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Jonnyhotrod's Bittersweet day... 1st drive in the coupe and I broke it.

Discussion in 'The Hokey Ass Message Board' started by Jonnyhotrod, May 23, 2007.

  1. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    I have spent the last week or so wailing on the coupe to get it to a small local show on Saturday under it's own power. Today, with the help of 3 friends we got it together enough to take her for a spin. We ran new brake lines and bled them, reworked the ebrake, mounted the wiring to the inside after running some new leads, painted the inside w/ black Corroless Installed the seat and mounted a fuel line.

    I decided to take her for a couple jaunts to my grandmother's next door... First run I idled her, testing the brakes and such... No problems. On the second run, I decided to tap the trottle a bit. When I did, my '36 Ford radius rods SNAPPED OFF CLEAN at the casting!! BANG, the driveshaft hit the floor in the back when the rear end rolled backward a bit. I didn't know what had happened, so I nursed her into my grandmother's driveway and shut her off. I was completely shocked and glad it didn't happen on the road at speed. Here's the video:

    Pics below.

    HOW DO I FIX THIS!? Should I reinforce then somehow with gussets or something. Has this ever happened to anyone here? Common problem, or do I just have too much torque (413 Chrysler)? Any suggestions are appreciated for a safe sollution... Thanks.


    Attached Files:

  2. I have a friend with a '34 Ford with '36 bones and a 9". He drag races the car and tore the welded bracket off the axle housing (while just taking off lightly from an intersection).

    I have not seen one break where your's has (were the welds ground smooth?). I would re-weld it, and irregardless of running a torque tube or a conventional driveshaft I would build one or two tubular torque arms or tubes (7/8" or 1" DOM with heims) to run from the top of the center section forward and tie into the front of the wishbones.
    Atwater Mike likes this.
  3. there are a bunch of guys here who will argue that it's ok to run Ford radius rods like that on an open drive rear with no torque tube or torque arm, and/or that it's just fine to run the leading end of the rods out at the frame rails.

    yours is a graphic example of why NOT to run radius rods that way.

    I'd sure inspect them REALLY THOROUGHLY for other fatigued areas before I took the time to repair them. Or, keep the forgings and replace the tube parts completely.

    then go back and re-examine your whole rear suspension setup, search on here for proper geometry, add torque arms, etc.
  4. Jeff Norwell
    Joined: Aug 20, 2003
    Posts: 13,520

    Jeff Norwell
    Staff Member

    I completley AGREE!
    Your very lucky you were not going all out at high speed.Could have been very tragic.
    I had the same set up on my 40 rear.....with a open driveline.(I purchased the car like this)
    The split bones were cracking at the same place yours did.Heavy fatigue.

    I installed a P&J ladder bar set up.......never a worry or problem.

  5. If you want the look of split rear radius rods - and they do look cool - why not put a poly bushing ring in the rear of the radius rod and use it as the lower bar of a 4 bar setup.
    The upper bars can be fairly well hidden most times.
  6. I posted on the HAMB a while back about using this type of setup on my 32 pickup truck,,,,the majority of the guys that answered my question advised against using the early radius rods with a open drive.

    I ended up using a P&J ladder bar setup,,,,

    I hate you had to go thru this and glad you were not flying down the interstate when it did,,,,HRP
  7. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    I like these two ideas. NUROADSIR's idea seems to be the fastest solution, but I'd like more feedback on it's viability. I really want to retain the radius rod looks, but will change it if need be. I don't want it to look too modern, which may be the case w/ a 4 bar. I'm searching for various rear end set-ups now on the HAMB. If anyone has any pics of thier setup, so I can get an idea of where to go with this, I'd really appreciate it.

  8. flash
    Joined: Mar 12, 2001
    Posts: 652


    Hey Jonny, thanks so much for posting this! I've been contemplating the same deal with my rear suspension. After seeing how easily the bones can snap, I'll definitely be adding some upper torque arms. (though I doubt my flathead has enough torque to really match the damage you can do with that 413!).

    Dont' let it get you down, test drives are meant for busting shit and working out the bugs! Looks like you could be back on the road soon.
  9. Andy
    Joined: Nov 17, 2002
    Posts: 4,803


    If you keep the arms where they are now, you really have no choice but to make the connection at the rear a movable joint. The rear rotation can be held by little links on top as suggested or one torque arm like the last Camero's.
  10. chaddilac
    Joined: Mar 21, 2006
    Posts: 13,917


    may have had a bit of rust inside as well. These guys make a lot of sense, when you compare how they a used open drive vs. torque tube, there is no torque on them when the tub is there.

    I'm reconsidering mine now?? crap!
  11. SUHRsc
    Joined: Sep 27, 2005
    Posts: 5,079


    when you split the arms in the rear its causing a twist on the rear axle at any point where the suspension doesnt move in a perfect flat movement
    so this stress has to go somewhere and the weakest point is the wishbones in this case
    the same problem occurs when you split the bones on a v8-60 tube axle...
    when you split them on an I-beam it can twist and actually almost benefit you in the form of an anti-sway device
    but a tube cant take that twisting motion and starts transfering the forces elsewhere....and....SNAP

    ontop of all of that they're just not designed to take the kind of torque put to them in the set-up like this

    best to leave the banjo wishbons on the banjo and go with some other design

    glad it happend to you when it did and not on the open road
  12. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    I've been searching the board and found a post on truck arms (60s-70s GM). Was wondering if it may work.

    The pic in post 31 by MP33 looks fairly promising. Noticing he's running a spring-behind, open drive rear end, essentially what I have... They reay don't seem much different than radius rods, other than the bushings... Seems that for some reason they may work better due to the bushings, maybe? No good or do I have a possiblity here?

    Attached Files:

  13. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    I'll be researching this tonight to decide what to do. Here are my options:

    -Retain the castings for the spring mount
    -Ditch the radius rods altogether and cut the mounts off the frame
    -Devise a 4-link setup with all new mounts (Any charts/diagrams/pics are helpful)

    -Make new radius rods to attach to the stock spring castings incorporating bushings and attaching up front in the same position (or make rods of chrome moly with new mounts on the axle near stock location as in pic below)
    -Add a torque arm to make a 3-link setup as shown in the pic below or this post:
    from root post:

    The other option I thought of was:
    -relocating the frame mounting location of the radius rods closer to the center of the frame, triangulating it more
    -Adding a link similar to the one pictured or two to make a 3 or 4-link setup.

    I need to know the correct geometry for the links in relation to the travel of the rearend. Anything and everything is pretty helpful right now. Thanks again.


    Attached Files:

  14. 29SX276
    Joined: Oct 19, 2003
    Posts: 469


    Jonnyhotrod;Sorry about you breaking your ride,but the good thing is that no one was injured.
    Very good info here about '36 'bones;I'm running the same on my flathead powered Essex.The car has an open drive line running a Ford 9"axle.I didn't split my wishbones,but I replaced the original ends with two 3/4" tie-rod ends so basically the rear end pivots like the original Ford rear.This prevents the wishbones from acting like a sway bar;am I correct in this?I'm thinking I might have to add a panhard rod for any side to side movement.
    Comments more than welcome.
  15. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    If it were as simple as moving the mounts in, that would be great! I don't think that will do it though from what's been said so far. I think that the flexion caused by the torque of the spinning driveshaft (becoming essentially shorter or longer) pulls in and pushes the rear end out, as there's no torque tube to keep it in place as in the original design. The inward or outward flexion combined with the twisting causes the rods to snap under the load. Hence the additional links. From what I've gathered so far, the rear axle mount must have a bushing. If there's a way to run the radius rods in thier current position (last position before being ripped out) without rear bushings, I'd like to see examples of what needs to be done to the rest of it to take the strain. Maybe it would work on a low HP mill, but I have 500 ft lbs of torque to bear.

  16. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


  17. When I replied I was assuming the bars were not parallel. I really can't tell from the pics. If they are parallel you may be getting more of a twisting moment that a torque issue. From the video it looked like torque is what did you in though.

    For my 27 Roadster I was thinking of using 36 bones bushed at both ends as the lower links of a four-bar or maybe even a three-bar set up. It does give a traditional look with ease of travel and strength.
  18. MercMan1951
    Joined: Feb 24, 2003
    Posts: 2,654


    Looks like they broke before...they look odd to me, --the way they broke...almost like they had been welded in the past...
  19. pasadenahotrod
    Joined: Feb 13, 2007
    Posts: 11,776

    from Texas

    It has been practice for decades by racers and street rodders to weld a 1/4"thick tapered steel gusset on top of the forging going forward across the factory fusion weld on down the tube about 8-12" to prevent exactly this scene from happening when using 35-36 radius rods on an open drive rearend.
    Even if you are running the ends up under the car similar to a torque tube stock style rearend with rod ends, tie rod ends, or bushing & eye ends to retain the factory triangulated rotation design.
  20. hiboy32
    Joined: Nov 7, 2001
    Posts: 2,781

    from Omaha, NE

    I also have an open drive with early wishbones. I made brackets on top of the rearend and have bars going from the top of the rearend to the top of the wishbone mount. Basically makes it ladder bars. Now, I know that I only have a flathead, but I have absolutly punished this set-up and everything is still intact.
  21. a question in the same vein, what about a 9" with '40 bones re-worked to run on the frame rail (like the front end) on a model A.
  22. you'll break 'em eventually. '40 style bones have even less meat than '36's.

    In theory, the leading ends of the bones should be as near the front driveshaft u-joint as possible both in length and width, so that the maximum articulation is allowed.
  23. haring
    Joined: Aug 20, 2001
    Posts: 2,335


    Watching the video, the radius rods broke there at the end of the clip, when you got on the gas a little?

    Wow, didn't take much.

    And BOTH of them broke?

    You are one lucky SOB. Thanks for posting this, along with photos. I have the same rear rods that I am planning on using with a '48 open drive banjo (w/ flathead). Your photos were good reminders that some additional gusset work alont with a panhard or torque bar will be necessary. I plan to keep my rear rods triangulated as much as possible (not run out to the rails).

    BTW, your coupe looks great -- good proportions, and heartwarming to see the New England truck grille style alive and well. :)
  24. COOP666
    Joined: May 8, 2007
    Posts: 724

    from Austin TX

    Good info here - I'm building my phaeton with '36 radius rods, this makes me realize I need to do some thinking about how to set it all up properly.
  25. COOP666
    Joined: May 8, 2007
    Posts: 724

    from Austin TX

    BTW, I had something similar happen soon after getting my sedan on the road. The rear end is a four-bar set up with coil springs on an 8-inch Ford rear. I took a corner hard on the way to dinner, and on arriving noticed the car was sitting weird in the parking lot. Turns out the rear upper shock mounts had never been properly welded, merely tacked at the bottom where the tube connects to the bracket. (This was an old P&J frame that the previous owner had done work on. My fault for not checking this when everything was going together.)

    I cut out the old mounts, made some seriously over-engineered new ones out of 1/4 inch plate, and asked my fabricator friend to TIG that shit up good. I also re-did the panhard bar, as it was set up all wrong, too, which didn't help. Now, the frame will bend before those mounts go!
  26. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    Thanks! You learn from this kinda stuff, and this is what it's all about. Glad to have all the input here. Thank you.

    I have decided to go with a triangulated 4-link set up. I bought a parallel 4bar from a local shop, and promptly cut it up to work with radius rods, as I didn't want to compromise my original look. Also the parallel set up interfered w/ the spring mounts. Figured it saved me SOME fabrication.. maybe not, having everything tapped out and brackets drilled etc.

    I separated the shock mount/rear bushing mount and cut off the upper tab to weld to the inboard of my rear end. I measured an equal distance in toward the pumpkin and tacked them on. The shock mounts went back in the box as I already have them welded on from before. I then put in a set of bars and saw where they landed in space. I angled them down slightly to intersect an imaginary line to the frame mount. Is this correct? I understand if they are tilted downward they essentally lift the center of the car under acceleration and take the forward shock of braking forces. I have built a chassis cross-brace to accept the front mounts of the upper arms, gusseted foward to the trans cross brace and mount. Please let me know if this is right, or if the upper bars should be parallel with the lower bar.... I'm taking a break from welding now. :)

    From there, I ground the casting of the original radius rod, and the lower bushing mount slid right under it, as so I may solid weld it for the radius rod bushing to be recieved. I then sliced a long section out of the bottom of the radius rod to accept the heavy steel tubung from the 4bar setup. This will be solid welded, with tie rod ends at the frame.

    Pics to come.. I have to drive back to where the car/camera are. I'm open to any suggestions. Biggest thing is if the uppers should tilt out and down or out and parallel to the lowers. It's been jumped on and dropped from the jack to see if anything acts wierd while just tacked together and it all moves and nothing broke. pinion angle seems pretty static. Thanks.

  27. Jonnyhotrod
    Joined: Jul 27, 2003
    Posts: 430


    What's the bushing? Are your uppers parallel to the radius rods? Thanks.

  28. brandon
    Joined: Jul 19, 2002
    Posts: 6,349


    did this on my current a pretty slick....brandon:D

    Attached Files:

  29. Gigantor
    Joined: Jul 12, 2006
    Posts: 3,825


    Jesus Johnnyy - sorry to hear about that. If you plan on running to that yard in Elliot to look for some new(er) parts, let me know.
  30. budd
    Joined: Oct 31, 2006
    Posts: 3,478


    the chevy 60/66 truck arms are very close where they mount at the front, just enough room for the steady bearing in between, plus they have large soft rubber bushings that allow them to flex when one wheel is on top of a bump. next time you see a nasscar upside down take a look at how they have this style of arm done.

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