540 rpms or less?

[thcri]

</font><font color="blue" class="small">( I can't think of any reason to run below 540 RPMs. )

Here's two: 1. Noise 2. Fuel consumption )</font>


Noise probably, fuel consumption I don't think so. Speed your motor up and go a bit faster, getting done faster and you won't see a bit of change in fuel consumption.

Running your motor at the lower RPM's goes against everything I learned about Diesels. I have never had a mechanic, manufacture or dealer tell me to run one at low RPM's. It even looks like your dealer told you to watch it. So I guess why would one want to do it? But, it is your motor and I will let it at that.


murph

 

[theboman]

It's DIESEL. Running it wide open will not hurt the thing, it's designed to be used.

Noise: Buy ear plugs.
Fuel conservation: Buy a goat.

You'll mow more grass faster and with a lot less fuel than a with a gas tractor/lawn mower.

 

[OkieG]

<font color="blue"> fuel consumption I don't think so. Speed your motor up and go a bit faster, getting done faster and you won't see a bit of change in fuel consumption. </font>

Hi Murph,
How fast does your TC-29D go? Probably faster than my 24hp JD. Do you mow full speed ahead? 11 mph is full speed for my tractor. If I mowed my "fairly" flat yard at 11 mph, I'd be airborne half the time, have blood in my pee, and need the crinkles taken out of my spine by the time I was done.

At my perferred mowing speed of 80% of rated PTO speed, I can travel as fast as I want to, and still have some forward speed left over. So, for me, less throttle is more economical, but that's not why I go slow. At full throttle, everything seems to be spinning so much faster than it needs to.

I've cut my yard at full throttle before, but don't see any noticeable improvement in cut quality over a slower speed, just more noise, more engine and deck wear, and more fuel burned.

Don't get me wrong. I'm not commited to 80% no matter what. If the grass is thick or long and the engine starts to bog, I bump up the throttle and/or travel slower. I have a section of yard that grows thick and can cause my tractor to bog down a bit even moving slow at full PTO rpm.

I understand the point of view of you and theboman and others. This is just one of a small handful of deviations from tractor norms that makes sense to me, and I'm comfortable with.

OkieG

 

[BrettW]

I have been running the mower slower only because I was using my senses that told me it was spinning fast enough. It sounded more like an airplane than a mower to me. Now, this is my first finish mower and first tractor so I'll readily admit that this might be wrong. But just going with my ears and common sense seems to be OK for now. The grass is new and not thick at all. I suppose very heavy,wet crab grass might slow down the mower and thus lug the engine a bit but really, the tractor has tons and tons of power to just be cutting grass.
I do value all the advise so keep it coming if you have an opinion. thanks, brett w

 

[Bob_Skurka]

Well as far as all this goes, the thread seems to have changed a bit from the original question, but if you think about it, most of the tractor manufacturers are probably going to have the torque curve and the hp curve magically meet somewhere around that 540 rpm PTO speed. So to have the best combination of hp & torque, you'd probably want to run at 540 HPT speed. As far as the noise issues, yup, run an engine faster and it makes more noise, but that noise brings power, speed and torque. JMHO

 

[thcri]

</font><font color="blue" class="small">(
At my perferred mowing speed of 80% of rated PTO speed, I can travel as fast as I want to, and still have some forward speed left over. So, for me, less throttle is more economical, but that's not why I go slow. At full throttle, everything seems to be spinning so much faster than it needs to.
)</font>

80% is probably ok. A bit low but I don't have a problem with it or the original posters speed. But I think most of the people will say keep it as high as you can. Now with that JD's hydro you have, keep the rpm's up a bit and slow the hydro down a bit. Lugging a diesel is no good and the problem we have is we don't really know when we are actually lugging it.

murph

 

[PM1]

The importance of PTO speed also depends on the implement you're using. A rotary cutter (bush hog), for example, is designed to run at 540 -- not slower. The blades are mounted with bolts that leave some free play. The only thing keeping those blades straight out during mowing is the centrifugal force of high-speed rotation. If you turn it too slowly, then the blades pivot back and forth during every rotation -- they pivot back when they encounter resistance from uncut grass up front, then they pivot forward when they emerge from the uncut grass for the rearward half of their rotation.

That back and forth pivoting of the blades causes wear at the mounting bolts. Keeping your rotary cutter at 540 rpm ensures that there's enough centrifugal force to keep that pivoting to a non-existant minimum (until you hit a stump or rock, of course... which is the purpose of the free-swinging design).

As for damaging the engine, my JD owners manual specifically says the engine can be subjected to full power loads between 1600 and 2400 rpm. I would guess other tractors would have a similar full-load working range, albeit perhaps at different rpms.

Parker

 

[RichNJKubota]

"I have never had a mechanic, manufacture or dealer tell me to run one at low RPM's."

I'm a mechanic and give you permission to run at less than full 540 PTO speed.

Rich

 

[OkieG]

<font color="blue">...and the problem we have is we don't really know when we are actually lugging it.</font>

That's something I'd never thought of. I kinda thought I did know when I was lugging it. I wonder if there is a practical definition of "lugging"? Is it just a subjective thing? I guess I expect engine rpm to dip a bit when the mower engages the grass. That's just the engine working. If rpm dips more than a little, that could be lugging...time for more power or slower pace.

<font color="blue"> ...the torque curve and the hp curve magically meet somewhere around that 540 rpm PTO speed. So to have the best combination of hp & torque, you'd probably want to run at 540 HPT speed. </font>

I think you're right, Bob. It just seems to me that some tasks don't always require the tractor to be giving 100%. For me, mowing my "not too thick" yard is one of those tasks. It's just one of my quirks, but I usually start most tasks at about 80% of PTO speed, then bump up the throttle if needed to maintain rpm. At 80% my tractor engine runs comfortably, doesn't sound so "urgent", there's ample transport speed and hydraulics are snappy enough.

On the one hand, <font color="blue">Why would you want to run below 540 RPMs? I can't think of any reason to run below 540 RPMs. It's DIESEL. Running it wide open will not hurt the thing, it's designed to be used.
</font> But, on the other hand, <font color="blue"> the tractor has tons and tons of power to just be cutting grass. </font> A point I consider in all this is that the hour meter on my tractor doesn't really measure hours!! Many of you know that, but it may be a shock to some. The meter measures out one hour when the engine turns the number of revs turned in one hour at PTO speed. In other words, at half PTO speed it takes two hours for the meter to register one hour. I know some hour meters actually do measure hours, but mine (and many others) actually measures revs disguised as hours.

That can be taken one of at least a couple ways. First, it might mean that the manufacturer thinks every owner is smart enough to always run at PTO speed, so the hour meter will reflect actual hours logged on the tractor. The second option that comes to mind is the way I take it...That is that total engine revs are a better measure of engine age/use/wear/etc than clock hours are. So, if the job doesn't require 100% effort, why give 100%? Save some fuel, and wear and tear on your investment. Throttle back a bit when you find a job that isn't so tough.

See the tractor...Be the tractor.

OkieG

 

[normde2001]

Brett, are you sure that 2600rpm = 540pto rpm on your tractor? That sounds like top speed on most diesel compacts, with 540pto rpm at about 2200 engine rpm.