Hydraulics on a sawmill question.

[rasorbackq]

Seems most of my posts on here are for hydraulic questions . I wish I could do a course on hydraulics and have a better grasp of it.
Anyways .
DIY sawmill. Has hydraulic head lift and travel up and down carriage to saw a log into a board. One pump, 2 valves 2 motors, one for travel and one to lift head. Seems lately the sawmill hydraulics both functions work well when its just started . Within 15 minutes the travel is very slow to the point I have to pull the saw head back. Travel forward cutting it goes great. When its not working right in the back travel I can see the pump pulley slows to a point where I can count the rpm Maybe 15 RPM per minutes. . Going to assume the belt going to the pump from motor is not slowing down as I can sometimes smell burnt rubber.
So when after 30 minutes of running time I lift the saw head. 20 HP Honda at full throttle is applying power through a belt to the pump I lift the saw head and pump continues at same RPM no slowing.
Do the different operation. move the travel back on the carriage.
20 HP Honda at full throttle is applying power through a belt to the pump I use the valve to run the saw head back to start position pump almost stops . I'm thinking its my travel valve or Danfuss hydraulic motor causing the issues.
If I am right what is happening to cause the pump to almost stop?

 

[rasorbackq]

Motors are Danfoss DH 50 151-2121 or could be a 151-2128

 

[PILOON]

Perhaps the answer is here:
"Going to assume the belt going to the pump from motor is not slowing down as I can sometimes SMELL burnt rubber."
Could it be slippage?
Perhaps try some belt dressing, (often sold as a paste) or perhaps a tensioner system.
Belts do stretch and slip as they wear and or become glazed.

Swapping out the belt drive for chain and sprockets would for sure eliminate those issues if slippage proves to be the problem.

 

[rasorbackq]

Let say it was slippage ...... why only when the travel valve is used? Could the valve be plugged somehow after warm up period?

 

[oldnslo]

Can you install a pressure gauge between the pump and valve or at the valve inlet. What you are describing sounds like something is restricting flow causing increased pressure when gets warm. Opposite of most systems..

 

[rasorbackq]

I have no pressure gauges. . Both valves are the same so Im hoping I can swap them and see it the problem moves.. Want to check the level on the sawmill just in case its downhill a bit