72" finish mower on a 21hp tractor???

   / 72" finish mower on a 21hp tractor??? #1  

IslandTractor

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Joined
Sep 15, 2005
Messages
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Location
Prudence Island, RI
Tractor
2007 Kioti DK40se HST, Woods BH
Now that I have finished bush hogging and otherwise clearing an old 3-4 acre pasture, I'd like to get a finish mower to make the mowing task go faster. I have a 21hp tractor (Kioti CK20 HST) and the land is sloped. I mention the slope because I need to be in low HST to climb directly up which is the long direction and the preferred mowing direction (up and down rather than sideways).

As I need to be in low HST range anyway, it seems reasonable to consider a 72" mower instead of a 60". The PTO horsepower is 15.5 however and Kioti's own 72" mower specifies 20 PTO hp. A Caroni 72" mower (same basic design) also specifies 20 PTO hp as the minimum. I understand these are not really precision engineering considerations but rather rule of thumb calculations that are based on cutting lush lawns.

That bring up another factor: this is a pasture not a lawn. The mixed grass is fairly thin and is cut to about 3-4 inches high every couple of weeks May-Sept. The soil is sandy and does not support a luxurious growth of grasses.

Other than mowing slowly (remember I will be in low range anyways) is there any reason not to stretch things a bit and get the 72" rear discharge finish mower? I figure the bigger mower would save me about 15-20% of my mowing time.
 

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   / 72" finish mower on a 21hp tractor??? #2  
I guess you've been using a rotary cutter for the initial clean up. I'd also guess the cutter was a 48" unit.
If those guesses are correct, how did the unit run? Any bogging?

I operated a 60" rotary cutter behind a Deere 670 with 16.5 PTO HP. The minimum recommended HP for the cutter was 20 PTO HP. I had no problems at all. I just went slow or made partial width passes if the machine bogged.

That said...
I think the 72" RFM would work behing your Kioti as long as the grasses are dry and not allowed too much growth.
Since your property has some slope to it, I wouldn't want to cut grass that was wet anyway...wet grass is pretty slick! Making partial width passes with a 72" RFM negates the advantage of having a wider mower. Operating slower (then you could with a 60" RFM) also negates the advantage of the 72" unit.
I would be concerned about the weight of the mower (when transporting it with the mower raised on the 3PH).That could be a limiting factor. You'll want to leave the FEL on or get some front weights.
Also 72" mowers are pretty expensive. You're dealing with implements that cost $1500 plus, so take that in consideration.
Also, is the field really ready to cut with a finishing mower? It looks as if it is in the picture, but pictures can be deceiving. Only you can answer this question...

In conclusion, your machine can probably handle the 72" mower albeit it would be marginal. There may be times the mowing may be slower then it would be with a 60" mower due to making slower or partial passes.
BTW, if you were using a 60" rotary cutter (rather then the 48" cutter I guessed at) and had no problems, the 72" RFM should be no problem.
 
   / 72" finish mower on a 21hp tractor??? #3  
I use a 6-ft. finish mower behind my 1520 Ford. It handles the mowing task fine, but the mower will push the tractor around when mowing on steep slopes...and the 1520 is the heaviest 19 PTO hp tractor that you will find!

In short, I think that the 6-ft. finish mower will work behind your CK20 but be very careful.
 
   / 72" finish mower on a 21hp tractor??? #4  
I ran a 6 ft Woods finish mower behind my JD 870, it was a bit bigger than your Kioti 20, and had no problems. The JD had about 22 pto hp and I was mowing on fairly level ground. You will want some weight on the front of your tractor. I had 120 lbs of extra weight and that made a difference when mowing up along the driveway. The quality of the cut from the Woods was very good.
 
   / 72" finish mower on a 21hp tractor??? #5  
I think you'd be happier with a five footer in the long run. Consider that a six footer will put at least 20% more weight on your TPH - after all, a CK20 is only a 1900 pound tractor. I have an seven footer (>800 pounds) behind my KM454 (~4000 pounds), and I can still make the front end bounce if I'm not careful with the hydraulics.

Also, you'll likely end up wasting time and fuel going back over the spots that didn't get cut level on the first pass.

//greg//
 
   / 72" finish mower on a 21hp tractor??? #6  
Mornin Ed,
Very pretty piece of property you have !

Im with Greg, I would go with a 60" RFM. I think you will find that your going to be taking less than a full width cut because of bogging especially going back up that slope ! I lean towards the smaller mower.

BTW, My oldest boy graduated from Univ of RI in 04, computer science. We have stayed in Narraganset and Kingston, very pretty area !
 
   / 72" finish mower on a 21hp tractor???
  • Thread Starter
#7  
Thanks guys. I have been using a 48" Bush Hog with no trouble at all but want something wider that doesn't scalp as much.

Besides the 60" or 72" finish mower, I've considered a 59" Caroni flail mower. The 60" finish mower (using the Kioti brand numbers because they are convenient) weighs 450lbs, the 72" 495lbs and the Caroni flail weighs 485lbs. That makes all of them just a bit heavier than my current 48" Bush Hog which weighs 430lbs. By comparison, the Bush Hog 60" rear finish mower weighs in at a beefy 536lbs and their 72" version is 588lbs.

For what it's worth, my backhoe with bucket weighs more than 800lbs and Kioti recommends 600lb ballast for the FEL anyway. Also, as the finish mower has four wheels, it is really more of a towed weight than a 3PT hung weight that I'll be dragging around while cutting anyway.

I'll need to ponder the real world benefits of pushing the envelope here as any theoretical efficiency gains would, as Roy points out, evaporate if I end up needing to go over areas a second time or slow down. I don't think I'll need to slow down much as I would be in low range anyway so not moving that quickly.

I've wondered about what the fair comparison is between mowers of different widths as real world conditions don't really get taken into account when one just compares the width ratios in calculating expected cut times. One thing that may increase the benefit of wider mowers is that you need to overlap the cut area just a bit to ensure you don't leave uncut grass at the margin. If you overlap by six inches, then the effective cutting width of 4, 5 and 6 foot mowers is really 3.5, 4.5 and 5.5. The proportional benefit of the bigger mowers is therefore a little greater than it appears. However, I would guess that the increased manuverability of the smaller mower would sometimes be useful and save time. Also, we tend to compare mowing times without considering the time involved in setting up or putting the tractor and implement away which presumably is identical for all mowers.

Decisions, decisions.
 
   / 72" finish mower on a 21hp tractor??? #8  
I ran a 60" LandPride with my YM 1700 for 14 years. At 17 HP on the PTO it was a perfect match. My Yanmar only weighed 1550# but with loaded tires tipped the scales around #1900 or so. That's pretty close to what you have with your current rig. HP wise your tractor would probably handle the 6 footer but the weight of the unit is what would be at issue. My LandPride was only 440# per factory specs. A 6 footer is gonna weigh in more.

I would try to find a unit that I could possibly try out first to see how the tractor handled the mower. Do you have a neighbor that has a 6 foot unit that you could use?

BTW you have a beautiful piece of property.
 
   / 72" finish mower on a 21hp tractor??? #9  
With a view like that... the slower the mower, the better. More time to enjoy the view (and the seat time).
 
   / 72" finish mower on a 21hp tractor??? #10  
"I'll need to ponder the real world benefits of pushing the envelope here as any theoretical efficiency gains would, as Roy points out, evaporate if I end up needing to go over areas a second time or slow down. I don't think I'll need to slow down much as I would be in low range anyway so not moving that quickly."

Have you considered a brand yet?
I'm not one to run my tractors excessively hard, but they are working tools. It seems like most folks here recommend larger equipment then is really needed for the job at hand.

As an example, I'd written I used a 60" cutter behind my 16.5 (PTO) HP tractor. The cutter is a Land Pride (still got it).
Land Pride recommended 20 PTO HP minimum to run this cutter. However, the dealer (a Kubota dealer, BTW) said they sold a number of these to B7500 owner/operators.
I was somewhat skeptical but did buy the cutter.
The tractor/cutter combination did an excellent job, especially considering the heavy brush I was mowing (first time this field had been cut in several years). I've attached a picture of some of the brush, but not the heaviest areas).

The next post will continue this...
 

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