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Technical How much driveshaft runout is ok?

Discussion in 'The Hokey Ass Message Board' started by 36-3window, Nov 13, 2015.

  1. had a driveshaft for my latest project shortened by a local shop that does a lot of them for the dirt track guys . apparently they are not as fussy......

    .110 run-out by my dial indicator...think that will cause a problem?

  2. Well .0625 is 1/16" and you are at nearly .125 wich is 1/8. Length of driveshaft will make a difference in what will be the most tolerable the shorter the shaft the closer the tolerance, I may run it and see but I am going to guess that you are going to notice the vibration more then the local short track racer.
  3. thirtytwo
    Joined: Dec 19, 2003
    Posts: 2,640


    I know you checked but.... just make sure your pinion and trans are the exact same .. The only way that thing should move almost an 1/8 is if something is very wrong I'd take it back ...clutch and u joint or cat-co?
  4. maybe try another spot with the paint sanded off.
    is the tube egg shaped?

  5. drtrcrV-8
    Joined: Jan 6, 2013
    Posts: 1,399


    THERE IS NO EXCUSE FOR THIS KIND OF SLOPPY WORK!!! Take it back & ask them(preferably the owner) to please re-do it RIGHT!!! Unless you like driving with a 'Vibro-Massage' & regularly replacing your U-joints, tail shaft seals, & possibly tail shaft housings(if the off-set is at the transmission end) or rear U-joints, pinion seals, bearings, etc (if the off-set is at the axle end)
  6. burl
    Joined: Nov 28, 2007
    Posts: 715

    from Minnesota

    .005 to .010 is considered the max run out.The way your checking could show some kind of alignment issue in the u joints.Realy need to fixture off the u joint yokes to check the shaft runnout by its self.
    firstinsteele likes this.
  7. Was it balanced? They would be my key concern.
  8. ratrod72
    Joined: Sep 23, 2014
    Posts: 82


    Looks like it is welded in crooked from what I can see in the pic.. I always face off the driveshaft tube in my lathe an the yoke usually has to be tapped in the ID of the driveshaft tubing.. They usually only runout about .005 ... I would not run that driveshaft !!
  9. Eric , not Catco or clutch & u-joint...a local guy and i was trying to save a few $$$

    the front of the shaft with a factory weld shows .008 run-out . in the rear you can actually see it move when turned by hand , it is obviously welded crooked. not sure how it happened , he showed me his fixtures for doing this. in the past i've actually shortened them myself with a lot better results

    i think the lesson is you should check everyone's work
    tb33anda3rd likes this.
  10. thirtytwo
    Joined: Dec 19, 2003
    Posts: 2,640


    Yeah , it seems the older I get and the more trust I put in people to do a good job.... the more I end up wishing I done it myself....

    Something went really wrong there must of have the job to the new guy ... Or maybe a few too many brewskis?
  11. I took a factory driveshaft to be straightened that looks like it's never taken an impact of any kind... it was 50 thou off. they straightened it and the vibration is gone.
  12. If it has that much run out it should have a ton of weight in i build 5 drive shafts daily at factory i aim for.005
  13. squirrel
    Joined: Sep 23, 2004
    Posts: 47,804


    that driveshaft looks like crap. go get your money back and find another shop to do your driveshaft work, or do it yourself.
  14. yeah , i knew it was crap...just how bad i didn't know until i put the dial indicator on it

    i'm out $50...lesson learned

    a totally new driveshaft is being shipped from a very reputable supplier. they guarantee less than .006 run-out and fully balanced
  15. $50? Give it the heavo-ho, try to get your $$ back or chalk it up. I just had a nice shaft made for my Ford, balanced, all Neapco and Spicer components, 3.5" tube and it set me back $300 cash at a drive shaft shop.
  16. 27troadster
    Joined: Mar 14, 2013
    Posts: 105


    From a quality / pride in workmanship and pride it what you bolt to your hot rod, I agree with everyone's comments.

    However, to answer your question: from a machinery standpoint, here is no "limit" to run out on a shaft suspended by its ends that doesn’t have anything attached along its length, like gears, pulleys, rollers, close tolerances to other pieces of machinery, etc. Provided that 1) it is balanced correctly and 2) the strength of the material is high enough to keep the shaft from bending under the centrifugal force caused by its own offset (this is a real problem in papermills, I’ve seen video of 20 foot long, 6 inch diameter solid steel shafts spinning at high RPM, turn into what looks like a wet spaghetti noodle as the machine flung it around and completely destroyed everything in its path! This was due to the centrifugal force caused by the offset being too great for the strength of the steel. But that is an extreme case and would not happen with a driveshaft.)

    From back when I ran a balance machine for a living...

    There are two things that cause a part to be out of balance:
    First is non-uniform mass distribution, which is what we typically think of when we think about balance.
    Second, is called eccentricity. Let’s say I was balancing a flywheel and the flywheel had perfectly uniform mass distributed about the locating hole drilled in the center and, therefore, was perfectly balanced about the center of the locating hole. Then, if I mount it to a crankshaft such that entire flywheel is offset from the center of the bearings, then the axis about which the mass is distributed is different than the axis through the bearings. In fancy terms, the center of gravity, or inertial axis about which the flywheel would rotate without bearings, is different than the axis of its bearings. As the part rotates, it will try to turn about its inertial axis which means the bearing axis has to move in a circle, which is what causes vibrations. Now, we can correct the imbalance caused by excessive eccentricity by adding mass to the flywheel on the opposite side of the offset.

    In other words, the drive shaft will work just fine IF it is properly balanced on a dynamic balancer to account for its mass being offset from the bearing axis.

    So if the guy put a brand new, very large weight on the “low” side of the run out, actually there should be a weight on both ends in this case, then maybe it’s okay, and maybe he knows what he’s doing……… But……. I would lay down money, based on his shoddy workmanship in the fit up and welding, that he doesn’t have a clue about balancing!

  17. do we know if it vibrates?
    i made a drive shaft for a stock car once. the car needed to just finish the final race and he had broken it in practice. i made it up from junk i had and welded it on my work bench BY EYE from measurements it was picked up and brought to the track.
    under 100 mph it was fine, no vibration, under 120 it was tolerable, any thing above that he had a hard time keeping his hands on the wheel.
    he finished 3rd from last and held his position in the standings.
  18. That looks so crooked. Ive done it myself dozens of times by taking my time a measuring 20 times to make sure its square, and phased correctly and then welding it. Then get it balanced later locally. that thing will tear shit up in your driveline.
  19. convx4
    Joined: Jan 22, 2006
    Posts: 95


    I believe that having the yoke ends clocked in the same plane is most important in keeping the shakes away. To do this I use use bubble level on the caps flat area on each yoke. I have a 50's Bear Dynamic Balance that I have just started to play with. IMG_2184 (Small).JPG

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