Rotary Cutter Rotary cutters vs. RFMs

JayC · Aug 25, 2003

I'm just curious what is the difference in the quality of cut with a rear-mount rotary cutter versus that of a rear-mount finish mower? To tell you the truth, I don't know much about tractors, but ever since I found this site, I have learned a LOT of useful info. /forums/images/graemlins/smile.gif

TimSullivan · Aug 25, 2003

We have been cutting an old orchard that had been let go to brush for several years. The grass has grow in well this year with all the rain and it is about time to buy that finish mower.

The project started buy using a five foot bush hog behind a 4300 Deere to cut down the brush and nasty rose bushes. Some of the rose bushes were too big for the cutter and had to be pulled out. All in all the cutter did a great job of clearing the land. After the stubble of the brush was gone the grass did not look bad at all. The bush hog is still our main cutter but as the grass improves we cut more and more with a lawn tractor. It just looks better.

Our plan is to buy a 6 foot RFM to use on the large areas and use the bush hog to cut the rough areas in and around the woods. The finish mowers just do a nicer looking job as the grass improves. The lawn looks OK after the bush hog cuts it but it does tear more than cut..

jcollins · Aug 25, 2003

Basically a RFM (Rear Finish Mower) is a lawn mower behind a tractor. It is designed to cut only grass and really lawn grass. It uses a PTO driven gear box that has a pulley below it. The pully usually has a belt on it that drives 3 or more lawnmower type blades. A bush hog (brush hog) uses a PTO shaft to the gear box and the gear box has a output shaft that drives your stump jumper. Attached to the stump jumper are usaually two free swinging blades that chop at the material rather than cutting the material as a RFM does. The RFM will give a very nice quality cut while the brush hog tends to tear at the grass. Brush Hogs are normally cheaper to purchase than the RFMs though. Hope this helps.

WVBill · Aug 25, 2003

( ... A bush hog (brush hog) uses a PTO shaft to the gear box and the gear box has a output shaft that drives your stump jumper. Attached to the stump jumper are usaually two free swinging blades ...)

Could someone explain what a "stump jumper" is? I've seen the term many times and assumed it was some kind of wheel/guard that made the rotary mower ride up over stumps. What would be a stump jumper that's driven by the output shaft?

shady1701 · Aug 25, 2003

Depends on what you plan on doing with it and the effect you want.

If you just want to cut grass in a rough or have hidden objects you'd go with rough cut mower.. I've seen alot of the good woods/jd cutters do a realy good job at cut quality almost rivaling a finishing mower i'd say. If you plan on mowing it high over 3" i'd go with rough cutter.
Generaly from $500-1400
The finishing mowers are just that for grass only with no objects and generaly can only mow grass about 4" high or so.

They have 3 spindles and can be damaged easily if you hit a good size rock, tree or anything else a lawn mower wouldn't go over. Blades run about $10 a pop x3 and can be fitted with hi-lift and produce a very smooth area which is idea for like golf courses, walking or kids playing.
prices are generaly $900-1200 some ultra high dollar befrco and others top $2K

Another good choice would be a flail mower basicaly a rototiller with a set of cutting knives on it in the shape of a Y said to be pretty much between the 2..
FLAIL MOWER EXAMPLES

The stump jumper my understanding is it's the round blade holder in the center of the rotary cutter when you hit a stump,rock or anything else that doesn't move the blades fold in and smooth with the round disc that is spinning. it the simply jumps over the object since the disc is rounded off keeping the spindle/blade assembly from getting caught up on object and ripping the spindle out like on a RFM. correct me if i'm wrong..

pruntyc · Aug 25, 2003

Well, the one who said the rotary cutter is not a cut, but that they chop and tear the grass. Well that will be true if you don't keep the blades sharp. Just like if you don't keep the blades sharp on a lawn tractor. They will do the same thing. but if you keep the blades sharp on the rotary cutter, they do a very good job. Maybe not a golf park look, but still very good. So if you are looking at keeping a large area looking nice, but don't need it to look perfect the rotary cutter is the way to go, but like the man said, you don't want any trash out there with a finish mower. Where that won't bother a rotary cutter, except you may need to touch up the blades to make them a little sharper after you cut up some heavy wood or hit a rock or two.

GSS · Aug 25, 2003

I just sold my RFM b/c I got a brush hog. The hog cuts the grass decently, but not as cleanly as the RFM. It will also not follow the more sublte curves in the land like the RFM with 4 wheels will. The hog blades seem to hit the ground a lot more on the more uneven terrain too. The hog will also leave more obvious "windrows" of cut grass. I do tend to wait longer to cut these areas though, so it might not be as obvious if you cut it when you cut the rest of your lawn.

The hog cuts the little bit of open grassy areas that we have well enough to justify selling the RFM.

- Gerald

LuvMy670 · Aug 25, 2003

I am using a rotary cutter in my pasture and it really leaves some gouges in some of the areas that are not flat. If you have a really flat area, then the rotary would be OK. I mow a pasture and I liked the rotary, but then out of laziness (I have to mow around the fence row with a lawn tractor to get closer cut) I went ahead and used the lawn tractor for the whole job. (Oh yeah, I keep that pretty clear of anything detrimental to mowers as I had to mow it with a lawn mower for 16 years before I got my "real tractor and bush hog".)

Well, guess what, I want a RFM now because I definitely like the look of the manicured pasture rather than the rough cut look. I can use the rotary to do the bulk of the heavy cutting and then finish it with the RFM.

I have a mini farm (ha ha, 3.5 acres) so either way, it doesn't take long to do the field. But horses do NOT eat grass in a nice manicured pattern and that long stuff grows FAST and thick.

djradz · Aug 25, 2003

Gerald, outfit your brush hog with check chains. You'll get a cut that's close to a RFM as far as level with no more gouging due to uneven terrain. They won't help however with the windrowing.

shady1701 · Aug 25, 2003

chains on the toplink i think what you're suggesting? will kick up and crush you..

rtimgray · Aug 25, 2003

I suspect that he is referring to the check chains that suspend from the top link (or the hole below it) on the tractor that keep the lower link arms from dipping too low.

There was a conversation a little while ago about using a chain instead of a top link on a bush hog (as I often do) and someone asked if anyone had actually known of a rotary cutter flipping up and crushing the operator, and no one had. I think it is theoretically possible, but it's gonna have to get a lot of force to flip it up almost 90 degrees, plus it will have to snap/crush/bend the PTO shaft too. I do agree it is potentially dangerous to use a chain, but not very much so (probably more likely to get injured in a car wreck driving home to drive the tractor than getting hurt driving the tractor with chain top link).

yellowsocks93 · Aug 25, 2003

Hi guys, everyone always says you can't cut tall grass with a RFM but with my JD 272 RFM I have cut 10'' tall, thick hay/grass in our hay field without the tractor or mower bogging down. I have not tried taller stuff yet but I know it could easily handle it. I can cut taller grass with the 990 and 272 RFM than with the 4300 and 60'' 7 iron MMM. The 272 is deaper decked and I think this helps with the dispersal of the clippings.

Nick
990 4x4 turf, 272 RFM, 430 loader, 25A flail

shady1701 · Aug 26, 2003

My papaw said he seen a couple of state contractors they had heard of it they indicated alot of times the u-joint will bind up and break allowing the pto to continue on i think they were running 1000 rpm with a HD cutter?.. also this was on some major hp tractors i think but that's what he said if it could happen to big it's possible to happen....

F350Lawman · Aug 26, 2003

This has ben my experience:

1. Large, relatively flat and not too bumpy a land and the rotary cutter cuts well. lmost as good as my lawn tractor.

2. Tight turns, hills and bumby areas will cause the rotary cutter to bounce and cut into the turf due to the lack of wheels on the corners.

My rotary cutter goes vey well through long grass and doesn't bog. I think the long grass helps stop it from scalping when it does bounce.

rtimgray · Aug 26, 2003

I haven't seen too many state mowing contractors using 3 pt hitch bushhogs - as you said, most used higher powered tractors and tow type rotary cutters - I guess they can flip up too, but again, that's not too likely. The state mowing crews in our area (i.e. state employees, not contractors) use 3 pt hitch rotary cutters, and all of them that I have seen recently use a chain for the top link. Of course, they have a very heavy ROPS with a steel bar grill (not expanded metal) behind the operator, so it's doubtfult that even if it did manage to flip forward, it still wouldn't hit the operator.

But I'll agree if it's possible to happen, sooner or later it will.

djradz · Aug 26, 2003

My reference to check chains is not a chain for the top link, but in order to use check chains, you do need to have some type of flexible top link, such as a toggle connection, moving top link bracing, or chain between the connection point and someplace further back on the deck.

With regards to a chain for the top 3-pt link (again, not what I was originally talking about), I wish everyone would get a little more realistic. Trailer-type implements, including rotary cutters and RFMs have been used forever and still are commonly sold, without incident. These only have one connection and not only could fly up but could flip around sideways. Has anyone ever heard of this happening? Let's get real and quit raising unfounded fear. Just my $0.02.

shady1701 · Aug 26, 2003

there's a website i seen also who had how this could happen i believe it was on an antique or some other website they were talking about the bush hog coming over is possible depending on tractor make and bush hog.. granted it's not very likely however it has happen before and it's like riding a loaded gun for little results..

slowrev · Aug 26, 2003

Yep never heard of a hog flying up and getting someone. However on my old 5 ft Hog I have replaced the straps from the toplink hookup point on the top of the Hog hookup back to the deck of the Hog with chain. Works great, toplink still there and the hog is allowed to follow the contours to minimize scalping and such. Less strain on the hitch on the Hog too.

rtimgray · Aug 26, 2003

granted it's not very likely however it has happen before and it's like riding a loaded gun for little results..

I still have yet to see any defined proof that this has actually happened to anybody - not to say it can't, but it seems like we keep getting "I knew a guy who heard from a guy that it happened to a guy he knew...etc".

As for the little results - it's a lot more forgiving when you are going down a hill to a level area or, worse yet, back up another hill (i.e. mowing a gulley). If you have a rigid top link and a rigid bushhog frame, you can actually lift your rear wheels off the ground, then you will free wheel (unless 4wd engaged). More likely, you will bend/break your top link/bushhog frame, etc. I think that the reward far, far exceeds the minimal risk involved. I honestly cannot imagine hitting something with such force with the bushhog that it will flip up 90 degrees and crush me...If I hit it that hard, it might bend/break the top link anyway...