Question. Aren't you tired of having to deal with fuel? Are you tired
of charging batteries that last all of ten minutes? I know I am. I'm
really tired of spending 160 dollars on a brand new engine and then
killing it on the first flight. I tried electric power too, but like I
said, it just doesn't last. So I was watching TV and saw some comercial
for AirHogs. I was thinking about it for a little while, what if you
were to have I really high pressure reservoir on a small rc airplane?
Is that possible? Could you, in theory even, have a longer flight time?
I suppose it would be dependent upon the pressure and size of the
reservoir, but does anyone else think that this persuit is worth
investigating thoroughly? I've already looked online (Google of course,
LOL) and I didn't find anything like it. I found alot of stuff on steam
engines, I'd think that it'd be about the same concept, right? And I
just figured that another pro to the idea is that engine weight would
be cut way down. I think total weight could be cut as well, maybe using
a carbon fiber reservoir. Anyone comment if you have any input, please!
Thanks, however it seems that size is a huge issue as far as this
concept is concerned. I was just wondering if it worth looking into.
I'm actually won over now on the idea of making an all-terrain flight
vehicle (basically one that can go on land, water, and air) like to one
in another post. Pretty cool! Alright thanks for the feedback.
Have fun and let us know how it turns out.
From your previous post, I guess you're planning to
use light composite materials. They should be safe.
Some folks done blowed up their own scale models
by over-pressurizing their air reservoirs for their
landing gear, if I remember correctly. And I seem to
misremember that some auto mechanics have been
killed or injured by over-pressurizing tires.
There's probably some law of nature that says anything
risky enough to be fun is going to kill and maim a few
people along the way.
Ummm... Stormburger? It might help if we narrow the catagories down a bit.
1. Endurance: Best choice would be a lighter than air aircraft. A
sailplane (can you say air powered) or solarplane under the right conditions
can stay up a very long time too.
2. Fuel costs: Sailplane best, standard electric second, gas third, Solid
3. Performance: Solid rocket is the best, "glow" and high grade electric are
a close second.
4. Reliability: Standard Electric, mostly solid state, period, full stop.
5. Convenience: Standard (<=4 foot) electric with a cigarette lighter
So unless we add categories for messy/smelly/inconvenience, the "glow" form
of propulsion isn't the best at anything ;)
There are of course other propulsion systems, but these are widely available
and largely affordable.
< It might help if we narrow the catagories down a bit.>
Very good points!
ah, we can always change the criteria to fit our view
I started with a sail plane (Ace High) and never made it do well, might try
again. Slope soaring sounds fun.
I play with electrics some, but for cheap(I'm a fry cok) and vert. and love
the smell, It's glow for me.(for now)
You forgot to very important categories. Endurance and return to flight
time. In both a fuel burning engine is by far the winner. That said,
when it comes to small planes in the 16 oz or less, there is no beating
electric IMO. I have a 4 OZ plane with a 2 cell LiPolly that will run
for 30 min or more easy. Not a 3D plane obviously.
I think that you'd find it dissapointing. Keep in mind that an AirHog
only has a 1 minute motor run, and it falls out of the sky before the
propellor stops (that doesn't keep it from being a fun little plane).
The basic problem is the energy density of a tank of compressed air vs.
batteries or fuel. Fuel is best, particularly since the oxidizer comes
from the air. Batteries are gaining, but they aren't there yet. You'd
need a magic material to contain that much energy in compressed gas.
Frankly, if compressed air were the way to go I don't think the auto
manufacturers would be dinking around with gasoline.
Steam engines are different. The engine itself is just a compressed gas
heat engine, but the compressed gas comes from boiling water. CO2
engines are basically steam engines, with boiling -- if you don't keep
that CO2 tank hot they won't work right. Scaling a CO2 engine would run
into problems of flow vs. tank area -- I wonder if anyone's tried it?
What is the best way to incorporate electric power? Basically, my
problem is this:
I bought a trainer airplane last may. .40 size engine, just a simply
amazing plane. I can't remember who it was made by, but anyways I was
landing it when the engine came loose on landing. Needless to say, I've
never seen an investment go up in smoke so fast. Anyways, the plane was
totalled, except for the radio system and three servos. So, up in the
attic I have the carcass sitting. The calm winds here are beckoning me-
and my AMA license is up. I feel the need to fly and quick. I want to
stay away from gas (or nitro) and I'm looking for a small wingspan
(less than 3 feet). The other plane was a kit, and this time I want to
make it myself. Balsa probably- you know the drill. But before I go on,
my radio system is standard size. I'm on a slim budget, but it seems
that all i need is a propulsion system that's cheap and reliable and
wont come apart and chop my next plane into a billilion pieces. Does
anyone have any ideas? If it's going to be an indoor flyer (which is
what I'd like) or a really compact park flyer, what's the best way to
go as far as electric? Li-ion, Ni-Cad, or what kind of batteries? What
things are needed? Any links would be great! Thank you all so much,
this is the best group that I've ever found. Thanks again.
Let me say first that I don't know why you are so set against glow
engines, I have used them a lot and have never had one come off the
plane. Even in a crash the firewall broke off but the engine was still
If you want small indoor plane this is what I would suggest. First in
my opinion any electric plane over say 16 oz is stupid if you are going
to go bigger than that you will spend way too much on batteries and
expensive motors and ESCs. Ok here is a plane I have a beginner could
have fun with.
if that link doesn't work try this
then click on the "Backyard & Park Flyers" link then "Our Classic
StarLITE Backyard Flyer" link.
This plane is amazingly easy to build. I recommend using yellow wood
glue over CA though. Sanding the joints on the small delicate wood will
be very hard if you use CA.
A DC5-2.4 gear motor from here.
You can find it other places too.
Also a 23cm x 12cm carbon prop from
you can find a much cheaper plastic prop of the same size that will
probably help move the CG forward.
The recommended HF100 ESC is kind of expensive you can find it here
A GWS 4-Channel Pico Receiver is is a cheap and very light (4 grams)
just keep in mind it has a very limited range(1000ft max), but that
shouldn't be a problem on an indoor plane like this one. You can find
one for Futaba or JR transmitter here
I use a 320mAh 2 cell LiPoly battery and it runs forever on that
battery, you can use a smaller pack but that makes it harder to keep the
CG far enough forward.
Finish it off with two Hitec HS-50 or similar servos, they can be found
lots of places.
One last thing, the plane comes with a tissue paper covering material.
I have read about how to use that apply that stuff, it's not something I
want to try. Standard plastic heat activated covering materials are too
heavy but there is some really lite stuff that is similar. It's called
Nelson LiteFilm or solite. Be warned though there are some head aches
when working with this stuff.
First it is very hard to get the backing to peal off. One thing that
helps is a small piece of tape on both the backing and covering in a
corner. Rub the tape on really good and carefully pull it apart. Be
careful not to get the tape stuck to it's self though. Once you do get
the backing off the stuff will tend to try and fold and end up sticking
to it's self. Once it does this it is pretty much impossible to pull
apart so you have lost the piece. Just be careful and practice on some
This stuff will shrink like crazy with a little heat. You may think
that is great and will help pull out wrinkles, well it does do that but
it will shrink so much and so tight that it can bend or even break the
balsa structure. So be careful to get it stuck down with a minimum of
wrinkles before you start to shrink it. Also note that the selection
and colors aren't near as nice as what you can get with the standard
covering like monokoat.
Here is one place you can order it from
If you later want to upgrade, you can make a new wing with ailerons and
a 3rd servo or upgrade to a brushless motor. The ailerons may require a
little bigger motor. They have a few brushless small enough for this
plane now but they didn't when I built it.
I would be willing to bet a very large sum of money that batteries will
never catch fuel, or even come close.
Storing lots of energy in compressed gas isn't hard, it's containing the
required pressure that makes it impractical. I have heard that it is a
good way to store small amounts of energy that you want to use quickly.
For example hydrostatic breaking pressurizing and accumulator and then
using that pressure to re accelerate the vehicle from a stop to reduce
the load on the engine. IMO that has far more potential that electric
I have heard a very high tech twist on a very old method of storing
energy. The fly wheel. A guy has discovered that if you spin a fly
wheel at ridiculously high rpm in a vacuum, riding on magnetic bearings,
you can store more energy than batteries and the "self discharge" rate
is not bad at all. Another advantage it has, is it can be recharged
very very fast and almost an unlimited number of times. Also it runs in
very hot conditions much better than batteries. Of course there are
down sides. The magnetic bearings are much harder to implement in a
dynamic application such as a car or plane. Also the speeds required to
store lots of energy are so high that the fly wheels have been known to
self destruct from the centripetal acceleration. For that reason they
have to be inside a heavy shell that will contain the fragments that
will be moving faster than a bullet from a hand gun. One application
where they work great though I have heard is for battery backup of
telcom switching stations in Mexico. It seems the climate is so hot
that batteries don't last very long in either run time or number of
charge cycles. But that heat doesn't bother these things at all. Ok
that's enough rambling.
I'll take that bet. Say, $1,000,000? Forget about "come close." Let's
just make it "surpass" (and you even get to define what that means).
My business associates who will cover the bet don't know anything about
technology. But they understand that their million is safe until the
end of time, while your million is at risk from a breakthrough in
battery technology (or even continuous improvement) any time between now
and then. They find those probabilities acceptable.
It seems to me (all things being equal) that the spinning
flywheel would act like a gyroscope in a dynamic application
and would resist any motion acting against the plane of
If you put the flywheel in a gimballed cage (like a gyroscope),
then you have the problem of getting the power back out
of the flywheel. How many degrees of freedom can you
let the cage have?
Fun stuff to think about ...
| It seems to me (all things being equal) that the spinning
| flywheel would act like a gyroscope in a dynamic application
| and would resist any motion acting against the plane of
| its momentum.
Couldn't you have two identical gyroscopes, rotating in opposite
directions at the same rate next to each other? I believe that would
take care of most (but not all) of the gyroscopic effects on the
vehicle it's in.
Of course, you'd still have the problem of the massive forces being
put on whatever bearings are used whenever the vehicle rotates
| If you put the flywheel in a gimballed cage (like a gyroscope),
| then you have the problem of getting the power back out
| of the flywheel.
I doubt that would be overly difficult. You could put a generator
inside the gimballed contraption, and use brushes to get the power
out. Or put magnets in the gyroscope itself, and put lots of
electromagnets around the gimballed enclosure and then you could use
the whole thing like one big brushless motor -- but with two
dimensions of movement rather than one. Could be a very interesting
| How many degrees of freedom can you let the cage have?
How many you got?
| Fun stuff to think about ...
Indeed. But for my R/C planes, for now, I think I'll stick with glow
fuel, batteries, and good old fashioned lift, both slope and thermal.
As time goes on, it seems to be less and less of the first, and more
of the rest, but so be it.
The gyroscopic effects we se in planes aren't that strong, but
helicopters are another matter entirely ...
Doug McLaren, email@example.com
Magenta: I ask for nothing!
On Sat, 18 Jun 2005 20:02:41 GMT, firstname.lastname@example.org (Doug McLaren) wrote:
I think that is the big issue.
The clever thing about the design is the frictionless, magnetic
The hard part in a vehicle in motion is how strong the magnetic
fields would have to be to resist gyroscopic precession of the
OK. If you can work out the gimbles and let the cages
move as needed, maybe it CAN go in a car or airplane.
I think you need 6--but two gimbles should do 3 each.
I'm using glow and gasoline these days. One little electric
helicopter, but it hardly counts.
You know, there are actually patents for this sort of thing. Every couple
of years somebody comes up with the clever idea of using flywheel storage
for spacecraft batteries. The theory is that you can combine the batteries
with the spacecraft's momentum wheels to come up with a lighter combined
solution. And spacecraft designers are willing to spend millions of
dollars to develop a clever idea.
AFAIK, the numbers never worked out, though - the energy storage density
wasn't significantly better than the NiH2 batteries that spacecraft were
using (and still are), and spacecraft are migrating to Lithium Ion
batteries because they're considerably more efficient than NiH2 so maybe
the flywheel idea will stop coming up. The Li+ batteries that spacecraft
are going to are basically the same technology that we put in our little
electric planes. If spacecraft designers using tailored-carbon-fiber
flywheels couldn't beat the batteries we put in our electric planes . . .
Another company spent a fair amount of money developing the flywheel energy
storage concept for cars. I know the company isn't around anymore, and you
don't see them advertised on TV, but I don't know the whole story. They
had some really bright people, though.
"There are two types of people: those who can be sorted into one of two
types, and those who can't."
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