EA81

[asra]

Well just chasing some info on the EA81"s. I"ve only done a few hours with my machine but it is a EA81 with a rotax 2.62:1 E box and swinging a 75" med chord prop of Rob Petroni"s. I run a 2" SU carby and don"t care too much about how much it burns (haven"t checked it either). Was lacking climb out power the other day and had a more experienced pilot fly my gyro and we put some more bite on the prop. It"s up around 15 degrees now(still waiting on prop protractor). It was around 13 when we built the gyro and the engine was revving to around 5000 RPM. It now revs to about 46-4800 and cruises at around 4100. What sort of revs do these puppies like to run at all day. My way if thinking is to give it some more bite on the prop and get the revs down even more. I also have a turbo sitting on another EA81 in the shed and was wandering what people think about putting it on my gyro. Can you run a low boost pressure to get just a few extra HP and still maintain the reliability of the NA engine. The engine was built with reasonably low compression for reliability but it does have a bit of a cam in it.

[Mark Horan]

Baz,Your motor is making more horse power at 5000 than it is at 4600. With a 72 in WD prop in my old EA 81 I would be climbing out ay 5000 and cruising around 4400 4500. In your case, this would depend on the weight of the machine and yourself and the alt that you are operating from.I remember, one time when I put more pitch on my old gyro, it seemed to climb better into a fairly stiff easterly on the day I did it, but the next day (with a higher density altitude) the performance was crap, to the point of trying to climb out downwind was impossible and ended up in the paddock.If you had a flight adjustable prop, you would climb out on a finer pitch to make max horse power from your motor and add pitch for reduced revs and a higer airspeed (low gear high gear).I think that a turbo with a courser pitch is a good idea because it gives you more hp to drive the heavier prop on take off and when in cruise you can lose the boost for lower revs. However the turbo adds weight which need more HP to kep the machine in the air etc etc.These EA81 motors are nearly as bullet proof as the ej22 motors and as long as you keep the oil fresh in them and they dont get hot, they dont seem to care how long they operate at reasonably high revs.Horsepower and airspeed is what gives you climb.Mark

[asra]

Thanks Mark, when i get my pitch gauge I will have a play around. Also do you know of any lightweight alternators that are easy to come by. I don"t see a need to run such a big alternator wieghing 4-5kg.

[Mark Horan]

Have a look around for an alternator off one of those small engined Mitsubishi colts or a suzuki with the 3 cylinder motor, they are small and do the trick. Mark.

[birdy]

I know a bloke who runs Kubota stationary engine alts on his soob. recons they is good, weigh buggerall and would fit ina bacco tin.

[hatrack]

Guys, how"s this sound? If your only doing 1 hour return flights or so, on your own property, why not work out what capacity battery you need to fly for , say, 2 hours and just jump start your donk? You could do quite a good start system, if you try. Gets rid of an alternator and you only need a small battery.

[asra]

Jees hatty, I reckon I would be worrying about the battery going flat on me. I like the idea of a little tiny one though, only needs to mbe about a 5-10amper i reckon. Got my radio working again today. Ended up making my own PTT unit, I just pulled the mike apart, removed the switch and wired in my own external one and wired in the mic from my headpiece. Took it for a fly and it works a treat. Still not used to talking and not hearing yourself talk but. Went for a fly and it works a treat, I was going to build my own circuit from he aerial pursuits website, had diodes, capacitors the works when I sat down it had a 2.5mm stereo plug for the mic with 3 wires and that had me stumped so come up with the idea of using the mic i got with the radio. Will be up next week. Might catch up for a beer some time.

[birdy]

If your go"n to go that far Hat, prop start it, hand start ya blades, then you could run the ignition for a coupla days ona coupla 6V dolfin batts.Better still, if you hada 912, you wouldnt need any batt, just a very heavy left hand glove for the prop starts.

[tonydenton]

your pitch and engine speed sound about the same as mine but with worked heads i have 17 degrees . i was told that about 14 was the best performance angle . the auto flight box with a ratio 2:47 gives the prop max tip speed so you can reduce the angle a bit . another alternative is rob now makes 1" longer blades on the shank to give a 78" prop diameter. higher tip speed , bringing the pitch back also . rob reconds its a noiser but he is paranoid about that.

[Russell]

Well just chasing some info on the EA81"s. I"ve only done a few hours with my machine but it is a EA81 with a rotax 2.62:1 E box and swinging a 75" med chord prop of Rob Petroni"s. I run a 2" SU carby and don"t care too much about how much it burns (haven"t checked it either). Was lacking climb out power the other day and had a more experienced pilot fly my gyro and we put some more bite on the prop. It"s up around 15 degrees now(still waiting on prop protractor). It was around 13 when we built the gyro and the engine was revving to around 5000 RPM. It now revs to about 46-4800 and cruises at around 4100. What sort of revs do these puppies like to run at all day. My way if thinking is to give it some more bite on the prop and get the revs down even more. I also have a turbo sitting on another EA81 in the shed and was wandering what people think about putting it on my gyro. Can you run a low boost pressure to get just a few extra HP and still maintain the reliability of the NA engine. The engine was built with reasonably low compression for reliability but it does have a bit of a cam in it.Baz........done a lap or 2 in ea81"s............your setup is in the ball park.2.62 yes, i found best prop was 76" warp drive, you have a bit of a "cam".........you should have oodles of power, soob will purr all day around 4200. No need to turbo what you have. Make sure she"s breathing ok, your revs are down, something will be causing thatEA81"s are deadset bullit proof, when setup right.Just a head polish gives a better engine performance without adding stress. Once you start bumping up the HP, the soob get"s out of it"s comfort zone.To reduce weight........toss out the huge battery, put in a tiny m/cycle one, toss out the heavy alternator, grab a thermatic fan motor, fit a model aeroplane propellor to it, then mount the thing up on your mast, run the wires down to the battery...........as the little prop spins it creates a "charge"....enough to maintain your battery. You need to experiment with the prop diameter to get best result. ( one fan motor in particular was the better one, trying to remember the brand.......standby )

[Mark Horan]

Russ, what happens if your hair gets caught up in the little airplane propeller??

[Russell]

Say nuthin russy.........count to ten pal..........say zip......Grrrrrrrr :-X

[asra]

I noticed my Patroney prop only has 12 degrees twist where a warpdrive has 24 degrees twist over a shorter length. Extra twist may help depending on what the climb out speed is, as at higher speed only the outer section is giving thrust.

[Brian]

Put in a little calcium battery and you would go months without charging the battery.

[Darrell Jones]

Hi ,any person wishing to fit an alternator, that will, charge a battery,weigh about as much as couple of cans of XXXX beer , is the unit fitted to the Kubota 3 cylinder tractor. If these aren"t what you want on your gyro, then try the alternators off the Mitsubishi cars. Some of these are internally regulated, and some need to have external regulators wired up .Cheers Darrell Jones