Boeing's Electric Taxi Motor

wrote:
It's probably some kind of ultra high voltage DC pancake motor that
would require it's own special APU to power it. It would have to
develope on the order of three to four hundred horsepower to be able to
reliably move a fully loaded jet around under all the taxi conditions
that a jet might see. In addition it would either have to be able to
spool up at a fast enough rate as to not rip the nose gear tires off
the rims on landing or be disconnected from the nose wheels on landing.

I was pondering a similar question earlier this week as I watched
gasoline prices increase.
The conversion from horsepower to kilowatts is 1:0.75, so a 400 hp
engine is 300 kw.
I was curious as to how large a 300 kw motor is and how massive the
power cables are to provide the requisite voltage and current.
1000 V and 300 A?
How much energy is lost to heating?
How does one reduce this heating loss?
How many kw does it take to start a given mass moving?
I am guessing there is an initial surge current, followed by reduction
in current once the mass is in motion and to keep it moving.

john smith wrote:
I was pondering a similar question earlier this week as I watched
gasoline prices increase.
The conversion from horsepower to kilowatts is 1:0.75, so a 400 hp
engine is 300 kw.
I was curious as to how large a 300 kw motor is and how massive the
power cables are to provide the requisite voltage and current.
1000 V and 300 A?
How much energy is lost to heating?
How does one reduce this heating loss?
How many kw does it take to start a given mass moving?
I am guessing there is an initial surge current, followed by reduction
in current once the mass is in motion and to keep it moving.

To give you a couple of size references, we had a 25 hp DC motor that
was set to move a carriage that could weigh as much as 1500 pounds up
and down a column. The engineering requirement was for the motor to be
able to accelerate the carriage from a stop to the furthermost position
(12 feet up)in something under 4 seconds and the placement be within
..1". The power was provided by a high voltage DC unit producing 900 VDC
and up to 100 amps current. The motor case was about 10" in diameter
and about 20" long and weighed over 75 pounds. The power supply was a
little bigger than a 21" monitor but required 220/3Phase to operate.

An air compressor that I used to run had a 1750 hp open frame motor
for the main drive. It was 10 feet in diameter and 3 feet thick. It
took a special 1700 VAC/3P feed and took nearly 2 minutes to come up to
steadystate speed.

What they are going to find in the end, is that putting some kind of
electric taxi system on the individual aircraft is going to backfire
and cost them seat and cargo capacity that outweighs the supposed saved
fuel costs.

Craig C.

wrote

What they are going to find in the end, is that putting some kind of
electric taxi system on the individual aircraft is going to backfire
and cost them seat and cargo capacity that outweighs the supposed saved
fuel costs.

I suspect that the electric taxi concept is to be used in precision taxi
movements, and pushbacks, to avoid jet blast issues. I don't think that
they would plan on doing long distance and/or higher speed taxi movements.
Smaller motors with much gearing could mean a pretty small unit, and wires.
It would mean that they could delay engine start, and also shut down
earlier. The APU will already be running anyway, right?

Unless someone knows more than has been mentioned here, all we are doing is
speculating on the configuration, and use. What results is bound to be a
WAG.

The whole idea of Boeing's new generation of planes, is to use the jet
engines for propulsion; only, and eliminate bleed air being used for a
bazillion other uses, thus stealing thrust and efficiency. It makes great
sense to me. It boggles my mind to see how much bleed air is used to run an
air cycle machines.
--
Jim in NC

wrote:

What they are going to find in the end, is that putting some kind of
electric taxi system on the individual aircraft is going to backfire
and cost them seat and cargo capacity that outweighs the supposed saved
fuel costs.

Silly Boeing, paying all those engineers, when the answer is freely
available on Usenet. ;-)
--
Alex -- Replace "nospam" with "mail" to reply by email. Checked infrequently.

And those of us on usenet seeing a possible breakthrough in engineering
technology saying, "why the hell did I spend all that time in engineering
school when these uninformed idiots comparing 1950s technology on usenet
have all the answers".

Jim


"alexy" wrote in message
...
wrote:


Silly Boeing, paying all those engineers, when the answer is freely
available on Usenet. ;-)

Well, if you went to school in the 50's, that was the current technology
then, so that is what you were taught. Some might say, old habits die hard!

RST Engineering wrote:
And those of us on usenet seeing a possible breakthrough in engineering
technology saying, "why the hell did I spend all that time in engineering
school when these uninformed idiots comparing 1950s technology on usenet
have all the answers".

wrote:
Silly Boeing, paying all those engineers, when the answer is freely
available on Usenet. ;-)

RST Engineering wrote:
And those of us on usenet seeing a possible breakthrough in engineering
technology saying, "why the hell did I spend all that time in engineering
school when these uninformed idiots comparing 1950s technology on usenet
have all the answers".



I'm not dissing their breakthrough on motor technology at all.

What I see from their publicly released design information is a system
that will add at least several hundred pounds of weight to the aircraft
and add significant maintenance problems to the gear as well as makeing
it even more complicated than the nose gear of the B-58 and the mains
on the F-111. Fixing the drive motor within the fuselage and then
having to transmitt the energy from there to the landing gear, down
the gear leg itself and then tee it to both wheels really drives up the
complexity. The test rig is a giant strap on box hanging off of the
back of the gear and uses belt drive to power one wheel. Even they
admit that they encountered significant engineering problems with the
test rig and the 767.

One of the things they don't seem to address anywhere is how or if they
are going to decouple the drive system for takeoff and landings. Also,
there is no mention of the actual speeds accomplished with the system.

When they get their motor package down the the point where it can be
mounted within the front wheel assmeblies and keep the installed weight
under a couple of hundred pounds and be able to taxi the bird at
10-15mph for several miles, then they will have a really viable product
that will have everyone clamoring for it.

BTW..Lufthansa tried a program for a number of years where the tugs
supplied motion to the aircraft as well as airconditioning and
eletrical power. The aircraft were towed ammost all the way to the hold
line prior to engine start. If I remember right, what they saved in
fuel and engine time costs was surpassed by labor and turn around time
costs and they dropped the program.

Craig C.

On 19 Aug 2005 15:41:47 -0700, wrote in
.com::

Fixing the drive motor within the fuselage and then
having to transmitt the energy from there to the landing gear, down
the gear leg itself and then tee it to both wheels really drives up the
complexity.

If this is the system Boeing is installing:

http://www.wheeltug.gi/technology.php
http://www.chorusmotors.gi/technology/

What makes you think the motor will be installed within the fuselage?

Larry Dighera wrote:
On 19 Aug 2005 15:41:47 -0700, wrote in
.com::

Fixing the drive motor within the fuselage and then
having to transmitt the energy from there to the landing gear, down
the gear leg itself and then tee it to both wheels really drives up the
complexity.

If this is the system Boeing is installing:

http://www.wheeltug.gi/technology.php
http://www.chorusmotors.gi/technology/

What makes you think the motor will be installed within the fuselage?

By what they have released to the press, such as the following:

http://www.flightinternational.com/A...oeing+767.html

I'm not sure how to make it a hotlink from the browser and system that
I'm using right now, but you should be able to copy and get to the
article, mainly the last paragraph.

Craig C.

wrote:
It's probably some kind of ultra high voltage DC pancake motor

No, the Chorus motors are far from being DC. They use phase manipulation
to get substantially higher torque (than traditional technologies) at low
speeds. Taxiing seems like a very good fit.

--kyler