Sorry Greg, I wanted to dump this in first, so I wouldn't forget or lose it. Forgiven?

Mr. Cox, surrender and greater thanks! (As posted in the Glow Engines section.)

CONCLUSION: Rotating the front housing 90° in the direction of stock prop rotation works. 'Nuff said.

Again trying it with the 35 III, with more careful observation of shaft port timing, I concede my error. In the intake shift against stock rotation direction, there is an occasional similarity of port timing, but it is not near the 'stock' numbers. Thus not usable. At the 180° shifted position, : The shaft port was open on the downstroke. It would pump any 'closed-case' volume OUT, not draw flow IN.

I can only figure that the 'intake moved left' proved an easy and effective solution, so I did not scrupulously check out the other two possibilities. Glad to learn this, finally.


A possibility: the Fox factory 'LH Shafts' simply reversed the 'side' of the intake 'hole' to the other side of the crankpin. As stock, the RH shaft is cut so that the 'opening edge' is aligned with the crankpin centerline -to- shaft centerline, and the full opening "lags" about 90° after in the prop rotation direction.

The LH shafts have their 'opening edge' located the same, but the full opening is to the other side of the pin-to-center line. Mirror-image, done completely by location of the rotary shaft inlet port. No wonder it runs identically as the stock shaft, but turning the other direction...

Glad I finally have that sorted out.

Other reversible engines? We all know that reed-valve Cox engines run happily either way. Induction is controlled by positive and negative (gauge) pressure in the lower crankcase, NOT dependent on mechanical valving.

The old 3-port spark engines only ran reliably in the desired direction because the spark timing only worked in that direction. Reverse operation could be done by reversing the action of the breaker points to suit. The engine did not care.

The weakness of the 3-port layout was that the induction timing was symmetrical. We enjoy induction timing biased to provide longer 'pure intake' flow with 'capped-off' case compression.

ENYA offers certain of their engines in left-hand rotation form. Apparently the only difference is that used in the Fox factory LH shafts. I wonder if ENYA offers LH shafts as separate spares... Would be nice for certain of us CL fliers, and for RC fliers who want opposed rotation engines on a twin.