PTO Wobble

[MHarryE]

U-joints create a speed variation. Here is a graphical representation for a 30 degree shaft angle - shaft varies in rotation speed from 850 to 1150 rpm twice each rev for this example. That's why the u-joints are phased on a drive shaft - opposite end at the same phase angle cancels the acceleration/deceleration - but the shaft sees the speed change and they wobble. Your posthole auger has a very large u-joint angle so speed changes in the shaft are extreme, but as the input shaft on the gearbox is at roughly the same angle as the pto shaft on your tractor, there is no speed change at the auger and it runs pretty smoothly.

 

[MBTRAC]

Suggest you check the indexing of your PTO driveshaft uni joints as they may be out of phase

Driveshaft Phasing & Its Importance

You’ve just received your BIT or DOT inspection paperwork and recap from Managed Mobile’s recent visit. One of the notes that grabs your attention states,

managedmobile.com

You may also wish to join Aussie/NZ Kubota BX Owners Facebook group as you'll find a lot of 'local' knowledge available for us Aussies.

 

[Madz]

Thank you all - didnt realise speed variation and phasing was even a thing! The alignment looks to be correct though from what I can tell. Hopefully it is just the angle as mentioned - I've tried it on a small test hole and it seems to operate okay so fingers crossed! Appreciate all the advice

 

[ruffdog]

That PTO shaft only runs 540 rpm so it should be fine.....run it.

 

[ovrszd]

Its just the shroud. if the shaft was bent it'd be shaking like crazy. I guarantee its fine.

Yep. Shaft is straight. Look at the shroud where the two pieces meet. No wobble at all.

 

[Railroadman1]

my thought is some of the wobble is in the U/joins when you lower it down the wobble will be less or none

 

[Railroadman1]

I don't think PHD u-joints are past maximum angle. I wonder if condition of PHD u-joints has been checked lately?

Have you ever wondered similar to me how the u-joints on a 4WD pickup that had a very high lift kit installed survive those extreme angles at high rpm's?

if the lift is done correctly they should change the angle to align the shaft/ U-joints

 

[ovrszd]

if the lift is done correctly they should change the angle to align the shaft/ U-joints

Actually, if there's no double cardan joint involved, the two shafts are parallel. Then the amount of difference between the shafts is limited by the max angle the joint can run. Most single joints max out at 15 degrees.

 

[LD1]

I see nothing to worry about. AS long as the shaft halves can slide in and out of one another....no worries

 

[dougtrr2]

This is interesting to me as we have a lot of loose rock here and it's definitely going to be an issue - the BX25 at idle though doesn't have any real hydraulic flow/pressure (not sure about the terminology) and the PTO leaver is basically engaged or not, so I'm not sure I'll have much ability to slow it further than shown in that video which was only reasonably low engine revs from memory

I have a BX24. I understand this comment about hydraulic flow/pressure at idle e.g. the loader and three point don't work until you get some RPMs up.

But I think the PTO must work differently. I have a logging winch and even at idle it pulls significant weight and can stall the engine if I get hung up.

Doug in SW IA