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Conversion to other fuel bases isn't worth the effort in my estimation.
Either sell them off and apply the money toward electric/gasoline
motor/engines, or put them in storage and switch to electric or gasoline for
flying.
Some of the new 26 and 40cc SPE conversions are inexpensive and are small
enough to fly 1.20 - 1.40 glow power designed models with little to no
conversion. Good luck.
Ed Cregger
Firstly, thanks for all the replies so far, folks.
Ed Cregger wrote:
I'm wondering if there is some way of using butane/propane and adding
oil somehow?
It's their main domestic fuel there.
Another thought was compressed air (!). I can get steel hydraulic tube
certified to 300Bar (about 4000psi?). I have a 200bar stirrup pump for
my precharged air rifle but usually people just fill diving cylinders
for filling their rifles.
Before anyone comments: Yes I am aware that crashing a small cylinder
pressurised to 200Bar might have interesting results....!
I have seen working free-flight planes using a plastic drinks bottle as
the air reservoir, the engine was some small glow with a bicycle
schraeder valve substituted at the top.
Makes one think the same should be feasible with a much higher pressure
supply and a bigger engine...
I can convert a strimmer/weedwacker or chainsaw engine for the camera
plane.
The Azores are pretty lush and everybody needs them so they are widely
available.
The main problem will be getting rid of vibration, as we hope to shoot
broadcast quality.
On 26 Oct 2006 11:23:28 -0700, snipped-for-privacy@digiverse.net wrote in
There are tiny C02 indoor planes.
In principle, you could probably construct an
air-driven engine of any size. Inject a little
oil in the air stream and off you go.
You might be able to do the calculations to see
how much air it would take to turn a .46-size
engine at (say) 11,000 RPM for 8 minutes. Looks
to me like it's all multiplication. Put a one
way valve in the top to hold the pressure
for compression, release it for the upstroke.
Figure how many degrees the input valve had to
be open for and rig a little cam of some sort.
My guess is that the weight of the bottle that
can carry the pressure to drive that much air
to turn a reasonable prop at a satisfactory
RPM is going to be a LOT higher than a battery
and an electric motor.
Marty
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Not necessarily, the air cylinder for my pcp rifle doesn't weigh much
at all and can hold over 200 Bar of pressure. Incidentally, they make
carbon fibre scuba tanks that can take 300 bar now.
Any engine specifically adapted for compressed air doesn't need cooling
fins either. The valve is simply operated by the piston by fitting it
where the glow would go. The amount of air going in each stroke can be
tuned by screwing the valve in or out and the throttle valve would be
real simple too.
The only model engines I know of that run on butane or propane are
turbines.
Theoretically, you should be able to configure a small piston engine to
run on compressed natural gas or propane. The question is whether you
would be able to find a pressure regulator small enough to fit in the
airplane. The regulators on the old butane powered tractors we used to
run when I was a kid were rather large. Even if you could find or make
a small enough pressure regulator you'd still have a lot of extra weight
because in addition to that you would still have to carry an ignition
system. It would be great to have the option if you were flying big
slow models, though.
Probably so. It's not a particularly trick technology. You could look
around and see if anybody has invented a micro gas regulator in the 60
years since it was popular to run equipment on propane.
Thinking about it, there are quite a few LPG vehicles around right now,
in GB:
http://tinyurl.com/yxzshw
It sure would be a lot easier to get hold of for modellers, though one
downside (and upside: no clunk) is a pressurised tank and potential
leaks. I can imagine quite a few mishaps with stored models leaking gas.
Couldn't you use a soda bottle? They hold lots of pressure. If you
could come up with a decent regulator in a small size, you'd have your
problem half solved.
Folks have used soda bottles as reservoirs for
retracts.
I've seen pix of planes torn apart when the
bottles failed.
If someone goes down that road, they sould probably
reinforce the bottle with a layer or two of fiberglass,
depending on the nature of their design and their
target pressures.
Overfilling happens. People should anticipate
human mstikaes and (within the limits set by
aerodynamics) built for some worst-case scenarios.
Marty
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You'd have to add oil, and you would have to come up with a way to vary
the amount of gas for throttling as well as attach it to the engine
intake. Seems like you could use a needle valve to get the oil right
into the intake stream easily enough.
This project is starting to sound like something that would require
about a year of experimenting in a well-appointed shop. If I wasn't
trying to start an amplifier company I might do it myself.
I think it would be simpler to just get a spark conversion kit for glow
engines, like these:
http://www.westonuk.co.uk/index_205.htm
http://www.nelsonhobby.com/prospark.html
Actually, since I do have a machine shop and a bit of electronics
savvy, I could just make a batch of them for all the glows I want to
use.
It would be easier if someone happens to already know of a DIY circuit
diagram for an ignition circuit. I could program PIC processors etc but
why re-invent the wheel.
Or I could just vandalise the latest cheap Ryobi PLT - 2543Y 25cc
strimmer:
"Powerful, 25cc 2-stroke Line Trimmer with diaphragm carburettor for
effective working at any angle. Maintenance-free electronic ignition."
I've converted several of the 18 and 25 cc Featherlite leaf blower
engines and they work wonderfully.Vibration is not bad but yuo can soft
mount the engine and get it even lower. I've had nothing but good
results with the Featherlite engines and they are dirt cheap.
snipped-for-privacy@digiverse.net wrote:
I'm going to suggest diesel if you like wet fuel or electric if you
don't. I've had nothing but praise for my MVVS diesels! The fuel is
easy to make and cheap and plenty of formulas are on the web to make
your own. If the diesel fuel is a problem, I'm going to suggest
gasoline. I've been able to hush them up pretty well! I suppose what
you are flying makes a difference as to your power requirements.
Try a diesel. I think you will be happy. Plus, diesel packs far far
more BTU than glow fuel or gasoline so you get by with a smaller tank,
etc.
snipped-for-privacy@digiverse.net wrote:
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