Min PTO HP for 7.5' finish mower

[GManBart]

I'm considering getting a dedicated mowing tractor to save myself some time, and I'm trying to figure out how small I can go (I already have a ZT for the tight areas around my house/fence). I picked up a super clean 7.5' finish mower (Sitrex SM230) at auction and have been running it behind my LS, which runs it like it's not even there. I'm in the middle of a long project to clear land, demolish buildings, backfill old foundations etc, etc, so I'm using the LS to move dirt, serve as a 4WD forklift, etc. Having the mower deck on it isn't convenient (or enough counterweight for moving dirt), so I wind up swapping for the counterweight back and forth every other time I go to do something. I have enough land that I need to mow pretty frequently, and would like to be able to leave the mower deck on a tractor, ready to mow, whenever I have time.

What do you think the minimum PTO HP should be for a deck that wide? It's also nearly 700lbs, so I can't go too small or it will be cumbersome. I was sort of thinking it might take close to 30hp at the PTO....thoughts?

Anybody run a finish mower this big with a smaller tractor?

 

[J_J]

The general rule is about 5 HP per ft.

 

[GManBart]

The general rule is about 5 HP per ft.

That's really for brush cutters, not finish mowers. My LS only has 38hp at the PTO if my memory is correct, and it isn't working hard to run this deck.

 

[J_J]

Depends on what you are cutting, lawn or field.

Look at the RDC72, requires about 25 - 35 and also look at the other finish mowers.


Finish Mowers

 

[rbargeron]

........ I was sort of thinking it might take close to 30hp at the PTO....thoughts? Anybody run a finish mower this big with a smaller tractor?

I can run a 90" finish mower on my smaller tractor - around 29 pto hp. It has it's hands full going uphill in tall grass - but by going slower or tasking less of a bite it will manage. 40 pto hp is a better match for a 90" cut but if you don't let the crop get too heavy 30 pto hp will get the job done.

 

[Turbys_1700]

I ran a 5' Land Pride finish mower 14 years with a YM1700 Yanmar...
That Yanmar is rated at 17 HP at the PTO and it ran the mower just fine...
I now run a 6' Woods PRD 7200 with a New Holland 1720 that is rated at 23.5 HP at the PTO and it runs it just fine...
I will say though that this is the absolute minimum HP per foot cut that I could recommend...
The Yanmar Land Pride combo was running @ 3.4 HP per foot cut and the New Holland Woods combo is running @ 3.9 HP per foot cut...
I can tell you that the 6' Woods PRD takes considerable more power to run than the 5' Land Pride...
The difference seems more than 20% due to the extra weight of the Woods...
If I was looking at a 7' or 8' RFM I would be looking @ minimum of 28 HP for the 7' and 32 HP for the 8'...

 

[J_J]

The Woods site says your 90 requires about.

Tractor horsepower 45 - 75 hp

Think of it as work, and work = HP and just turning the blades does not take much HP, but get into some tough grass and the engine will start to lug based on the load, using what HP is available.

We are talking about a useful match of HP and width of cut and type of cut.

 

[GManBart]

Depends on what you are cutting, lawn or field.

Look at the RDC72, requires about 25 - 35 and also look at the other finish mowers.


Finish Mowers

Good point. I have 5' and 6' brush cutters to go over the heavy stuff. The plan is to only use the finish mower for normally grassy areas, and the brush cutters for everything else. Ideally, I'd like to be able to run the 6' brush cutter on the smaller machine as well (which still puts me around 30hp at the PTO), but it's not critical.

 

[GManBart]

I can run a 90" finish mower on my smaller tractor - around 29 pto hp. It has it's hands full going uphill in tall grass - but by going slower or tasking less of a bite it will manage. 40 pto hp is a better match for a 90" cut but if you don't let the crop get too heavy 30 pto hp will get the job done.

Thanks...that makes sense, and was pretty much what I was thinking. I don't have any steep hills, and if I can mow for a while, and it gets really tall, I can always run the brush cutter first, or use the bigger tractor. R,

 

[GManBart]

I can tell you that the 6' Woods PRD takes considerable more power to run than the 5' Land Pride...
The difference seems more than 20% due to the extra weight of the Woods...
If I was looking at a 7' or 8' RFM I would be looking @ minimum of 28 HP for the 7' and 32 HP for the 8'...

Thanks...my Sitrex is pretty heavy, at almost 700lbs, so I was factoring that in as well. Looks like your numbers are working out pretty much the way I was thinking...ballpark of 30hp at the PTO.