I seem to recall problems with apex seal failures under heavy sustained loads as are typically encountered in an aircraft environment

Loaded seal failures were very much a common problem with all early rotaries; Norton worked long and hard on sorting this out. They were absolutely focussed on this as their major selling point was to be engine longevity and reliability. One of the early air cooled prototypes ran continuously for 24/7 for over four years without stopping. During this run, the engineers didn't bother opening it, but stopped it occasionally and stuck in an opthalmoscope to have a look at the crank and seals. No wear was observed - when the company stopped the trial and pulled it down, they were pretty surprised to find that they had no need to replace anything and it went back together after the crank was crack tested. For a while the engine was in the company museum, with just the measured number of crank rotations on display in front of it.

Also, don't forget we're not talking about the rotaries of the late 60's/early 70's (DKW, NSU, Mazda) - this engine design began life around 1965 in a seperate research group that survived the NVT collapse in '72. They were developing various forms of the engine for almost 20 years. They hold(held?) many patents on the engine, and a significant amount of their work was cross licensed by Nissan in the 80's to improve their own car engines (Norton and Nissan were pretty much alone in persisting with the design, with good results).

Small, highly efficient engines are not normally suitable for light aircraft use

...Except when the plane is going to get a SAM 7 up the pipe, in which case so long as it reached the target, it wouldn't matter so much

No, I know what you mean about loading and stress levels; but don't forget, the engine is radically different from reciprocating piston engines - the big cubes, low power argument is not directly applicable here. The crank was a short, single cast piece, and the rotors span epicyclically around it to reduce crank flex. The engine was a narrow sandwich of a pair of combustion chamber cavities, and so the crank was absolutely rigid. The crank bearings were just great big plain bearings, even on the race bikes! In fact, the rigidity of the engine on the race bikes turned out to be a problem - they used it as a stressed member in the frame and the resulting frame design was remarkably minimal. When they took it out on the track, the frame had such little flex, that the tyres could not cope with the cornering stress the bike could deliver. The most frequent observation of the race press at the time was "yet another tank slapper" as the tyres rapidly gave up the ghost half way through the race. One of the riders was rather a big bloke (Trevor Nation) and observed that the subframe they bolted onto the back of the frame to carry the seat used to bend about an inch or so when cornering, which moved the centre of gravity and destabilised the bike as the rider moved out due to centripetal force....

As I described, the long term engine ran for four years without a service. I have no idea what engine speed it ran at, or what percentage of output power, but it was definitely reliable.

those fans are going to make a good bit of noise, ducted or not, as the blade tips are approaching supersonic

Although I agree with this argument, you are assuming the use of conventional propellers inside the ducts. NASA researched a new form of multi-blade prop which was designed to prevent a leading edge causing the shock wave associated with close-to-mach speeds. They are effectively conical spirals with odd numbers of blades, designed to operate in ducts - so before you ask "why wasn't this built into fighter jet airfoils?" it has to be ducted to work successfully; or "why not in the guts of jet engine compressor structures?" it is not suited to multi-blade compressor application (for various reasons). When they got it working (I think it was the JPL did the work), they were proposing turbo-prop engined (eh? Lo-tech!) delta wing aircraft with ducted fan engines that could hit mach 1. Quite an interesting development; haven't seen a damn thing about it since I read the article - but the fan designs (if that is indeed what the Moller is using) were incredibly quiet and fuel efficient. I'll see if I can turn up the article (it was in OMNI years ago, and I might have kept it), but don't hold your breath!








One of the few remaining Mk1 owners... #00015