fixed pitch / constant speed prop

[mkoxxy]

(I have started a new thread - "700T install" took a turn to props - this
way, "700T install" can continue independently.)

Ken, since you brought it up, I think electrical propulsion has a distinct
advantage here, too: with the high torque available at low rpm, pitching
the prop for good cruise will still allow good thrust to be developed from
a stop (as Mark demonstrated at Arlington and Airventure). I see no good
reason to go to in-flight adjustable (and heavier) on my eGull. I would
imagine this low rpm / high torque adavantage would also come in handy in
seaplane operation. I wonder, though, if props designed for ICEs can handle
all that extra torque? Or is the added stress offset by the lack of
vibrations from the motor?

Martin

From: Kess Blaswich kessb@wavecable.com
via<http://support.google.com/mail/bin/answ ... 2&ctx=mail>
yahoogroups.com



to Earthstar_Airc.

Constant speed generally means that the prop has the pitch varied
according to the load, and has a mechanism, (even Ivo does) to keep the
prop load right where you want it. The non-constant speed, (no feedback
controller) are just fine for us cheaper type. Does anyone know if the Aero
hub able to fit a 503 prop flange? Oh, by the way, IÆm still drooling about
the possibility of changing the 52 hp 503 out for the 54 hp Zero electric
package. So what if the batteries are a little heavy. IÆm a little skinny
and can afford an extra pound or two. IÆve also stumbled across an ev
hot-rod site that has huge motors, controllers and batteries. Maybe the hot
rodders will be the ones to get us cheaper electric power as they strive to
have the fastest rides around.

k

[earthstaraircraft]

Hi
The Zero electric motor on the eGull works really well with a fixed pitch but top spread is increases with more pitch, a lot. But the range that an electric plane should be operating in is well covered be the fixed pitch prop. Kess would disagree. But those that are happy flying below warp speed will be quite happy with a fixed pitch prop. You get more range at slower speeds.
Happy Flying,
Mark
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[davidpeterson80]

Mark, Do you have enough numbers now on the eGull with the Zero motor and the batteries you are using to know what your max range would be? To me, max range is a good metric to shoot for with electric power (even though local flights are a better fit right now). Over the next few years I would think the electrics that flew the farthest getting to AirVenture will gain the most attention. That and a reasonable initial entry cost.

Dave P.

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[davidpeterson80]

Sorry. I meant to ask what your 'max range airspeed' would be for the packs you are using since the weight doesn't change during the flight.

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[earthstaraircraft]

80 mi

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[rahulchoudhary73]

That ELIPPSE propellor would go so well with (e)Gulls. Looks fixed pitched. It was refined further for unmanned systems with it's low noise and speed benefits, that'll quiet likely work for these engines too. In black now with the trailing edge smoothened out. Guess it'll take a while for such a prop to be generally available. That'll sure make Kess the fastest Gull in the west ;)

http://www.eaa.org/experimenter/article ... lippse.asp

rc

[blaswichk]

Ha! Now there is something I didn’t think about, a variable pitch on an electric motor. I was noticing that some of the electrics like to develop the most power at speeds similar to gasoline engines, like 2700 rpm. That said, there is probably enough torque to pull a coarse pitch way easier than a gasoline engine similarly loaded. Even though I’ve dreamed faster and cheaper with gas, I think the 54 hp Zero would make the ideal set-up, with 2 hours worth of batteries (fuel). My chunky 20’ wing Gull won’t be as efficient as a 28’ lightweight eGull, but will still give a great performance similar or better than my 52 hp gas (the venerable old 503). We are living in some interesting times now, and the electrics are out there on the edge, just like I like to be!!

k

[mkoxxy]

Ken, it will be difficult to carry 2 hrs worth of batteries with the 20'
wing. The 11kWh battery Mark demonstrated weighed 170 lb and had enough
juice for maybe an hour. I had originally wanted a 24' wing (easier
handling, transport), but Mark convinced me to go with 28'. The 40kW Zero
motor will proably get you in the air, but you will need more energy to
stay up there. But give it a few years - battery energy density may
dramatically improve. I fully expect to have to buy newer technology
batteries in 3 or 4 years.

BTW, one of the downsides of going with the Zero motor is that it develops
full power at 5400 RPM (unlike the purpose-built aviation motors). Mark is
designing a PSRU that retains Zero's motor pulley and the carbon fiber
belt. Should be light weight, quiet, low maintenance, and have good life
time (no motor vibrations!).

Mark, if you read this: can you feel the prop vibrations? Would those be
harmful to the belt?

Martin

[earthstaraircraft]

Hi
The 28 foot wing will give 1:10 and the 20 will give 42 min Due to the higher angle of stack required with the shorter wing.
Happy Flying
Mark

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[earthstaraircraft]

Hi, that sould have read angle of atack.

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