I'm working on a little project that involve hydraulics piston.  I need an oil/fluid that is,

1. Density => water

2. Slippery

3. Non reactive

4. Easy to find

5. Cheap

Maybe https://en.wikipedia.org/wiki/Propylene_glycol?  Might not be "slippery" enough.  Non-toxic.

I assume you already checked all the hydraulic fluids (brake, transmission, power steering etc...) https://en.wikipedia.org/wiki/Hydraulic_fluid

 

Water.

Perhaps with a little soap.

 

Glycerine solution.

Look here to find the % appropriate to your density requirement.

http://www.aciscience.org/docs/physical_properties_of_glycerine_and_its_solutions.pdf

8 hours ago, John Cuthber said:

Water.

Perhaps with a little soap.

 

Wouldn't the soup settle if the piston wasn't moved for a while.

8 hours ago, Frank said:

Maybe https://en.wikipedia.org/wiki/Propylene_glycol?  Might not be "slippery" enough.  Non-toxic.

I assume you already checked all the hydraulic fluids (brake, transmission, power steering etc...) https://en.wikipedia.org/wiki/Hydraulic_fluid

 

I checked in a few stores and they have 1Kg of Propylene glycol for only a doller but the density and the viscosity isn't ideal.

7 hours ago, studiot said:

Glycerine solution.

Look here to find the % appropriate to your density requirement.

http://www.aciscience.org/docs/physical_properties_of_glycerine_and_its_solutions.pdf

What concentration do you recommend (need it to stand winter so I'm thinking 40%)

Edited October 24, 20178 yr by Isila

Solutions barely settle out.

20 hours ago, Isila said:

I checked in a few stores and they have 1Kg of Propylene glycol for only a doller but the density and the viscosity isn't ideal.

What was the effect of viscosity being too low, did it leak? 

I had a project in mind and was going to use bladder actuators...  Wonder if it would work for that.

 

Don't tinker with hydraulic fluids if you want your circuit to work longer than a few hours.

The hydraulic pump fails after few weeks if you don't make a complete hydraulic fluid, with anticorrosion, defoamer, viscosity index, and so on and so forth. I know it from experience.

Water-polyglycol mixtures are available commercially ("hydrolube" is one trade name among many) and already made for hydraulics uses.

Instead of "water density", it would be better to accept the density of existing hydraulic fluids if possible, especially oil. There are many. Check manufacturers and Wiki for "hydraulic fluid" and "brake fluid".