Rotary Cutter HP required for a 15' Bush Hog?

[Ken45101]

I'm thinking of buying a 15' batwing Bush Hog. I know the general "rule of thumb" is 5 pto HP per foot of cutter. That would come out to a 75 hp requirement. Bush Hog specifies a minimum of 50 HP.

I know I'll need to upgrade the tractor. I'm considering either a Kubota M7040 (64 pto HP) or M8540 (76 pto HP). Both the tractors I have now are 43-44 HP pto.

Yes, I know it "all depends" but I'm wondering if the M7040 would be enough for most use (and yes, I can gear down or cut smaller swathes if it gets really thick). Would the M8540 be overkill? There is no sense buying the larger tractor if 95% of the time it would be coasting along.

This is for pasture mowing. My hope is to be able to get ahead of the pasture before it gets too high. Currently it takes me 35-40 hours to mow the pastures (about 35 acres). A bigger mower would help. Right now, with just a 6' mower, I'm finishing up first mowing and some of the patches of ironweed are 8' high

With all the rain here this year, things have been growing fast and it's been hard to get a chance to mow the pastures.

Right now, most of the mowing is just idling along with 44 HP and a 6' cutter. Occasionally, the tractor has to actually work a bit on the heavy stuff.

Thanks,
Ken

 

[LD1]

I'd say it would depend on price. If the larger tractor isn't very much more then why not?? The smaller one i think would run it fine, but it would be more of a load than the larger one. A tractor that spends a lifetime of easy work last a lot longer than a tractor that works hard all the time. So if it isn't much more $$$ get the bigger one, it will last longer, and you have the extra power if needed.

 

[radman1]

If you are not mowing really heavy stuff, either will work. Especially if it has been mowed recently. I have a 4 year old 15' JD HX and 110 hp pto tractor and it never bogs down for the stuff I mow. 50 pto hp would be very marginal for a 15' mower IMO. The guy I bought my 15' mower used a 74 pto tractor and he used it to mow 240 acres of thick, grassy, virgin CRP land with it. He said he had a lot of windrowing of the grass and bought a baffle kit for the bottom which helped at lot.
Most of the tractors I see mowing the roadsides in my state use 85-100 pto hp tractors. Most of the mowing of roadsides are not that dense IMO and the size of the tractors are probably overkill for the majority of the mowing. I have seen them running the same as my 110 pto hp tractor that I have. Personally, I would lean toward the bigger, M8540 Kub.

 

[Farmwithjunk]

Powering the mower is only a part of the issue. A 15'er will overwhelm a small tractor when trying to stop on hills, shutting down the PTO (pto brake not heavy enough) and hydraulic capacity can be questionable.

I know of one gentleman who uses a 20' batwing behind a 42hp tractor to cut what I'd describe as a "big lawn". Power wise, he's OK. But his ground is flatter'n a pool table and his old tractor doesn't even have a pto brake.

You're on the razors edge.....

I run 15'ers behind 3 tractors w/95 hp and 2 w/85hp. They rarely ever get into overgrown weeds, ect, but when they do, they labor when mowing at any sort of decent speed.

35 to 40 hours to mow 35 acres???? What'r ya mowin'? steel fence posts????? (I average 2-1/2 to 3 acres per hour with a 6'er behind 47hp in pastures or simular conditions)

 

[LoneCowboy]

I run mine behind a NH TN75 (69 PTO HP, on dyno) commercially. I've cut 1000's of acres this year.

But, it depends on what you are cutting.

Most weeds (not Kocia for isntance) are much easier to cut than most grasses.

I can fly right along (about 5.1mph) thru 6' tall thistles, but 2 to 3 feet of heavy pasture grass can slow me down 1 to 2 mph. (I have to gear down).

but it's still way faster.

7 acres an hour on average.

More HP would be better, but it's not a requirement.

Batwings are a TON of money. Figure $12,000 and on up.

If you are never transporting it, a straight cut (not a wing) is a lot cheaper.

BTW, the state uses MY money (taxes) to buy 115hp tractors to cut the exact same weeds and grass I cut with 75hp. Just saying. That tractor is twice as much as my tractor. Don't compare what government's are using, they have no sense of budget, they don't care. Find out what the commercial guys in your area are using.

 

[chh]

I have used my 15' Rhino batwing behind all three of my current tractors. The smallest a Montana T7074 (70 engine hp and 60 pto hp) will do an acceptable job in most conditions. Heavy grass/weeds will require shifting down or cutting a smaller swath. My next step up is a MF 4243 (85? engine and 70ish pto) really does a better job with it, but it is not a cabbed tractor so I don't use it as much for that. A bit more hp in heavy conditions really does help. I have had heavy bermuda bog down the MF 5455 (105 engine, 85 pto) , but in most conditions it acts like the batwing isn't pulling much at all.

Wow, I always thought Oklahoma was behind the curve on everything, but it looks like the state may doing things a bit cheaper than some others on this deal. Most of the states tractors here are in the 85 hp range. I have seen several MF4243's in the state fleet and Ford 6610's where the most common for years.

 

[Ken45101]

Powering the mower is only a part of the issue. A 15'er will overwhelm a small tractor when trying to stop on hills, shutting down the PTO (pto brake not heavy enough) and hydraulic capacity can be questionable.

I know of one gentleman who uses a 20' batwing behind a 42hp tractor to cut what I'd describe as a "big lawn". Power wise, he's OK. But his ground is flatter'n a pool table and his old tractor doesn't even have a pto brake.

You're on the razors edge.....

I run 15'ers behind 3 tractors w/95 hp and 2 w/85hp. They rarely ever get into overgrown weeds, ect, but when they do, they labor when mowing at any sort of decent speed.

35 to 40 hours to mow 35 acres???? What'r ya mowin'? steel fence posts????? (I average 2-1/2 to 3 acres per hour with a 6'er behind 47hp in pastures or simular conditions)

I'm on the razor's edge with what? 42 hp? 62? 75?

Yes, the hills are one of my concerns. I'll be going 4wd which should help some. It's possible that I will have to switch to the 6' cutter for some of the areas.

Why does it take me so long? I don't know, I guess because I have very irregular shaped fields, mostly 3-5 acres, this is ridgetop land. I spend a lot of time turning in big loops with at corners greater than 90 degree. Often I'm cutting triangles. I figure if I can cut 2-3x as much in one pass, I'll eliminate a lot of the lost time in the turns. A couple of pastures I have to cut by backing down the hill. Really time consuming when I'm only cutting 75-150' at a pass.

When I'm on ridgetop straight aways, I can run in 4th or 5th gear most of the time. I think the best I've done is 2-2.5 acres per hour with the 6' cutter.

If you are never transporting it, a straight cut (not a wing) is a lot cheaper.

I wouldn't get a 15' through the gates ;-) Besides, the land is irregular and I figure a batwing would follow the contours better.

Thanks to all for your real world horsepower data.

Ken

 

[Farmwithjunk]

I'm on the razor's edge with what? 42 hp? 62? 75?

Yes, the hills are one of my concerns. I'll be going 4wd which should help some. It's possible that I will have to switch to the 6' cutter for some of the areas.

Why does it take me so long? I don't know, I guess because I have very irregular shaped fields, mostly 3-5 acres, this is ridgetop land. I spend a lot of time turning in big loops with at corners greater than 90 degree. Often I'm cutting triangles. I figure if I can cut 2-3x as much in one pass, I'll eliminate a lot of the lost time in the turns. A couple of pastures I have to cut by backing down the hill. Really time consuming when I'm only cutting 75-150' at a pass.

When I'm on ridgetop straight aways, I can run in 4th or 5th gear most of the time. I think the best I've done is 2-2.5 acres per hour with the 6' cutter.



I wouldn't get a 15' through the gates ;-) Besides, the land is irregular and I figure a batwing would follow the contours better.

Thanks to all for your real world horsepower data.

Ken

I completely missed the 75hp tractor....That'll do OK. Not OVERLY large, but big enough in most cases. 42 is just too small in my book. 62 would be marginal at times.

Sounds like you have a place about like my old farm. Some of that acreage was like cutting an obstical course. In that case, a batwing won't speed things up nearly as much as if you were mowing in open country. I'd be VERY concern about using a tractor that is too small. A typical batwing is heavy. They can be more of a drawbar load than a pto load in some situations. That would be a deal breaker in hilly country.

One GOOD thing with a batwing....Their width can allow you to make 180 degree turns where you can double back on your previous pass. (provided you get a mower w/ correct pto shaft)

I'm looking at a tractor/mower set-up for next season that would probably be of interest to you. It's a "TIGER" brand, mounted on a NEw Holland tractor. It'll carry an 8' flail mower on the back with a side-mounted 7' flail that can be raised when not needed (and for transport. That'll give me the full 15' mowing width and still have the convenience of a mounted mower. Biggest issue is, it takes a dedicated tractor. (and a BUNCH of $$$$$)

 

[MESSMAKER]

A larger tractor and a 15' cutter is a huge investment to cut 35 acres. You could have it cut a couple times a year for the next 12-15 years and still be money ahead. Considering you already have a smaller tractor and a 6' unit, the best $$ route may be to trade up to an 8' cutter and use the tractor you have. If your fields are small and odd shaped, a 15' batwing may not be the best answer.

 

[gabby]

I run a 10 foot JD HX-10 mower and I have lots more acreage than you. I pull it with 85 pto hp and sometimes I wish I had more hp. I have uneven ground too but it follows it well.

I don't think you need a batwing. My mower was about half the price of a batwing and I'm very happy. I used to own a batwing and I don't miss it one bit. I pulled it with 65 hp and it was way too little hp. There's lots more weight and lots more moving parts that can go wrong on a batwing.

Since your hp is limited you will run faster ground speed and have better control with a smaller mower than with a batwing. You won't actually cut more acres per hour with a batwing unless you have a big tractor that can really pull it with gusto.