View Single Post
Old Mar 13, 2006, 12:40 AM
flieslikeabeagle is offline
Find More Posts by flieslikeabeagle
Got shenpa?
flieslikeabeagle's Avatar
Los Angeles
Joined May 2004
10,940 Posts
TT, the red curve (like all the others) is plotted against current, along the bottom edge of the graph. If you look at the green numbers along the right edge of the graph, they are in watts and apply to the green and red curves. So, for instance, at about 10 A current, the red line shows about 37 W of heating in the motor. At the same 10 A, the green line shows about 37 W of power output at the motor shaft.

Hey, wait a minute, you say, those are both the same - that means half the power is being wasted, so the motor must be running at 50% efficiency, right? Yes indeedy. If you look at the blue curve, you'll see that indeed it shows 50% efficiency at the same 10 A current. Those blue, green, and red lines in the graph were generated by completely independent calculations, so the fact that the green and red lines cross at the same 10 A current that corresponds to 50% efficiency from the blue line is a nice little self-consistency check.

I agree that GWS planes are much better with lipos - that's how I flew all of mine. I originally used the stock 350 motor, 5.33:1 gearbox, and stock 9x7 GWS RS prop on my E-Starter, powered by a 2000 mAh 2S Kokam pack. Despite the big heavy pack, the plane had enough power for sustained inverted flight - I used to fly inverted circuits and figure-eights over the flying field to practice my inverted flight and co-ordinating the rudder and ailerons while inverted. Loops and rolls from level flight were no problem at all, the rolls requiring a hefty forward push on the right stick as the model rolled inverted.

That same old E-Starter on which I learned to fly ailerons about a year and a half ago recently got pulled out of the closet and received a brushless upgrade: it now has a 400XT outrunner, APC 8x6 TE prop, and a small 3S, 900 mAh lipo pack. It is lighter and more powerful than before, and I was shocked at how much fun I'm still having with the old beater.

I agree that Elapor is far tougher than EPS - I've seen EasyStar's take a pounding that would reduce any GWS plane to styrofoam confetti. The trick to making a GWS plane last, of course, is not to crash. My E-Starter was my third plane and my aileron trainer, and it's still intact and in flying condition over a year and a half after its first flight - though it does have scars from the time I flew it inverted into a tree . I'd used packing tape along the LE of the wings, and that kept them in one piece, albeit with a few dents. My Formosa was my fourth plane - it's a few months younger than the E-Starter - and has never been crashed, though I managed to ruin it by leaving it in my car on a hot day.

The Formosa had a brushless Himax 2015/4100, 5.33:1 gears, and APC 9x7.5 SF prop, and was powered by an 1800 mAh 3S Polyquest lipo pack. It had unlimited vertical - I used to release it from my right hand pointed upwards at about 80 degrees, pull to vertical as soon as it got some speed, and do vertical rolls straight up to flying altitude. Fun!

The pico Moth had the stock motor/gearbox/prop, and ran off a small 2S, 650 mAh lipo pack, enough for 30 minute flights, with enough power for ROG's and touch-n-goes, but not much more than that.

I've got some good news on my TS-II build, I'll start over with a fresh post to avoid cluttering up this one.

flieslikeabeagle is offline Find More Posts by flieslikeabeagle
Reply With Quote