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, 07:14 PM posted to rec.crafts.metalworking
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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.

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Old May 12th 10, 07:46 PM posted to rec.crafts.metalworking
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"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



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Old May 12th 10, 09:28 PM posted to rec.crafts.metalworking
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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


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Old May 12th 10, 09:47 PM posted to rec.crafts.metalworking
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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
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Old May 12th 10, 10:17 PM posted to rec.crafts.metalworking
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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.




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Old May 12th 10, 10:26 PM posted to rec.crafts.metalworking
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"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


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Old May 12th 10, 10:32 PM posted to rec.crafts.metalworking
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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



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Old May 12th 10, 11:15 PM posted to rec.crafts.metalworking
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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.
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Old May 12th 10, 11:26 PM posted to rec.crafts.metalworking
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"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.


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Old May 12th 10, 11:46 PM posted to rec.crafts.metalworking
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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


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