Electrically Powered Ultralight Aircraft

wrote:
On Aug 7, 3:04 pm, "Gig 601XL Builder" wrDOTgiaconaATsuddenlink.net
wrote:
Larry Dighera wrote:
On Tue, 7 Aug 2007 14:51:55 -0500, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote in
:

all this talk of electric airplanes while a nice thought is
something that at best is way in the future.

That's only true if you overlook Randall Fishman's electrically
powered ultralight (http://www.electraflyer.com) and Mr. Monnett's
Sonex proof-of-concept Waiex aircraft
(http://www.sonexaircraft.com/press/r...r_072407.html).

But, I know, you were referring to electrically powered aircraft
with the same utility as today's GA aircraft, right?

Right. When the electric Sonex can do the same thing the VW powered
Sonex can do then it will become something more than an interesting
idea.


I have not seen any significant flight duration claim on the Sonex,
which speaks well for the design team.


I really hate to burst your bubble but, from the Sonex link above.

"Initial top speeds will reach approximately 130 mph, and endurance is
expected to range between 25-45 minutes or longer, depending upon power
usage on each individual flight."

George wrote:


Just a wild guess, but wouldn't this make for a very, very safe
airplane??
George

None would be safer, though you might find some people who would have a
problem with calling it an airplane if it couldn't get off the ground.

wrote

Well, to be fair, there is solar cell research that if it becomes
practical and cheap enough would work on sail planes with lithium
batteries.

Are you sure about that?

I think I recall seeing someone do the calculations of how much solar energy
hits the top surface of a sailplane and wing, and it was still not enough to
motor without thermals, if it was all converted to electrical energy.

Anyone better in math, than me, want to take on that supposition?
--
Jim in NC

On Tue, 07 Aug 2007 20:54:59 GMT, wrote in
:

In rec.aviation.piloting Larry Dighera wrote:
On Tue, 07 Aug 2007 19:14:59 GMT, wrote in
:

If you go to http://xtronics.com/reference/energy_density.htm you find
the energy densities of a lot of things.


Propane (liquid) 13,900 Wh/kg
Diesel 13,762 Wh/kg
gasoline 12,200 Wh/kg
Ethanol 7,850 Wh/kg
Methanol 6,400 Wh/kg
Secondary Lithium - ion Polymer 130 - 1200 Wh/kg
Primary Zinc-Air 300 Wh/kg
Lead Acid Battery 25 Wh/kg

So batteries have to improve by a factor of 10 to match gasoline.

When you compare the efficiency of internal combustion Otto Cycle
engines (30% - 40%) against electric motors (80% - 95%), it appears
that a factor of five might be a more realistic comparison of their
relative merits. Then there is the issue of power plant weight...

Well, you have to look at total system weight.

Agreed.

A 100 HP electric motor is not going to be particularly light

The ~100 HP Continental O-200 is about 170 lbs. If you look at the
motors offered by AstroFlight, it looks like they weigh about one
pound per horsepower, but that doesn't include the controller,
charger, etc.

and the power cables are going to weigh a whole lot more than fuel lines
for example.

True, but there are several trade offs: No oil cooler nor oil, No
gascolator nor fuel pump, etc... But the electric motor will require
a controller, a charging system, wiring, etc. It's difficult to
speculate about the weight without more specific information.

When you look at the total installed system, assuming you have batteries
5 times better than you have now, I doubt the total weight difference
will be all that much.

It's difficult to say.

Electric motors don't lose power in thin air either. With regard to
reliability, electric motors have only one moving part compared to
scores of moving parts for IC engines, their failure rate should be
substantially greater than IC engines.

AC motors have only one moving part but would require a beefy inverter
to generate (and induce more system loss) the AC.

But the controller has no moving parts either except perhaps a cooling
fan and contractor. I would guess the electrical propulsion system to
be potentially more reliable than an IC system, but there is the Sony
LI battery recall issue ...

DC motors have brushes but motor control is simpler.
If the DC motor was designed for easy inspection and replacement of
the brushes, then the failure rate should be much lower than a gas
engine.

Today, brushless DC motors, or even three-phase induction motors, are
used.

Sonex mentions a brushless DC motor:

http://www.greencarcongress.com/2007...aft-.html#more
Using a purpose-built AeroConversions brushless DC
cobalt motor, controller, and highly efficient battery ...

... the design team, in collaboration with Bob Boucher of Astro
Flight, Inc. (http://www.astroflight.com/), has designed and built
a completely new AeroConversions motor.

This motor is the most powerful, lightest-weight, and efficient
unit of this type ever produced. It is a 3 phase, 270 volt, 200
amp motor that will be over 90 percent efficient.


This works out to about 75 continuous HP by my calculations.

It will be interesting to see what the future brings.

Gig 601XL Builder wrote:
George wrote:
Just a wild guess, but wouldn't this make for a very, very safe
airplane??
George

None would be safer, though you might find some people who would have a
problem with calling it an airplane if it couldn't get off the ground.


That was my point, if it can't fly, how can it crash?? vbg

George

James Sleeman opined

On Aug 7, 3:39 am, Larry Dighera wrote:
Are external combustion engines as efficient as internal combustion
engines? Stirling engines are great for converting waste heat to
mechanical energy, but I'm not sure how appropriate they would be for
aircraft propulsion.

In theory, I think that stirling engines are quite well suited to
aircraft, all it needs is a source of "hot" and a source of "cold",
the cold is in abundance (stick a heatsink in the wind, higher you go,
colder it gets, more power the engine can deliver, directly the
opposite of IC), the hot could be provided with any number of
combustables (and some oxygen delivery system).

I found yesterday after writing my initial post an article about
exactly this - http://www.qrmc.com/fourpartstirling.html "Why Aviation
Needs the Stirling Engine by Darryl Phillips" from 1993/1994.

Given what was said in the article, I'm kind of surprised that nobody
has come up with a working protoype actually.

I see 2 problems. First is that although the temperature at 30,000' is low, so
is the air density, so the size of the heat sink is smaller than one might
think. Second is heat generated by compression of airby the high true airspeeds
at altitude.


-ash
Cthulhu in 2007!
Why wait for nature?

In rec.aviation.piloting Larry Dighera wrote:



Today, brushless DC motors, or even three-phase induction motors, are
used.

Sonex mentions a brushless DC motor:

http://www.greencarcongress.com/2007...aft-.html#more
Using a purpose-built AeroConversions brushless DC
cobalt motor, controller, and highly efficient battery ...

... the design team, in collaboration with Bob Boucher of Astro
Flight, Inc. (http://www.astroflight.com/), has designed and built
a completely new AeroConversions motor.

This motor is the most powerful, lightest-weight, and efficient
unit of this type ever produced. It is a 3 phase, 270 volt, 200
amp motor that will be over 90 percent efficient.


This works out to about 75 continuous HP by my calculations.

It will be interesting to see what the future brings.

I'm not totally convinced the internal controllers electronics for
a brushless DC motor are going to be that reliable at these power
and heat levels.

Time will tell.

The Civic hybrid uses a brushless DC motor, so there's a test bed
for that level of power.

--
Jim Pennino

Remove .spam.sux to reply.

In rec.aviation.piloting Morgans wrote:

wrote

Well, to be fair, there is solar cell research that if it becomes
practical and cheap enough would work on sail planes with lithium
batteries.

Are you sure about that?

I think I recall seeing someone do the calculations of how much solar energy
hits the top surface of a sailplane and wing, and it was still not enough to
motor without thermals, if it was all converted to electrical energy.

Anyone better in math, than me, want to take on that supposition?

In rough numbers, you get about 1 kW/m^2 of energy from the sun on
a clear day.

Current conversion technology is about 22% at best.

Technologies in the works are promising 50-60% (the check is in the
mail and I will respect you in the morning).

One presumes a sailplane is going to spend most of its time sailing
and only using the motor (with batteries) to get off the ground
and occassionaly cruise between thermals.

So most of the time you are just charging the batteries.


--
Jim Pennino

Remove .spam.sux to reply.

On Tue, 7 Aug 2007 16:12:16 -0500, "Gig 601XL Builder"
wrDOTgiaconaATsuddenlink.net wrote in
:

Here is a 100hp electric motor. I don't know if it is typical for an
electric motor but damn the thing weighs over half a ton. I might make the
601XL a little nose heavy. But it's priced right up there with a Lyc of
equal power.

http://www.baldor.com/products/detai...neralPur pose

Catalog Number: D50100P
Description: STOCK MOTOR,368AT,100HP,1750/2000RPM,DPFG
Ship Weight: 1,118 lbs.
List Price: $21,195
Multiplier Symbol: N2


Right. Those are the type I used to install in the early '70; that
was about forty years ago. Today the situation is a bit different.

Here's a small electric motor manufactured by the same fellow, Bob
Boucher, who designed the Sonex motor:


http://www.astroflight.com/store/sto...y3CKHwWtA02470

Cobalt 90 Direct Drive Motor
Cobalt 90 Direct Drive Motor, 30 to 40 cells, 1500W

Astro 90 Cobalt Motor p/n 690
Model No. p/n 690
Name 90 Cobalt
Armature Winding 10 turns
Armature Resistance 0.111 ohms
Magnet Type Sm Cobalt
Bearings Ball Bearings
Motor Speed /volt 256 rpm/volt
Motor Torque/amp 5.3 in-oz /amp
Voltage Range 24 to 48 volts
No Load Currrent 3 amps
Maximum Continuous Current 35 amps
Maximum Continuous Power 1200 watts
Motor Length 3.7 inches
Motor Diameter 2.1 inches
Motor Shaft Diameter 0.25 inches
Prop Shaft Diameter 5/16 inch
Motor Weight 32 oz


Expected Performance of Cobalt 90
Battery Prop Amps Watts Rpm
36 Nicads 14x7 20 amps 800 watts 9,000 rpm
36 Nicads 14x10 25 amps 1000 watts 8,500 pm
36 Nicads 15x10 30 amps 1200 watts 8,000 rpm
36 Nicads 16x10 35 amps 1400 watts 7,500 rpm


This is a small motor, as you can see, but it uses ~1,500 watts, so at
720 watts per horsepower, that's about two horsepower, and it weighs
32 oz, or about two pounds. That works out to about one horsepower
per pound for this type of motor. I have no idea if a one hundred
horsepower motor of this type would weigh 100 lbs or not, but it seems
reasonable.

On Tue, 07 Aug 2007 14:34:36 -0700, wrote in
. com:

If the ability to get off the
ground were the sole criteria we are there already but practical
flight characteristics for mass consumption are way down the road.

Of course. But it seems it's getting closer all the time.