My 8n is dead in the water with a blown engine. Recently bought a Case 1490 rated at 83hp and 70hp at the pto. Have a Rhino SE5 mower rated to 50hp. Will I certainly destroy the gearbox on the cutter maintaining previously mowed ground if I'm running at low throttle? I was reading that the risk of damage is associated with getting the cutter bogged down and then using the tractor hp to get it unstuck which makes sense but isn't it just running at 540 on either tractor otherwise?
- Thread starter ratface
- Start date
Matt from Oz
Member
Hi Ratface
Your case 1490 will run it no problem and you need to run it at a reasonable PTO speed so it will cut properly. If the area is clear and you aren't chopping young trees or overloading the cutter by upping the ground speed you should be fine.
Your case 1490 will run it no problem and you need to run it at a reasonable PTO speed so it will cut properly. If the area is clear and you aren't chopping young trees or overloading the cutter by upping the ground speed you should be fine.
Ultradog MN
Well-known Member
- Location
- Twin Cities
I can see a couple of issues with that scenerio.
First of all, to spin the pto at 540, which the mower likes you'll have the full horsepower of the tractor in front of it. And it's not the obstacles you know of that will get you but the ones you don't know.
Secondly, the width of the rear tires on a tractor that big are probably most of 6'. So you wont be able to cut up real close to snything with that narrow of a mower.
Lastly, the lift pins on the mower are only cat 1 and the tractor is probably cat 2. But you and buy bushings to upsize your pins.
All in all though I would do it if that is all I had.
Does the tractor have both 540 and 1000 rpm pto?
A lot of them did. If so you could get a adapter and hook the 540 mower to the 1000 side of the tractor and just run the engine about 1K tpms to give you good blade speed on the mower and not have full hp to it.
What is the old saying?
Oh yeah, Necessity is a Mother ;(
First of all, to spin the pto at 540, which the mower likes you'll have the full horsepower of the tractor in front of it. And it's not the obstacles you know of that will get you but the ones you don't know.
Secondly, the width of the rear tires on a tractor that big are probably most of 6'. So you wont be able to cut up real close to snything with that narrow of a mower.
Lastly, the lift pins on the mower are only cat 1 and the tractor is probably cat 2. But you and buy bushings to upsize your pins.
All in all though I would do it if that is all I had.
Does the tractor have both 540 and 1000 rpm pto?
A lot of them did. If so you could get a adapter and hook the 540 mower to the 1000 side of the tractor and just run the engine about 1K tpms to give you good blade speed on the mower and not have full hp to it.
What is the old saying?
Oh yeah, Necessity is a Mother ;(
I've been cutting all these areas for fifteen years so I know most of the obstacles but stuff changes every year as you know. Yep she has the 1000 pto option by reversing the shaft, interesting as I would have guessed wrong that the 1000 rpm would have been more harmful. The back wheels are out to 84" and I didn't think of that issue. With the 8N I could get right next to the fence rows, I'm not going to like this!
Obviously, it would be best to have tractor and motor matched in terms of capability but what you are talking is not the end of the world but the PTO shaft will be the weak link. Further, it has the potential to be dangerous as the yoke could break allowing the shaft to flop around wildly. If it is shear pin protected staying with an OEM spec shear bolt will prevent shock load damage but maxing the mower out will make the machine wear faster. Probably a happy medium would be to run maybe 1 MPH faster where ground conditions allow versus what the travel speed was with the 8N. If you think that this will be a problem then maybe it is time to change tractor or mower. Some guys can't help themselves as long as the tachometer needle does not budge they will push to an extreme.
NY986, to answer your question about the mower shear pin yes it is original spec. Could you please tell an ignorant fellow why running the tractor 1mph faster would be more advantageous. Given that the 1490 tractor is a 12 speed four range tractor I should have no problem doing this. I just need to look up the 8n 1st gear speed and pick the closest range selection.
At last a positive aspect of using the 1490.
At last a positive aspect of using the 1490.
Ultradog MN
Well-known Member
- Location
- Twin Cities
Just so we're on the same page here on the 1000/540 pto speeds.
Most tractors make full hp at about 540 pto speed. And lets say they make about 50% hp at 50% of pto speed. So by doubling your pto speed using the 1000 shaft you could halve the engine rpms - which would likewise halve the the hp - and still have good blade speed for mowing.
We know it doesn't work exactly in those ratios but you could substantially reduce the likelyhood of busting up your mower's driveshaft and gearbox by running it on the 1000 side at half throttle.
Again, I would try it if that was all I had.
Most tractors make full hp at about 540 pto speed. And lets say they make about 50% hp at 50% of pto speed. So by doubling your pto speed using the 1000 shaft you could halve the engine rpms - which would likewise halve the the hp - and still have good blade speed for mowing.
We know it doesn't work exactly in those ratios but you could substantially reduce the likelyhood of busting up your mower's driveshaft and gearbox by running it on the 1000 side at half throttle.
Again, I would try it if that was all I had.
Ultradog, I must admit it made no sense to me as it seems intuitive that turning faster would cause more harm but I just spoke to a gentleman who explained to me that the higher rpm reduces the torque on the driveshaft and is the reason they went to the higher rpm in the first place. To further your suggestion I would need to reverse my shaft to the 21 spline side and then adapt it back to the 540 mowere spline, how will the gear box react to turning twice as fast?
Ultradog MN
Well-known Member
- Location
- Twin Cities
It won't be turning twice as fast because you now know to only run the engine about 900 rpm max on it.
Let me try it another way.
Your 8N engine running at 1800 rpm = 540 rpm at the pto.
Running the 8N at 900 rpm = 270 rpm at the pto.
Running the big tractor with the 1000 pto shaft at 1800 rpm = 1000 rpm at the pto.
Running it at 900 with the 1000 pto shaft = 500 rpm at the pto.
Let me try it another way.
Your 8N engine running at 1800 rpm = 540 rpm at the pto.
Running the 8N at 900 rpm = 270 rpm at the pto.
Running the big tractor with the 1000 pto shaft at 1800 rpm = 1000 rpm at the pto.
Running it at 900 with the 1000 pto shaft = 500 rpm at the pto.
I am not necessarily recommending going 1 MPH faster but obviously you could not make maximum use of the mower due to the power limitation of your 8N. If you felt the need to be more productive I am saying you could attempt going just a little faster but also keep in mind the conditions of where you are operating for unseen obstruction and unevenness of the terrain. Farmers operate power driven equipment that is not exactly matched to the power unit in terms of output but it is up to each operator to take every step possible for safe operation. The operators that are mindful of safe operation usually incur the fewest injuries and breakdowns. If the temptation is there to max out the capability of the tractor without regard to the mower it is far more likely that injury could happen so then I would recommend finding something more evenly matched to either the mower or tractor.
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