Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Old May 12th 10, 04:00 PM posted to rec.crafts.metalworking
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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



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Old May 12th 10, 04:06 PM posted to rec.crafts.metalworking
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Default rotational vibration


"Karl Townsend" wrote in message
anews.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



I should have added, this is what the harmonic balancer on an engine is for.
I have no clue about building or designing these. Also there's serious
torque here, 60 horse being transmitted at 540 RPM.

Karl


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Old May 12th 10, 05:02 PM posted to rec.crafts.metalworking
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Default rotational vibration


Karl Townsend wrote:

"Karl Townsend" wrote in message
anews.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



I should have added, this is what the harmonic balancer on an engine is for.
I have no clue about building or designing these. Also there's serious
torque here, 60 horse being transmitted at 540 RPM.

Karl


Since most of us don't have farms / orchards or use these items, a link
to them might help us understand the issue.

The "bucking forward to reverse" description makes it sound like
something is momentarily freeing up and jumping forward only to have the
drive slam into it a fraction of a second later, i.e. uneven loading on
the drive.

Adding rotating mass somewhere in the drive should change the resonant
frequency. Also, you say slowing it down a bit helps, can you speed it
up slightly to change the frequency without hurting performance? bumping
up to 600 PTO RPM isn't likely to critically over speed anything, but
might get you out of the resonant range.

The harmonic dampers on an engine are basically a balanced flywheel
mounted to the rotating shaft via an elastic (rubber) coupling.
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Old May 12th 10, 05:04 PM posted to rec.crafts.metalworking
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Default rotational vibration


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

"Karl Townsend" wrote in message
anews.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



I should have added, this is what the harmonic balancer on an engine is
for. I have no clue about building or designing these. Also there's
serious torque here, 60 horse being transmitted at 540 RPM.

Karl

One thought, if it is a square shank pto shaft it could be
slide together 90 degrees out, causing all kinds of vibration.

basilisk


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Old May 12th 10, 06:14 PM posted to rec.crafts.metalworking
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....
Since most of us don't have farms / orchards or use these items, a link
to them might help us understand the issue.


Sorry, I couldn't find a good link. An airblast spray has a huge squirrel
cage fan hooked by a gear box and belts to the tractor PTO. the air from the
fan is nozzled down so the air leaves at over 200 mph. Takes a lot of
horsepower to do this.



The "bucking forward to reverse" description makes it sound like
something is momentarily freeing up and jumping forward only to have the
drive slam into it a fraction of a second later, i.e. uneven loading on
the drive.

Adding rotating mass somewhere in the drive should change the resonant
frequency. Also, you say slowing it down a bit helps, can you speed it
up slightly to change the frequency without hurting performance? bumping
up to 600 PTO RPM isn't likely to critically over speed anything, but
might get you out of the resonant range.

The harmonic dampers on an engine are basically a balanced flywheel
mounted to the rotating shaft via an elastic (rubber) coupling.


I'll try the rotating mass idea by just boltinh a plate to a large pulley.
Thanks, I wasn't thinking this simple. Still, if there was some way to have
mass with the elastic coupling, it would work far better. i just have no
clue how to build this.





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Old May 12th 10, 06:18 PM posted to rec.crafts.metalworking
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Default rotational vibration

I don't know what an air blast sprayer is, but I have used a lot of 540
rpm pto equipment and I have never had that sort of an issue with the
PTO shaft itself.
My guess is that the problem is deeper inside the machine and not
really related to the PTO shaft at all.
If you are repairing it "for about the fifth time", It sounds as
though you haven't ever gotten to the real problem.
Could you contact the mfr about it or a dealer? It may be a common
problem.

I guess you have a lot more modern tractor than any of mine. My 60 Hp
Case 800 diesel only goes 1450 rpm's at 540 PTO speed.
Have you really checked PTO speed? Could it be that you are over
revving the sprayer?

Pete Stanaitis
--------------

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


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Old May 12th 10, 06:27 PM posted to rec.crafts.metalworking
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Default rotational vibration

here's a pic of a similar unit:
http://www.jacto.com/sprayers/agricu...arbus_400.html


"spaco" wrote in message
.. .
I don't know what an air blast sprayer is, but I have used a lot of 540 rpm
pto equipment and I have never had that sort of an issue with the PTO shaft
itself.
My guess is that the problem is deeper inside the machine and not really
related to the PTO shaft at all.
If you are repairing it "for about the fifth time", It sounds as though
you haven't ever gotten to the real problem.
Could you contact the mfr about it or a dealer? It may be a common
problem.

I guess you have a lot more modern tractor than any of mine. My 60 Hp
Case 800 diesel only goes 1450 rpm's at 540 PTO speed.
Have you really checked PTO speed? Could it be that you are over revving
the sprayer?

Pete Stanaitis
--------------

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


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Old May 12th 10, 06:42 PM posted to rec.crafts.metalworking
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First recorded activity by DIYBanter: Apr 2007
Posts: 3,138
Default rotational vibration

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


A harmonic balancer is the mechanical equivalent of a second-order low
pass filter for electrical signals. The differential equations are
identical in form. In addition to mass (inductance) and elasticity
(capacitance) you need damping (disspation). In a harmonic balancer
this comes from losses in the elastic material (typically rubber), or
it may come from the load.
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Old May 12th 10, 06:48 PM posted to rec.crafts.metalworking
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Posts: 22
Default rotational vibration

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


So what do you repair to fix the problem? Changing over to 1000 RPM
shaft would help if its a PTO shaft problem.
You can check that the PTO shaft is telescoping freely. Also check that
the tractor PTO shaft and machine shaft are the same height and point at
each other.
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Old May 12th 10, 07:05 PM posted to rec.crafts.metalworking
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Posts: 6,746
Default rotational vibration


Karl Townsend wrote:

...
Since most of us don't have farms / orchards or use these items, a link
to them might help us understand the issue.


Sorry, I couldn't find a good link. An airblast spray has a huge squirrel
cage fan hooked by a gear box and belts to the tractor PTO. the air from the
fan is nozzled down so the air leaves at over 200 mph. Takes a lot of
horsepower to do this.


So this is basically a leaf blower on steroids? Unless something is
loose in the drive line, this should provide a very stable drive line
loading.



The "bucking forward to reverse" description makes it sound like
something is momentarily freeing up and jumping forward only to have the
drive slam into it a fraction of a second later, i.e. uneven loading on
the drive.

Adding rotating mass somewhere in the drive should change the resonant
frequency. Also, you say slowing it down a bit helps, can you speed it
up slightly to change the frequency without hurting performance? bumping
up to 600 PTO RPM isn't likely to critically over speed anything, but
might get you out of the resonant range.

The harmonic dampers on an engine are basically a balanced flywheel
mounted to the rotating shaft via an elastic (rubber) coupling.


I'll try the rotating mass idea by just boltinh a plate to a large pulley.
Thanks, I wasn't thinking this simple. Still, if there was some way to have
mass with the elastic coupling, it would work far better. i just have no
clue how to build this.


I don't know what your "bolt to large pulley" setup looks like, but if
you can have oversized holes in that plate and fit rubber tubing around
the bolts that go through it you'll get your elasticity. use a rubber
washer on each side of the plate as well and some secure stop like
nylock nuts, double nuts with a lock washer between, castle nuts and
cotters, etc. so the bolt connections are secure without being over
tight.


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