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.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration

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


  #2   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
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


  #3   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 6,746
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.
  #4   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 553
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


  #5   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


....
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.





  #6   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 687
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


  #7   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
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


  #8   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
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.
  #9   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
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.
  #10   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
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.


  #11   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 6,746
Default rotational vibration


Karl Townsend wrote:

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


Ah. Looking at that, it brings up the question of the spray pump. If
there is a problem with the triplex pump with one cylinder not working
for some reason, you would get a lighter load each time that piston was
supposed to be on it's pressure stroke, possibly allowing the flywheel
effect of the blower to drive the pump ahead of the PTO drive
momentarily with the PTO catching up a fraction of a second later
causing the drive line to experience the forward - reverse bucking you
noted.
  #12   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 124
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


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



  #13   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


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


I bet this would work real well if I could redesign the drive line to use a
coupling. maybe this winter.

Thanks for the link.

Karl


  #14   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 852
Default rotational vibration

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



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


What happens when you change the tension on the fan drive belts? If they are
implicated at all, that'll change the resonant frequency. It's a bit far to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM
  #15   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,138
Default rotational vibration

On Wed, 12 May 2010 13:46:32 -0500, "David Courtney"
wrote:

"Karl Townsend" wrote in message
tanews.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.




  #16   Report Post  
Posted to rec.crafts.metalworking
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


  #17   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


What happens when you change the tension on the fan drive belts? If they
are
implicated at all, that'll change the resonant frequency. It's a bit far
to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM


I've never tried that. I keep the eight belts pretty tight, 1/2" deflection
in the three foot between pulley spacing. can't go tighter, I'd take out
bearings. What do you think running loose would do? Not much margin here, I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl



  #18   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 6,746
Default rotational vibration


Karl Townsend wrote:

What happens when you change the tension on the fan drive belts? If they
are
implicated at all, that'll change the resonant frequency. It's a bit far
to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM


I've never tried that. I keep the eight belts pretty tight, 1/2" deflection
in the three foot between pulley spacing. can't go tighter, I'd take out
bearings. What do you think running loose would do? Not much margin here, I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl


I recommend you closely inspect the spray pump as noted in my other
post. If it is a triplex pump like the one on the other unit you posted
a link for it could very well produce a "lumpy" torque load if one of
the pistons was not functioning like from a stuck inlet valve.

The other thought, is that if this lumpiness occurs once per PTO shaft
revolution i.e. 9 times a second, something may be bent, such as the
shaft the pulleys are on, causing the belt tension to cycle every
revolution.
  #19   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 99
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


Karl: I'm not clear on how your system would lose mechanical balance. And
I don't know all the variables here but it sure sounds close to my balancing
my helicopter rotor which was turning at 500rpm. With an electronic
balancer that senses where the rotating item is when the accelerometer, or
in our case the velocimeter, reading is maxed, it is relatively easy to
determine where weight needs to be added to achieve balance. This is
however a simple explanation of a single plane balancing operation. Items
with some lateral extent like the cranshaft and flywheel system of a car
have two planes to worry about. If a single plane balancer could work for
you, most helicopter operations have the equipment. My guess is that you
are quite a trip from my zip code 93527. If you were close, I do have a
balancer and some experience with it on helicopters.


  #20   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 199
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


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.

SW


  #21   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


"Pete C." wrote in message
ster.com...

Karl Townsend wrote:

What happens when you change the tension on the fan drive belts? If
they
are
implicated at all, that'll change the resonant frequency. It's a bit
far
to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM


I've never tried that. I keep the eight belts pretty tight, 1/2"
deflection
in the three foot between pulley spacing. can't go tighter, I'd take out
bearings. What do you think running loose would do? Not much margin here,
I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl


I recommend you closely inspect the spray pump as noted in my other
post. If it is a triplex pump like the one on the other unit you posted
a link for it could very well produce a "lumpy" torque load if one of
the pistons was not functioning like from a stuck inlet valve.

The other thought, is that if this lumpiness occurs once per PTO shaft
revolution i.e. 9 times a second, something may be bent, such as the
shaft the pulleys are on, causing the belt tension to cycle every
revolution.


Thanks for the thoughts. This unit has a centrifical pump, no bumps there
plus it only uses a couple horse. You have a thought on bent, I know its not
in the shafts, but possibly the fan itself is bent. The entire fan could be
removed and put on some sort of unit to check balance and vibration. Anyone
know where I might find equipment to do this?

Karl


  #22   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


"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


  #23   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 6,746
Default rotational vibration


Karl Townsend wrote:

"Pete C." wrote in message
ster.com...

Karl Townsend wrote:

What happens when you change the tension on the fan drive belts? If
they
are
implicated at all, that'll change the resonant frequency. It's a bit
far
to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM

I've never tried that. I keep the eight belts pretty tight, 1/2"
deflection
in the three foot between pulley spacing. can't go tighter, I'd take out
bearings. What do you think running loose would do? Not much margin here,
I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl


I recommend you closely inspect the spray pump as noted in my other
post. If it is a triplex pump like the one on the other unit you posted
a link for it could very well produce a "lumpy" torque load if one of
the pistons was not functioning like from a stuck inlet valve.

The other thought, is that if this lumpiness occurs once per PTO shaft
revolution i.e. 9 times a second, something may be bent, such as the
shaft the pulleys are on, causing the belt tension to cycle every
revolution.


Thanks for the thoughts. This unit has a centrifical pump, no bumps there
plus it only uses a couple horse. You have a thought on bent, I know its not
in the shafts, but possibly the fan itself is bent. The entire fan could be
removed and put on some sort of unit to check balance and vibration. Anyone
know where I might find equipment to do this?

Karl


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?
  #24   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


"Pete C." wrote in message
er.com...

Karl Townsend wrote:

"Pete C." wrote in message
ster.com...

Karl Townsend wrote:

What happens when you change the tension on the fan drive belts? If
they
are
implicated at all, that'll change the resonant frequency. It's a bit
far
to
drive over to Blighty so we can instrument it up and workout where
the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM

I've never tried that. I keep the eight belts pretty tight, 1/2"
deflection
in the three foot between pulley spacing. can't go tighter, I'd take
out
bearings. What do you think running loose would do? Not much margin
here,
I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl

I recommend you closely inspect the spray pump as noted in my other
post. If it is a triplex pump like the one on the other unit you posted
a link for it could very well produce a "lumpy" torque load if one of
the pistons was not functioning like from a stuck inlet valve.

The other thought, is that if this lumpiness occurs once per PTO shaft
revolution i.e. 9 times a second, something may be bent, such as the
shaft the pulleys are on, causing the belt tension to cycle every
revolution.


Thanks for the thoughts. This unit has a centrifical pump, no bumps there
plus it only uses a couple horse. You have a thought on bent, I know its
not
in the shafts, but possibly the fan itself is bent. The entire fan could
be
removed and put on some sort of unit to check balance and vibration.
Anyone
know where I might find equipment to do this?

Karl


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


  #25   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 1,624
Default rotational vibration

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

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?


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


  #26   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 1,624
Default rotational vibration

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


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

"Karl Townsend" wrote in message
. octanews.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.


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


BTW, pretty good info in the catalog David found.


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
  #27   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 2
Default rotational vibration

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




  #28   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration

....
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.?

....

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



  #29   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 7
Default rotational vibration

On May 12, 11:00�am, "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.


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



  #30   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 124
Default rotational vibration

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

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


I bet this would work real well if I could redesign the drive line to use
a coupling. maybe this winter.

Thanks for the link.

Karl


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?
http://www.lord.com/portals/0/vibrat..._couplings.pdf
Catalog page 103... which is page 17 of the pdf; shows the LCR series.
There is a note that they can be either "through bolted"... or the metal
inserts can be tapped or counter-bored to accept fasteners; so there is a
variety of mounting choices.




  #31   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 3,286
Default rotational vibration


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?
http://www.lord.com/portals/0/vibrat..._couplings.pdf
Catalog page 103... which is page 17 of the pdf; shows the LCR series.
There is a note that they can be either "through bolted"... or the
metal inserts can be tapped or counter-bored to accept fasteners; so there
is a variety of mounting choices.


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



  #32   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 124
Default rotational vibration

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

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?
http://www.lord.com/portals/0/vibrat..._couplings.pdf
Catalog page 103... which is page 17 of the pdf; shows the LCR series.
There is a note that they can be either "through bolted"... or the
metal inserts can be tapped or counter-bored to accept fasteners; so
there is a variety of mounting choices.


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


  #33   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 852
Default rotational vibration

On Wed, 12 May 2010 16:32:59 -0500, "Karl Townsend"
wrote:


What happens when you change the tension on the fan drive belts? If they
are
implicated at all, that'll change the resonant frequency. It's a bit far
to
drive over to Blighty so we can instrument it up and workout where the
resonance is :-(

Mark Rand (Did similar work on power station foundations once)
ETFM


I've never tried that. I keep the eight belts pretty tight, 1/2" deflection
in the three foot between pulley spacing. can't go tighter, I'd take out
bearings. What do you think running loose would do? Not much margin here, I
smoked all the belts once, pretty spendy to rebelt this unit.

Karl



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
  #34   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 457
Default rotational vibration


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

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?
http://www.lord.com/portals/0/vibrat..._couplings.pdf
Catalog page 103... which is page 17 of the pdf; shows the LCR
series.
There is a note that they can be either "through bolted"... or the
metal inserts can be tapped or counter-bored to accept fasteners; so
there is a variety of mounting choices.


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



Demand Strawberries!


  #35   Report Post  
Posted to rec.crafts.metalworking
external usenet poster
 
Posts: 22
Default rotational vibration

Karl Townsend wrote:
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


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.
Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
OT, but not so much: Rotational _molding Bob Engelhardt Metalworking 0 October 7th 08 01:42 AM
Rotational Molding Machines [email protected] Metalworking 1 November 9th 07 04:24 PM
vibration [email protected] Woodworking 2 December 9th 06 10:09 PM
Rotational to Linear Gear Reduction calculation gtslabs Metalworking 9 February 25th 06 11:41 PM


All times are GMT +1. The time now is 02:30 PM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"