Flail Mower Let's talk flail mowers

[ronjhall]

Thanks for the response!
I'd already pressure washed and greased the unit and the PTO driveshaft is in the garage. I'll tarp it this weekend, when it dries up a bit. Oh, and the mower is setting on a pressure treated pallet...I guess that'll work.

Pressure treated lumber can be very corrosive on metal.

 

[def38]

Thanks for the response!
I'd already pressure washed and greased the unit and the PTO driveshaft is in the garage. I'll tarp it this weekend, when it dries up a bit. Oh, and the mower is setting on a pressure treated pallet...I guess that'll work.

Sounds like you're way ahead of me.

 

[jonsstihl]

those airplane wing blades I've seen before and I do see the resemblance now I was thinking a single wing and not the entire delta wing concept. I would call that a regular scoop knife though. it is interesting that people have different opinions about the type of cutting versus the type of knife. I have a mott finish mower flail with side slicers but I don't particularly care about the finish it leaves in fine grass. I have my roller set at max height but the bottom of the knives are 2 1/2 inches off the ground at max height. I'm not mowing a fine lawn so I think that is low enough.

I would think scoop knives may do better at grass and brush because my side slicers don't hurt the brush much other than stripping the leaves off of it.

 

[EdwardB]

I am appealing to Flail Mower Nation for some assistance. I have a Mott 72 that had a bolt (#71 on the attached diagram) rattle loose that held the non-drive side cutter shaft bearing in place. This resulted in the bearing and a large washer working its way out and depositing themselves on the ground. The noise was not pleasant... However, the bearing is intact.

I have consulted the parts diagram which is lacking in detail. I have two questions.

First, what is the attached washer and where does it go? I don't believe it is #69, but perhaps the equivalent of #57 that is shown on the other side?

Second, what is the size of #69 Bearing Clamp Washer?

Thank you for any assistance!

Ed

 

[whirly]

The parts list says there are two #57 washers required. The diagrams only show one of each part regardless of the number required .... that's why you don't see 152 knives in the diagram.

 

[EdwardB]

Thanks Whirly. That makes sense, although I think I'd have still shown it on the diagram. Obviously, showing the 152 knives makes no sense.

 

[Dan in MN]

I prefer these...

Flail Mover Blade, Flail Hammer Blade | Steel Forging


They mistakenly call it a mover blade.

What an astonishing lack of proof reading on that page...not only do they have "mover" all over they mixed in "mower" a few times....

The airplane wings of the old jet aircraft like the B58 valkyrie and the jet aircraft fighters used during the vietnam war have the delta wing shape which resembles the stamped and folded scoop knives.

The sawtooth pattern noticed in good grass sod occurs due to mowing shorter and the mounting stations securing the side slicer knives in the vertical position as the mounting holes for the knives are punched circular mounting holes.

The proof of this "theory" is my 48 inch lawn Genie Pick up mower in my backyard under a waterproof tarpaulin.

The sharp long tapered edge of the old style side slicer knives creates lift and as a result the knives become horizontal when the flail mower rotor reaches 2200 rpm plus as the slotted mounting holes allow the knife to slide outward do to the centrifugal force and become airborne even though they are secure in the mounting station as it is a wide loop allowing the knives to become near horizontal due to the long tapered edge of the side slicer knife that is much longer than the current side slicer knives that are available.

If you look at the old gas powered carrier based aircraft they have the folding wings and when you see how they fold out flat you will see what I am describing as these airplane wings look like these flail mower knives when folded out and the tapered side slicer knives are horizontal.

I don't see any 'proof' in your examples. A delta wing aircraft just means a triangular shaped wing as viewed from above, has nothing to do with the leading and trailing edges of the wing that still define an airfoil shape nothing like the angled rise and drop of the side slicer knives. There hasn't been an aircraft that ever got off the ground without an airfoil profile to the wings. The side slicers when just hanging there in a pair are pushing inward against each other as the center of gravity of each knife is outside the mounting point. You would have to overcome that along with high amounts of centrifugal force from spinning a weight at 2000+ rpm. The faster you spin the pair the harder they are going to push against each other due to the center of gravity location. As far as airflow with an angled leading edge and without a proper trailing edge I think it more likely that the force of air cast off the blade actually pushes the knife outward from center, which is also what would be required (pulling air in towards center) to create any lift on the grass. I personally haven't experienced any real suction lift from either of the flails I've run with side slicers, and yes I've run them low and parallel with the ground. I've run the mowers over leaves in my yard hoping the mower would pick them up and mulch them, but they just lay there so there's little to no suction being generated (in my experience). On the other side even if the knife profile did generate a bit of lift on the knife itself, due to being attached to a rotor and pulled in a circular motion, the knife is already being yanked away in the direction the lift would try to move it. In short, this supposed 'airplane effect' where the side slicers move apart from each other just doesn't happen.

 

[def38]

It is doubtful that aeronautical engineers designed mower flails.

 

[leonz]

Hello Dan in Mn.,


The mounting stations on the mathews lawn genies are different in that they are a tool less spring tensioned mounting loop.

My original mathews knives have 2 long tapered trailing knife edges leading to a 1/2" blank end of the side slicer knife. This side slicer knife also has an oval punched mounting hole.

The side slicer pair has enough side movement when combined with the long length of the mounting loop to allow the knives to become an air foil and allow the knife pair to slice the grass at a level cutting edge.

 

[whirly]

It is doubtful that aeronautical engineers designed mower flails.

No but fluid dynamics is a big part of how they work.