Flail Mower Let's talk flail mowers

[Walter63]

Flail mower basics and knife rotation

I'd like to add some general observations regarding cutting tall grass and weeds with flail mowers. I've owned and used Seppi, Rears, Trimax, Alamo, and Befco, and all types of knives. I've had these flails on 3 point tractors and more sophisticated front mount machines as well. I've used flails with and without gauge wheels.
A lot has been said on this forum regarding flail knife rotation. By way of definition, forward rotation is rotating the same as the tractor wheels, backwards rotating is the opposite. Some brands of flails rotate forward, some backwards.
In my own experience, the backwards running flail knives give a poor cut on tall grass. The mower housing bends the grass over enough that unless the flail is set very low, the tall stuff doesn't get cut. They thoroughly mulch what they do cut, which uses a lot of horsepower.
Forward rotating flail knives give a much cleaner cut on grass, and can cut tall grass cleanly without using an undue amount of horsepower. On a rear mounted forward rotating flail, the grass is pushed over forwards by the tractor tires and the mower body, which puts it in the perfect position to be neatly up-cut by the rotating flails. The cut is clean, there are no tire tracks, and the grass is easily ejected from the mower, reducing the necessary horsepower. I use 50 HP on a 8 foot flail in tall grass. With the same 8 foot flail set up for reverse rotation, 100 HP wasn't always enough, and the cut was awful.
It took me years of using different makes of flails to figure out this simple principle. On some makes you can change rotation by moving a gear inside the gearbox. Better to buy a flail already set up for the rotation you want.
The other thing two things that effect cut are the knife tip speed (based on rpm and cutting circle diameter), and the mower housing height. The more room there is inside the mower housing, the easier it is for taller grass to stand up , get cut, and be smoothly ejected out the back.
These observations relate mostly to cutting grass and weeds with a flail. If you are using hammer flails to mulch tree branches, etc., your needs may be much different. In that case, a reverse rotation may be better for mulching wood into smaller pieces.
I hope these observations are helpful.

 

[troverman]

Re: Flail mower basics and knife rotation

I'd like to add some general observations regarding cutting tall grass and weeds with flail mowers. I've owned and used Seppi, Rears, Trimax, Alamo, and Befco, and all types of knives. I've had these flails on 3 point tractors and more sophisticated front mount machines as well. I've used flails with and without gauge wheels.
A lot has been said on this forum regarding flail knife rotation. By way of definition, forward rotation is rotating the same as the tractor wheels, backwards rotating is the opposite. Some brands of flails rotate forward, some backwards.
In my own experience, the backwards running flail knives give a poor cut on tall grass. The mower housing bends the grass over enough that unless the flail is set very low, the tall stuff doesn't get cut. They thoroughly mulch what they do cut, which uses a lot of horsepower.
Forward rotating flail knives give a much cleaner cut on grass, and can cut tall grass cleanly without using an undue amount of horsepower. On a rear mounted forward rotating flail, the grass is pushed over forwards by the tractor tires and the mower body, which puts it in the perfect position to be neatly up-cut by the rotating flails. The cut is clean, there are no tire tracks, and the grass is easily ejected from the mower, reducing the necessary horsepower. I use 50 HP on a 8 foot flail in tall grass. With the same 8 foot flail set up for reverse rotation, 100 HP wasn't always enough, and the cut was awful.
It took me years of using different makes of flails to figure out this simple principle. On some makes you can change rotation by moving a gear inside the gearbox. Better to buy a flail already set up for the rotation you want.
The other thing two things that effect cut are the knife tip speed (based on rpm and cutting circle diameter), and the mower housing height. The more room there is inside the mower housing, the easier it is for taller grass to stand up , get cut, and be smoothly ejected out the back.
These observations relate mostly to cutting grass and weeds with a flail. If you are using hammer flails to mulch tree branches, etc., your needs may be much different. In that case, a reverse rotation may be better for mulching wood into smaller pieces.
I hope these observations are helpful.

These are good observations. However, why is it then, that virtually all flail mowers designed to be operated behind a tractor, rotate the opposite way? I would also think flails that rotate in reverse would be in a much better position to cut grass that has been bent over by the front of the mower, and it popping up in the housing?

 

[TheFarmerInAdell]

Mott, Alamo, Ford and JD all have "forward" rotation flail mowers. In fact, I believe all Alamo/Mott mowers are forward rotation from the factory unless requested otherwise (you have to basically mirror the mower to change direction). The Ford 907 and 917 are both forward rotating. And JD 25A is forward rotating (not sure on the 390). And these are just the mowers that I researched when I first looked into it. So to generalize that "virtually all flail mowers" are reverse rotating is a misconception. Many of the imported ones are reverse rotating, but many of them also have or offer the forged hammers which are used for mulching brush and woody material making a good reason to be reverse rotating.

When the grass is bent over the blade is contacting at a glancing angle if rotating in reverse keeping the grass pushed over. If forward rotating you get a more perpendicular contact angle to the bent over grass and the grass is "pulled" back upright by the blades as it is cut. Plus it can spit out the cut grass quickly and move onto the next stalk instead of trying to mulch and cut at the same time.

In order for the grass to pop back up in the housing it would need to be short enough to pop up before the blades make contact with it. If the grass is short enough to pop back up either rotation would work to cut it. Forward rotation would leave the tractor in cleaner condition, though (3 point mount applications).

I had a Ford 917 and now a Alamo SHD88 (both forward rotation) and they cut tall grass quite well and both tractors they ran on didn't notice the mower unless I hit dirt. They both struggle with cutting the tire tracks, but they're both course cut mowers with the Y blades. If I switched to the scoops I'm sure it would cut much cleaner, or if I got a fine cut mower it would cut the short stuff better.

 

[leonz]

Clockwise rotation or counterclockwise rotation is determined by looking at the left side weldment of the flail mower as it works.

Clockwise rotation would indicate the side slicer knives travel forward from the bottom of the flail mower rotor to clip and shred grass and then left it over the flail mower rotor.

European Orchard and vineyard flail mowers and INO flail crop shredders utilizing cast flail hammers are typically set up with flail mower rotors that have spiral mounting stations welded to the flail mower rotor to increase the amount of lift as they break the pruning's and small limbs in a vineyard or orchard.


My fathers JD25A operated in a clockwise rotation cutting the clippings as the mower advanced and lifted the clippings over the flail mower rotor and back down.
My Mathews Company Lawn genie operates in the same manner.
Using European grass flail mowers for cutting hay-they are mounted in front of the engine of the mule it is connected to discharge so that the clippings
are discharged forward "over" the rear roller which is essentially clockwise rotation if you were looking at the left side weldment.

Many European flail mowers are set with gear boxes with two stub shafts to allow the flail mower to be mounted in the front of a tractor or the rear as many small farms use small 4 wheel drive articulated tractors with front three point hitches and power take offs from the crank shaft pulley of the smaller 4 wheel drive mules engine.

 

[TheFarmerInAdell]

My fathers JD25A operated in a clockwise rotation cutting the clippings as the mower advanced and lifted the clippings over the flail mower rotor and back down.

All of the JD25A I've seen rotate the other diretion. Cut and then shoot it straight out the back, not over the rotor. Either your father's was spinning backwards or every other JD25A I've seen has the knives on backwards and the belt has the tensioner on the wrong side.

Direct from Alamo on "forward" vs "reverse" rotation:

 

[troverman]

As an update on my Vrismo Mighty Max bearing issue, I ordered two near complete flange bearings from Vrismo. They are $131 each.

 

[Walter63]

Re: Flail mower basics and knife rotation

I'd like to add some general observations regarding cutting tall grass and weeds with flail mowers. I've owned and used Seppi, Rears, Trimax, Alamo, and Befco, and all types of knives. I've had these flails on 3 point tractors and more sophisticated front mount machines as well. I've used flails with and without gauge wheels.
A lot has been said on this forum regarding flail knife rotation. By way of definition, forward rotation is rotating the same as the tractor wheels, backwards rotating is the opposite. Some brands of flails rotate forward, some backwards.
In my own experience, the backwards running flail knives give a poor cut on tall grass. The mower housing bends the grass over enough that unless the flail is set very low, the tall stuff doesn't get cut. They thoroughly mulch what they do cut, which uses a lot of horsepower.
Forward rotating flail knives give a much cleaner cut on grass, and can cut tall grass cleanly without using an undue amount of horsepower. On a rear mounted forward rotating flail, the grass is pushed over forwards by the tractor tires and the mower body, which puts it in the perfect position to be neatly up-cut by the rotating flails. The cut is clean, there are no tire tracks, and the grass is easily ejected from the mower, reducing the necessary horsepower. I use 50 HP on a 8 foot flail in tall grass. With the same 8 foot flail set up for reverse rotation, 100 HP wasn't always enough, and the cut was awful.
It took me years of using different makes of flails to figure out this simple principle. On some makes you can change rotation by moving a gear inside the gearbox. Better to buy a flail already set up for the rotation you want.
The other thing two things that effect cut are the knife tip speed (based on rpm and cutting circle diameter), and the mower housing height. The more room there is inside the mower housing, the easier it is for taller grass to stand up , get cut, and be smoothly ejected out the back.
These observations relate mostly to cutting grass and weeds with a flail. If you are using hammer flails to mulch tree branches, etc., your needs may be much different. In that case, a reverse rotation may be better for mulching wood into smaller pieces.
I hope these observations are helpful.

Note: I offered these observations because of the confusion and variety of opinions that seemed to exist regarding flail knife rotation, and the very dramatic differences I had noticed in performance. Most striking to me was the difference I noted in two different flails after I had reversed the rotation of the knives by changing the ring gear position in the respective gearboxes. The difference in cutting and horsepower requirements was like night and day. In tall grass, forward rotation of flail knives was a necessity for a good cut.

 

[leonz]

Re: Flail mower basics and knife rotation

Note: I offered these observations because of the confusion and variety of opinions that seemed to exist regarding flail knife rotation, and the very dramatic differences I had noticed in performance. Most striking to me was the difference I noted in two different flails after I had reversed the rotation of the knives by changing the ring gear position in the respective gearboxes. The difference in cutting and horsepower requirements was like night and day. In tall grass, forward rotation of flail knives was a necessity for a good cut.

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I have always mentioned the Mathews Company lawn genies my father and I have owned I owned being his first lawn genie after he traded it in on the larger 48 inch lawn genie and was given the second one that he could no longer safely use.

I mention the Lawn genies as they were pick up flail mowers wherein they had baskets to hold the lawn clippings which allowed the user to pick up leaves and long grasses if the lawns grew too fast because of the rain or excess fertilizer.

The Lawn Genies with pick up baskets had diverter doors and a full width discharge duct that directed the clippings up and into the fabric bag basket used on the 36 inch lawn genie pick up mower and the metal pick up baskets on the 48 and 60 inch lawn genies.
The lawn genies required that the flail mower rotor rotate in a clockwise direction to enable the flail mower rotor and the air paddles and the
side slicer knife pairs and the thatching blades acting together to lift the thatch and grass clippings up and into the pick up basket or back over the flail mower rotor and back to the ground to dry even further to lose moisture to reduce the weight of the clippings prior to picking them up with the lawn genie with the diverter door in the open position.

Sadly you have to purchase a very large flail mower that is three point hitch mounted with a pick up basket from an importer and they no longer have an engine to power them unless that has changed in the last 29 years.


The 25A finish flailmower that my dad bought from Arsenault tractor sales in 1980-81 utilized the clockwise rotation method to clip and lift the mower clippings over the flail mower rotor and then they dropped back down on the ground.

Just to add more fuel to the flail mower debate(a fire that needs to be doused with water) the flail mowers that have recutting bars with fewer hammer knives lift the material up and over the flail mower rotor where the material is cut a second time with the wide cast hammer knives passing by the wide recutting bars where the material is shredded to a much, much, smaller length and then drops on the ground.

The original mott flail mowers had clockwise rotation as most all of them were capable of using thatching blades that dug thatch out of the ground and lifted it up and over the flail mower rotor and back down to the ground to be picked up with lawn sweepers

For the person that is unfamiliar with flail mowers in general and how safe there are 2 tractor mike videos on you tube are excellent in describing flail mowers. the rhino flail mowers in the examples use the wide cast hammer knives and recutting bars.

Chores and errands in town drag me away from the forum now.

 

[The Bog Man]

All of the JD25A I've seen rotate the other diretion. Cut and then shoot it straight out the back, not over the rotor. Either your father's was spinning backwards or every other JD25A I've seen has the knives on backwards and the belt has the tensioner on the wrong side.

Direct from Alamo on "forward" vs "reverse" rotation: View attachment 612223

I have a JD25A and it rotates exactly how leonz explained it.

 

[def38]

When mentioning bearings, I am confused by the terms shielded and sealed. There is a major difference. Which style are used in our flail mowers? Are they interchangeable? Which one is better?