Engine lubrication

[Rustkolector]

I have a horizontal 1" bore x 1.4" stroke open crankshaft engine that will use drip or gravity flow to lubricate the cylinder. The engine is throttle governed and normal speed should be 400-600 RPM. It won't be doing much work. Fuel will probably be propane. My question is how can an adequate oil drip or flow rate to the cylinder be determined.

Jeff

 

[matt-jaysey]

When you say gravity flow, gravity flow from where, sorry I dont understand much about static model engines whats the layout?

 

[Lakc]

Rule of thumb for nonrunning engine is 1 drip per second off each journal. Thats for an automotive V8 with the oil pressure at ~60 psi.

 

[Rustkolector]

A gravity system is a lost lube system with a small oil reservoir an inch or to above the cylinder. Oil drains by gravity thru tubing to a vented hole in the top of the cylinder just as the drip systems do in old hit & miss engines. In this case, I find that a .040" ID tube will yield about 1 drop of oil every 25 seconds of 10W/30 oil at 66F. Adding an adjustable restricting valve can slow it to up considerably longer. I use the term "drops" of oil, but in use, the tube end is in contact with the cylinder therefore providing continuous flow. No drops form. Actually, in model engine terms, a drop of 10W/30 oil forming on the end of a .063" OD tube is a fair amount of oil. I use "drops" to help visualize the flow.

I was hoping someone using drip or gravity lubrication could assist with a good starting point.

Jeff

 

[chipenter]

How about a wick oiler a brass cup with a tube in the centre , and a wick through the tube bent over into the cup , with the wick touching the part to be oiled . The drip oilers have an adjustable needle valve for oil control but are a bit bigger than you would want on a model .

 

[Rustkolector]

Chipenter
Thanks, but I would not think a wick would last long with the reciprocating motion of the piston in the cylinder. Contact would be intermittent and, I think it would be chewed up in short order. I am familiar with oil cup wick oilers for bearings, and they seen to work well.

Jeff

 

[deverett]

As a follow on question to Rustcollector's, how is the little end bush lubricated in open crank engines?

Dave
The Emerald Isle

 

[t.l.a.r. eng]

On my Coles small hit-n-miss, the cylinder oiler indexes with the wrist pin location at bottom dead center through a small hole in the piston skirt.

 

[johanvanzanten]

Hi Jeff,

The amount of oil needed for proper lubrication of your engine depends on many factors. One of them is the materials used. I mostly use cast iron for the cylinder, piston and ring(s). I should go for one drip a minute, the suggested one drip a second creates a mess. During the breake-in period I suggest two drips a minute depending on the cylinder temperature. Alu pistons like some more oil. It is mainly a question of trail and error, not exact science. Good luck with your engine and I am looking foreward to see the picktures!

Kind regards,
Johan.

 

[deverett]

On my Coles small hit-n-miss, the cylinder oiler indexes with the wrist pin location at bottom dead center through a small hole in the piston skirt.

Thanks for that suggestion.
What sort of size is 'small', thinking of a 1-1/2" bore? The oiler hole size into the cylinder is no.50, so I'm guessing at 1/16".

Dave
The Emerald Isle

 

[Rustkolector]

Thanks Johan. That pretty much confirms what I had decided to use as a starting point. I have a bit more work to do before it is finished.

Jeff

 

[t.l.a.r. eng]

Thanks for that suggestion.
What sort of size is 'small', thinking of a 1-1/2" bore? The oiler hole size into the cylinder is no.50, so I'm guessing at 1/16".

Dave
The Emerald Isle

If memory serves correctly, it was about a .073 hole. It wouldn't take much as the wrist pin and piston are allways oily and wet even after running 2 hours continuous with only a periodic drop of oil from the drip oiler.

Actually, once it all gets oiled, the oil pretty much stays there. The grease cup on the big end of the rod will need attention before the cylinder oiling does.

 

[deverett]

If memory serves correctly, it was about a .073 hole. It wouldn't take much as the wrist pin and piston are allways oily and wet even after running 2 hours continuous with only a periodic drop of oil from the drip oiler.

Thanks for that.

Actually, once it all gets oiled, the oil pretty much stays there. The grease cup on the big end of the rod will need attention before the cylinder oiling does.

That's reassuring.

Dave
The Emerald Isle