L3800 and RMM

[WS6Man]

I am going to purchase a 60" rear mount for my L3800. Is there any way to increase the pto speed for mowing? I have plenty of hp for the task but I hate to run the tractor almost wot for hours on end while mowing.

Can I change the gear box on the deck?

Does anyone mow at less than 540 and still get good results?

 

[Eric McCarthy]

If your going for a new purchase the L3800 can power a 6 foot rear mower no problem. Look for a mower with a high blade tip speed and you should be good to go. You shouldn't really need to run the tractor at wide open throttle, the 540 rpm is well suited to mow anything within reason of a rear finish mower.

 

[dmanlyr]

As Eris states, you should have plenty of power and if you choose a high blade tip speed you will be golden.

The correct engine rpm though to achieve the 540 rpm PTO speed is not the maximum RPM of the engine, check your owners manual for the rated rpm for the desired 540 rpm pto speed.

As a sidebar, there is nothing wrong from a mechanical standpoint at running the engine for a prolonged period at its rated rpm. In fact, it is better than running the engine slower and potential lugging it. In fact, I would hazard to guess that if you did add a aftermarket gearbox and ran the drivetrain slower than it was designed to be operated while still producing the horsepower and torque required it would shorten the gear train (including the engine part of the drivetrain) life.

Of course from a noise standpoint, it does become obtrusive to ones ears. I would certainly pay more for a sealed and sound proofed engine compartment like on a mini excavator.

David

 

[Dune33]

I have a 3800 with a 72"KK mower and i do not not need to run at 540, i back it offf about 200rpm, i had a L1500 and that tractor just sipped fuel (i miss her) when pulling a set of reel mowers, now that i have the 3800 with the 72"KK its a nice ride just burns fuel. Dune

 

[WS6Man]

As Eris states, you should have plenty of power and if you choose a high blade tip speed you will be golden.

The correct engine rpm though to achieve the 540 rpm PTO speed is not the maximum RPM of the engine, check your owners manual for the rated rpm for the desired 540 rpm pto speed.

As a sidebar, there is nothing wrong from a mechanical standpoint at running the engine for a prolonged period at its rated rpm. In fact, it is better than running the engine slower and potential lugging it. In fact, I would hazard to guess that if you did add a aftermarket gearbox and ran the drivetrain slower than it was designed to be operated while still producing the horsepower and torque required it would shorten the gear train (including the engine part of the drivetrain) life.

The L3800 engine is rated at 2700 and the PTO(540) is 2580RPM. So is the "rated" refering to max rpm or where the engine makes peak hp? If it is max rpm, I just don't like the idea or running the engine at 95% of its rated rpm.

So far all have said that 38 hp (30 PTO) will handle a 72" finishing deck with no issues. That being said, I would like to run my engine at about 2100 (75% duty) for mowing which at best guess would give me 22 hp at the PTO running an overdrive gear. A B2920 has 21 PTO hp and will still run a 72" mower just fine. I plan on using a finish mower only for the yard and will not be mowing tall grass with it so I would think that the tractor would never have any bogging issues. I know I am just being overly anal about the engine rpm, but I just wnat some feedback because if I have the necessary power, why not invest a few $ now and save on the engine and fuel consumption over 30+ years might make this mod worth it.

 

[Eric McCarthy]

I'll put it to ya this way. My dad has an L275 which is a 27 hp tractor and its a little over 30 years old and still runs like a top. The tractor was used as a grade tractor in a landscape business and we've bush hoged and ran a finish mower with it for 30 some years at the rated 540 rpm and its still kicking.

It's your tractor and you're free to do whatever you want with it. But bottom line tractors are designed to do certain task's at a rated rpm from the factory and no modification is needed.

To me its a waste of time and money trying to put another gear box on something to run a tractor at 75% capacity when its designed to run at a rated rpm for a reason.

 

[Stumpy]

I'll start by saying this is probably an imagined problem but I've done stranger things. The easiest method if you really want to do this would be changing the vbelt drive pulley on the deck to speed it up slightly. You need to make sure you've got the clearance for the larger pulley. I don't think you need to worry about a decrease power transmission capacity because the bigger pulley will have more belt contact. This is a good start if you want to check the power requirements just in case.

Have you tried cutting as is with the engine running slower? I know when I did that on our old Wheel Horse it tended to leave uncut patches of grass behind but every setup is a little different.

 

[chim]

My last tractor was a B7500 with a 5 foot Landpride side discharge RFM. It did a nice job, but the RPM's needed to be at or very near the "540" hashmark. It was replaced with an L3200 and 6 foot rear discharge Landpride RGM.

Like Stumpy said, each setup is a little different. With the 6 foot deck, the RPM's can be varied quite a bit and it still gives a great cut. I had shied away from a rear discharge deck because of the windrows my in-law's Deere left behind. I had 3 side discharge decks before this new rear discharge and knew what could be expected of them (including the clumping if the grass was a little too long).

Your tractor has 6 more horses than mine, and mine handles the 6 foot deck easily. Are you sure you aren't going to regret a 5 foot deck?

 

[Eric McCarthy]

The easiest meothod instand of dicking around with gear boxes and pulley's is to buy a finish mower with a high blade tip speed from the start. Problem solved no screwing around with gear boxes no V-belts and no more money spent. A rear discharge mower which a high blade tip speed will do everything you could ever want.

 

[Eric McCarthy]

I just spent a few mintues and looked up 3 top brands for finish mowers. Woods, Landpride and Bush Hog.

Landpride comes in as top dog with the highest blade tip speed of 18,130 FPM

Go with a Landpride and call it a day!

 

[chim]

It would be a shame to go to the expense of modifying the deck for more speed only to find out the engineers designed the aerodynamics of the deck - or worse yet - the bearings for the RPM's that you just increased 140%.

 

[WS6Man]

Thanks, you each have great points and as I stated earlier, I know I am putting way too much thought into this so I will always appreciate a good sanity check!