz
    Member

    Point well taken pitman. I thought about that and feel the braces will handle the rotational force well. They are fastened to the torque tube and any rotational force should be transferred to the tabs on the rear in shear. They should take around 560K lbs. of force in shear. Not sure what is placed on them but I'm sure it is less than that. I've never seen anything like this done before, (doesn't mean it hasn't, just haven't seen it), and that worries me.
     
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  11. Koz
    Joined: May 5, 2008
    Posts: 2,180

    Koz
    Member

    I'm thinking OJ may be unfamiliar with the engineering of an early Ford rear. If I was running a 9" or something with the Model "A" traverse spring I would understand his concern. Ford torque tubes are in addition to being the driveshaft, the principal suspension control arm. Way different than an open driveline rear. To OJ, I've seen a few cars done like you suggest, the Proulx roadster comes to mind. I understand they made the radius rods super flexible accommodate and still had a lot of trouble with it. What may get by on a race car is often unacceptable on the street.
     
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  12. I like the way you lowered the tank over the crossmember. On my modified I cut the top off the crossmember and plated it to get the Fordson tank a couple inches lower

    IMG_0258.JPG


    Sent from my iPad using The H.A.M.B. mobile app
     
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  13. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,179

    gimpyshotrods
    Member

    If you use the area under the seat, you can run radius arms way up the torque tube. Your design puts about the maximum possible force, via the longest levers, on the smallest possible area. Adverse conditions could result in a bent torque tube and/or a a bent axle tube, or tubes.
    20130111_165709.jpg
    20130315_194909.jpg
     
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  14. Ebbsspeed
    Joined: Nov 11, 2005
    Posts: 4,720

    Ebbsspeed
    ALLIANCE MEMBER

    If you're trying to control rotational force, would you be better served to have your braces attached to the top and bottom of the torque tube, and connected to the top and bottom of the center section?
     
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  15. So just how Large and Wide of a tire are you going to run on the back? How much weight ya got there to make them hook up? If the Tire don't Hook the Torque amount is a Zero issue. From the looks of that 40 Ford style rim I still going with, "there's no problem".
    The Wizzard
     
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  16. mgtstumpy
    Joined: Jul 20, 2006
    Posts: 7,582

    mgtstumpy
    Member

    I like the idea however I think that some additional triangulation will strengthen things up considerably. The weak link is still where the torque tube bolts to centre section. All the stress and force goes through this area during braking and acceleration.
    What about similar bolt on brackets where the bells on each side bolt to the centre section with reinforcing brackets connecting to additional gussets welded to your new bracing. These would not take up a lot of space and be hidden and best of all everything unbolts for servicing should the need arise.
    upload_2018-7-30_7-45-31.png
     
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  17. Norfab
    Joined: Dec 1, 2006
    Posts: 48

    Norfab
    Member

    The radius rods also handle the forward thrust to push the vehicle forward. You're asking that torque tube to do way to much work, recipe for disaster.
     
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  18. Koz
    Joined: May 5, 2008
    Posts: 2,180

    Koz
    Member

    Great idea mgtstumpy! I don't think the radius rods on a banjo do as much work as most folks think. They keep the "wiggle", side to side, out of the rear and the torque tube does about everything else. As Gimpyshotrods notes above, nice setup but you have way more room than I have and for the same reasons noted in earlier posts, you can't run that type of radius rod on a closed rear. Your seat seems to set 6-8" above the driveshaft/suspension. My driveshaft, inside the torque tube is 8" above the seat. This car has about 5" road clearance with 7.50-16 rear tires so everything is up inside the chassis. I didn't want anything below scrub line, and I live in Pa. where most Jeeps have a hard time with the roads. About 4 1/2" tread so it's not like I'm hooking Mickeys up. I think Pist-n-Broke is probably right on the rotational thing. Chances of a car this light hooking up are non existant and with the '39 fuse, (trans) I'm using I'm not going to be sidestepping the clutch anytime soon. Especially with what the Lincoln gears cost these days. Some good thinking in this thread!

    Blackjack, you're a man after my own heart. The Fordson tank works so nice on your roadster. The one I have is a '34 Dodge sedan repop from Tanks Inc. I flipped it over closing all the factory holes, put my holes in what would have been the bottom and rolled some new ends to get rid of the stamped X's and logo on the tank. With the recess cut in I still have about 14 gallons which is just fine for me. My car is built to take both a flatty and the 283 neither of which is a gas hog. If I new I was going to do that much work to it I would have just rolled the shell as well. Things have a way of getting out of hand around here.... The quality on the Tanks Inc. unit is outstanding and is a really easy part to modify.
     
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  19. While unconventional; the braces should do what you intend. Methinks some guys should look under an early Ford before they attribute all kinds of strength and purpose to the rear radius rods.
     
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  20. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,179

    gimpyshotrods
    Member

    I know exactly what they do, why they are located where they are, and why they don't need to be any stronger than they are, and can still do the job.

    Ford did testing nearly equivalent to modern finite element analysis to build them that way. Their design is no accident, or wild-assed-guess.
     
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  21. Fabber McGee
    Joined: Nov 22, 2013
    Posts: 750

    Fabber McGee
    Member

    Engine torque is a non issue. Sprint cars run 800 to 1000 horsepower (probably more now) with nothing but the torque tube attached to the cast aluminum center section of a quick change by the same 6 bolts on a 4 inch circle (or whatever it is) and they run 18 inch wide tires with 5 or 6 pounds of pressure on rough surfaced tracks that cause them to hook up and wheelie, or spin, or wheel hop and generally do things that no torque tube should ever have to stand up to and they do it reliably.
     
    Last edited: Jul 30, 2018
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  22. Tim_with_a_T
    Joined: Apr 30, 2011
    Posts: 992

    Tim_with_a_T
    Member

    First of all, I think your solution is very abstract and very unique, and I can see what you did and why. But... I don't know how well it will hold up. I'm no expert here, just thinking out loud. The early Ford setup has the radius rods as far out as possible and as long as possible, and I believe this is to spread the stress across the entire assembly (stress = force / area..... larger area = less stress if force stays the same). Keep in mind I'm speaking about the rear axle assembly in general, not cross sectional areas of individual components.
    If you look at a top view, the early Ford rear axle assembly forms two large 90* triangles, with each triangle sharing a common side (the torque tube). What you have done is shrunk those two triangles from being as large as possible to as small as possible. In other words, you created a stress concentration at the banjo's center, instead of being spread out across the assembly as the original design intended. To further explain, your stressed area went from large to small, so referring back to the stress equation again, stress must go up if area goes down.
    At this point, the individual components of your assembly are exposed to a greater amount of stress than they were in their original configuration. The most concerning one that stands out to me is the unbraced length of the torque tube from your gussets forward to the transmission. You're asking the driveshaft and torque tube in this section to take almost all of the dynamic forces of the assembly, with a maximum stress just forward of your gussets (stress concentration). I would imagine that if it were to fail, it would fail due to bending in this location, likely due to hard deceleration. Remember, almost all cars not using parachutes for brakes stop much faster than they accelerate, no matter how sticky the tires or how much power the engine has.
    One other thing that stands out to me is your 5" road clearance with a 7.50-16 tire. I think those are around 31.5" tall.... after taking away the diameter and lip of the wheel and accounting for half of what's left, you've got just over 7" to the ground... take that 7" away with a flat tire and you're laying frame, which could get interesting...
    I think you've got a lot of creativity going on with your build, but you might want to rethink the rear axle assembly.
     
  23. blackout78666
    Joined: Jul 3, 2009
    Posts: 581

    blackout78666
    Member

    The sprint cars have "birdcages" or basically a bracket with bearings that fit on the ends of the axle. They are FIRMLY attached to the frame with 2 "radius rods" per side. And a "panhard" bar for side to side motion called a Jacobs ladder. Lot more going on there. But different animal for sure.
     
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  24. Why does everybody seem to believe that the radius rods control torque on a banjo axle set-up?
     
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  25. Hnstray
    Joined: Aug 23, 2009
    Posts: 10,693

    Hnstray
    ALLIANCE MEMBER
    from Quincy, IL

    I also think I understand the torque tube and radius rod design and purpose. Some posts here are closer to reality.......others exaggerate the forces applied under the various loading conditions. The factory radius rods contributed some resistance to axle wrap (rotational force) to the torque tube. However, I feel certain their greater purpose was the additional triangulation strength they provided the torque tube (described by Tim-with-a-T) that controlled the varying horizontal driving forces from either wheel, and similar for side to side braking forces.

    Also there is a vast difference in the overall loads your modified vehicle will apply compared to the original application. The stock Ford cars and light trucks, empty, weighed I’m estimating at 1 1/2 times your car. And, loaded, probably weighed up to 2 times as much. That weight differential alone would, in effect, make your parts much stronger in your application than in their original use.

    All that said, one could quibble over details and section shapes a bit, but overall I think what you are doing in your particular application should be fine.

    Ray
     
    Last edited: Jul 30, 2018
  26. oj
    Joined: Jul 27, 2008
    Posts: 6,138

    oj
    Member

    You release the clutch and that right rear tire digs in do you think that gusset will keep the rear straight? You hit a pot hole while driving with just 1 rear tire and you think that gusset will keep the rear straight? Those shackles won't help in the slightest, I can twist them clamped in a vise with a sizeable screwdriver passed thru them.
    Isn't there enough room for a 4 link? Be tight up top but even the production cars have very short upper links.
     
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  27. gimpyshotrods
    Joined: May 20, 2009
    Posts: 16,179

    gimpyshotrods
    Member

    You are exactly correct.
     
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  28. Stock early Ford, you release the clutch and the right rear tire digs in; what keeps the rear straight?
    Stock early Ford, you hit a pot hole while driving with just one rear tire; what keeps the rear straight?
     
  29. alchemy
    Joined: Sep 27, 2002
    Posts: 14,294

    alchemy
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    I don't have an answer, or an educated opinion, to it's strength or longevity. But I do want to applaud your reasoning and willingness to try it. Please get back to us with real-world results after it's been on the road a while.
     
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  30. Stock torque tubes don't bend up and down at that point due to hard braking or acceleration and they have more length past the radius rod attachment point than Koz's creation, later '40's have even more length past the attachment point than the '35 in this picture.
    2864.jpg-999 (Medium).jpg
     

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