Rethinking rotary cutter sizing

[bdog]

I have always thought 5HP per foot was a good guideline for rotary cutters and then I saw these videos. They are guys running 10’ batwings with ~30 PTO HP in some fairly thick stuff.

I am in the market for a batwing and have 63 PTO HP. I was originally thinking 12’ but after watching these videos I am thinking I could run a 15’ effectively? My dilemma is I want to mow as big of a swath as possible but I don’t want to overdo it on the cutter and have to be mowing a 1 mph and constantly bogging It down.

 

[Slowpoke Slim]

It depends on how thick your grass is that you're cutting. Super heavy thick grass and you'll have to slow down for sure. But brush, weeds and "junk" you wouldn't. I've watched the TTWT videos of him running that 10' Rhino, and he even says when it gets *really* thick he has to slow down. Otherwise he goes as fast as normal (or comfortable) most of the time.

I've been thinking pretty hard on that 10' Rhino, and I've got 32 pto hp. If I had more mowing jobs lined up, I'd probably do it. I'm not sure I'd want to try the 12' cutter.

Personally I don't like flying over the fields anyway, bouncing and jarring myself and my equipment. So for me, ground speed isn't normally a factor, especially if I'm mowing tall grass with an unknown surface underneath. And watching for unknown objects that could be in there that the property owner "forgot about". But I bid my mowing jobs "per acre" not "per hour".

But to your question, how much of an issue would it be if you had to slow down in a few spots that were really heavy? How big a deal would it be if you sacrificed more time by having to slow down to get through certain tough areas? Are you working jobs for hire, that are bid tight for time already? If so, maybe it's more a "big deal" for you than, say someone who has the time built into their bid to be able to slow down? Or someone who was only mowing their own place, and not "for hire"?

 

[bdog]

Thanks for the very good reply. I won’t be mowing anything for hire but I do own just over 350 acres. Not all of it will be shredded of course. I get what you are saying about how big of deal would it be to slow down with a 15’ but if that is likely to occur might I just be better off with the 12‘? The whole is goal is to do my mowing as quickly as possible. About 25 of my acres are at my house and it really isn’t a big deal how long it takes. The bulk of the acreage is 1.25 hours from home and my time there is limited. I might get 2-3 ”work” days there a month. I want to be able to get as much done in my limited time there as possible.

I don’t like mowing super fast and bouncing myself to death either but there is a big difference in comfortably mowing at 4 MPH vs having to go 2 MPH so you don’t bog your machine.

The 12’ mowers are considerably cheaper than the 15’ as well. Both are in the budget I just would hate to pony up for the 15’ and then realize I am underpowered But at the same time I would sure like to have that extra 3’ if my machine can handle it.

 

[redman135]

Hello bdog, what are you farming on the home block and the main block, ie how do you normally control the grass?
Would you be better to get a hay / silage contractor in to conttrol the grass, or is it weeds?
How smooth is the ground? Changes your options
Are you trying to trim the long grass to allow fall / autum grass growth for winter feed or what?
I don't know your growing season in texas, so what season is it for you spring or early summer? Are you mowing to prevent grass fires getting away on you?
I am in New Zealand and on stock farms we would be topping/brushhogging to trigger grass growth to setup for winter feed(in Waikato we only get frost, no snow and 35 - 45 days of no grass growth).

 

[stuckmotor]

The toughest grass I've ever mowed was bahia there were times when half of a 5ft. slasher was slow going for my AC and the bahia wasn't very thick at that.

 

[DieselBound]

One can "mow" forests with a huge, hand-held saw, but it will take time! The component to consider is SPEED. Running cutters is about the speed in which the blades are able to cut through material. If one were to creep something slow enough it would be akin to sawing.

I recently purchased a 7' flail knowing that I'd be running it slower than my 6' RC. My expectation is that the over-all time to mow is going to be quicker with less passes even though each pass is expected to be slower: turning time amounting to more cumulative time than the reduction in travel speed.

As noted, composition of material to mow makes a ton of difference. I could run my B7800 with a 5' RC at a slow walking pace through nearly 10' tall grass whereas running it through my neighbor's 3' - 4' tall grass (more like thick, green steel wool!) required a snail's pace: later was the worst experience in mowing I've ever had (it was bordering on tractor abuse).

 

[Zebrafive]

Another consideration is hills, if you have them. Will you be able to go up them? Will you be able to control going down hill with a 15' batwing in tow?

 

[Slowpoke Slim]

His Kioti is pretty big. And pretty heavy, think along the lines of a Utility Tractor.

I doubt he'd get pushed around by a 15' batwing.

The real question is if he has enough pto hp to drive it with the conditions that he frequently mows with.

I've breezed through junk taller than my hood, and 6' high weeds. But very thick heavy grass is more of a load on the pto hp than brush and weeds, just due to the density of what the blades have to spin (and cut) their way through.

 

[bdog]

A 15’ batwing weighs around 4,000 lb. My tractor weighs around 10,000 lb. I think I will be ok With regards to the tail wagging the dog. I have some hills to traverse to get where I am going but the areas mowed are flat.

 

[K5lwq]

You could go with the 15' and in thicker stuff, if the tractor does not like it, take smaller bites. That way you could mow at the same speed and when conditions allow, take the full 15'.