# How many people are interested in a GOOD safe psru for the rotary?

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#### Billrsv4

##### Well-Known Member
I'm working with a tested psru that is designed for the rotary. Tested for torsional vibration. All orders out of the RPM range for normal operation. (2 rotor) It works and we can prove it. The problem is how much to invest in building it? How many takers are there for a $4000 psru? For a$3000 one? I want to know if there is anyone ready to go for a professionally designed and tested unit. Not helical auto parts. Purpose built?
Bill

#### rv6ejguy

##### Well-Known Member
How many flight hours on your unit and how many examples flying? Weight?

#### Vigilant1

##### Well-Known Member
I'm working with a tested psru that is designed for the rotary. Tested for torsional vibration. All orders out of the RPM range for normal operation. (2 rotor) It works and we can prove it. The problem is how much to invest in building it? How many takers are there for a $4000 psru? For a$3000 one? I want to know if there is anyone ready to go for a professionally designed and tested unit. Not helical auto parts. Purpose built?
Bill
Bill,
I would be among many people interested in a proven PSRU for the 13B and Renesis if the weight and price were right. But that's "proven" in the aviation sense--with thousands of total flight hours with an engine and prop like the one I'll be using. If "purpose built" means eschewing perfectly serviceable and tested off-the-shelf commercial parts, then I wonder 1) why and 2) what the cost will be.

Welcome to the board.

As I'm sure you know, you are traveling down a path littered with previous efforts (and some successes). Lou Ross was a heck of a good machinist, and his PSRU held up fairy well, but was not perfect. Tracy Crook's effort was a solid one, but that drive also had some warts that customers had to discover on their own. I wish you the very best of luck, because a PSRU (and a fairly standardized set of other FWF bits for the Mazda engines) could be an important development for the E-AB community.

#### Billrsv4

##### Well-Known Member
How many flight hours on your unit and how many examples flying? Weight?
Hi Ross,
Bill

#### Billrsv4

##### Well-Known Member
Glider,
The Mistral unit is a good one. Planetary units do have their own set of problems. Most have to do with the inability to set the backlash. At least the Mistral was spur gearing and easier to control pitch circle on. They did nice work but won't sell into the non-certified market. The gearset I am talking about is a single reduction, spur gearing and has the ability to set gear lash. Quality wise I would consider it to be at least as well made as the Mistral, but talk is cheap, and Mistral's gearbox is not! That is if you can even buy one. The originators of the gearbox I'm talking about first built a planetary but found that without a VERY expensive damper unit it wasn't reliable enough. They built the damper and it worked great but cost so much that nobody would buy it. They licked their wounds and went back to the drawing board and designed the unit I talking about. It has been built. It has been flown and found to be trouble free in its production form. It has even been tested for torsional vibration and found that with the "stiff" system used all the orders were above the operational range of the 2 rotor. That it was test for this may make it unique for something designed to sell to the home building market. There are no rubber dampers or flex plates. It replaces one of the balance weights of the stock Mazda with an integrated counterweight flywheel, and starter gear. I'm am trying to bring it back, and adapt it to a modern machining market.
Bill

#### Billrsv4

##### Well-Known Member
Vigilant,
One of the reasons that I am working on this design is to update it to a ratio better fitted to available props. The reason for purpose built is so that you can build a unit that has the ability to adjust the gear lash, which helps greatly to prevent the torque reversals that force many of the planetary units to idle so high, and puts all the torsional vibration orders out of the RPM range. That is "why." The question is totally reasonable though. The use of OTC transmission planetary gear sets requires that in addition to idling sky high there is a large end thrust to be dealt with because of the helical gears. Used more for quiet operation than strength. I have seen the end thrust of one of these planetarys turn the thrust bearing blue when high HP was used. There are some with hours under their belt but at much reduced power output. For aircraft we must design our engine gearbox combo like a race car that will face an hours long flat out straight-away! Anything less than a 100% duty cycle is hazardous. BTW you are totally correct that the field is littered with failures, partial successes and backyard efforts, that while well meaning, may get people hurt. I want to see this system remove one of the obstacles home builders face. I also want to have a unit for my own plane, which will run a 3 rotor. As to cost, it is hard to estimate without some kind of idea of what the customer base may be like. There can't be a huge number of people just waiting for this to come along. I have built and sold products for the Motorcycle market, which is small, and this is likely to be even a smaller market that that. That is the reason for my troll like first post. I wanted to see how many people would even respond. That can give me some idea of number of people interested. If modern production techniques can hold the cost down I'm sure more folks might become interested. I am not fooling myself that this will be some kind of big business enterprise. If I could just break even, or only pay for my own parts it would be OK. Many of the parts are out for quote now and I won't be shy about passing the info along. I'm working with one of the originators of the system and he wants me to keep all his work from being lost. He is also most adamant about only offering it for sale if flying in a airplane that is fully sorted and ready to prove to the builders that it is good to go. For Ross's benefit I should mention the gearbox would be easily set up for other engines including a Subaru. Only 2 or 3 parts need be changed.
Bill

#### gtae07

##### Well-Known Member
Bill,
I would be among many people interested in a proven PSRU for the 13B and Renesis if the weight and price were right. But that's "proven" in the aviation sense--with thousands of total flight hours with an engine and prop like the one I'll be using. If "purpose built" means eschewing perfectly serviceable and tested off-the-shelf commercial parts, then I wonder 1) why and 2) what the cost will be.
Same here. I want to see that there are several engines with a lot of time on them, not just one.

a PSRU (and a fairly standardized set of other FWF bits for the Mazda engines) could be an important development for the E-AB community.
That's important. If you want to sell to anyone other than hardcore gearheads, you're going to have to supply things like the engine mount, and either supply or provide a "buy this" list of the other accessories. And you'll have to provide good instructions with pictures, not just a pile of parts.

#### rv6ejguy

##### Well-Known Member
Thanks Bill for the detailed answers rather than the wishy washy nonsense we get here from many other PSRU makers.

I believe the present market is relatively small as you already know but if you can produce a slick, reliable, light and fuel efficient package, you can start taking market share from existing piston engine vendors and grow your numbers to make the business more viable. That will take a while, but if you have the finances and will, it could be successful as we've discussed before. Small is good to start out with anyway as you can keep things under control and give good customer support while things are tweaked. Many similar companies have failed due to poor business models, poor customer service, lack of testing or trying to certify their products.

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#### spaschke

##### Well-Known Member
I've got a belt psru on a chevy v8 now. It's not worth $3000. But I'd be interested in a geared one if rated for an over 300hp (3 rotor) engine. I think$3-4000 is reasonable for something like that.

#### Vigilant1

##### Well-Known Member
Bill,
Thanks for the solid info in your posts.
As you've probably already considered, I think there would also be a market for a proven PSRU and "kit" for a single rotor engine (P-ported versions up to 110 HP). Obviously, it would be a separate effort from what you are doing now. I think it would be quite a challenge: the TV issues are bigger than for a twin, the need to keep weight low is even more important, etc. But if you are doing machining anyway and could sell your own single-rotor eccentric shaft and counterweights guaranteed and tested to work with the PSRU, that might be pretty attractive for users needing an engine in that HP range.
I'm personally not head-over-heels for single rotors due to HP/weight issues, but there does seem to be interest in them.

#### TFF

##### Well-Known Member
Starting out batches of five sounds close. 100 a year is not reasonable. Probably take five years of no problems to get traction.

#### bmcj

##### Well-Known Member
HBA Supporter
The Mistral unit is a good one. Planetary units do have their own set of problems. Most have to do with the inability to set the backlash. At least the Mistral was spur gearing and easier to control pitch circle on. They did nice work but won't sell into the non-certified market.
There's a certified rotary powered aircraft?

I've got a belt psru on a chevy v8 now. It's not worth $3000. But I'd be interested in a geared one if rated for an over 300hp (3 rotor) engine. I think$3-4000 is reasonable for something like that.
Bill stated that his unit is designed for the rotary engine. Will that work on a V-8?

#### narfi

##### Well-Known Member
Log Member
My projected timeline is starting a project in 2yrs and flying in 4.
That is a lot of time for changing my mind on direction, but current plans are 80% in favor of a zenith 750stol, and 80% in favor of a rotary engine.

That puts me at ~3yrs to start buying engine parts and at that time I would be interested in a well developed and established reduction unit. (+1 or 2 more a few years later)

#### Billrsv4

##### Well-Known Member
There's a certified rotary powered aircraft?

Bill stated that his unit is designed for the rotary engine. Will that work on a V-8?
Bmcj,
It would work but there would be significant redesign. There also wouldn't have been testing for torsional issues. The Rotary eccentric shaft is SUPER twist resistant. A V-8 crank isn't, it has necessarily small solid overlap on the crank throws. The rotary really has 100% due to the basic design. It would be very easy to adapt to a smaller piston engine like the Subaru. Again torsional vibration issues would need to be checked. Mistral's rotary package was attempting to be certified. A very long and expensive process. Everyone that is attempting to mate a high RPM engine to a gearbox or belt drive should go to their browser and put in "BD5 and torsional vibration" The article you will find is anecdotal but revealing about how even so-called experts run afoul of vibration problems.
Bill

#### Billrsv4

##### Well-Known Member
Starting out batches of five sounds close. 100 a year is not reasonable. Probably take five years of no problems to get traction.
TFF,
If you have ever designed and built a product that is sold complete you have found that 5 units is a prototype quantity. Economies of scale really start at about 20 or more units. I believe your 5 units is about the right number for aircraft, but if one of your gears costs $1500 it can be hard to get started. Bill BTW If I could sell 100 units I would pass out from the excitement! #### Billrsv4 ##### Well-Known Member Same here. I want to see that there are several engines with a lot of time on them, not just one. That's important. If you want to sell to anyone other than hardcore gearheads, you're going to have to supply things like the engine mount, and either supply or provide a "buy this" list of the other accessories. And you'll have to provide good instructions with pictures, not just a pile of parts. 07, I agree with you on both counts, but realistically in a market as small as ours it is likely that the designers aircraft is going to be the test bed. There is just no way most of us can spend the money for multi-engine and aircraft testing. That said there are customer examples of the gearbox I am talking about flying. They are fun-flyers and I don know their hours to date. No gearbox issues though. I am working to bring back a well tested design not re-invent the wheel. The originator of the design I'm working with doesn't want their work to be lost. Bill #### Billrsv4 ##### Well-Known Member I've got a belt psru on a chevy v8 now. It's not worth$3000.
But I'd be interested in a geared one if rated for an over 300hp (3 rotor) engine. I think \$3-4000 is reasonable for something like that.
Spaschke,
Belt drives that will handle full engine power for a long time tend to be HUGE and can be difficult to get belts for. Gates is one of the best manufactures, (of the belts), and if you even say the word airplane they won't sell to you. Therefore there is no customer support from the belt maker. The other thing a lot of the belt reduction builders err on is thinking there is some shock absorbing in the belt. There is not with composite fibers there is just no give to them at all. I hope yours is well put together.
I'm designing for 400 HP because a 3 rotor can easily get into the 350 Hp range if done right (P-port) even normally aspirated. I am hoping that I can bring the gearbox in around those figures.
Bill

#### TFF

##### Well-Known Member
I did not think its a preferred number, but as tight and careful as homebuilt owners are, those prototype numbers are probably what you got. Until your experimental is less experimental. I'm changing a main gearbox in one of my company's helicopters. Certified of course. The rebuilt one is about 20k. actually not bad in terms of what it is but it is a low volume item. They stock parts for 5 a month for OH and new. This is a company that is 50 years old.

#### gtae07

##### Well-Known Member
07,
I agree with you on both counts, but realistically in a market as small as ours it is likely that the designers aircraft is going to be the test bed. There is just no way most of us can spend the money for multi-engine and aircraft testing. That said there are customer examples of the gearbox I am talking about flying. They are fun-flyers and I don know their hours to date. No gearbox issues though. I am working to bring back a well tested design not re-invent the wheel. The originator of the design I'm working with doesn't want their work to be lost.
Bill
I didn't say all the flying examples had to be "company" airplanes In fact, if there are multiple customer airplanes with a consistent configuration (base engine, gearbox, prop) and at least a few of them with significant time, that's even better. Demonstrated performance in customer installations is better in many ways than on a company aircraft because it's more of a real-world test. This would at least demonstrate the reliability of the gearbox.

The trick is putting the rest of the engine install into a format that a substantial fraction of the market can work with.