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PSRU options-what's flying?


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I've been surfing though the process of building (I know, I need to go ahead and build it!) and I have some questions on PSRU design-


What's Flying?


I know Ross's PSRU is flying, as well as Crook's enhancement of it,


I'm reviewing George Graham's conversion of a RX-7 gearbox-he has 320 hours on it, is anyone else flying this design?


Are there any that I've missed?

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I think there's a guy called Marcotti in Canada that makes something, but in my book the PSRU (Redrive) choice is a no brainer. Get it from Real World Solutions. Tracy has hundreds of hours on his own unit and a bunch of them are flying. The only reason to consider anything else might be the ratio, but 2.17 is ideal for my application.

I can be reached on the "other" forum http://canardaviationforum.dmt.net

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Have been looking at for one for a Subaru. It needs around 1.82:1.

Tracy Crooks are the wrong ratio and as of last week the only different ratio he was looking at was 2.85:1 for the RV8 engine. (250hp at 9000rpm).

Subaruaircraft (Engenfellner) have the right ratio and some of their drives have hundreds of hours on them but they sell the complete package and wont sell a drive.

SUB4, a New Zealand company have one (search SUB4)its around 2.4:1 and around $2500 US. It is capable of 300HP, not sure how many are in service. They have a smaller one that is used on Gyros and there appears to be quite a few of these in service.


Using a anything above a 2:1 ratio on a Subaru means the prop has to be of large diameter (not poss on a Cozy) or highly pitched, not desirable.

Someone may have more info on this side of things it but the two that have putSubarus in Cozys have used 1.82:1


Marcotte is 2.2:1.


From a bit of research I would think that a planetary drive has more chances of surviving for the greatest time.


Only planetary drives that I see are the Crook one and the Ross one.


Is Ross still in production?

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For a prop speed of 2750, engine speed 6000, I need a 2.18 ratio, Crooks are at 2.17 IIRC.


So the subie peak is at 5000 rpm?


If you don't mind me asking, why subie? If I were going the piston route I'd go Lycoming myself, but then I don't know a whole lot :)


Crook's does have the advantage (over Graham's) of using one oil system , but that may be a disadvantage in a piston engine, as their oil systems have a tendency towards varnish that rotaries don't.

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George Graham flew in to LNA for a visit a couple of years back. Keep in mind that his plane is a LongEz (or is it a converted VarieZ) which needs considerably less power than a Cozy. It would be my guess that the stock gearbox approach is close to it's maximum load in George's installation. I considered it also, but decided it wasnt strong enough to handle a 3rd gen turbo putting out 250hp +.


For a prop speed of 2750, engine speed 6000, I need a 2.18 ratio, Crooks are at 2.17 IIRC.

Correct. I'd say that's as close as you're gonna get. The other thing about Tracy is that he's a great guy to deal with. Honest as the day is long in summertime, and VERY concientious. There isnt much money in the redrive business so there's a danger of "scraping the barrel" in business ethics and/or longivity. Over the years I've heard plenty of negatives about Ross and Marcotte, but never one about Tracy. I have pretty much everything he makes. Unfortunately Tracy recently smashed his elbow. He's using the down time to finish off his engine monitor which, in a way is good because I want the first one out the door. :)

I can be reached on the "other" forum http://canardaviationforum.dmt.net

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  • 2 months later...

Besides being insanely expensive, has anyone heard anything about the PowerSport redrive? As I sit and day dream about my future engine installation I'm often seeing a constant speed prop. It's not enough that I plan on using an engine that is much smaller, and about 70 HP stronger than a Lycoming. I just won't feel right swinging a prop that is only at its best in one flight mode. But....when the checkbook comes out, I bet it will be for a fixed prop and one of terry's redrives. $6500 vs $2890. Maybe Terry will develop a version that can handle a constant speed prop.



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Originally posted by John Slade

George Graham flew in to LNA for a visit a couple of years back. Keep in mind that his plane is a LongEz (or is it a converted VarieZ)

George is flying an eracer. I looked at his installation several years ago (summer 99, I think), and talked many airplane things with him. His plane was built on a budget, and is a great example of how you can build a flying machine without pouring in huge piles of money. But, it is perhaps not a good example of how an auto conversion is going to run circles around the conventional aircraft engines.


The roadblock I hit with the rotaries was the issue that many of the support systems were not commercially available. Intake manifolds, carburator or injection system, exhaust system, mufflers, mounts, etc. Plus, complete lack of agreement on what might be the correct way to accomlish these things. So, each person was really on their own to develop the entire package. More than I wanted to bite off. (Plus I found a Lycoming that was appealing!)


I also suspect that the 13B is a good substitute for the 150-160 hp engines, without a great amount of fine tuning required on the intake and exhaust. Squeezing another 20 hp through those pipes is going to take a lot more attention to detail. More than 200 hp in a Cozy sounds like a good way to make noise and heat the air behind the plane!


As more of these machines take to the air, we will learn what works, and what does not work. If the concept is viable, perhaps there will be some intakes and exhaust systems that are commercially available, or flight proven designs that can be replicated.


I still have three 13Bs out at the hanger, two completely broken down, and one that has been reassembled. Some day, it would be fun to get them running. But that will be after the Lycoming is pushing my plane through the sky!




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  • 5 years later...

I came across a discussion on the FlySube forum where the Autoflight H6 system was discussed. I contacted the designer to get a bit of information and he replied as follows:


"This Autoflight H6 unit was based on the SUB4 unit I designed when I was at SUB4. The heavy duty SUB4 unit has a good track record also, although not available any more.

What is the rating of the PSRU

"Hennie, the H6 unit is good for up to 300 HP at 6000 rpm. NZD price is $4000.00 plus freight. Ratios are 1.9 or 2.2 or 2.4 to one. I have these units on the shelf ready for assembly and dispatch."




How many of these units are in operation and do we have a trackrecord on operating hours to date?

"Eleven sold in 08, two on airboats in US, one at 200hrs and one at 500hrs. Two into South Africa, one at approx 350hrs, others not sure. Tend to dissapear to customers and I never hear again. I imagine if there were problems these customers would let me know. "



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