What should should I run the tach at on my machine?

[Gorman]

An entry level question I admit, but I must bury the axe on this subject with my brother. When he runs my asv he is adamant about maxing the rpms out around 3200 so the relief valves aren't used. But people have said that you only need around 2200 rpm unless you really need it at the time. I don't want to beat my machine into the ground so what do you guys recommend?

 

[xcmark]

2/3 power , roughly 2000 rpm unless your running attachment that need more flow. If it isnt stalling why put more power to it? I run mine at 1/2 to 2/3 and hit the floor throttle if I think its going to lay down going in for a bucket full. Mine has a low boost turbo so at part power it just about making steam anyways.

 

[Scrub Puller]

Yair . . . Gorman. On any machinery I only use the amount of rev's I need to do the job . . . and that amount can increase as familiarity and skill levels increase but I would be amazed to think I was doing any harm by running reduced RPM's.

Others here will be far more qualified to give an opinion.

Cheers.

 

[JDOFMEMI]

As Scrub says, just use as much power and rpm as it takes for the task at hand. That is why I like the Cat with the foot throttle. I spend an awful lot of time at barely above idle speed, but have no reservations about using all it has when the task requires it.

By doing it that way, I use a lot less fuel for the amount of work I get done, and the side benefit is that everything runs smoother, lasts longer, and costs less to maintain.

There are very few machines that have problems running less that full rpm. Vibratory rollers are one that comes to mind, and generators are another. I am sure there are a few more, but they are the exception, not the rule.

 

[stumpjumper83]

Relief valves are adjustable, they are basically the load sensing part of the hydraulic system. They use them to keep the hydraulic thumbs from overpowering the curl cylinders on excavators. They would be used to set the tipping load on a skid steer. They are adjusted with a pressure tester and have little do do with engine rpms. You engine turns a pump, the pump makes pressure to what its regulated for, and the reliefs adjust that down to what is needed at a particular circuit. Running the motor faster makes for more flow but changes pressure very little.

Personally on my equipment I run things about 3/4 or a little less depending on what im doing. Touchy feely work with the excavator is occasionally done at idle, and Heavy bulking with my dozer will see wide open in tough going, but that is unusual.

 

[andoman]

We run them all out all the time, but we're usually ripping up asphalt or milling a with ours.

 

[AlloaExcavating]

All of my machines are pilot controls with the throttle pedal. I always use the pedal and change engine rpm with it as I am working.

 

[Gorman]

this is quite helpful. thanks. One more question. If I operate the machine at full rpm, will I get less hours out of the engine or pump as opposed to running the tach at just what I need it at?

 

[Scrub Puller]

Yair . . . Gorman

If I operate the machine at full rpm, will I get less hours out of the engine or pump as opposed to running the tach at just what I need it at?

Yes.

Cheers.

 

[mancavedweller]

Here's my 2c on this one. You need a certain amount of revs to make a skid-steer run smooth, the engine is just going to stall if it's running too slow. This is because the variable displacement swash plate pump has to displace more for each revolution for the same travel speed. That requires more torque from the engine. For an identical travel speed, when the engine is running fast the pump is only displacing a small amount per revolution so that doesn't need much torque input from the engine, and overall it makes the whole machine seem to run better and smoother. Sounds to me like your brother is confusing an engine bogging down or stalling at low rpm with hydraulic pressure relief.
A hydraulic releif valve comes in at a given pressure, not at a certain flow rate. I think your brother needs to explain to you why engine speed is related to pressure, and also what relief valve is he talking about. I'd say at the least you'd have relief valves for the closed loop circuits for the wheel drives, and a separate releif valve(s) for the rams / aux pump. I can't see how engine rpm is going to increase the pressure in these circuits, it's only going to create more flow.

Technical arguments need technical discussions. Sorry if I've sent anyone to sleep.