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CV Plunge Demystified

Discussion in 'Shop - Driveline' started by Pharaoh XJ, May 6, 2010.

  1. Pharaoh XJ

    Pharaoh XJ Member

    Joined:
    Jan 20, 2008
    Location:
    Cairo, EGYPT
    I heard a lot about 930 cv, with plunging & non plunging joints.

    I am working on a design & I cant seem to get more of 18" of travel at 25deg, 18" is ok with me, but when I looked at axle plunge I found around 2 1/4" of plunge per axle.

    I never found the specs of plunge of 930 (series 15, 108mm) joints, The GKN catalog says 18mm ( ~1/4"), then I read on a forum 60mm (2.3" per axle ).

    I think I was taking here about the Star's plunge, but what about the axle's plunge inside the star, Sway aways have 3" splined axles


    Then the total should be
    Excuse my metric

    2 x 30 mm = 60mm joint plunge
    2 x (76 mm - 40 mm) = 72mm Axle plunge

    Total 132 mm per Axle = ~ 5 1/4"



    Does that make any sense ?
     
  2. Jess@HighAngle

    Jess@HighAngle Member

    Joined:
    Jan 25, 2007
    Location:
    Paradise , California
    You could certainly see that kind of plunge especially with the increased angles - the shorter the 1/2 shaft the more slip it requires as angles increase . I used to run into this issue with 18" ff 1/2 shafts that had 38 degrees max - its difficult -Jess
     
  3. fasttruck ryan

    fasttruck ryan Member

    Joined:
    Apr 13, 2010
    Location:
    temecula
    that sounds correct to me, the 5 in. i run the 930's on 3x3 arms,and get about 18" also, i could get more but am limited out on cv angle at full droop, then at full bump the car has only about 3 in. ground clearance.i run a 33x10.50, i guess if i ran a 35 in. tire i could get a little more.
    I never measured the cv to cv length droop to full bump but i know when i take them apart, you can definitely tell that the axle slides about 2 in. at both ends.

    what vehicle is this going on?
     
    Last edited: May 7, 2010
  4. Pharaoh XJ

    Pharaoh XJ Member

    Joined:
    Jan 20, 2008
    Location:
    Cairo, EGYPT
    its going into a class 10/ trophy bug car
    still in drawing phase


    I like the idea of non plunging CV joints with a slip joint axle shafts this will allow to 40deg of travel.

    How hard can it be to weld axle shafts to slip joint from a driveshaft ? I ve seen it done before but never heard any feedback from it .
     
  5. partybarge_pilot

    partybarge_pilot Well-Known Member

    Joined:
    Feb 19, 2002
    Location:
    Easton, KS
    That will open another whole can of worms. It has bee tried by many and the results range from very limited success to out right expensive failure..........
     
  6. Pharaoh XJ

    Pharaoh XJ Member

    Joined:
    Jan 20, 2008
    Location:
    Cairo, EGYPT
    I looked at the GKN catalog the Type 116 size 15(930) or Size 21(934)
    You get 40deg of articulation & up to 12" of slip :)

    Static load is half that of a solid shaft but can be compensated by moving to a larger joint

    Why not ?
     

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  7. Ramsey_ElWardani

    Ramsey_ElWardani Ironman

    Joined:
    Apr 1, 2001
    Location:
    Carlsbad, CA
    Torsional loads bind the slip joint and cause failure. High dollar attempts have failed as has your suggestion which has been tried with CVs and U-joints.
     
  8. Pharaoh XJ

    Pharaoh XJ Member

    Joined:
    Jan 20, 2008
    Location:
    Cairo, EGYPT
    I cant see why it will bind TT driveshaft slip joints withstand 800 hp axle shafts with 4.1 R&P & a 250 bhp motor

    250 x 4.1 = 1000
    1000/2 = 500 bhp per side

    Theoretically it has less load than a TT driveshaft joint
     
  9. Ramsey_ElWardani

    Ramsey_ElWardani Ironman

    Joined:
    Apr 1, 2001
    Location:
    Carlsbad, CA
    Because a correctly set up Trophy Truck has little to no driveshaft plunge. You are looking at several inches - it has been tried and it does not work so save yourself the time. If you search hard here there are several threads over the years about plunging axles and the like.
     
  10. partybarge_pilot

    partybarge_pilot Well-Known Member

    Joined:
    Feb 19, 2002
    Location:
    Easton, KS
    Also, your axle twists like a torsion bar taking shock load out of the R&P. The slip joints do not twist if the are going to have a chance in hell of plunging.........

    Your HP figures are off also. You need to be looking at torque. Torque is what breaks things.

    Say the TT has 650#'s of torque, at 3.21 low bear your DS is seeing a little over 2000#'s of torque.

    Now take your buggy motor at say 250#'s of torque. 3.21 low gear and a 4.88 R&P. This gives you almost 4000#'s of torque, divide by 2 and your in the ball park for what a TT drive shaft sees.................
     
  11. Pharaoh XJ

    Pharaoh XJ Member

    Joined:
    Jan 20, 2008
    Location:
    Cairo, EGYPT
    I was looking lately at the sand buggies with slip axles & u-joints & a lot of them seem to destroy the transmission flanges or their hubs because the slip joints don't plunge under loads, so the shaft doesnt compress breaking the drivetrain.

    If that case is true then the same should apply to the shafts NOT plunging inside the stars under heavy acceleration/braking
     
  12. partybarge_pilot

    partybarge_pilot Well-Known Member

    Joined:
    Feb 19, 2002
    Location:
    Easton, KS
    If your axles are made correctly then the main diameter of them is about 75% of the minor diameter of the splines. It will take a lot of torque before the splined sections start to twist. I can happen, but it's not enough to worry about. Your also dividing the amount of plunge between 4 areas rather than one so your plunge speed is a lot less.......
     
  13. fasttruck ryan

    fasttruck ryan Member

    Joined:
    Apr 13, 2010
    Location:
    temecula
    valid points partybarge....the splined section is designed to NOT twist but the center of the shaft can, allowing that greasy star to move.
     
  14. fasttruck ryan

    fasttruck ryan Member

    Joined:
    Apr 13, 2010
    Location:
    temecula
    how much travel are you looking to get pharaoh? what are you track width limits? is a solid axle ruled out? on a short wheel base or any for that matter, too much travel can cause some adverse side affects.
     

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