HP for mower?

[corelokt]

If I have a 6ft finish mower, made for 540 rpm, how much HP at 1200-1800 rpm engine speed, reduced to 540 rpm?

 

[joeysmith]

Rule of thumb is 5 hp per foot

 

[Geo-TH,In]

If I have a 6ft finish mower, made for 540 rpm, how much HP at 1200-1800 rpm engine speed, reduced to 540 rpm?

My Jubilee, around 30 HP, can handle a 6 ft finish mower in First and second gear depending on how tall the grass is.
My Farmall C, around 20 hp, can handle a 6 ft belly mower in first and second gear.
My Boss may use first gear and makes the grass look better.
My Kubota, around 37 HP, can handle a 6 ft finish mower going 6.5 mph with no stress.

 

[corelokt]

I need to know if I'm mounting a motor to the deck. No PTO.

 

[Geo-TH,In]

I need to know if I'm mounting a motor to the deck. No PTO.

PTO HP is the same horsepower as engine HP.
Mose small engine HP is rated close to 3600 RPMs.
How will you gear 3600 RPMs down to 540 rpms?

 

[corelokt]

Pulleys and belts, or sprockets and chain.

 

[timcasbolt]

I need to know if I'm mounting a motor to the deck. No PTO.

I almost bought one of those a long time ago for my F-12. Bet it would be a fun project.

 

[timcasbolt]

Pulleys and belts, or sprockets and chain.

Speaking as an old sprocket and chain man from way back, I recommend pulleys and belts.

 

[wore out]

If I have a 6ft finish mower, made for 540 rpm, how much HP at 1200-1800 rpm engine speed, reduced to 540 rpm?

As an example of what's been done, this 5' Swisher tow-alongside mower has a 13HP 3600 RPM Briggs, (2.6 HP/foot). What are you powering yours with that will be operating at 1200-1800 RPMs, an old tractor engine, perhaps? (A typical air cooled engine would probably not cool properly if working hard at such low RPM's.)

 

[Geo-TH,In]

Pulleys and belts, or sprockets and chain.

My Farmall C PTO turns 550 RPMs
Woods put a large pulley on the PTO shaft to get the blade speed right.
You will need to do some calculating to get the right mover belt speed
When the engine is turning 3600 RPMs.
Good luck. Keep us posted what you come up with

 

[corelokt]

I very likely have the rpm wrong. It would be either a rebuilt K series, or harbor freight special.

 

[Duner Wi]

If I have a 6ft finish mower, made for 540 rpm, how much HP at 1200-1800 rpm engine speed, reduced to 540 rpm?

I think you could get the more correct answer if we knew how many blades and if high lift blades or not.

 

[corelokt]

I am planning before buying, for a change.

 

[Duner Wi]

I would rather have too much power than not enough.

 

[Fixingfarmer]

I suppose rpm wise my reply will be waaaayyyy off base. So you are planing on buying the tractor and have the mower from the wording of the question?

I wouldn’t be scared of a 6 ft on almost any tractor if it came down to it you could stagger over. They cover the tracks of most of our tractors both of these at 16 and 20HP did fine I didn’t switch to the John Deere A because they couldn’t handle it on the lawn I switched because the cooling system was larger it was electric start lights and had a better backrest. But the A with double the hp can mow the lawn in 3rd gear in a dry spell (what’s that?!??)

I ended up with a 3 point mower since the C and B had them and the A got one.

The B could actually mow off one row of cornstalks with the 3 point at a time. But it had to be cool out and it is working it.

Height of grass. Sharpness of blades. There’s enough rocks and weird obstacles here as we are perpetually in a state of contraction and clean up mine just get new blades

 

[Fordy20]

I just bought a GM2084 Frontier finish mower and the manual states up to 50 hp for the 5, 6 and 7 foot mowers. So, if you're like my neighbor that mows three acres of grass with a riding lawn mower that he lets grew to three foot high before he mows, you might want to limit the hp to whatever the gear box is rated for. But if you're just mowing shorter gress it probably don't matter.

 

[BarnyardEngineering]

I suppose rpm wise my reply will be waaaayyyy off base. So you are planing on buying the tractor and have the mower from the wording of the question?

I wouldn’t be scared of a 6 ft on almost any tractor if it came down to it you could stagger over. They cover the tracks of most of our tractors both of these at 16 and 20HP did fine I didn’t switch to the John Deere A because they couldn’t handle it on the lawn I switched because the cooling system was larger it was electric start lights and had a better backrest. But the A with double the hp can mow the lawn in 3rd gear in a dry spell (what’s that?!??)

I ended up with a 3 point mower since the C and B had them and the A got one.

The B could actually mow off one row of cornstalks with the 3 point at a time. But it had to be cool out and it is working it.

Height of grass. Sharpness of blades. There’s enough rocks and weird obstacles here as we are perpetually in a state of contraction and clean up mine just get new blades
View attachment 123956

To me, it sounds like he is planning on mounting a small engine to a mower deck in order to pull it around behind a smaller/older tractor, or possibly an ATV.

If that's the case, just look at what's been done. There's no "formula" because so few people tackle this kind of project. Most buy something that somebody figured out for them.

Example of "what's been done:" I have a 61" cut zero turn mower with a 23HP 680cc Kawasaki V-twin engine. Consider that not only is it powering the deck, but is also moving the mower. At the very least if you put a ~680cc V-twin on the deck you will have plenty of power.

 

[jddrawbar]

I suppose rpm wise my reply will be waaaayyyy off base. So you are planing on buying the tractor and have the mower from the wording of the question?

I wouldn’t be scared of a 6 ft on almost any tractor if it came down to it you could stagger over. They cover the tracks of most of our tractors both of these at 16 and 20HP did fine I didn’t switch to the John Deere A because they couldn’t handle it on the lawn I switched because the cooling system was larger it was electric start lights and had a better backrest. But the A with double the hp can mow the lawn in 3rd gear in a dry spell (what’s that?!??)

I ended up with a 3 point mower since the C and B had them and the A got one.

The B could actually mow off one row of cornstalks with the 3 point at a time. But it had to be cool out and it is working it.

Height of grass. Sharpness of blades. There’s enough rocks and weird obstacles here as we are perpetually in a state of contraction and clean up mine just get new blades
View attachment 123956

Nice looking tractors!

 

[Fixingfarmer]

To me, it sounds like he is planning on mounting a small engine to a mower deck in order to pull it around behind a smaller/older tractor, or possibly an ATV.

If that's the case, just look at what's been done. There's no "formula" because so few people tackle this kind of project. Most buy something that somebody figured out for them.

Example of "what's been done:" I have a 61" cut zero turn mower with a 23HP 680cc Kawasaki V-twin engine. Consider that not only is it powering the deck, but is also moving the mower. At the very least if you put a ~680cc V-twin on the deck you will have plenty of power.

Ahh I see the second reply I must have missed that. My 54 inch on the zero turn has a Briggs 23 hp as well and it doesn’t bog down at all would be more than sufficient I would think deck only on a 60. It can be a pain in the buns to use the pull behind ones around tight trees we had a Dixie chopper deck we setup that way it got used for a few years then since we mostly used it for brush and have a couple trees we upgraded to the tractor ones. It was time consuming to get everything right like you say I bet my uncle had most of a winter messing with it.

He is better off though starting where he’s at with a finish mower deck instead of junk mower. Mine has 4 bolts where the gear box goes through I assume put a motor on top of that and away you go.

 

[Watthour]

My Jubilee, around 30 HP, can handle a 6 ft finish mower in First and second gear depending on how tall the grass is.
My Farmall C, around 20 hp, can handle a 6 ft belly mower in first and second gear.
My Boss may use first gear and makes the grass look better.
My Kubota, around 37 HP, can handle a 6 ft finish mower going 6.5 mph with no stress.

I had a Deere 997 that would run the 6' "7 Iron" deck through 7" turf at 15MPH, and the load on the diesel was almost not noticeable. The other Deere 6' 797 with the Kawasaki twin would almost do the same, but the load was definitely noticeable and speed reduced to maintain tip speed and cut quality. The diesel was rated at 38HP, and some of that would have been used to drive the unit, so calculate the deck power requirement accordingly.