Teach me about mowing width & PTO requirements

[Valorum]

I've been going through just about 20 pages of threads, but haven't found an answer yet. So i hope you can either point me to the thread i couldn't find that talks about this, or maybe educate me (and potentially others!) Thanks in advance.

We're looking at getting a rotary mower at some point in the near future. We have 5-7 acres of established pasture & "lawn" to maintain, most of it fenced in. We need to mow a handful of times each year (the rest is done by the horses ). There is no heavy / thick brush to cut through, no trees / saplings or anything like that. It's grass and some weeds with stems potentially, but most of it shouldn't be anything a regular beefy lawnmower couldn't take care of i think.

I have some question marks swirling around in my head (plenty of room in there next to the pea size brain ) about mower sizing etc.

First of all, should the mower be wide enough to cover the tractors tracks or not? The good thing about a mower being as wide / slightly wider we thought would be that you can get closer to fences to cut the grass right up to the fence. If the mower is narrower than the tires, you can't do this nearly as easily, if at all? Or can you?

A wider mower however has some clearance issues when you get right up on the fence i guess? When you try to steer away from the fence, the mower swings towards the fence? And thus a narrower mower would be better?

Then what about the grass that's been pushed down by the tractor tires? If the mower is as wide as the tires (and we're talking outside of the tires here, not inside of the tires?), is it even going to cut the grass that the tires just crushed? If not, we might as well get a mower that's as wide as the space between the tires then instead of wider?

Secondly - What about PTO requirements? I saw on the Bush Hog site that some mowers had a PTO HP requirement listed of something like 25-50HP. That's quite a range! What's up with that? I guess that's related to the thickness of the brush you intend to chop up with it? For our situation, i think we don't need a heavy duty type of mower, and thus we can get away with a lower HP model?

And then finally - When you combine the two things above (width & HP)... If you say we should get something as wide or wider than our rear tires, that means going with a 6' mower. 6' mowers require a little more HP than a 5' one. What's the minimum model mower (in terms of HP) we should expect to be looking at?

Thanks!

 

[J_J]

How much PTO HP do you have? Are you talking MMM, or bush hog, or finish mower?

 

[Valorum]

How much PTO HP do you have? Are you talking MMM, or bush hog, or finish mower?

The spec says 26 PTO HP. Definitely not MMM. Since this is pastures, i'm thinking bush hog mower.

 

[zzvyb6]

I have 35 hp and have run 6' Bush Hog, MMM, rear finish mower and front mounted finish mowers in the horse fields. Get a mower wider than the wheels (even when the wheels are spaced out as much as possible (rim and spider). Remember that the horse poop is an additional element of the cutting job. That means a rear discharge to prevent and minimize plugging, concentrating and spreading the manure. A side discharge will aggravate the plugging and spreading UNLESS you also use a vacuum system to suck it all up. If you do it a few times in the summer and fall, you will greatly reduce the fly and power requirments at the same time.

 

[kthompson]

I have a 27 hp tractor that I use a 6 foot rfm on with good results. You want your mower to at least be as wide as the rear wheels but wider is fine. If you find you have a hard time judging the distance you need to be from the fence, they take some thing flexible like small diameter PVC pipe, cut it to the length the mower is and mount it (nylon tie straps work fine) to the front of your tractor aligned with the mower. Works great.

Get the read discharge as zz said. Then either side can run up to the fences also.

If you are cutting lawn you need a finishing mower, if the pasture is level a finishing mower should also handle that well. You may need to raise it for the pasture.

The HP range is affected by, the speed you will be running, how low you will be cutting (lower is harder) and what and how thick you will be cutting. Again my 27 hp (not sure to pto) with hydro trans works well and seldom bogs down. Do have some real thick Zoysia that it hard on it and either must slow down or take narrower cut. This is mowing about 1 1/2 to 2 inches high. It higher would be no issue. Also cut some Johnson grass and Bahia grass on sides of road with same set up. Be sure you give it the RMS it needs.

 

[Runner]

Valorum,

I'm a newbie at this, but have a few thoughts on the topic.

First, since I elected to go with both a rear finish mower and a rotary cutter for different areas of the property, I had the same question as you about whether the tractor would mash the grass down too much to give a good cut. I was relieved to see that even the rotary cutter seemed to have enough blade suction to stand the grass up for proper cutting. The rear finish mower was even better and gives as good a cut as a belly mower in my opinion.

Because of this, I would recommend getting as wide a mower as the tractor can handle. One way to figure out what the tractor can handle is look at the mowers recommended by the tractor manufacturer. Even if you don't want to buy one from the manufacturer of the tractor, it will at least give you some idea what they recommend for your particular tractor.

Also, part of what goes into that recommendation is how heavy the mower is, not just how much horsepower it needs to work. For instance, JD recommends a 5 foot light duty rotary cutter for my 2520, but none of the medium or heavy duty models, mostly because of the weight.

The other thing I've gathered about the HP requirements for rotary cutters is that they may need a certain HP to be able to handle their rated capacity, like cutting a 3" tree, but you may be able to operate the cutter fine on less HP if you are just cutting grass. Again, I think you can do a little interpolation between what the tractor and cutter manufacturers' recommend and your own conditions.

Finally, you are right, it's a little hard to judge how far you are from, say, a fence line when pulling a rear mower. I have a 72 inch rear finish mower and a 60 inch rotary cutter. I will occasionally get in a situation where I've gotten too close to my fence line and don't have enough room to "correct" by steering away from the fence without bashing it with the mower. So (when nobody's looking) I stop, back up a little and start again. I'm getting better at this though.

I would say that the narrower mower (but still wider than the rear wheels) is easier to maneuver along a fence line, but the wider mower is worth a little more attention in the tight spaces to get more cutting width out in the middle. Obviously, the wider mower also allows you to stay farther away from trees if that is a consideration.

kthompson,

I like your idea about the "curb feeler" on the front of the tractor to help judge distance from the fence.

Best of luck on your purchase.

 

[MichiganIron]

Here's a decent rule of thumb for mowing/PTO hp:

For finish mowers - 3-4 PTO HP/Ft of Width
Brush Cutting - 4-5 PTO HP/Ft of Width

These numbers can vary depending on conditions, but they are good starting pointfor most mowing applications. Some of the larger finish mowers actually can run a little under the rule of thumb numbers. Brush cutters could need a little more in tough conditions. They are good safe numbers we have used for years.

 

[gerard]

1. Your tractor can handle 6 footer

2. If right tight to a fence, you have to steer away gradually to avoid having the mower swing into the fence. Not a big deal, you just can't take a hard "lock to lock" turn when up tight.

3. IF all you're going to do is knock down the pastures AND they are flat AND there are no rocks, halters, feed buckets or other assorted sundry, you could get away with a finish mower. BUT they are more expensive, more easily damaged if you hit any of the aforementioend things, and it's a pasture, not a golf course. Id go with the bush hog - they actually give a decent cut and you don't want to mow the grass that tight anyway. The horses need something to eat, and in GA mowing it that tight will increase burning which you DON't want so you're going to be cutting it fairly high anyway.

4. A little wider than the tires is better than a little narrower for the reasons you mentioned ie getting up tight to things.

5. For your purpose I'd look at a medium duty one. They generally have light , med, and heavy duty. Difference is the thickness of the deck steel and the gear box. You're going to be doing pretty light duty so save some money and go light or med.

6. The blades will come fairly dull. Designed that way for cutting saplings etc. If you want a nicer grass cut you CAN put a little better edge on them with a small grinder.

 

[Valorum]

Thank you for the very informative replies, they're very helpful

 

[kthompson]

To me it was implied here you can not cut grass as high with a finish mower and with a rough cut mower. Not true. Even though all finishing mowers I have seen have wheels to run on you can run them just supported by your lift to any height you may wish. There is no reason you can not cut decent grass with them, even in a pasture. May need to keep the wheels off the ground. I have used my RFM in some heavy grass in the manner where for years it was only cut with rough cut mower with good results. At my MIL have some very heavy grass that has to be cut about once a month and which ever cutter is on my tractor does it well.

Now consider a flail mower also. Look at threads here for some thoughts. Might be your best options.