Nova Tractor MFZ 195 rotor balance/vibration?

[keenlanp]

I bought a used Nova Tractor flail this spring from a gent who said it was vibrating to the point it was unusable. He was convinced that the main rotor had been damaged during transport and due to some physical limitations he didn't want to deal with replacing the rotor and was willing to sell it for a fraction of what he paid for it. After I bought it, I confirmed that the vibration was going to destroy the mower if used as it was. I couldn't see any signs that the rotor was damaged, but ordered a new rotor since it came with a new set of hammers I could use as spares (we have lots of rocks). After installing the new rotor, the mower is still trying to shake itself to pieces if I try to use it. The only thing I can think of is that both of these rotors came from the factory unbalanced. They both have what seem to be excessively large weights welded near the ends of the shaft (to balance out the shafts which weren't balanced after manufacturing?) and I can't think of anything else that would lead to this kind of vibration. There are no hammers missing. My questions are: is there something I am missing that could cause catastrophic vibrations other than the shaft being unbalanced and would a machine/fabricating shop be able to check the balance on the shaft? Thanks as always for the knowledge.

 

[leonz]

UGGHH!!

Starting at the beginning, if you really intend to keep this flail mower you are going to spend a great deal of money.

Both Flail Mower rotors should be taken to a repair shop with a high speed balancing machine(2,200 RPM+) to balance them CORRECTLY.

If the repair shop has a high speed-2,200RPM+ balancer they will know what they are doing.

The first thing they will do is check the flail mower rotor to assure it is straight; no amount of bending will bring it back to the x horizon(level) if the Flail Mower Rotor
is bent at any point.

The repair shop with the high speed balancer will look at the mounting stations and determine if they were welded properly.
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First, the flail mower rotor must be balanced without the hammer/scoop knives and the mounting hardware attached.

Second the flail must be balanced for the second time with the mounting hardware ONLY.

Third the flail mower must be balanced with the hammer/scoop/spoon knives mounted and secured in each mounting station.

High quality roller bearings with a full set of rollers and seal on one side must be used.

 

[Jack Yuan]

I bought a used Nova Tractor flail this spring from a gent who said it was vibrating to the point it was unusable. He was convinced that the main rotor had been damaged during transport and due to some physical limitations he didn't want to deal with replacing the rotor and was willing to sell it for a fraction of what he paid for it. After I bought it, I confirmed that the vibration was going to destroy the mower if used as it was. I couldn't see any signs that the rotor was damaged, but ordered a new rotor since it came with a new set of hammers I could use as spares (we have lots of rocks). After installing the new rotor, the mower is still trying to shake itself to pieces if I try to use it. The only thing I can think of is that both of these rotors came from the factory unbalanced. They both have what seem to be excessively large weights welded near the ends of the shaft (to balance out the shafts which weren't balanced after manufacturing?) and I can't think of anything else that would lead to this kind of vibration. There are no hammers missing. My questions are: is there something I am missing that could cause catastrophic vibrations other than the shaft being unbalanced and would a machine/fabricating shop be able to check the balance on the shaft? Thanks as always for the knowledge.

This mower must hit something and its balance condition was damaged, the only solution is that replace a new rotor shaft. For example the big stone or stump hidden in the tall grass.

Just call them, I see they have the this rotor in stock.

Spare parts: MFZ195 rotor shaft

Nova Tractor MFZ195 rotor shaft. Parts number: 02.MFZ.195.016

nova-tractor.com

 

[Jack Yuan]

UGGHH!!

Starting at the beginning, if you really intend to keep this flail mower you are going to spend a great deal of money.

Both Flail Mower rotors should be taken to a repair shop with a high speed balancing machine(2,200 RPM+) to balance them CORRECTLY.

If the repair shop has a high speed-2,200RPM+ balancer they will know what they are doing.

The first thing they will do is check the flail mower rotor to assure it is straight; no amount of bending will bring it back to the x horizon(level) if the Flail Mower Rotor
is bent at any point.

The repair shop with the high speed balancer will look at the mounting stations and determine if they were welded properly.
------------------------------------------------------------------------------------------------------------------------------------------------------------

First, the flail mower rotor must be balanced without the hammer/scoop knives and the mounting hardware attached.

Second the flail must be balanced for the second time with the mounting hardware ONLY.

Third the flail mower must be balanced with the hammer/scoop/spoon knives mounted and secured in each mounting station.

High quality roller bearings with a full set of rollers and seal on one side must be used.

Hi Leonz, how are you? Nice to meet you here again.
You mentioned the rotor balancer, is there repair shop use balalncer for flail mower? Another issue is that for some badly damaged bent rotor, even the balancer can't rebalance it. So I guess most repair shop will not keep a rotor balancer in their workshop. And next problem is the transport fees, it's expensive to deliver a rotor shaft to repair shop and get it back, plus the repair fees, maybe the amount will be more than $1000 ?

 

[doneill127]

Anything is possible, but seems unlikely two rotors would have the same issue. Could be bearings, pulley alignment, rotor alignment
excessive pulley or shaft runout. Also might want to pull the hammers and weigh each of them to see how close they are. While hammers are of see if vibration still occurs
Do you have a dial indicator ?

 

[Torvy]

Sounds like some good advice here. If the replacement rotor didn't fix it, Occams razor would point to the most likely issue...it is not the rotor. Sounds like damage due to misuse or abuse and something else is twisted or bent.

I would venture to guess that if you put those rotors into a new machine the problem would not follow the rotor. Kind of a pricey troubleshooting step, though.

 

[leonz]

Hi Leonz, how are you? Nice to meet you here again.
You mentioned the rotor balancer, is there repair shop use balancer for flail mower? Another issue is that for some badly damaged bent rotor, even the balancer can't rebalance it. So I guess most repair shop will not keep a rotor balancer in their workshop. And next problem is the transport fees, it's expensive to deliver a rotor shaft to repair shop and get it back, plus the repair fees, maybe the amount will be more than $1000 ?

Hello Mr. Yuan,

Did you receive the manual for the Lawn Genie Pick up mowers that I sent you?

High speed balancers are a pricy item for small repair shops
unless they do a great deal of drive line manufacturing in house.

Engine rebuilding shops will have high speed balancers in house
especially if they machine their own cam shafts and crank shafts in house.

Flail mower builders here in the states also manufacture farm implements, tractors
and thier own brand of engines in some cases. They will have thier own large high speed balancers for all their needs.

The tubular flail mower rotor shafts which can be up to 25 feet wide (762 centimeters) have to be balanced
in each step of the process of welding the mounting stations on the flail mower rotor for each type of flail knife or flail hammer used.

If a flail mower rotor is damaged and bent the only real solution is to scrap it.

If this gentleman knows of a machine shop nearby the one option to check both of these flail mower rotors is to ask if they have
a metal lathe large enough to support the flail mower rotor and check it for the correct orbit on the x plane(horizontal plane) with
a dial indicator provided they have a support roller that can be used to allow placing the dial indicator on the stub shaft of the flail
mower rotor.

Hopefully it is a simple case of replacing a bad set of roller bearings to solve the issue.

 

[Jack Yuan]

Hello Mr. Yuan,

Did you receive the manual for the Lawn Genie Pick up mowers that I sent you?

High speed balancers are a pricy item for small repair shops
unless they do a great deal of drive line manufacturing in house.

Engine rebuilding shops will have high speed balancers in house
especially if they machine their own cam shafts and crank shafts in house.

Flail mower builders here in the states also manufacture farm implements, tractors
and thier own brand of engines in some cases. They will have thier own large high speed balancers for all their needs.

The tubular flail mower rotor shafts which can be up to 25 feet wide (762 centimeters) have to be balanced
in each step of the process of welding the mounting stations on the flail mower rotor for each type of flail knife or flail hammer used.

If a flail mower rotor is damaged and bent the only real solution is to scrap it.

If this gentleman knows of a machine shop nearby the one option to check both of these flail mower rotors is to ask if they have
a metal lathe large enough to support the flail mower rotor and check it for the correct orbit on the x plane(horizontal plane) with
a dial indicator provided they have a support roller that can be used to allow placing the dial indicator on the stub shaft of the flail
mower rotor.

Hopefully it is a simple case of replacing a bad set of roller bearings to solve the issue.

Hi Leon,

Yes I received your manual, it's interesting to read it. Thank you. If it has any problem and need customize any spare parts, welcome to contact with me.

About the flail mower rotor shaft, you are completely right and understand how the manufacturer deal with it, sometimes when the factory finds some rotor can't be balanced, the only way is that throw it away. There are always some strange reasons cause such lost for the factory. The major reason is that the steel pipe dealer sells them the bad quality pipe. Wrong way to transport or stock the long steel pipe is next reason, you can image how they transport those long steel pipe which is 30 to 60 feet long, a little bent on the steel pipe can make the rotor unable to be balanced.

For the flail mower factory, beside the problem on steel pipe itself, there are many other problems can make the rotor unable to be balanced. For example, the rotor end is welded at a little wrong position. Too much electric current during welding the hammer seat on the rotor, it can "melt" the rotor and bend it. Make a wrong size mower deck. Even sometimes an unhappy worker make mistake intendedly. Too many strange problems.

Quality stablity is always a challenge for a factory. The factory manager often suffers from insomnia

He never know what will happen tomorrow, so does our life.

 

[Rich_Z]

Look at this video starting around the 2:45 time mark. That flail mower is vibrating like crazy. Perhaps there is an issue with this brand of mowers?

To add to this, I just got an email from Nova-Tractor when I inquired about two I might be interested and they told me they were not going to restock the models MFZ135 & MFZ155. Tried to sell me a broken 135 with bolt on the rotor bearing loose and jammed up against the pulley for a $800 discount. Gee.. Thanks but NO thanks! Bad smell, me thinks.