My 13B engine configuration (tentative)

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athomp58

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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.

Aubrey
 

dwalker

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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.

Aubrey

I agree and think that the need is for two ratios- the 2.18 for pushers and boosted or "high powered" planes and a 2.4 to 2.8 for tractors and NA/Renesis.
Neil Unger has everything but the propshaft figured out, and I am actually going to talk to my machinist buddy about working up a PSRU along the lines of the RWS/Neil Unger designs but with some refinement to the prop-shaft. Production cost on the propshaft seem to be the largest issue for the Unger unit.

The Marcotte 2.4 400hp unit is a solid piece and I feel like most builders should be using it. The only "downside" I can see to the Guy Marcotte setup is the 3" offset from crank to prop, but that is likely more of a help than a hindrance as when you lower the motor in respect to the prop you make room for better intake manifold fabrication and routing.
 

rv7charlie

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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.
 

dwalker

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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.
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.
 

athomp58

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Tracy's prop shafts were fabricated from a vehicle rear axle. I don't think he ever told us what vehicle.

Aubrey
 

dwalker

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Tracy's prop shafts were fabricated from a vehicle rear axle. I don't think he ever told us what vehicle.

Aubrey
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.
 

athomp58

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The Ross prop shafts were in two pieces. The flange was press fitted to the shaft and then pinned. That design made disassembly of the unit difficult without special equipment. Lou Ross was a master of masters at machining technique. His son, when he took over, when Lou retired, was not as particular. Cheap CNC machining was not available to Lou or to Tracy.

Here is an article on Lou Ross. The two engine photos show a rotary with Tracy's PSRU on the left and a Subaru with the Ross PSRU on the right.
 

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dwalker

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The RWS design is now open source; IIRC, even the machine shop sources Tracy used.
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.
 

rv7charlie

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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.
 

FinnFlyer

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I think one of the reasons Tracy stopped producing the PSRU was increased cost/lack of suppliers. Can't remember for which parts.
 

Lendo

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Rv7 Charlie, I have the information somewhere on the Mistral, but from memory I'm pretty sure it's about 2.7:1. I loved the design of that Mistral PSRU. Mistral was very conservative with their engine developments and went the 3 Rotor for extra power - longevity was their main Goal. For that reason they kept the power to the level of RPM that rv7 charlie suggests. at 4,000 rpm the Rotary engine is well down on power. Like most engines there is an RPM that the engine is happiest with, where it is at least stress and that's around 6,000 rpm, again as rv7charle indicated ( lowest gear/ bearing load) and Mistral followed the same methodology. Powersport also followed the same principles. I believe Bill who is developing his own type of PSRU is looking at 2.7:1.

dwalker, Lots of things to consider other than just the engine development, in the case of Aviation. I would look closely at those Pioneers of the Rotary development.
George
 

Cardmarc

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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.
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.
 

Lendo

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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.
George
 

dwalker

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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.
George
It would be a step in the right direction for sure.
 
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