Flail Mower Let's talk flail mowers

[thoner7]

L3200, 25hp PTO (actually probably 20% less due to my 7,000' altitude) & the 7' 917... I was going pretty slow in this grass, but covering about the same acres per hour as with the 5' rotary.

I rarely go 4mph with my new L4060HSTC (32.5hp PTO, actually probably 20% less due to my 7,000' altitude) & 8' Peruzzo. Even when its light material not taxing the machine the fields I mow get to rough at 3-4mph. Sometimes I'll kick it into M-high & 5mph or so on smoother light stuff.

Grass is the biggest HP requirement to cut, way more than writs sized woody material at times. 8" of thick green grass is a lot more mass than a few feet of tall thin dryer material.

Your real 40hp PTO vs the grass in my photos might be able to keep up 4mph with a 719. May need to drop a gear to 3mph or so, but it should be pretty doable.View attachment 623844View attachment 623845

Thanks for the explanation. I don't think I'd let the grass get quite that long either.

I'm wondering tho if different makes of flails need more HP because they are less efficient I. The gearbox, rotor, knives, etc

 

[leonz]

Mowing at 2 inches of cutting height is fine and no problem for a flail mower.

I have to go

 

[Fallon]

Thanks for the explanation. I don't think I'd let the grass get quite that long either.

I'm wondering tho if different makes of flails need more HP because they are less efficient I. The gearbox, rotor, knives, etc

Most flails throw material up & over the rotor. Lifting the material & recutting it a few times as it goes over results in better mulching & even clippings distribution. But that takes a bit of extra HP compared to a rotary. Duck foot & hammers especially are going to have more surface area & drag. I assume between the belts & couple of extra bearings, not to mention the aerodynamic drag of all knife options while spun up & cutting nothing a flail will use a bit more power than a rotary in the same state.

I find the benefits outweigh the costs, even perpetually getting a bigger flail than I should compared to my HP.

 

[TheFarmerInAdell]

So I found a 7 foot offset Ford 917H and a 7 foot Alamo.

The seller of the Ford says "55 hp will handle 6inch tall stuff no problem will bog down in taller grass. 30 hp when just like mowing a lawn about 4 inches tall"

The seller of the Alamo says "I ran it with a 50 hourse tractor 40 at PTO. And yes it is more of a rough cut mower for high grass in fields. cut good was over 5 feet"

I'm getting wildly different advice on the amount of HP required to run one of these mowers. One guy can cut 5 foot grass with 40 horse but another need 55 to cut 6"?!?!?!

I have 40 at the PTO and want to cut 16" high grass down to 4" or so. Driving 4 mph or so. What do I need to turn a 7 foot mower?!?!?!

My advice would be to go with the Alamo for parts availability.

I had a 5 foot Ford 917 (not the "H" version) and I now have an Alamo SHD88. I ran the 917 with course cut blades on a 40 pto HP machine and it cut 3 foot tall grass just fine. I went a little slower, but didn't really bog down much. I now run the 88 on a 52 pto HP machine (dyno'd at the dealer) and can cut 3 foot grass without problems. I only slow down because of the rough terrain and to make sure I cut everything.

You should haven no problem cutting 16" grass with 40hp on the Alamo. You may need to run a bit slower, but you probably won't notice much bogging as long as it's not super lush grass. If the grass is thick you will want to slow down to make sure everything gets fully cut and mulched.

 

[TheFarmerInAdell]

Most flails throw material up & over the rotor. Lifting the material & recutting it a few times as it goes over results in better mulching & even clippings distribution. But that takes a bit of extra HP compared to a rotary. Duck foot & hammers especially are going to have more surface area & drag. I assume between the belts & couple of extra bearings, not to mention the aerodynamic drag of all knife options while spun up & cutting nothing a flail will use a bit more power than a rotary in the same state.

I find the benefits outweigh the costs, even perpetually getting a bigger flail than I should compared to my HP.

Actually from what I've discovered it's about half and half for the rotation direction. The Ford 917, Most Alamo, and all the JD 25A units I looked at spun the same direction as the tires. Most imported seem to spin opposite of the tire rotation. Alamo comes standard with "forward" rotating rotor. You can get them reverse rotating, but it seems quite rare.

The benefit of forward rotating is you only cut the material once and it also lifts up grass that was mashed down by the tires. You will still end up with tire tracks when cutting really long grass, but they're not as bad as the reverse rotating mowers. If you go slow this seems to help as well. I just mow it again a few days later to get rid of the tracks.

Revers rotating will mulch the grass more, using more HP, but leaving smaller clippings for nature to deal with.

 

[TheFarmerInAdell]

I'm not sure I know what you mean when you say "4 inch of cutting height is too high". Are you saying I should actually cut the grass shorter? I'd have no problem doing that, I just figured it would be easier to cut it to a longer finish height.

This is essentially a "lawn" which is why I'm not looking at shredders.

Flails actually have an easier time cutting shorter than longer because the grass is stiffer the closer to the ground you get making it easier to cut. If you are cutting for lawn and you intend to keep it short then look for a fine cut unit. If you want to just let it grow to 16" before cutting then the course would use less HP to cut that length grass, but will not leave as nice of a finish. I use a course cut on my lawn and I see the "V" shape from the cutters after mowing. It goes away in a few days, but it looks like freshly groomed ski hill right after cutting. If that bothers you then I would suggest the fine cut. You can get the Alamo in a fine cut. The standard Ford 917 can be easily changed to a fine cut, but I'm not sure about the 917H. If it has the same rotor then you're good to go.

 

[Fallon]

Actually from what I've discovered it's about half and half for the rotation direction. The Ford 917, Most Alamo, and all the JD 25A units I looked at spun the same direction as the tires. Most imported seem to spin opposite of the tire rotation. Alamo comes standard with "forward" rotating rotor. You can get them reverse rotating, but it seems quite rare.

The benefit of forward rotating is you only cut the material once and it also lifts up grass that was mashed down by the tires. You will still end up with tire tracks when cutting really long grass, but they're not as bad as the reverse rotating mowers. If you go slow this seems to help as well. I just mow it again a few days later to get rid of the tracks.

Revers rotating will mulch the grass more, using more HP, but leaving smaller clippings for nature to deal with.

Reasoning I've heard is the highway mowers need to reject trash better. Forward rotation would try to bounce over junk as opposed to driving it into the hood.

Both my flails are absolutely worthless mowing in reverse. I'm sure most of that has to do with the roller pushing all the material down. But I've never investigated & just planned on driving forward over anything I back over.

 

[CADplans]

So I found a 7 foot offset Ford 917H and a 7 foot Alamo.

The seller of the Ford says "55 hp will handle 6inch tall stuff no problem will bog down in taller grass. 30 hp when just like mowing a lawn about 4 inches tall"

The seller of the Alamo says "I ran it with a 50 hourse tractor 40 at PTO. And yes it is more of a rough cut mower for high grass in fields. cut good was over 5 feet"

I'm getting wildly different advice on the amount of HP required to run one of these mowers. One guy can cut 5 foot grass with 40 horse but another need 55 to cut 6"?!?!?!

I have 40 at the PTO and want to cut 16" high grass down to 4" or so. Driving 4 mph or so. What do I need to turn a 7 foot mower?!?!?!

I ran my JD 390 (either 7 or 8 feet, I do not remember) behind my JD 4105 (41 engine HP) ONE TIME!

That combo would cut light grass,, but, I would not try tall or thick grass,,

I normally pull the JD 390 with my IH 584 which is 50+ PTO HP,,,

Oh, yea, with any 7'+ mower, expect to need front end weights,,,

 

[bruceha2000]

Actually from what I've discovered it's about half and half for the rotation direction. The Ford 917, Most Alamo, and all the JD 25A units I looked at spun the same direction as the tires. Most imported seem to spin opposite of the tire rotation. Alamo comes standard with "forward" rotating rotor. You can get them reverse rotating, but it seems quite rare.

The benefit of forward rotating is you only cut the material once and it also lifts up grass that was mashed down by the tires. You will still end up with tire tracks when cutting really long grass, but they're not as bad as the reverse rotating mowers. If you go slow this seems to help as well. I just mow it again a few days later to get rid of the tracks.

Revers rotating will mulch the grass more, using more HP, but leaving smaller clippings for nature to deal with.

I'm confused as to why rotating in the same direction as travel would lift the grass better than when the flail runs opposite. Seems like since the grass was flattened by the tires, it would be laying with the top toward the back of the flail. Cutters would be following that direction, reverse would be "blowing" against the top of the grass and more likely to pick it up. What am I missing?

 

[ericm979]

When the tractor rolls over the grass while driving forwards, the grass is pushed over forwards (top towards the front of the flail). So the rotor turning the same direction as the tires will pick up the grass.