RPMs vs Hydraulic fluid heat?

[MNBobcat]

I believe my tractor needs to run about 1,500 RPM to make full hydraulic pressure. I'm running it pretty hard with a hydraulic post pounder. I'm curious if the amount of heat generated in the hydraulic fluid has anything to do with the engine RPM and indirectly pump pressure?

In other words, if I run the tractor at say 1,000 RPM and work the hydraulics hard would it build more heat than if I ran it at 1,500 RPM and made full pump pressure or conversely would it generate less heat?

 

[4570Man]

If I work my backhoe hard the cylinders get too hot to hold. Obviously it will generate more heat running 2700 rpm vs 1200 rpm.

 

[J_J]

Pressure is determined by the resistance to the fluid flow, so if no work is being done, the fluid is getting hot from just flowing through all the ports.

The engine rpm's, determine the GPM's.

You can build up the max pressure with one GPM of fluid flow.

The hyd system will just be slow, because GPM's determines the speed of operation.

 

[Tractor Seabee]

Here is an interesting article discussing temperature effects on lubricants. 4570Man, you may be working above the critical temperature of your hydraulic fluid. The factory specs on my BX 25 are 113-131 degrees F. I cannot find the critical temp on Kubota SUDT2. Another question to track down an answer too. I have run my BH steady for 4 hours and the temp never gets to where I cannot put my hand on a cylinder. Do any tractors have a temp gauge for the HST? That may give a clue on range if it has a red line.

Temperature Stability of Lubricants and Hydraulic Fluids

Ron

 

[4570Man]

You can put your hand on the cylinder, but you can't hold it there very long. My wood splitter is worse. After several hours of use the cylinder on it will burn you.

 

[Tx Jim]

The more rpm's you operate engine the more air the fan should pull through the hyd oil cooler on your 3020 that is if cooler fins are clean. I've seen many JD hyd oil coolers overlooked when it comes to cleanliness.

 

[MNBobcat]

The more rpm's you operate engine the more air the fan should pull through the hyd oil cooler on your 3020 that is if cooler fins are clean. I've seen many JD hyd oil coolers overlooked when it comes to cleanliness.

My oil cooler was pretty dirty. A couple of days ago I blew it out with air but I haven't used the hydraulic post pounder since cleaning it. I'll be pounding all day today and tomorrow so we'll see if cleaning made any difference.

Mainly I was trying to decide how hard I should run the engine. I can pound with the engine at maybe a 1000 RPM.

But I do have to rest the hydraulics twice when pounding in one post. I assumed it was due to heat. The hydraulics start chattering and I have to shut them down for 3 or 4 minutes. I thought maybe running the engine faster would help.

Apparently I should pull and clean the suction strainer but I assume I'll lose hydraulic fluid so I will wait for a better time to work on it when I can change out the hydraulic oil too.

 

[Tx Jim]

Intermittent chattering of hyd's on CC system usually indicates insufficient supply oil to frt pump. Even though I know you stated post driver control valve had CC plug installed by dealer I suggest to remove male hyd tip on return hose. Aim this open return hose into hyd filler hole then with post driver valve in neutral engage tractor hyd control on dash & no oil should exit open hose. If no oil exits post driver hose during test then I'll suggest again to plumb your post driver directly to tractor hyd system by-passing the rear scv's. By passing scv's will give post driver more flow by putting return oil back into supply circuit.

 

[JimRB]

I pounded hundreds of posts (about 400) using my JD 870 and Shaver driver. It has been 18 years ago but I recall I was doing it in 3-4 minutes a post which may have included positioning. I grabbed fluid from one port of my front end loader valve (bungie cord to open port to driver) and dumped waste oil back in via the fill port on the transmission. I dumped straight back in the fill hole is so there is no restriction when the driver is slamming the post down. I never had chatter, heat or any hydraulic issues. My tractor does not have a hydraulic cooler.

The post driver I was using just needed pressure to lift the ram up. It did not use hydraulic pressure to drive it down. That it the job of weight and springs. That driver worked a lot better with new springs than with old sprung springs. Translated, I did not have to keep the engine at any high idle except that the ram would rise faster if the engine was running faster.

My transmission is pretty hot after two hours of "heavy or tall" brush cutting. Hot enough that you will not hold your hand on the transmission. Manual transmission.

 

[Egon]

Increase the RPM and more heat will be generated. It will also increase the hydraulic/air flow thru the cooler which may remove more heat. These variables may not be linear so temp gauge would be required to give a definite result. Then that will vary as the air flow passages of the rad. get plugged up and alter the cooling properties.

At times hydraulic oil temperature gauges are quite useful.
many hard worked hydraulic systems will be to hot to touch.