DeviousDave
Posts: 490
Joined: 2/25/2007
From: , MI, USA
Status: offline
|
Lot of posts here that I'd love to address point by point, but here are a few things that come to mind:
Speed: Electrics have been capable of over 200 mph for over ten years. Heck, 200 mph electric ducted fans were a long time ago. How's this for fast? http://video.google.com/videoplay?docid=-6008855978316732278&q=electric+pylon+racer&total=6&start=0&num=10&so=0&type=search&plindex=0
http://video.google.com/videoplay?docid=3648450921656463082&q=f5d&total=72&start=0&num=10&so=0&type=search&plindex=3 A Nelson powered Quickee500 won't run with one of these, and don't think Quarter40's will either. Something worth noting is that these models are HALF A SIZED. They are limited by the rules of the event, not what technology will allow. They can't use a pack over a certain number of cells or more than a certain weight. The airplanes have to weigh X or they aren't legal etc. You can't fit a lot of battery (which really is what limits your speed at that level) in a 1/2A sized fuse, these things would be unbeatable if the gloves came off and the contestants were allowed to runwhatchabrung. This is what electric pylon racers looked like 8 years ago: http://video.google.com/videoplay?docid=-6008855978316732278&q=electric+pylon+racer&total=6&start=0&num=10&so=0&type=search&plindex=0. At the time it was a ragged edge setup, but today anybody can fly this fast for not a lot of effort or slide rule calculations...
Duration: I suppose if you built a special purpose diesel powered glider with a generator to power the reciever and a huge tank you could outlast a similarly purposed electric, but as it stands, nobody has stepped up yet with a glow powered 48 hour airplane. It's worth noting that the transatlantic flight was done before Lithium Polymer cells were available... Had that been the case, the airplane could have been radically different than it was designed. Essentially, the Aerosondes were made with a current high performance glider wing from a readily available kit. This wing was mounted on a big-azz fuse that was mostly big-azz because it had to contain several gallons of fuel, a big honkin' gas converted 4 stroke, a generator and ignition. Designing an electric for a task like this is a lot easier: Flying X airframe at Y weight at z speed will require Q number of watts. Go buy a motor that is efficient at that power level. Find out how many volts and amps it takes to produce those watts. Solder up a pack that will produce that amount of power for the umpteen hours it would take to cross the Atlantic Ocean. Call Dave Brown so that he can violate AMA's rules on someone else's soil by flying it.  (or something like that)
Power to weight and other efficiency gains: Electric systems are lighter than glow on a performance to performance basis. A lack of vibration lets you build a lot lighter too. Props are better, and unlike glow, you have dozens of options. A .40 sized glow airplane makes about .75hp or 400 watts. You mount it on your airplane, and generally have to choose between a 10-6 and 11-6 prop that looks like it was designed to stir paint. With an electric you have dozens and dozens of choices for a 400 watt motor.... Direct drive, gear it, or it might be an outrunner. The prop you bolt on to it will work a heck of a lot better too since it also doesn't have to be designed to take the pounding of an ignition cycle.
Climb: How do you get better than 2 and 3 to 1 power to weight ratios? Imagine a hot 1.20 glow motor in a 1-1/2" fuse: These guys only get to use the motor when they are OUTSIDE the course: http://video.google.com/videoplay?docid=-6008855978316732278&q=electric+pylon+racer&total=6&start=0&num=10&so=0&type=search&plindex=0
Perfect example of flying a large airplane with a tiny motor: F3P Indoor pattern. You are using a 1/2A amount of power to fly a .20-25 sized airplane. Unlimited vertical, and light enough to walk next to at low throttle: Cool Video Alert! http://video.google.com/videoplay?docid=-6008855978316732278&q=electric+pylon+racer&total=6&start=0&num=10&so=0&type=search&plindex=0
To boil it down, there are three advantages that electric has over IC power: The flexibility to tailor a motor to your airplane, light weight, and better efficiency all around.
Oh, before I forget-Fuel was mentioned: Glow engines have several problems... As mentioned, thermal efficiency in our small motors sucks. Then there is the part where our motors don't actually burn all the fuel they push thru the cylinder, and finally, 20% of our fuel has to be OIL-and there's no power gain in that.
Not trying to be an electric Bible Thumper here, just showing what can be accomplished by average people who look deep enough into the dark side. Fly what you like, I am an equal-opportunity enjoyer.
< Message edited by DeviousDave -- 10/26/2007 12:39:33 PM >
|
Printable Version
All Forums >> RC Airplanes >> "1/2 A" & "1/8 A" airplanes >> RE: Crazy prices? 
RE: Crazy prices? - 
