My interest here is in promoting the rotary for use by the broader aviation community. My comments are not directed at dwalker's specific implementation. In general, the rotary community needs an off the shelf PSRU to replace Tracy's product.
The RWS prop shaft is fine, the sticking point is the apparent cost to make it, as it is a very well made one-piece affair that starts as a 6.5inch steel round and is machined into the prop-hub, shaft, and splined end to tolerance. Which costs money, especially in small lots. Which puts Ungers price point pretty high and even then he makes almost nothing per unit. Until that process is somehow refined or a design change to say, a properly splined propshaft with a tapered/keyed/bolted prop hub machined in two pieces instead of one unit, the cost will remain very high per unit, which means it will be some time before we see one. My last communication with him was he was going to machine up the propshaft in-house on manual machines, and if I wanted he would be glad to sell me the individual pieces he has in inventory and I could make/develop my own propshaft.I can't recall anyone having issues with the RWS prop shaft. There have been a few issues with the *input* shaft/sun gear mating, in, let's say, 'abusive' environments.
Unger was having "a Colorado company", most likely Mark Williams, make his propshaft, because they make very very strong axles. The thing is, they are on the high side as far as pricing for small jobs, and he was having them make it out of a single piece. He did tell me he had looked all over Australia and the US for a source, but that seems to be the bit he was lacking. I have the CAD drawing he is using.Tracy's prop shafts were fabricated from a vehicle rear axle. I don't think he ever told us what vehicle.
I have been looking around and not found that info. It would be pretty helpful though. I have pretty much zero ambition to be in the redrive bidness, but the lack of a good redrive seems to be the issue with the 13B as a flight engine.The RWS design is now open source; IIRC, even the machine shop sources Tracy used.
Mistral’s redrive was almost perfect. Planetary with constant speed gov pad, and supplemental alternator. There are a few out there, we just need to copy it. I think Mistral may have dissolved as a company.I agree on both counts. I haven't accessed the data set (already own two complete drives). I do know of a couple of others who've obtained the data, and Tracy has said he'd make the data available to anyone desiring to build the drive.
It would be a step in the right direction for sure.Cardmac, From just looking at all the Photos, the Mistral PSRU looked bulletproof , if someone could just find out who did the Machining of components, it would be a good start, providing Mistral is no longer in business. Apart from that if someone has one to be copied, it originated in Europe somewhere. Perhaps parts were made in the US for the Certification process.