Re-engining the Camel with a rotary Gnome

Which type of oil would you prefer to be sprayed with? Castor is probably better for you.

Regards,

Art S.

 

Russ,

The attributes of castor oils, specifically high surface tension is something that I could see that you might need for a rotary engine. In particular, lubing the bearings on the crankshaft and insuring that they don't starve is a key issue here.

While most modern oils are very good, they don't and won't have some of the attributes that you could need for your particular application.

We are doing some work for the Navy on a small 2 stroke spark ignition engine that is running on heavy fuel (in compliance with the "one fuel forward" directive). Heavy fuel is nasty in a low compression two stroke because it gets on the cylinder walls and, as opposed to lighter fuels that evaporate off, it stays on the walls and dilutes the oil and causes high cylinder wear. The heavy fuel also creates increased carbon deposits, and when combined with the deposits created by the normal lubricating oil you have a situation, not unlike your rotary, where combustion deposit buildup is a big problem.

To address this we are using an oil developed by Mercury Marine for the heavy fuel outboards that the Special Forces are using. This oil is expensive, at $500/5 gallons, but can be had for a good bit less if you can get a Mercury dealer to work with you since the wholesale price is about $320 for 5 gallons. This is really a fantastic oil in that it actually cleans deposits off of the piston and combustion chamber and rings and really improves ring life. It has very high lubricity and good high temperature properties and other racers using two strokes have been using it with excellent results. The Mercury P/N: 92-858092A01.

The downside is that I don't think you would want to breathe this stuff if you didn't burn it completely, and that may preclude you using it in your engine. The point being that there are a number of new 2 stroke oils out there that are very good and provide better lubrication than conventional dyno oils.

Mercury also had a much more reasonably priced version on the commercial market for a while that was called "Rejuvenate" and was recommended as a way to clean up deposits from older engines. That was discontinued because it wasn't capable of being TCW rated because the detergents in it weren't compatible with at TCW rating. The oil was excellent however, and was being used and highly recommended by some of the best 2 stroke engine builders (Wienant Racing for one http://www.wptracing.com/2-cycle-lubricants ) around. I've managed to corral a few gallons of that (at about $40/gallon) and am using that in my 2 cycle racing outboard. I would look at what oils racers of 2 stroke air cooled motors are using. Also you want a JASO FD rated oil or the equivalent, and stay away from TCW rated oils, they aren't good for air cooled motors.

Here is a link to a discussion of oils for racing outboards (which run a lot hotter than typical outboard 2 strokes) and there's a discussion of ratings and some recommendations of some oils that might work well for you.

What 2 stroke oil yall runnin? - Page 2

Hope this helps shorten your search, there was an oil by Schaffer mentioned in the thread that might be what you are looking for, but a racing castor is probably a good safe place to start.

The nasty problems with castors is that the engine can get so gummed up that it will lock up and be a holy mess to deal with. Not a problem if you aren't the one doing or paying for the maintenance, but it could get to be a royal PITA if you have to try to keep it from getting locked up. I don't know about degummed castors, but my understanding was that castor oil oxidized and that's what caused the engines to bind up, the stuff eventually became a glue and nothing turned after a while. Lots of racing outboards are still using castor oils and are still having problems with engines becoming bound up.

One thing you might think about is running the engine with a remote tank of modern oil for a short period after you fly it to clean out the castor. Since you would be doing this at low speed and power the oil doesn't really have to be that good, and most any good quality 2 stroke oil would be just fine. I think if you ran the engine for about two or three minutes with a good 2 stroke mix it would wash out most of the castor and that would solve the problem by getting rid of the castor oil in the engine so that it doesn't get gummed up. You could put a 1 quart tank of fuel with a good 2 stroke mix in it and switch to that once you are on the ground and when you ran that thru the engine at the end of the day you would be fine and never have an issue with the engine locking up.

 

Castor oil was compatible with gasoline when mixed in the crankcase, and that is why it was used. The Germans ran out of Castor Oil in 1917 because of the RN blockade and tried to use a synthetic made of mineral oil and other oils, but it never worked that well and service life on the Oberursel Ur.IIs in Fokker Dr.Is and E.Vs/D.VIIs was miserable as a result. Only late Siemens Halske Sh.IIIs (SSW D.III/IV, Pfalz D.VIII) seemed to run well on the substitute oil. For that reason, the Germans relied mainly on fixed cylinder engines and the rotary engine fighters were very limited in numbers and were initially sent only to elite units, filtering down to lesser units as the elite units replaced them with newer aircraft.

 

Russ, your description of turning is reminiscent of taxiing a Pietenpol. Forward stick, a blast of power , and full rudder. It works beautifully every time. I know that the forward position of WW1 landing gear was to put more load on the tail skid because that was your brake by digging the skid into the turf. Then to perform a turn , forward stick and power. You are having way too much fun for an old fart.

 

Russ- Tailskid looks like the real thing. With that big prop blowing, lots of rudderability on the ground. Plus with Camel dihedral on the bottom wing, not as much worry about dragging a wingtip (skid) as on a Dr.I.