Gyro brothers out there, i have got EA81 subaru engine with me , that needs rebuilding ,meaning rebuilding it need money , the appearance is very appealing compared to Ej 20 ,which is currently installed in my single sit gyro , EA81 engine weighs less compared to ej 20, i think this will cut my gyro weight , isn't it ?

ALL ADVICE IS WELCOME ... THANKS IN ADVANCE

Samuel

Uganda

Others on this site will know much more about Subaru's. All I would offer is this. The more weight you carry you end up with having to make a series of design compromises. The average Euro Tub gyro - which I don't dislike per se if you have $100 000 I'm sure they are comfortable etc. and some have good specs in terms of rate of climb etc. However that often comes at the cost of requiring a very expensive engine, longer rotors etc. However in your case you already have the engine installed on a single seat machine and I'd assume you are not going to go through a whole process of adding the advantages of having a lighter machine. That is you are not going to shorten your mast, buy a new set of shorter rotors, install a shorter prop. So you will have a lighter machine but presumably loose some hp into the bargain? So the EJ20D produces 150hp at 6800rpm? the E-81 about 100hp? so the e81 weighs 100kg installed (correct me if I'm wrong here). The Ej20D weighs 140kg. So not an insignificant weight saving. But this is the critical bit how much excess weight does your airframe have?

Many gyros are massively heavy. The Calidus is 265-305kg empty weight depending on features. Empty. My instructor built a chrome molly framed two seater which had electric pre-rotator, massive disks, electric trim etc and only weighed 190kg empty weight. This was with a rotax 912s engine fitted. Now this is significant. What did he gain by not having that weight. Firstly he didn't require a bigger rotax 100hp was more than enough. But secondly he didn't need massive rotors to lift the enormous weight. So he had on that machine 23ft rotors 8 inch chord N8H12 section the Calidus has about 27-28 ft rotors. This is significant as the longer rotors require greater takeoff distance, this sounds counter intuitive but its true. I have seen rotors as short as 19ft, 22ft and 23ft on the same gyro design (all very light) and the 19ft rotors always got off the ground quicker and were quicker to 500ft. Now they may not have had as good a rate of climb (I don't have these figures) but in general longer blades take more distance to get off the ground. Having a lower weight allows you to get that advantage.

So as I see it the problem you have is your single seater was probably made with the weight hp etc. available. The advantages of less weight are real but so are hp. However the maximum advanatges are cumulative in a lighter weight machine. That is shorter mast, shorter prop, shorter rotors (all of which also reduce weight). But if you are not planning on making a brand new gyro and just loosing 50hp for a 40kg weight saving but keeping the same long rotors, the same possibly heavy airframe etc. I've no idea if you'd be better off. How about build a new airframe with the e-81 with re drive and build a single seater that is lighter with smaller rotors, etc. Then sell which ever you prefer the least. My opinion is we've come a long way from the sort of performance Wallis had in his 116kg empty weight machines (abeit with a very unreliable motor) but even his version with the Rolls Royce engine could get off the ground in VERY little space and that was with 20 ft 6 inch rotors. Keeping everything as light as possible matters but driving a massive rotor with less hp is costing you take off distance. If I'm wrong show me a Caladus getting off in less room than he did on his heaviest machine.

Woops! I posted this in the duplicate thread (Which I will remove)

The EA81 is a great size motor for a gyro, but a bit lacking on power if direct drive... need a turbo to have enough power i the pilot is heavy. A redrive on an EA81 makes it useable.

The EJ22 usually has to run a redrive and is physically bigger and heavier, but makes an awesome gyro motor.

If you are doing a simple, open frame single seater, I would be using an EA81 with a C or E box pr direct drive and turbo... if you want a canopy and or lots of instruments (a heavy machine)... I would tend to go for an EJ22 with some sort of reduction

There was a guy I used to fly with occasionally when I was living in Maryborough (nice guy wish I could remember his name now), he had a turbo on a direct drive Bensen style machine. It went great him and another guy who was into car racing had done something with the cam also I assume they'd gotten it producing more power down low not sure how they set up the turbo. Do you happen to know who I'm talking about? I've been trying to remember his name for a couple of years. He had a domed perspex sort of windbreak canopy. You live pretty close to that area ever heard of him or met him? Him and his mate (who did up the engines) had the best performing Subaru's I ever saw. Owen Dull I think used the ej22 in his two seater and it performed quite well.

Replie from Samuel. THANK YOU AGAIN FOR YOUR ENLIGHTENMENT ! I SEE where light engine ,lower hp works well with shorter rotors . my rotors are 28feet , i think the ej20 will be suitable for my gyro , i am heavy pilot too i weigh 115kgs

Thank you Sir

The only gyro DuuuDe I know of up this way is Rob Patroni... but I thought he was further north? Like Hervey Bay or Bundy?

He lived at just outside of Maryborough when I was teaching there WAY BACK. But thanks anyway. I think Patroni was somewhere near Bundie (at least when I was up around that area - tranferred to Rosedale State High School - man that was an INTERESTING school. Some of the nicest and some of the craziest people I've ever come across up there. I spoke to him on the phone a couple of times he was just starting to build his rotors when I got in touch with him (I think I was chasing airstrips to fly off). Nice guy.