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?

 

[def38]

There seems to be some reluctance to use Chinese manufactured single row grooved ball bearings. I have used FAG, NTN, NSK as well as Chinese made ball bearings in a number of applications. I find little performance difference. The Chinese bearings are often lower in price. Am I missing something?

 

[leonz]

Hello Def38.

Some of the newer flail mowers have "sealed" one row ball bearings with two seals as they are packed with grease at the bearing factory..

Most flail mowers typically have a seal on one side to hold the grease in the bearing and allow the old dead grease a chance to melt out and
away over and be flushed out with new grease.

 

[Fallon]

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?

Shielded = washer or a shield of some that covers most of the balls & keeps some stuff out.

Sealed = plastic/rubber seal that keeps lube in & contaminatinants out.

Seals increase friction & wear faster than shields or nothing. But they keep lube in & grit out. If you pump lube into or outside of a sealed bearing the hydraulic pressure can blow the seal out or in.

There are 2 sides to a bearing so one side can be shielded & the other side sealed or any combination. You need to make sure you install the bearing in the correct orientation. Popping a seal or shield out will turn an sealed bearing into an unsealed one.

If you regularly lube the unsealed bearing to lubricate it & flush out contaminants the bearings should live a long life. Fail to lube them they will die prematurely. A sealed bearing will likely not last quite as long as an unsealed bearing that has been ideally maintained under harsh (tractor impliment) conditions. A sealed bearing has the advantage of not needing constant maintnance/lubrication. Industry is tipping towards sealed bearings as they are less maintnance, but may not be ideal for all instances. Historically most rotor & roller bearings on flails have not been sealed or only sealed on 1 side. Anything with a grease zerk on it is unsealed on at least 1 side.

You can usually put a sealed bearing into a greasable housing, but greasing it would probably cause problems. I've done that on my old 917 flail as sealed bearing were all Messicks had in stock as an OEM replacement. Putting an unsealed bearing into a place designed for a sealed one end up with a bearing you cant lube & dies a quick gritty death.

 

[troverman]

Good info Fallon, thanks.

 

[cscholz]

1) Those shackles look to be roughly the same cost as the ones I got from Flailmaster but have the advantage of not needing modification to install. Looks like they are the ones to get rather than the ones I got from Flailmaster. (GME Supply Co, SHA38LRBT 3/8" bolt type safety shackle for future reference). I presume there was no difficulty getting the blades over the ears. If the slight binding bothers anyone, a touch up with a grinder would only take a second or two.

IslandTractor, TDVT, Jelf (and anyone else who has them) - how have the GME Supply SHA38LRBT shackles held up? I'm about to buy a full set of clevis' and blades, and Flailmaster sent me a sample of their clevis. It took more bending and a bit of grinding than I expected to get it to fit. So I'm thinking of getting just the blades from them and getting the GME shackles. Any reason not to (other than more cost due to shipping mostly)?

Carl

 

[ericm979]

There seems to be some reluctance to use Chinese manufactured single row grooved ball bearings. I have used FAG, NTN, NSK as well as Chinese made ball bearings in a number of applications. I find little performance difference. The Chinese bearings are often lower in price. Am I missing something?

The chinese bearings can vary more in quality. I've had some that did not last long. If it's a lot of work to replace the bearings I tend to use the name brand ones; if it's easy and a failure won't be safety critical I'm ok with chinese.

 

[Eagleview]

Re: Flail mower basics and knife rotation

Hi guys, just called in, been a while .
Some flail mowers can cut cleanly with the rotor spinning in the same direction as the wheels . You will find that the flail stations on those rotors are attached to the rotor in straight rows along its length . There can be 3, 4, 5 or 6 rows .
Imagine a rotor with 4 rows, each row is mounted 90 degrees apart . As the mower moves forward, lets say a foot and the rotor has revolved twice in that foot of forward travel . The blades have struck the grass 8 times .
Now imagine a helical/spiral mounting arrangement that many mowers use now , and rotate in the opposite direction to the wheels and only have ONE cutter per spacing .
As our imaginary mower, now with a helical rotor (using the same blades)moves forward that same foot and the rotor has revolved the same two revolutions, the blade has only struck the grass twice . This is why people get crappy results when the try to cut going backwards with a helical rotor type flail (the roller also holds the grass down that makes it worse).
Gearing on helical rotor flails is tall to keep tip speed high which helps overcome the fact there is only one blade per position . The advantage of the helical design is that there are only 3 or 4 blades contacting the grass at a time, unlike a full row in the straight type rotor .

Also, helical rotors need big counterweights for balance, straight row rotors may just have a little one, as the straight rows at equal spacing balance themselves out .















.

 

[troverman]

I have an opportunity to buy a Ford 917 flail mower in working condition with a newer belt for $1000. It is 78 cut. Are these quality? Can parts still be had? What to look for that might be wrong?

 

[Fallon]

I have an opportunity to buy a Ford 917 flail mower in working condition with a newer belt for $1000. It is 78 cut. Are these quality? Can parts still be had? What to look for that might be wrong?

My decades old one is thrashed, but still holding together. I paid $100 for it & have $600 into it now. It was well worth it for my starter flail for a few years of side work. I replaced it but keep it around as a spare & have no plans to ever sell it. Flailmaster has knives. I got replacement bearings from Messicks. Make sure the gearbox is sound, the roller & rotor are round & it doesnt vibrate when you wind it up to PTO RPM. Cracks in the hood can probably be repaired, but may not be worth it. A tweaked roller rotor or gearbox will total most any used flail. Replacible or repairable, but not likely worth the cost or effort.

 

[Eagleview]

Re: Flail mower basics and knife rotation

Hi guys, just called in, been a while .
Some flail mowers can cut cleanly with the rotor spinning in the same direction as the wheels . You will find that the flail stations on those rotors are attached to the rotor in straight rows along its length . There can be 3, 4, 5 or 6 rows .
Imagine a rotor with 4 rows, each row is mounted 90 degrees apart . As the mower moves forward, lets say a foot and the rotor has revolved twice in that foot of forward travel . The blades have struck the grass 8 times .
Now imagine a helical/spiral mounting arrangement that many mowers use now , and rotate in the opposite direction to the wheels and only have ONE cutter per spacing .
As our imaginary mower, now with a helical rotor (using the same blades)moves forward that same foot and the rotor has revolved the same two revolutions, the blade has only struck the grass twice . This is why people get crappy results when the try to cut going backwards with a helical rotor type flail (the roller also holds the grass down that makes it worse).
Gearing on helical rotor flails is tall to keep tip speed high which helps overcome the fact there is only one blade per position . The advantage of the helical design is that there are only 3 or 4 blades contacting the grass at a time, unlike a full row in the straight type rotor .

Also, helical rotors need big counterweights for balance, straight row rotors may just have a little one, as the straight rows at equal spacing balance themselves out .

.

Straight rotor in red mower, helical rotor in orange mower .