taxi in reverse?

"James M. Knox" wrote in message ...
I always figured if I was building a homebuilt I would investigate some
relatively small motor/brake assemblies that are used on smaller electric
automobiles. May be WAY too heavy, but they make great brakes that don't
fade with heat ... *AND* you could just taxi out of the hangar (before
starting the engine).

My first thought when reading this was, "sounds cool!". And I started
to think it through. The motor part is clear enough, you can taxi
with electric power and not with the engine power. That'd lead to a
real difference in taxiing of course. You can't use engine power to
bring the rudder around for example. But this is workable, it just
becomes part of this plane's checkout procedure.

In the brake mode though, there's a problem. Either the motor/brakes
now work as generators or as motors in reverse. If the first, where
you put the power that's generated? Your battery's been charging off
the engine, it's already full and not drawing current. Your braking
power is directly related to the power you can cause to be used up on
something else. I imagine you can make your landing light really
bright or something... grin

The generator mode makes more sense in a hybrid aircraft, like hybrid
cars with regenerative brakes. But the problem with this is that
lightweight high-capacity batteries are not yet available.

If the brakes are operating as motors in reverse that solves the
generator problem. But it creates a new one. What happens if your
battery or electrical system dies? No brakes. But if you've got the
power, you should be able to get more braking from reversed electric
motors than current braking systems. Current braking systems convert
momentum to heat. Their braking capacity is directly releated to
their limit in heat capacity. Electrical reversed motors would have a
heat limitation, but the initial limiting factor would be the power
input.

Fun idea!

-Malcolm Teas

(Malcolm Teas) wrote in
om:

"James M. Knox" wrote in message
I always figured if I was building a homebuilt I would investigate
some relatively small motor/brake assemblies that are used on smaller
electric automobiles.

My first thought when reading this was, "sounds cool!". And I started
to think it through.

All true. Of course, I was thinking primarily in terms of taxiing only a
short distance - into or out of a hangar, for example. I haven't done the
brake calculations, but I *think* (back of the hand calculations) that the
amount of power generated stopping the plane on the runway and taxiing in
is small enough that even a "fully charged" battery can easily absorb it.

Mostly just amusing and idle speculation... But I've seen some cold rainy
days when it would sure be nice to preflight in the hangar, climb in, and
just drive out. G

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"James M. Knox" wrote:

Mostly just amusing and idle speculation... But I've seen some cold rainy
days when it would sure be nice to preflight in the hangar, climb in, and
just drive out. G

So, build a steel frame which supports the wheels of the plane. Put that frame on
wheels. Use a garage door opener to move it in and out of the hangar.

George Patterson
Love, n.: A form of temporary insanity afflicting the young. It is curable
either by marriage or by removal of the afflicted from the circumstances
under which he incurred the condition. It is sometimes fatal, but more
often to the physician than to the patient.

You can put a small winch at the back of the hangar to pull
you in, but yes, you must get out to attach it.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Shortly after I first got my ticket, I took my wife and kids to see family
in a 172. At the other airport, we were told to back up to a fence. So, I
shut down and pushed the plane into place.

My wife was furious about something as we walked thru the terminal to meet
family...finally she blurts out "I've never been so embarassed in my life!
I'm not going anywhere with you again until you learn to use the reverse."


"David Lesher" wrote in message
...

You can put a small winch at the back of the hangar to pull
you in, but yes, you must get out to attach it.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

That's funny!

--
Dan D.



..
"Boogerz" wrote in message ...
Shortly after I first got my ticket, I took my wife and kids to see family
in a 172. At the other airport, we were told to back up to a fence. So, I
shut down and pushed the plane into place.

My wife was furious about something as we walked thru the terminal to meet
family...finally she blurts out "I've never been so embarassed in my life!
I'm not going anywhere with you again until you learn to use the reverse."


"David Lesher" wrote in message
...

You can put a small winch at the back of the hangar to pull
you in, but yes, you must get out to attach it.
--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

Mostly just amusing and idle speculation... But I've seen some cold rainy
days when it would sure be nice to preflight in the hangar, climb in, and
just drive out. G

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

Two things: 1. Some hangars have slightly slanted floors such that
when the chocks are removed, the airplane wants to roll out. They
have to be winched in of course but lots of hangars have winches to
reel the airplane in without a slanted floor.

2. If it's cold and rainy, you're flying? ;-)

Corky Scott

Thats a cool idea even if it goes counter to the homebuilt creed "Keep
it simple stupid." Maybe you compromise on the brake function,
keeping your brakes on the mains, and put the motor on the castering
nose gear. Steer like usual with differential braking.

That might be a lot of juice stopping a 1,000 lb airplane from 60mph
to 0 in 10 seconds. Loads are easy though, you don't have to dump
that power into your battery. Think of it the other way around, how
much power would you need to accelerate 1,000lb to 60MPH in 10
seconds?

Modern jet fighters dump waste heat from the hydraulic system into
their wing tanks. Worst case scenario, heavy manuvering on low tanks.



"James M. Knox" wrote in message ...
(Malcolm Teas) wrote in
om:

"James M. Knox" wrote in message
I always figured if I was building a homebuilt I would investigate
some relatively small motor/brake assemblies that are used on smaller
electric automobiles.

My first thought when reading this was, "sounds cool!". And I started
to think it through.

All true. Of course, I was thinking primarily in terms of taxiing only a
short distance - into or out of a hangar, for example. I haven't done the
brake calculations, but I *think* (back of the hand calculations) that the
amount of power generated stopping the plane on the runway and taxiing in
is small enough that even a "fully charged" battery can easily absorb it.

Mostly just amusing and idle speculation... But I've seen some cold rainy
days when it would sure be nice to preflight in the hangar, climb in, and
just drive out. G

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------

"James M. Knox" wrote in message I haven't done the
brake calculations, but I *think* (back of the hand calculations) that the
amount of power generated stopping the plane on the runway and taxiing in
is small enough that even a "fully charged" battery can easily absorb it.

The electric motor on my hybrid car is 6 cm thick and the diameter is larger
than some homebuilts' tires. It's rated for 10 hp and it's hooked into a 144
volt battery which weighs more than I do. The motor goes into regenerative
mode for braking. It recharges the battery in quick order, but it doesn't
stop the 2800 pound car very well. Based on this, I'm inclined to think that
you will still need traditional brakes.

D.

What one should use is to replace the front weel hub wtih a hub-motor
http://www.goldenmotor.com/ .
I am sure that this would not add that much weight and if the hub-motor is
selected corectly, the original tyre used, one could not distinguish it form
original.
Now, I wander if this could be installed on a certified aicraft with some
field approval as a minor modification...

"James M. Knox" wrote in message
...
(Malcolm Teas) wrote in
om:

"James M. Knox" wrote in message
I always figured if I was building a homebuilt I would investigate
some relatively small motor/brake assemblies that are used on smaller
electric automobiles.

My first thought when reading this was, "sounds cool!". And I started
to think it through.

All true. Of course, I was thinking primarily in terms of taxiing only a
short distance - into or out of a hangar, for example. I haven't done the
brake calculations, but I *think* (back of the hand calculations) that the
amount of power generated stopping the plane on the runway and taxiing in
is small enough that even a "fully charged" battery can easily absorb it.

Mostly just amusing and idle speculation... But I've seen some cold rainy
days when it would sure be nice to preflight in the hangar, climb in, and
just drive out. G

-----------------------------------------------
James M. Knox
TriSoft ph 512-385-0316
1109-A Shady Lane fax 512-366-4331
Austin, Tx 78721
-----------------------------------------------