WOT on diesel tractors

[burnieman]

Yes I do run my car at full throttle when I have the loader attached to it so I get max cycling rates when I'm tryin to get a truck loaded faster. I know what everything means on the machine. Was asking a question on others reasoning. No need for anyone to get funny. So the census seems to be to save fuel. Fair enough

Touchy!

 

[mikehaugen]

Correct me if I am wrong, but don't most newer tractors use axial piston pumps? If so then this means there is no "bypass"... once pressure is reached the pump simply stops creating any more pressure. Therefore no excess heat build up.

I have a gear tractor with a gear pump for the hydraulics so yes, for me higher rpm's means excess pump flow and probably more heat generated.

 

[jenkinsph]

Correct me if I am wrong, but don't most newer tractors use axial piston pumps? If so then this means there is no "bypass"... once pressure is reached the pump simply stops creating any more pressure. Therefore no excess heat build up.

I have a gear tractor with a gear pump for the hydraulics so yes, for me higher rpm's means excess pump flow and probably more heat generated.

Most of the new tractors compact and utility size are using gear pumps today because they are cheaper. Closed systems use the axial piston pumps (Sundsrand is an example of a popular brand) and have some advantages such as lifting and curling a bucket at the same time. When you get into larger premium tractors you see an increase in the closed systems.

 

[glc24]

Rated RPM for cutting grass. For every other task, I put my throttle position where I think it needs to be,and full throttle isn't one of them.


Greg

 

[TomSeller]

The idea that you must run at pto speed to use all pto implements is a gross misunderstanding alot of people seem to have. .

Could you expand on this? Not disagreeing, but curious of your thoughts. Thanks.

 

[Sysop]

I think he's getting at there are PTO driven implements that 540 is the max, but not what it should be ran at for normal operation. Stuff such as a posthole auger, you run it just hard enough to get it in the ground and once the soil is broken up you increase the speed to toss the dirt out of the hole. Trying to sink the bit at PTO speed would result in gobs of sheared shear bolts and tear up the cutting edges of the auger bit.

 

[arlen4720]

Originally Posted by JDTank
For tractors with hydrostatic transmission, the pumps are designed VERY SPECIFICALLY to run at their rated RPM input speed, which is full throttle.

Originally Posted by JDTank

Tractors with gear transmissions and a controllable throttle are a different story, to some degree. While the drive-train is not controlled with hydro fluid, your hydraulic pump powering your loader, power steering, 3 pt arms, all of that stuff, is still suffering the same fate. The higher the RPM, the easier it is for your pump(s) to do their job. In turn, they will last longer.



Fraid not. ... Hydraulic pumps leak internally somewhat. Amt of leakage is related to pressure and time. Higher revs allow less time to leak per revolution. Therefore delivery per revolution is greater at higher rpm. This becomes more pronounced as the hyd fluid thins with heat.
larry

Yes, There is internal leakage of all pumps, I'm not sure what you are trying to say here. Gear pumps are a "fixed displacement" pump, they are nameplated for a certain amount of fluid per revolution. There is leakage, and that leakage increases with wear. So what? If you are saying that if you need more flow, then you should run the pump faster, then I say "no ****".
What my original point was...spinning the pump faster doesn't reduce wear...it increases it. Often less flow is desirable, and gives smoother more controllable hydraulic motion. JdTank is saying that it's all designed to run at WOT and your machine will be damaged and/or experience more wear if you don't. That is pure BS.

 

[Xfaxman]

You have a loader on your car? Cool!:thumbsup:

I also found that to be the most interesting thing in the whole thread. I hope he posts some pictures.

Indeed, pictures rock.

Here is a loader on a Jeep.


A loader on an Edsel.

Weekend Edition An Edsel turned Art Car Construction Shovel, and it痴 for sale?|*Hooniverse

And a loader on a Mercedes. :laughing:


Pictures from Google Image Search.

 

[arlen4720]

Here is a loader on a Jeep.
View attachment 334735

A loader on an Edsel.
View attachment 334736
Weekend Edition An Edsel turned Art Car Construction Shovel, and itç—´ for sale?|*Hooniverse

And a loader on a Mercedes. :laughing:
View attachment 334737

Pictures from Google Image Search.

You're a god among men.

 

[jenkinsph]

Could you expand on this? Not disagreeing, but curious of your thoughts. Thanks.

Just because an implement has a speed rating of 540 rpm doesn't mean it is necessary to run it at that speed. More at the speed rating should be considered the maximum speed. Some things such as finish mowers will do a better job at the rated speeds but others can work at a slower speed without issues tillers, post hole diggers and harley rakes. But if you take that same implement and hook it to a 1000 rpm or 2000 rpm pto it may fly apart. Some things such as ac gensets need to be run at rated speed even with light loads but others such as a dump truck hydraulic lift will work at low idle or fast idle.