HayDr, or others that knows drum mowers.

Is there a reason cut heads are so big in diameter with only 2 cut heads, instead of smaller and more heads? More efficient? Simpler? More robust? I see smaller and more heads having less scalping issue a big plus with the lesser quality fields I do so I'm curious why.

Drum mowers have two disks in each cutting unit, Upper rotates and carries the knives. Underneath is a large flat disk with it's own bearing, free to turn any direction. This disk slides on the ground, holds the cutter disk off the ground a fixed distance. Scalping doesn't seem to be an issue. Large disks travel at a suprising speed, cutting very efficiently. The two cutting units counter-rotate, shooting the cut material out in a stream, almost a windrow to the rear between them. Close enough to each other that they overlap in the middle. They don't clog, and you can cut as fast as you can ride, (at least as fast as I want to ride!) I got one this June, and it revolutionized my cutting operation. I can keep up with larger machines, but the no clog, no down time replacing guards and sickle bar knives is the real advantage. New set of blades costs $10 at TSC, takes ten minutes to swap out. Since blades are double sided, swapping sides gets you a new cutting edge. My hay fields, crops win no beauty prizes, but my drum mower doesn't care. They're an amazing machine.

Thanks for the info, but I have one too. LOL I know how they work.
The scalping I see is due to uneven surfaces and the large diameter making a large height difference when the tractor changes attitude over rises and or the mower meets a rise or fall in terrain. Just wondering if there's a mechanical advantage to using just 2 heads or why they're all pretty much the same design.

The reason most drum mowers have two large disk is that they are usually driven with belts. The smaller cutter bar type of disk mowers are gear driven. With the gear drive you can get a larger ratio to step up the disk speed. So with the belts you need the larger disk to get the tip speed. Also the gear driven disk add cost to the mower. Your drum mower cost much less when new than a disk mower.

Small Farm Innovations, a Texas Company sells a box of 25 double sided blades for $25 to go with your SFI Drum mower. Blades are universal and fit several other domestic cutters.

The mower is driven by 4 heavy duty V belts and has few moving parts. It functions as I think Ray it was, stated. Unlike sickle bars it cares not what it cuts, crawdad mounds, wet ground, ant hills, rocks or what have you. I don't know how fast the disc blade rotates but the drum turns at an incredible speed, like 10,000 or so and with the 3' diameter drum, the tip velocity is sorta rapid. But at that speed it just hums and there is no vibration. Like a disc mower it does hang off the side in the cutting position and requires a tractor large enough to counter the weight. I have a 65 hp Branson with a FEL and with the bucket off it has no problem with the 6'. For mobility, the mower tucks straight behind the tractor rather than up in the air like a disc or sickle and trees along the road are not a problem like they are for the others.

The mower rides on the ground as Ray stated and follows the contour up to 10 or 15 degrees. You can drive down a road and cut the ditch bank along side.

It doesn't have all the gearing that a disc requires and that saves a lot of expense as the unit ages....I have seen many with welds on the underside from cracks.

The crop is discharged at the center as Ray states and forms a wind row. Personally I like that. Some folks don't. If you don't like it you can always come back with a tedder, but unlike a sickle bar, you can cut clean corners in irregular fields without a big pileup of cut matter like sickles love to do. It doesn't scalp on my fields but I don't have irregular holes and such that would yield to scalping regardless of type cutter.

I have had mine for 2 years now and love it. I had 3 cutters per drum (2 drums on a 6' cutter) and noticed holes for 6 so I ordered and installed an extra set of blades for about $200 with transportation and an extra box of blades. I plan on cutting thick stemmed sudan/sorghum for hay next year which I feel the extra blades will help with a clean cut. I don't know that the original 3 per wouldn't do the job.

Best thing is the price. I got mine for $3750 which is way cheaper that the more complicated disc would cost and dealer service is super.

Might try one. You might even like it.

Mark

I think the main thing is the savings in weight, and fewer moving parts. Also I have seen the gear shaft between the turtles on a disc mower bend enough to change the timing of the turtles, on high hour units. Cost per lb is the factor to consider!

Well maybe the welding marks on the bottom of every used one I have seen for sale are fixing cracks from what you say.

Mark

If you choose to add more cutters (and I don't see the need,) you will need to remove bottom disks. They are attached with Allen head screws. When you drop the disk, you'll want to support it on a wheeled hydraulic floor jack. DISK IS HEAVY, ALMOST BROKE MY HAND WHEN I DROPPED ONE OF MINE.
You'll need six knife holders - (triangle shaped pieces with two bolt holes on one end, pin on other to hold cutter blade.) (Dealer available part.) And of course, proper sized carrage head bolts. I have cut some very thick swamp grass with mine -stuff I couldn't cut but with a brush hog, otherwise. Just reduced my ground speed a couple gears and walked right through it! When I first got mine, mowed about 300 yards, hit some rocks and broke one of the pins off a knife holder. Welded a bolt in it's place, and reassembled it. Still working. Dealer warranted the part, and I have it in stock, but took a while for them to get the replacement for me.
When I took my bottom disk off, the screws had some sort of rubbery compound on them, probably to prevent loosening.... Suggest you squirt some silicone gasket material in hole before reassembly to secure screws - loctite wannabee!

Mine has 4 v-belts from PTO shaft that drive a 90 degree gearbox, and actual disks are shaft/gear driven from overhead.

Actually the very first drum mowers (e.g. The Fahr KM4 and The Bamford Wizzler which appeared in Europe during the late 1960's) even though they only had a cutting width of about 5 and a half foot did indeed have four small drums. however they soon ditched the idea in favour of two big drums. There must have been a reason. Less moving parts for one thing.

Job is done but thanks anyway. I loosened all 3 hex allen bolts and removed 1 until I could get my hand inside to tighten the nuts on the bracket that holds the blade. That way I didn't have to fight the weight, nor have to fuss over getting the bolts lined up in the holes to reinstall them.

Timing change was a piece of cake. Removed the top cover, 4 bolts to loosen the drive shaft connecting the two drum drives, slightly raised the outboard end just enough to clear the other gear, set the top disc about 60 degrees off and put her all back.

Did the whole job alone and spent more time ensuring that I was safe than the job took.

Like I said, had nothing to do, saw the extra set of holes in the top drum, had read on here where another guy had added to his (another brand); price wasn't all that much. So I just decided to do it. Have to wait till next summer to see how she does.

Thanks,

Mark

Not sure I agree with your logic sir. On the disc you have multiple small diameter cutters gear driven as you said. On the drum you only have 2 drums regardless of the width. The speed is set by the gear/pulley ratio and as I said, mine runs really fast, don't remember the number but it's something like 10,000 rpm at PTO speed. Having only 2 discs 3 feet in diameter gives you a bodacious blade velocity.

Mark

Mine is 4 belts off the pto to a reduction up top then one belt to each head.

Mass. Once that big drum is spinning the mass and velocity keep it going, cutting. If you stop the power to a drum mower it will spin for several minutes. Cut the power to a disc mower and the internal friction, and oil drag will stop it is a few seconds.

Well, what does that tell you about power to drive the disc, obvious heat loss, and wear and tear the disk has over the drum.

By the drum continuing to run for several minutes, tells me that it is built like a fine watch.....more or less. Frictionless! I'll take it. Ha! I already did.

Mark

I deliberately spent a lot of time on this subject as you never hear about drum mowers on the site. I think that a lot of folks are missing out on a fine cutting machine that has few moving parts and should provide many years of reliable service.

The problem with the belt shield was no biggie and probably has a reason why it wasn't corrected in earlier models. Possibly the belt supplier was changed and maybe the new supplier's belts were slightly longer or had more of an initial stretch which was not accounted for in the original design of the machine.

Mark