Hydraulic oil for models - what's in it?

[fhhhstix]

I work for a CAT dealer and we have a rental store as well and if I had to guess 90% of the equipment we have CAT included uses 10WT hyd oil thicker oils will make hyd systems sluggish and build up excessive heat thinner less dense oil will dissipate heat quicker.

[Lil Giants]

Originally Posted by fhhhstix

thicker oils will make hyd systems sluggish and build up excessive heat thinner less dense oil will dissipate heat quicker.

No, that's not entirely correct. Heavier hydra oils are sluggish when cold, but once at operating temperature, they're fine. The heavier hydra oil purpose over thinner oils is for continuous duty in warmer climates, as thinner hydra oils will heat up too quickly, break down much sooner and loose their lubricity at higher temperatures which will lead to equipment failure. Lighter oils will also foam & become "spongy" if they get too hot!

My summertime tractors use Hydraul 56. With the Panther, as an example, the small hydraulic orbit motor that powers the fan on the airdrill @3000rpm will run for 3 to 4 hr intervals. Then another orbit motor to refill seed/fert tanks. Then seeding again for another stretch. The hydra oil never has a chance to cool much in a 14hr day, especially at 25° or more climate. A combo of steel piping, oil cooler ahead of engine rad and large oil reservior helps to keep temps within perameters. A lighter oil would cause the small orbit motors to run erractic and would likely trip an alarm during the heat of the day.

Some guys in our hobby, like rc guy Scott have used 30W engine oil in their model hyds while running outside during the summer heat greater than 25° b/c the 10W becomes like water & spins around the gears & does virtually nothing.

[Lil Giants]

Originally Posted by fhhhstix

I work for a CAT dealer and we have a rental store as well and if I had to guess 90% of the equipment we have CAT included uses 10WT hyd oil thicker oils will make hyd systems sluggish and build up excessive heat thinner less dense oil will dissipate heat quicker.

Heavier hydraulic oils don't build up excessive heat, they absorb heat, which why they're better to use in warmer climate than lighter hydraulic oil.

Lighter oil heats up quickly and if it gets too hot, the oil will scorch itself & the components it propelling... that's if the cooling system is pushed beyond it's capabilities.

I just caught up with the retired gent that used to own/operate the locate Esso depot, he knows his petrolium products... hydraul 50 is 10W and hydraul 56 is 30W.

I spoke to a few other ppl at Case/New Holland as to why heavier oils are better and their response was vague, they pretty much use what the manufacture warranties...

I knew the hydrostat in my 9060 combine uses 10w hyd oil and I was shocked to find out that the bypass psi for the system is set at 6100psi! ... so much for my original thought that light oil was better suited to low pressure/high flow.

As far as these minature hydraulic systems are concerned, what weight oil a modeller would use depends on the climate and cooling system implemented within the model.

Freddy's heat sink & fan within his excav model helped immensely to control the temperature of oil, as well as it's viscosity from getting to thin while he was running his model in 90° sunshine.

I myself don't need a cooling system of any kind b/c I'm in 65° shade.

It was your comment Travis that "heavier oils build up heat" that sparked my attention and question the accuracy of that statement... I learned some other interesting things about oils & equipment along the way too.