handirifle
Veteran Member
What is the gear ratio, usually, for a rough cut PTO mower vs a finish mower? Or is their any difference?
gearing question
- Thread starter handirifle
- Start date
- Views: 1222
RickB
Super Star Member
- Joined
- Sep 18, 2000
- Messages
- 15,143
- Location
- Up the road from Dollar General WNC
- Tractor
- Just a Scag
Gear ratios don't tell the whole story. Compare blade tip speeds, which are usually published for both styles of mower.
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
Bush hog 6 ft bld
A 1:1 ratio gear box on a 6 ft bush hog will turn at 540 rpm produce a blade tip speed velocity 10,173 fpm. A higher ratio will turn the bld faster and give better bld tip velocity
Finish mower 6 ft, 25 in bld X 3
A 1:3 ratio gear box on a finish mower will turn at 1620 rpm, and produce a bld tip velocity of 10,173 fpm.
So the ratio has to be higher for the finish mower.
The circular path for the bush hog bld is is 18.84 ft. and the path for the finish mower bld is 6.28 ft.
The finish cut bld is also thinner giving a better cut.
The larger bush hog's should have the lower gear ratio's. If they keep the same ratio, and the cut size increases, the bld tip velocity increases.
A 1:1 ratio gear box on a 6 ft bush hog will turn at 540 rpm produce a blade tip speed velocity 10,173 fpm. A higher ratio will turn the bld faster and give better bld tip velocity
Finish mower 6 ft, 25 in bld X 3
A 1:3 ratio gear box on a finish mower will turn at 1620 rpm, and produce a bld tip velocity of 10,173 fpm.
So the ratio has to be higher for the finish mower.
The circular path for the bush hog bld is is 18.84 ft. and the path for the finish mower bld is 6.28 ft.
The finish cut bld is also thinner giving a better cut.
The larger bush hog's should have the lower gear ratio's. If they keep the same ratio, and the cut size increases, the bld tip velocity increases.
OP
handirifle
Veteran Member
Wow, there's a lot more to this stuff than meets the eye. Thanks,
So, is the 10,xxx fpm, pretty much a std for rough cut mowers? You say more is needed for the finish cut, approx how much more? Oh yes, when you figure the fpm, do you only figure the distance a single blade (tip?) travels or double it for a 2 ended blade? Make sense?
Appreciate the very informational feedback you guys give.
I gotta pay more attention to what forum I'm in when I make a post. Not sure how it got in hydraulics???? Duh! It's gotten so if I don't capitalize on an idea, when I get it, I forget what the idea was by the time I do get to the correct forum. very sad, this gettin old stuff.
So, is the 10,xxx fpm, pretty much a std for rough cut mowers? You say more is needed for the finish cut, approx how much more? Oh yes, when you figure the fpm, do you only figure the distance a single blade (tip?) travels or double it for a 2 ended blade? Make sense?
Appreciate the very informational feedback you guys give.
I gotta pay more attention to what forum I'm in when I make a post. Not sure how it got in hydraulics???? Duh! It's gotten so if I don't capitalize on an idea, when I get it, I forget what the idea was by the time I do get to the correct forum. very sad, this gettin old stuff.
LD1
Epic Contributor
Single tip to answer your question. It doesnt matter how many tips are on the blade, the speed will be the same.
It may also help if we knew WHY you were asking.
Are you looking for a replacement??
Are you trying to build something and just need a gear box???
Are you trying to make a bushhog or mower???
For reference my bushhog model 105 has a 1:1.5 ratio box. So @ 540rpm PTO, the blades are spinning @ 810RPM. With a 5' cutter, that is ~ 15.7 ft circumfrence. 15.7 x 810 is 12,700fpm tip speed.
I Also have a 5' JD261 finish mower. Not sure what the gearbox ratio is (I can always check if you would like). But the output drives a large pully. Like maybe 12" diameter. And then is belt driven to the smaller maybe 4" spindle pullies. That is a step up of ~ 3:1 roughly. And thats AFTER the gearbox.
And I also think I read of heard somewhere that the good commercial ZTRs run a blade tip speed of 19000-20000 fpm
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
It is not that difficult to work out the figures. You should start with the blade tip speed you want, and back the rpm's to the source. That will tell you the required rpm of the power source motor be it PTO, or hyd motor.
If you wanted to go hyd bush hog or hyd finish mower,
Surplus Hydraulics sells a hyd PTO hyd motor as a substitute for the 540 tractor rpm.
As with any gear system, you can go fast, or develop lots of torque.
With a 1:1 single gear reduction gearbox, you gain nothing but the shaft turning in the opposite direction. If you want the shaft to turn the same direction as the input, you need a double gear reduction.
Just to deviate a little. Have you seen those small chainsaw winches. They are geared down to pull 3000 to 4000 lbs.
If you wanted to go hyd bush hog or hyd finish mower,
Surplus Hydraulics sells a hyd PTO hyd motor as a substitute for the 540 tractor rpm.
As with any gear system, you can go fast, or develop lots of torque.
With a 1:1 single gear reduction gearbox, you gain nothing but the shaft turning in the opposite direction. If you want the shaft to turn the same direction as the input, you need a double gear reduction.
Just to deviate a little. Have you seen those small chainsaw winches. They are geared down to pull 3000 to 4000 lbs.
OP
handirifle
Veteran Member
Thanks for further feedback. My reasonings are a little on the odd side, but I'll tell anyway.:thumbsup:
I am mildly considering changing the tires and wheels on my MF1010 to turf, and adding a belly mower. The problem is it doesn't have a mid PTO. I can easily add a rear PTO mower, I know that, but I give up a LOT, that I need, in maneuverability with the rear mount. My property is only 3 acres. I just used my brother in laws 16hp Craftsman mower to mow about 90% of it, but it nearly beat it up. His blades were shot to begin with, and I welded re-inforcements on the tips, and even those were shot before it was done.
It's not the rocks, I can move those and keep most of em clear, but it's the hidden 2" oak limb that falls in the tall grass. I've had it mowed by others with a bush hog, and frankly didn't like how it looked afterward. Maybe he was in too big of a hurry, don't know, but at $150 a pop I can't keep doing that forever.
That's part one of the problem.
Part two is I live in a bottom land area, where most of the runoff from rains ends up. last year I had mallards trying to nest 50ft from the house. :licking: The only reason they didn't is cause it scared em every time they saw us come out. I put about 100hrs on the little MF1010 moving dirt and making chanels, that are now running creeks (that will dry up in late summer), and borrowing backhoes to make numerous french drains and a pond.
The good news is, now, it's dry out front, except the newly formed creek, but down at the bottom of the land there is still some standing water. It's not nearly as bad there either, cause I dug a pond for the water to collect. It works as designed, but not big enough. This summer that will be corrected.
But, since it is still soggy elsewhere, no, make that VERY soggy, I cannot use the tractor with any pull behind mower. I tried to move a few soggy bales of straw a couple weeks back and burried the front axle to the pumpkin. That was 50yds from any standing water. Had to use the Tundra in 4Lo to pull er out. That is part of the reason for the turf tires. In order to make (hopefully) this work, I'd have to remove the FEL, the gannon, and add the mid mower and turf tires n wheels. Hopefully that would make it light enough with a big enough foot print to not bog.
The aformentioned Craftsman allowed me to go within inches of standing water for those same reasons. I know the MF1010 will still weigh almost twice the ride on mower, but that's my reasoning.
My other option is to go ahead and buy a ride on mower (used) and proceed to beat it to death, slowly, maybe.
If I made a belly mower, it would be a hybrid of bush hog and finish mower. Not a full stump jumper, per se, but a smaller version, that would be more durable than a finish mower setup.
In fact, if I buy a rider I will most likely make it a hybrid, with blades that "sling" like a bush hog, but at the speed of a finish. The blades would be heavier duty than stock as well. My thoughts there would be even though the blades were heavier duty (thicker) the pivoting action would absorb most of the impact energy, and hopefully not strain the arbors as much.
The other big issue with a ride on mower, is they don't raise high enough to avoid the friggin gopher holes that are all over the place. Now you see why I come up with all these crazy ideas.....
I am mildly considering changing the tires and wheels on my MF1010 to turf, and adding a belly mower. The problem is it doesn't have a mid PTO. I can easily add a rear PTO mower, I know that, but I give up a LOT, that I need, in maneuverability with the rear mount. My property is only 3 acres. I just used my brother in laws 16hp Craftsman mower to mow about 90% of it, but it nearly beat it up. His blades were shot to begin with, and I welded re-inforcements on the tips, and even those were shot before it was done.
It's not the rocks, I can move those and keep most of em clear, but it's the hidden 2" oak limb that falls in the tall grass. I've had it mowed by others with a bush hog, and frankly didn't like how it looked afterward. Maybe he was in too big of a hurry, don't know, but at $150 a pop I can't keep doing that forever.
That's part one of the problem.
Part two is I live in a bottom land area, where most of the runoff from rains ends up. last year I had mallards trying to nest 50ft from the house. :licking: The only reason they didn't is cause it scared em every time they saw us come out. I put about 100hrs on the little MF1010 moving dirt and making chanels, that are now running creeks (that will dry up in late summer), and borrowing backhoes to make numerous french drains and a pond.
The good news is, now, it's dry out front, except the newly formed creek, but down at the bottom of the land there is still some standing water. It's not nearly as bad there either, cause I dug a pond for the water to collect. It works as designed, but not big enough. This summer that will be corrected.
But, since it is still soggy elsewhere, no, make that VERY soggy, I cannot use the tractor with any pull behind mower. I tried to move a few soggy bales of straw a couple weeks back and burried the front axle to the pumpkin. That was 50yds from any standing water. Had to use the Tundra in 4Lo to pull er out. That is part of the reason for the turf tires. In order to make (hopefully) this work, I'd have to remove the FEL, the gannon, and add the mid mower and turf tires n wheels. Hopefully that would make it light enough with a big enough foot print to not bog.
The aformentioned Craftsman allowed me to go within inches of standing water for those same reasons. I know the MF1010 will still weigh almost twice the ride on mower, but that's my reasoning.
My other option is to go ahead and buy a ride on mower (used) and proceed to beat it to death, slowly, maybe.
If I made a belly mower, it would be a hybrid of bush hog and finish mower. Not a full stump jumper, per se, but a smaller version, that would be more durable than a finish mower setup.
In fact, if I buy a rider I will most likely make it a hybrid, with blades that "sling" like a bush hog, but at the speed of a finish. The blades would be heavier duty than stock as well. My thoughts there would be even though the blades were heavier duty (thicker) the pivoting action would absorb most of the impact energy, and hopefully not strain the arbors as much.
The other big issue with a ride on mower, is they don't raise high enough to avoid the friggin gopher holes that are all over the place. Now you see why I come up with all these crazy ideas.....
J_J
Super Star Member
- Joined
- Sep 6, 2003
- Messages
- 18,952
- Location
- JACKSONVILLE, FL
- Tractor
- Power-Trac 1445, KUBOTA B-9200HST
handirifle,
About how much money would you spend on this project?
About how much money would you spend on this project?
OP
handirifle
Veteran Member
JJ
Well, I guess I'm looking at about $600 for a decent sized and condition riding mower, so I guess that's my limit. Harbor Freight has a 4ft rough cut mower for $600, on sale. So that seems a fair comparison. Ambitious, I know, but the budget is what the budget is, and I'm not afraid to scrounge.
Well, I guess I'm looking at about $600 for a decent sized and condition riding mower, so I guess that's my limit. Harbor Freight has a 4ft rough cut mower for $600, on sale. So that seems a fair comparison. Ambitious, I know, but the budget is what the budget is, and I'm not afraid to scrounge.
Last edited: