View Single Post
  #16   Report Post  
Posted to rec.crafts.metalworking
Karl Townsend Karl Townsend is offline
external usenet poster
 
Posts: 3,286
Default rotational vibration


"Don Foreman" wrote in message
...
On Wed, 12 May 2010 13:46:32 -0500, "David Courtney"
wrote:

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


Elastomeric coupling? (page 2): "The flexible element absorbs the
unavoidable torsional vibrations..."
http://pdf.directindustry.com/pdf/ko...-46550-_2.html


Put a flywheel on the load side of this and you have a harmonic
balancer.

Karl, what is the frequency of the vibration? Is it about 9 Hz
(synchronous with PTO speed) or is it considerably lower? If it's
lower, and if there is some sort of governor that maintains PTO speed
at 540 RPM in presence of varying load, then the vibration might be
that governor hunting.


How's you know that??? Yes its right at 9 bangs per second.

BTW, pretty good info in the catalog David found.

Karl