1/2A runs

[Gary Dowler]

Just concluded a little testing of some curiosities with the 1/2a's.  Both engines used were Cox Golden Bees.
Byron fuels, 25% nitro used. As bought 16% oil, all castor.

Neither engine would run out a tank on this. They overheated and stopped about 1/2 way through. Upped to 20% castor. Improved some, but out of 4 tries each only one engine got a full run.   Upped to 22%, problems solved. Both engines repeatedly ran out the tank. At 24%, no detectable difference seen.

Interesting side note if anyone ever wondered. One engine is single port, one a double port. The double port consistently ran 1300 rpm faster with identical 5.5-4 nylon props.


Gary

[Wayne Collier]

I've been using 18% oil - castor/synthetic mix- and only 15% nitro with no issues.  It's what I used in a TD before I sold it and what I still use in my other Cox engines. I do play with head shims till I get a run I like and then leave it be until the head has to be replaced. I'm probably happy with less top RPMs than some folks. I like easy starts and consistent runs. I did try 30% castor and no nitro once. A little hard to start but the engine ran so cool you could touch the head while it was running. Might not of been a good idea to hold on to it for long though.

[kenneth cook]

             I find it very hard to believe that your findings are concluding that more oil allowed the engine to run a tank. What I possibly see here is that the crank is full of varnish and castor goo. The lesser percentage oil is allowing more rpm's which is possibly heating the varnish up which doesn't rid itself. It acts like a brake on the shaft causing the overheating and sagging  your describing. It must be manually removed as it won't flush itself out. This requires removing the drive washer and a thorough cleaning. I've been using full synthetic in 2 Cox engines now for almost 2 gallons worth as a experiment. I have not had the ball socket failure so many claimed nor any overheating issues. The engines run terrific. This is 30% nitro Cool Power Heli fuel.

[Gary Dowler]

Both engines were very clean and varnish free, turning with almost zero resistance without the glow plug, having proper degrees of compression with glow plugs.
Total of 10 runs between two engines produced one complete run, and that during the test at 20%, and not the last run.  2-3 runs after this also failed to complete a tank.
All I can say is what I saw today, that anything less than 22% castor would not produce a full run. 22 and above worked perfectly.    These were also proven engines.
Not trying to argue, this was simply my experience today.

Gary