Re: The smallest engine in the world

balogh Mon May 11, 2020 1:40 pm

Fred I think Brad aka 1/2ANut runs his TeeDee-s over 30k..had COX engines bronze bushings on the crankpin end of the rod, I believe even the frequent runs over 30k would not be detrimental. Anyway COX ran a stock engine up to 400 hours in an experiment and the motor survived..I would not expect that from a ringless aluminum piston of any other engine, NV included.

1/2A Nut Mon May 11, 2020 3:29 pm

Lil Speedy - Cox TD .049 / 118 MPH / 30,492 RPM on vid.
Ball socket did not require reset after the flight. 4.1x4.1N prop.
6.1oz RTF / 3 mins 20sec / 15cc tank / 16.5"x4" span wing 66sq. in
Numerous runs no reset required prop and plane load is key.

Followed by

NANO X / Tuned Pipe: 4x4.5 prop
- Before boost 28,908 rpm
- After boost 33,672 rpm
+ 4,764 rpm boosted pass down wind kicked in on vid.
Ball socket was fine no reset.
25" span 75 sq. in. wing / 8.2oz RTF
Very lean fuselage / narrow cord wing
Design allowed more weight by having less drag than the Lil Speedy.

Peak down wind passes on vid Cox TD's 20% castor:
TD .010 / 41,985 rpm
TD .020 / 37,304 rpm
TD .051 / 33,672 rpm

GallopingGhostler Mon May 11, 2020 3:51 pm

In spite of the newer and later technologies, seems that Cox still holds their own. This is not bad considering the Tee Dee design is 60 years old. (Introduced in November 1961 Aeromodeller,

Sceptre Flight Model Engine Tests: Cox Tee Dee 020 & 049

Fred, I don't mean to imply anything, because I really don't know much. I do find math somewhat fascinating.

Overall, Cox still holds its own in the half-A circles. I am amazed at the innovation that comes up here to extend the life and improve performance, longevity of these miniature marvels.

ian1954 Mon May 11, 2020 7:34 pm

These are all excellent observations and points of view.

As a general point of view, my experience with many engines that have passed through my hands is that, particularly in mass produced engines, they are of variable quality when new. Cutting tools wear as batches progress ................. This can often explain the short life of some engines as well as a noticable difference in performance.

The largest effect on a short engine life is, more often than not, a result of them not being run in correctly and typically with a cast iron piston not being heat cycled correctly. The piston then stays soft and wears quickly.

Engines with tapered pistons have to be heated up very quickly or rapid wear occurs

Running in engines is quite a long and involved topic and this is a brief outline but relevant here.

These tiny engines cannot be heat cycled effectively , will wear quickly and rely on the qualities of castor to maintain compression. In fact, gummimg can be an advantage here but the engine has to be run up regularly - cleaning it will stop it running again. Letting it harden up will render it useless. !!!!!

The longevity of engines is extremely variable. RC engines can be long lasting because they are not run full tilt all the time.

A 2.5cc diesel running in vintage combat with an 8x4 prop turning 16k+ will not last as long as the same engine running a 8x6 prop at 10k+ for stunt. Both will last a lot longer than team racing with a 6.5x6.5 or 7x6 using only 10% castor.

Run a glow too lean or a diesel over compressed and the life span will be minutes.

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