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
600 rpm. Rent, buy, or borrow an adjustable strobe light and check
different areas as it runs. If the fan is easily dissembled rest shaft of
each end of the fan on parallel, level angle irons with the ^ up to check
for balance.

"Karl Townsend" wrote in message
anews.com...

"Sunworshipper" wrote in message
...
On Wed, 12 May 2010 10:00:08 -0500, "Karl Townsend"
wrote:

I'm repairing the same issue on my airblast sprayer for about the fifth
time. Own something long enough and the same problems keep repeating. the
sprayer has a vibration in it at 2500 tractor RPM, 540 PTO RPM. The
vibration is not like a tire out of balance but its a bucking forward to
reverse. When it gets a little lose, in a few more hours of run it will
damn
near shake the tractor off the ground. Its also a natural harmonic at
this
RPM, slow down and the vibration goes away. Unfortunately, this REALLY
reduces sprayer performance.

I'm replacing the entire PTO shaft and tightening up the clearance in the
gear box again. if everything is tight, the problem is less severe. The
is
working on the symptom, not the cause.

This is a long shot, anybody know about balancing this sort of vibration
or
changing the natural harmonic frequency?

Karl


I'll take a stab at this one. This is a insecticide sprayer, right? If
so, that kind of stuff is awfully hard on equipment. It eats at metal
and is sticky. Is the fan clean? Could it be nasties built up in the
clutch, maybe when on down time leaking in the same position.
Bad bearings, that would do it. Sucking air between the tank and pump?

Just someone tring to help that klnows what a
Malathion-Methyl-Parathion-Ketone Flop is.

Gosh, I don't know what that is.

SW

Thanks, everybody, for all the thoughts. Still waiting on Julie to get
back with parts. She's been gone eight hours now. Looks like I work the
night shift to get back in the field tomorrow. I'll plan on tearing the
unit down for a rebuild this winter. its due.

Karl