Model aircraft engines have a lot of oil coming in with the fuel. 15-20 percent of the total fuel volume, depending on blend. Mine suck down an 18% lube package, of that, half is castor oil and half is synthetic. Rest of the fuel is, for the most part, methanol with a whiff of nitromethane for that extra kick.Blowby is identical to the fuel/air mix coming thru the intake manifold (reason for the PCV valve). How does this lube anything?
Maybe with premix? Considerations on my BR2 build....
Glow plugs are 1/4 32 threadModel aircraft engines have a lot of oil coming in with the fuel. 15-20 percent of the total fuel volume, depending on blend. Mine suck down an 18% lube package, of that, half is castor oil and half is synthetic. Rest of the fuel is, for the most part, methanol with a whiff of nitromethane for that extra kick.
Same exact fuel my 2-cycles run on, in fact.
If you want to simplify lubrication...and ignition...on your BR2 build, aim for a CR of around 7.5:1 and use model aviation fuel in it. Glow plugs use a quarter-20 thread and the fuel is designed to work with them. Give 'em 1.5v on startup and, once it's warmed up, it should self-sustain from there.
Some of the larger ones run on gasoline, use a CDI ignition system, and use the same oil that your strimmer uses. Saito recommends a 16:1-20:1 mix in theirs.
I'd been procrastinating over a number of loose ends related to the Offy's oiling system, and so I decided to tie them up before the holidays. First, the crankcase passages behind the pumps were drilled using the holes' coordinates and a previously machined drilling template as a sanity check. Two of the risky small diameter holes were nearly five inches deep. After starting out with jobber length drills, I switched to aircraft drills that I had on hand, but their long flute-less shanks tended to heat up and bind inside the holes even at half depth. I eventually switched to using long Guhring drills, but in order to reach full depth I could only grip the upper eighth inch of their shanks. The drilling of these two passages was sketchy, but I managed to get through it without breaking off a drill deep inside a finished crankcase.
The oil manifold holes on the lower front side of the crankcase were trivial in comparison. A .010" thick Teflon gasket was made to seal the manifold to the crankcase.
The tortuous path between the scavenger pump's output and the engine's top-end was completed up through the top of the gear tower. A 2-56 grub screw located in the side of the engine will eventually control its flow. A 3.5mm o.d. x 1mm thick o-ring seals the passage as it crosses the boundary between the crankcase halves. Another o-ring groove was machined around the transfer trough between the gear tower and the crankcase to control oil leakage at their intersection with the block. This groove was designed for a standard 7mm o.d. x 1mm thick o-ring under 10% compression.
A machined passage on the rear surface of the gear tower carries oil from the transfer slot up to the head. After entering a shallow drilled passage in the head, the oil splits into two streams that will carry oil to the cam boxes for eventual distribution to the top-end. A groove for a length of 1mm o-ring cord stock was machined around the vertical passage on the gear tower in order to seal it to the block/head assembly.
The rear face of the front cover had to be slightly modified to clear the pump assembly. A .010" thick Teflon gasket was added to seal it to the crankcase. Finally, mounting holes for the water pump were added to its front side.
An exploded assembly drawing shows the parts behind the front cover related to the oil pumps. Parts for the water pump and starter shaft components will be added later as they are machined. - Terry
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We used magnetically coupled gear pumps in an R&D lab to pump water and even ethanol and it seemed to work fine. I believe that the manufacturer specified different gear and seal kits depending on the fluid being pumped.That is some impressive work! I'm eager to hear the results.
FWIW - I've seen and heard of gear pumps often in connection with oil, but never water - wonder if the gear pump needs the higher viscosity?