Excessive vibration/shudder with flail mower

[super55]

Thought I would give everyone an update on the progress of my flail mower.

Well I did a complete teardown of the mower. Put new seals in the gearbox, inspected all bearings which all ended up being good, put a piece of flat stock and inspected the main rotor shaft for straightness which was good, and replaced a few missing knives.

Upon inspection of the shaft I seen a spot that appeared to be the place where balance weight was once located. I figured I would just keep tacking on steel blocks and try to balance it that way and sort of guess-timate my way to get it as good as I could. As I was staring at it thinking of what weight to use I just happened to notice that directly 180 degree on the other side of the shaft was a bracket with knives. (Both spots were on the extreme ends of the shaft and offset from the rest)

Anyways long story short I made myself a make shift bracket using 1/2 a piece of chain with two knives through and welded it on in place where I once thought a counterweight was located. Went out and tried it out and it worked halfway decent. I can at least get up to RPM speed on the tractor now without a complete shudder. It still has some vibration but I think I can balance it out with some angling, RPM speed manipulation and possibly by adding some weight to further balance it. It's not perfect yet but at least it is a functional piece of equipment now.

 

[greg_g]

Mine uses self-adhesive balance weights similar to those used on car wheels. I think I remember seeing them in the FlailMaster catalog. But in this case, you simply stack them - sticking one on top the other - until you achieve the desired degree of balance.

//greg//

 

[super55]

thanks for the tip greg.


I was just going to keep adding weld beads and grind away if excess but the adhesive weights seem to be a much easier route.

 

[Industrial Toys]

Such a thing can be very hard to balance. I have wrestled with that issue and have come up with no easy answer.

I for one, rarely ran my Ford 917 at full 540. Sometimes on account of resonance, you can pick a sweet spot (rpm) with reduced vibration. I have also had my 917 (regular cut) start to vibrate when dried grass was wrapped around a number of knives.

I'm not talking about a vibration that will shake the thing to pieces, and I know it's not right, but sometimes I just put on my FM Radio Hearing protection and turn up the music!

 

[super55]

Turned out all the vibration was just resonance.


Figured I would comeback on this thread and give a little update on the results. The flail mower works great now. Turned out all the vibration was just caused my resonance from operating at a two high of an RPM. Appears the sweet spot from mower is about 1900 rpms. The tractor Im using it with now has live PTO which seems to be critical for my particular mower to keep the RPMs at a consistent speed. If I go up 300 more RPMS that thing will start with a mild shutter and than just keep on magnifying.

Thought I would pass it along to any other people out there in case anybody has similar issues. The owners manual actually even mentions resonance but this is the first time I ever experienced it in an implement.