aux tank for csm

[savvman]

im building an aux bar oil tank thats preasurized. my thought is a more constant and easier to control flow rate. what are your thoughts?
it would only need 4-5 psi so a bicycle pump is small and easy to supply preasure.

 

[agrams]

I would think flow rate would be more variable, especially the more volume in your tank is oil vs air. Just think if you drop 4" of liquid in a drip tank, your head only changes 4" (.14psi roughly) but if you have a low volume of air (say 25% in a 1 liter bottle at 5psi), when you use up 1/4 of your tank, your air volume would increase by two fold, and you would experience a drop in pressure of 50% down to 2.5psi, much more than .14psi (4" of head). I think the only advantage of a pressurized system is if you are trying to force oil into a tight spot and you need the motive force. Otherwise, gravity will be a much more constant driver.

 

[BobL]

I would think flow rate would be more variable, especially the more volume in your tank is oil vs air. . . .

I agree.

Variability in the flow under gravity is determined by the relative rather than absolute change in head.
This means it helps to have the aux oil tank as high as possible on the mill.
A 4" change in 20" produces less of a change in flow than a 4" change in 10".

The other trick to getting a more consistent flow is to use a small drip hole which given the viscosity of bar oils then dominates the back pressure in any system. Not too small or it may get blocked.