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Sep 09, 2009, 06:45 AM
Thread OP

nitromodels cessna 337 twin gas engine, convert to single electric pusher

I just ordered this plane What do you guys think would be a good power system for this, converting it to single electric pusher.

now I have a 60 amp pentium ESC (I am assuming I will need a new one of these) but i would really like to make use of some of my batteries..

5000mah 4cell lipo, (doesn't seem like i will get long flight times with this)

I also have (2) 4000 mah 3cell lipo seems like i could make it into a really good 6 cell 8000mah to power the motor.. also keep in mind im willing to pay the extra dime for new batteries to get about 1 hour flight times. god I wish it told the weight of the plane and the prop size for the rear motor.. but i also load it with some wireless camera gear, osd/gps...

anyway I need some of you experts to help me power my 200$ balsa/plywood plane.

EDIT: I also have 1250KV turnigy SK axi 2820 but it only does 2-4 cell lipo and a 800KV turnigy SK axi 2826 2-5 cell lipo..
Last edited by dr_patso; Sep 09, 2009 at 07:18 AM.
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Sep 09, 2009, 09:32 AM
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Bruce Abbott's Avatar
The specs say "Flying weight: 10lb / 4540g". Assuming this is the AUW, taking out the two .46 glow engines and ancillary equipment (tanks/servos etc.) would make it about 3.5Kg without power system.

Now add in a .46 equivalent outrunner (eg. Scorpion 4025-10) with 12 inch prop, 60A ESC, 4000mAh 6S Lipo, and 300g of camera gear, to give an AUW of about 5.5Kg.

However, I estimate only 30 minutes cruise time with a 4000mAh battery. To get 1 hour I think you will need at least twice as much battery, pushing the weight up to ~7kg (which will adversely affect climb rate and stall speed).
Sep 09, 2009, 07:27 PM
Thread OP
would two 3 cell 4000mAh turned into 1 6 cell just be a 4000mAh 6 cell or an 8000mah 6 cell?
Sep 09, 2009, 07:36 PM
Thread OP
I think I just figured out yes to my first question, (2) 3 cell 4000mah would = (1) 6 cell 4000mah
Sep 09, 2009, 08:11 PM
Thread OP
you think a 12" prop would fit on the back? I'll just have to wait till I get it i guess.
Sep 10, 2009, 04:04 AM
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Bruce Abbott's Avatar
A .46 engine usually runs a 10 inch prop. If that's one in the photo then a 12" prop might fit, if not then you could run a higher Kv motor with a smaller prop.
Sep 10, 2009, 04:25 AM
Thread OP
cool thanks for all your help bruce!
Sep 10, 2009, 02:03 PM
jackerbes's Avatar
The specs on that:

Wing span: 81in / 2060mm
Wing area: 1085 sq in / 70 sq dm
Flying weight: 10lb / 4540g
Fuselage length: 62 in / 1570 mm
Engine Required: 2c 0.46 cu in x2
Radio Required: 5-channels, 9 servos !!!

Those specs put the wing loading at 21.2 oz./sq.ft. at the 10 lb flying weight. That is about an average wing loading for high winged, full fuselage, airplanes. I think that the two 0.46 engines in that are propped down quite a bit from where their full power potential would be because of the confinements of the twin boom tail and trying to maintain a more or less scale appearance. In other words, the two 46's were needed because they were propped down and being used inefficiently.

Since you want to use a single motor, you might have to put the motor in the front so you can swing a bigger prop and use that one motor efficiently.

As a comparison, I have a SIG Rascal 40 conversion that weighs 8.25 lbs and is using a Torque 4014T-570 motor. That is propped with an APC 14 x 10 Thin Electric and pulls about 45 Amps from a 15 Volt 5S2P A123 pack (1100 cells) for a little over 600 watts of power. That motor is capable of 65A continuous and 80A peak (20s burst) so if it was propped for bigger props and had enough battery to pull the 65A it would undoubtedly develop enough power to fly a 10 lb. plane.

But I think the problem you are going to run into will be with ground clearance for a single prop as the prop is going to have to be a bit more than a 14" prop to get you up around the 750-1000 watts or so you probably need to fly the plane.

The Rascal takes off very quickly and easily at 625 Watts (75 Watts per pound of AUW) and flies the pattern nicely at 250 Watts or so (30-40 Watts per pound). It will do basic aerobatics (the Rascal is a sports flyer) at full or near full throttle. So I would guess that your 10 pound plane would want to have around 750-1,000 Watts for similar performance. It might be hard to get that much power with a single motor and stay within the constraints of the boom clearance and/or ground clearance.

Sep 10, 2009, 02:34 PM
Registered User
Fourdan's Avatar

I think that is very sad not to put two brushless, two ESC and contra-rotative props on this pretty ship.

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