Balancing flail mower rotor

[tlj87]

In many, many other threads, when someone mentions the need to get a flail mower rotor balanced due to vibration, the response is typically "find a reputable driveline shop and they'll fix you up." I've called all of the reputable driveline shops within 2 hrs. and they all stated they can only balance a shaft with U-joint ends. I also called tractor dealerships that sell flail mowers and they responded that they don't balance shafts and don't know where to direct me.

Where are you all going to get your flail mower shafts balanced?

 

[Tinhack]

Unless you've knocked a few flails/weights off the rotor, it should be in balance from the factory. Make sure all your flails are in place and they are the same. Having a mix of flails will throw it out of balance. The balance weights are welded in place so it pretty hard to knock those off. Also, don't expect a flail mower to be as smooth as a fan.

 

[dieselscout80]

I feel your pain.

I called all around me last fall and found a place a almost 3 hours away that would do the job.

 

[tlj87]

Unless you've knocked a few flails/weights off the rotor, it should be in balance from the factory. Make sure all your flails are in place and they are the same. Having a mix of flails will throw it out of balance. The balance weights are welded in place so it pretty hard to knock those off. Also, don't expect a flail mower to be as smooth as a fan.

The subject Alamo mower is 35-ish years old, was owned by the state of NY and was well used. I had the non Pulley side of the rotor built up and turned down then replaced bearings and housings on both ends. All blades are brand new from Flailmaster. I’ve also swapped PTO shafts to rule out that as the source of the vibration.

Next step is to remove all blades and run it without them to see if for some reason the blades are not equal, which if they aren’t would have to be a manufacturer defect as they only have about an hour on them.

This is the vibration:

 

[John0829]

When I had work done on the New Holland 918H it was done by an old machine shop but then again they also did driveshafts too but I would check with any machine hop in the area, ya never know... might get lucky.

 

[Locoweed]

Here is a video of a guy making his own.

At about the 9 minute mark he balances the rotor

 

[ruffdog]

I would not be checking for vibrations at idle or with the flail lifted high so the pto shaft u-joints are at such an angle. I would find a hollow for the flail to sit as close to cutting height as you can and sit it on blocks. You don't cut with it 18" in the air at idle, instead, you have it resting on the roller running pto speed (flails flung out) and the u-joints are straight. The video is only showing you testing the u-joints.

 

[tlj87]

I would not be checking for vibrations at idle or with the flail lifted high so the pto shaft u-joints are at such an angle. I would find a hollow for the flail to sit as close to cutting height as you can and sit it on blocks. You don't cut with it 18" in the air at idle, instead, you have it resting on the roller running pto speed (flails flung out) and the u-joints are straight. The video is only showing you testing the u-joints.

Thank you. I agree, and I can tell you that the behavior is basically the same when stationary, on the ground, at higher RPMs. There are certain RPM ranges when the the vibration is slightly less or more, but is always there.

I did find that I could register and get a OP manual from the Alamo website, although it's a current version. I did learn the following: "FOR FORWARD ROTATION: Knife pins must be installed with their heads facing away from the cuttershaft
pulley." This is not the case currently, as I put one half on facing one way and the other half facing the other way.