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Old Nov 09, 2001, 03:36 PM
VequalsIR is offline
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Co2 slowfly nearly ready


Maiden should be on Sunday.

Hope there's enough power; the motor's a Gasparin 160rv and tha AUW is 4.25 oz.

Steve
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Old Nov 09, 2001, 03:38 PM
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Close-up of throttle arrangement



Steve
Old Nov 09, 2001, 03:50 PM
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VequalsIR
Nice plane-How bout some specs ws,fuse length, etc
and I'd like to ask some questions I've always been facinated with those co2 motors
1. What e-motor would you gasparin 160 compare to a 280? probably smaller huh?
2. Can you turn the prop around ie pusher, and can you use a regular prop or do you have send to Europe for them?
3. Flight times?
4. fast-slow?
5. Any areobatics?
Thomas
Old Nov 09, 2001, 03:54 PM
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One more. I've noticed(reading catalogs) that you can adjust power on some co2 motors buy turning the cylinder head(increase the intake timing?) is that was your disc is for or is it a regular throtle. thanks for the nice pics.
Thomas
Old Nov 09, 2001, 04:02 PM
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Hi Thomas

I hope to answer these questions on Sunday; if it works-out, that is.

The prop. is about 7x6 and the 160 should turn it OK up to 3000rpm.
These Co2 motors are happy to run in reverse- no problem.
Run-time- I'm hoping for a couple of minutes- land- quick refill and back in the air!

Most Co2 are throttled by screwing the whole cylinder up-and-down. On the RV it's just the cylinder-head.
Throttle control on my set-up is incredible. It's just a ply-plate cyano'd to the head.

Weather conditions affect power-output a fair bit and you can't fly inverted with liquid Co2 in the tank


The model is a scaled-up rubber-job 30" span

Steve
Last edited by VequalsIR; Nov 09, 2001 at 04:20 PM.
Old Nov 09, 2001, 04:30 PM
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Steve
Thanks go get'em sunday!
Thomas
Old Nov 09, 2001, 04:35 PM
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eschew obfuscation
That's a pretty big CO2 bottle you're hauling there. You'll have flight durations longer than your transmitter batteries will last! ;-)
Old Nov 10, 2001, 02:36 PM
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These Co2 motors are real torque machines! I've just tried a run across the living-room carpet; the 7x6 was pathetic- a 9" rubber prop. had it accelerating quite briskly.

..........A bit more confident for tomorrow's maiden.



Steve
Old Nov 11, 2001, 02:09 PM
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Flight Report


YES...........it flew very nicely but the duration was lacking. The perforformance improved throughout the day as the hall warmed up.
A 9" 3-blade Co2 prop. was found to be the best- giving a 2min. flight.
There was about a minute with loads of power followed by a 30sec. cruise and a 30sec struggle.

The enlarged rubber design- the 'Meda', by Jerry Johnson, handled superbly.

The consensus of opinion suggested that the model needs to be made 1oz. lighter and that more experiment is needed with props.

Then a 3 - 4 miinute flight should be achievable- which would make it practical slow-flyer.

Steve
Old Nov 11, 2001, 02:57 PM
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Quote:
Originally posted by VequalsIR
I'm hoping for a couple of minutes- land- quick refill and back in the air!
Steve, it may help to let the tank warm up (bit like an electric motor cooling down between flights ). On my free-flight model the tank frosts up as it empties, and if I do lots of flights in quick succession the power declines.
Last edited by Bill Glover; Nov 11, 2001 at 03:04 PM.
Old Nov 12, 2001, 09:50 AM
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Spot-on Bill...........It was best to leave it a few minutes between each flight.



Steve
Old Nov 12, 2001, 01:04 PM
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Pardon me guys cuz I don't really know much about co2 motors.
I had thought I had read that if you fill the tank with co2 then dump it immeadiatly and then fill it up you can cram more gas in.
In the same artical they were talking about some guys in competion storeing thier tanks in dry ice to get that extra edge and that being made illegal although you could use regular ice water.
I believe in the same artical they were saying that a heat sink on the fuel line right before entry into the cylinder head to bleed off some cold or more likely add some extra energy to the expansion in the cylinder.
Again I really don't know much about this stuff other than what I've read and I'll look through my bookmarks to see if I can find that artical(might take awhile)
Thomas
Old Nov 13, 2001, 04:49 AM
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I guess that the colder the tank is, the more liquid CO2 (rather than gas) you can get in ... so longer run time. But once you've filled the tank, the colder it is the lower the pressure (= power). On my model I've got a coil wound into the pipe just before it goes into the cylinder head, to help the gas warm up before it goes into the motor.

I'm definitely not an 'expert' on this btw, just a guy who has messed around a little with these motors!

Incidentally, the model I have was originally built for CO2 r/c (it's 36" span IIRC) approx. 10 years ago and has a thin 'Gottingen curved plate' (undercambered) wing hot wire cut from white foam. Never did fly it r/c, but maybe now ...

Free-flight it flys at a walking pace (indoors only), I'm using an ancient (and cheap) Telco CO2 motor turning a big rubber power prop (plastic) at fairly low RPM. That worked far better than the 'proper' (much smaller) CO2 props, which gave much shorter runs.

I used to fly this model at Olympia inbetween manic bouts of r/c pylon racing ... talk about from one extreme to another! The guy from Aeromodeller liked it a lot and they printed a picture of it (and RCM&E bought & published my pylon racer design, but that's another story ).
Old Nov 13, 2001, 10:12 AM
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Quote:
Originally posted by Thomas vogel
if you fill the tank with co2 then dump it immeadiatly and then fill it up you can cram more gas in.
a heat sink on the fuel line right before entry into the cylinder head to bleed off some cold or more likely add some extra energy to the expansion in the cylinder.

Thomas
An ordinary liquid-charge gave satisfying flights, but a bit short on duration. The model landed still with a lot of power that could have kept a lighter model aloft.
What I also did between flights was to run the motor at tickover to empty the tank of any gas- allowing a more complete fill.

There's tons of experimenting to do yet: the 'supercharging' as described by Thomas. A lightweight carbon/mylar airframe and the correct prop? should up the flight-times considerably.

The Gasparin 160RV would seem to perfect for our needs- it carried the 3-channel micro setup with ease.

Steve


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