HI FOLKS!
I am glad I found this thread!
About 10 years ago a .61 O.S.VF ABC GS rear exhaust - geared ( 2 gear boxes: A1 - 1:1.4 and A2 - 1:1.89 ratio) was laying on a hobby shop and I bought it second hand without getting any information about the engine performance or the prior owner.
I maneged to gather some information on it during the last years, and now I am trying to use that engine on a 1:6 scale Tucano- 72"wingspan, 11.6 lb weight.( engine completely cowled, home made muffler, nose gear on the right location!).
Accorging to the leaflet on that engine, the 1:1.4 gear ratio (A-1) was meant for stunt, ( recomended props : 13-14dia. x 9-7pitch) and the 1:1.89 one (A-2) for scale( 18dia. x 6-8 pitch props).
As for price, one add I found on a 1980 magazine cover, indicated 150.00 for one gear unit ( I can check for that info later)
I have actually test flown the tucano with the 1:1.89 unit running a 16x10 master scimitar wood prop at 7,300rpm - engine at 13,800rpm and burning a 20% nitro fuel.
The plane flew right, but it is taking me a new glow plug per each flight, and I wonder what I can do fix that.
Too much compression? There is a .30mm metal shim under the cylinder head.
Poor ventilation for the cowled engine?
I wood like to hear from you guys what could be done to cure it.
If there is interest, I can e-mail or attach sketches, pictures and test bench results with different gear ratios / props.
How can I check if the home made muffler is delivering enough pressure? Pressure nipple is located right after the engine"s exhaust outlet.
Hope you can help me!
Geared.