I flew one belonging to Dave Gardner in the Ringmaster-a-thon earlier this month. It was fast, but oh my, did it vibrate, and this on a real S-1, and a heavy one at that. The guys with .25LA or B.25 on ARF Ringmasters had no such problems, but the .19 had more suds. On one flight, the Fox quit early because the post of the glowplug vibrated off. Made me say "Whoa!".    Steve

It was a Rev-Up...and stock at 9.5"d x 5"p, if I rememberer right. When it was rich, it would barely stay in the air, but when it peaked, it really hauled tail. I have no idea about the peak rpm, or the launch rpm, tho I did put my tach on it (first opportunity with the modified Hanger 9 tach).

How well balanced were stock Rev-Up props? It wasn't balanced after the factory. Not my plane, engine, tank, or prop. All I did was get neutral adjusted, shove glowplugs in it, pump fuel in, and hang onto the handle. The vibration left a big impression. Did I mention that the muffler flew off on one flight? It was recovered and bolted on again on Saturday night. LocTite made it stay put for Sunday.

Not sure what the original Fox glowplug was, but it was too cold and the engine slowed after battery disconnect. I put in a Thunderbolt 4-Cycle, which eventually had the post break off and disappear. I probably put in another of the same. I can't imagine glowplug elements lasting long under that vibration. But maybe that was the prop?

We're going for over 100 flights next year, so we're going to need better stuff and a serious strategy!  Steve

I have a few of both the 19/25 engines. I  never flew them on a C/L model but did use the 19's on a few R/C combat wings in the 90's. Remember that 21 was the displacement limit then. They were box stock with the only modification of turning the cylinder 180 degrees to put the muffler on top to save it from the immediate destruction on the first flight. Oh and they were given the mandatory check for trash in them and making sure that they were free.
The wings were 36 inch and with the addition of strip elevons and 2 non moving rudders it was basically a VooDoo. They were fast on an 8/6 prop with Byron 15% fuel.
Break in in the normal terms was non existent consisting of firing it up new and flying it wet 2 for about a dozen flights and then screwing it in a letting go. I don't have any memory of them being vibrators but the mounts and tripler were beefy and probably absorbed it. I never lost a muffler or any other parts from the model. All props were balanced. Fuel consumption wasn't bad with a 4 oz tank and they ran as fast as anything else in the area and amazingly they weren't bad restarters. Probably would have been a little less stellar dragging lines around. I did not use an R/C carb on these engines. Didn't want the weight of the throttle and servo and linkage.
Actually they were 2 of the better looking engines that Fox produced and were cleaner than a lot of other Fox engines I owned.
I still have the engines and they are still in excellent condition with great compression. I used K&B plugs and APC props.
From what I have heard a few have used them in speed limit combat. Perhaps one of them will weigh in with their opinion.

Dennis

Dennis