Matt Kirsch

My Feedback: (21)

That thread about the Kyosho .40-size Pitts got me thinking about my, "If I Had All The Money In The World This Is The Plane I Would Get" project, the Great Planes 1/3 Scale Pitts.

Here's my thought process. Hopefully it'll give some of you guys some ideas on how to power your conversions, and some of you might offer me some ideas on this one. Heck, I may just decide to do it!

I like to start out with a target of 100 Watts/lb for aerobatic planes. That said, this one will need at least 1400 Watts, given the recommended AUW of 14-16 pounds, and the warning that if you get even close to 16 pounds the plane will fly like crap. I'm thinking 36 cells at 40 Amps. That'll give me 1440 Watts.

In my travels, I've read about a guy who did up a Lanier Stinger 1.20 using a geared AXi outrunner motor. 10lbs AUW, and enough power to pull out of a hover. That got me to thinking about getting one of those REALLY big AXis, gearing it down 2:1 or so, and spinning a really huge prop. If the airframe is really light, I might be able to get away with 30 cells at 40 Amps on a geared AXi spinning something like a 20"+ prop at scale speeds.

36 Sub C cells will make a battery load of approximately 4-3/4 pounds. I've used the HR4/5FAUP NiMH cells on my .40-size Corsair with great success, saving a half pound in 16 cells. My calculations say that the NiMH pack will weigh about 3-1/4 pounds, and they hold up to 40 Amps admirably. I can replace the pack with LiPolys later, or just start out with them if they get cheap enough.

Just musing here, but boy wouldn't it be cool to bring this plane in around 12 pounds. 1200 Watts on a 12lb airplane spinning a big efficient prop. 14 pounds seems to be the target weight, though. The nice thing about it is by going with the AXi, the conversion will be fairly inexpensive!

Maybe I should lurk over in the giant scale forums and see if anybody's weighed the empty airframe of the Great Planes Pitts...

Sprink

Careful, this sort of thought process will lead in only one direction [&:]

Shawn-Palmer

Matt, you need to change the title from "Pipe Dream" to "send money" - You've already got it all figured out!

Shawn

Matt Kirsch

My Feedback: (21)

Say Shawn, you guys thinking about producing a 30+ cell Phoenix ESC?

Shawn-Palmer

Yup, and that's all I can say right now.

Shawn

stefanP

My Feedback: (2)

Matt I'd look at the Actro 40-5 .Swings big props with no gear box Also if I where doing the conversion I'd get the plane strip the covering and look for area's to lighten up this plane.My 2cents,stefanP

Hannu Vuorinen

Hi,

Actro 40-5/6 is not enough, I would go to Flyware -T-REX series, Or Torcman 430.
I have Actro 40-6 Kokam 10s2p in Piper Cup 1/4, and it is enough for 11kgs tow combination, but
it is different story make bipe plane doing nice aerobatics, you have to calculate power ratio +20-25% more than
monoplane. I noticed this with my 1/5 Stieglitz ( 15lbs), it flies just beautifully, very scale like 20minutes, but thinking Pitts 1/3
(same size closely) would need a lot more power to get real aerobatic performance.

SoarNeck

I recently used an Aveox 1817/4Y in an electric tug project (Liftzone.com article in a week or so), and I don't see why it wouldn't work in this situation as well. That motor spins a Zinger 20x11 cut down to 18" at 5600 through a 1.6:1 belt, drawing 40.9A (measured, not MotoCalc) from 30 GMVIS 2400's (or an APCE 20x13 @ 5900 & 40.5A). If your controller can handle the extra cells (Schulze fut 40-70 is good to 40, I believe), that's a good way to drop the current requriment a bit.

The 1817 motors are offically 30A continuous, but even running at 40A my I/R gun only puts them at about 37 degrees C after a flight.

Matt Kirsch

My Feedback: (21)

I've kind of come to the conclusion that I need about 2HP, ~1500 Watts, to fly this plane the way I think it should be flown. That's 30 cells at 50A, 32 cells at 47A or 38 cells at 40A. I dunno if the biggest AXi will take more than 30 cells, but I do plan on getting a big AXi some day in the near future.