rotational vibration

If the "bump" is indeed at the rotational frequency of the PTO, I'd be looking at the drive sections that rotate at that RPM. Presumably the fan is overdriven from the 540 RPM PTO to a higher RPM so an issue there wouldn't manifest once per PTO rev.

If the drive pulleys from the PTO shaft aren't concentric, there would be a cyclic variation in belt tension on each revolution, and since the belt will tend to move in and out in the groove with tension, it would also translate into a cyclic change in the drive ratio. It could be subtle, but with that much HP and mass involved, it could become significant at that resonant frequency.

Since you report that the problem keeps coming back, it may be that an issue like pulley concentricity has always been there, but becomes more apparent over time as everything loosens up and the vibration can have more effect. Perhaps get out the dial indicator and mag base and check the run out on the drive pulleys?

Thanks Pete, more good suggestions.

Julie hit a home run on the PTO rebuild. The fleet farm store was stocked out. So, she found a specialty drive line shop and had everything rebuilt with top-of-the-line parts. She's not only a great go-fer, she's a good looker too. (That means she can find stuff)

I'm puttin' the machine back in the field tomorrow but a complete rebuild on this unit is job 1 at end of season.

Karl

On Wed, 12 May 2010 10:00:08 -0500, "Karl Townsend" wrote the following:

C'mon, Karl. You know better than to ante up with such scant tidbits of info. What sprayer, what tractor, what pump, how straight is the PTO shaft in use, does it happen with the pump disconnected, is there any play in the PTO yoke-to-shaft interface, are the yokes greased up good and slick, etc.?

-- You will find that the mere resolve not to be useless, and the honest desire to help other people, will, in the quickest and delicatest ways, improve yourself. -- John Ruskin

On Wed, 12 May 2010 16:26:55 -0500, "Karl Townsend" wrote the following:

Aha! 540/9 = 60. It's merely a 60 cycle hum, Karl. Throw a capacitor at it.

I thought your Arbus exploded diagrams were fantastic, too.

-- You will find that the mere resolve not to be useless, and the honest desire to help other people, will, in the quickest and delicatest ways, improve yourself. -- John Ruskin

Is the shaft 'in phase' and not twisted? I have put as high as 140 hp through a 540 pto shaft running a 66 inch blower spinning a fan weighing close to 200 pounds. I never had any vibration problems at any speed up to

...

...

All Right, Larry, you're agitating.

I have to say RCM really came through for me this time. Whole bunch of good ideas. Even with all the political OT crap, this is a pretty good group. BTW, this problem is all Obama's fault - everything else is.

Karl

On May 12, 11:00=EF=BF=BDam, "Karl Townsend" wrote:

Universal joints are widely used to transfer rotational motion through shafts which are not perfectly aligned. A feature of these devices is that the output shaft does not rotate in precise synch with the input shaft. There is a cyclic "lead" and "lag" introduced by the mechanism. A nice explanation of this phenomenon is presented in the wikipedia posting on universal joints. Use google with search words "universal joint" and pick up on the Wikipedia link. In practice, universal joints are used in pairs, aligned so that the cyclic lead and lag introduced by the first joint is cancelled out by by the second joint. This correcting action is dependent on having the two joints mounted in phase with each other, and this is why many setups use a rectangular telescoping shaft to connect the two joints. That way, it is impossible to get them connected out of phase. If mounted incorrectly, a pair of U-joints can aggravate the lead-lag problem rather than correct it. The symptom described in the case of Karl's sprayer is the sort of pulsing torque which would be introduced by either a single U-joint or a pair of U-joints which got mounted out of phase. My belated input to this discussion is a suggestion that Karl to grab a cool refreshment and take a reflective look at his setup. Are the U-joints in phase? (Refer to the wiki photo to see the right way.) Are the PTO shaft and sprayer shaft set up to be parallel, and not too far out of alignment? With power off, rotate the shaft by hand to feel for increased resistance at some point in a complete rotation.

Pat

It looks like the DynaFlex LCR series is made for PTO applications... maybe there is one that will "bolt right on" without too much effort?

BINGO!!!!

This is just what I need. And I've got room to install this.

You get a FREE BAG OF APPLES. But, just ask Bob Swinney, its hard to collect the prize.

Thanks a bunch,

Karl

You're welcome... don't worry about the prize, it's the thought that counts. LOL David

Going looser will drop the resonant frequency of that part of the system. Doesn't help if the field ends up smelling of burned rubber instead of insecticide though.

Lots of ideas from lots of folk. We have faith in you :-)

regards Mark Rand RTFM

Demand Strawberries!

If your PTO shafts are not the same height as in this picture it WILL give you vibration! When the rear U joint is not the same height, the speed change from the front U joint is not cancelled by the rear U joint. This is why all good designed machinery has a way to adjust the PTO shaft or drawbar up or down to align the PTO shaft.