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Old Dec 27, 2012, 03:53 PM
I hate waiting for parts
Mike_Then's Avatar
United States, NC, Garner
Joined Apr 2001
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Question
Advice on converting Top Flite T-34 - help save it from the swap shop!

Hi guys, I'm trying to help a friend with a glow-to-electric project and he's got some pretty specific parameters. He says that if he can't successfully convert the plane to electric then it's going to the Swap Shop in January. I wanted to reach out to the community to see if we can help save this beautiful plane from the chopping block!

He has a Top Flite T-34. It currently has a four stroke 1.20 that seems to fly it quite well. Not overly-powered nor underpowered but just right. It's swinging a 15 x 8 glow prop. It has an 80" wingspan. The advertised weight is 10 - 14 lbs. but we don't know the exact weight so let's just say 12 lbs. for the sake of this discussion. It has E-Flite electric retracts.

Here are the specifics: My friend has an Exceed RC Monster Power 110, which is an E-Flite Power 110 clone. It's 295 kV, and it will take 9-cells max. He wants to use this motor if at all possible so he doesn't have to buy a new one. The other restriction is prop clearance. The T-34 is a trike so that means he can go a max of a 16" prop.

My suggestion was a slightly hotter motor with a deeply-pitched 15" prop and at least 8 cells. I was thinking 10s would get the job done but the motor has a max input of 9s. He's pretty adament about using this motor. He was looking at an 15.75 x 13 x 3 APC glow prop but I've been down the road with 3-blade props on .60-sized planes and never really been happy.

First, can the conversion be done with that motor and if so, what prop and cell count would you recommend? Help me keep this plane out of the swap shop! Thanks!
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Old Dec 27, 2012, 07:07 PM
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Running the number through this free online calc programs says the motor running on 8 cells swinging a 16X10 prop will produce about 216 ounces of thrust. that is about 13.5 pounds of thrust.

http://www.s4a.ch/eflight/motorcalc_e.htm

Going to a 3 blade 16X10 thrust goes up to 257 ounces of thrust or 16 pounds of thrust.

http://www3.towerhobbies.com/cgi-bin...?&I=LXRF50&P=7

http://www3.towerhobbies.com/cgi-bin...?&I=LXRF51&P=7

So he can use (2) 4s packs through a "Y" cable for 8s.


Buzz.
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Old Dec 27, 2012, 07:51 PM
It's electric Boogie woogie
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Will that 16x10x3 exceed the 65amp Max Burst Current?
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Old Dec 27, 2012, 07:56 PM
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I bet that 13" pitch 3-blade APC on 6s would be a real good set-up.
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Old Dec 27, 2012, 08:25 PM
I hate waiting for parts
Mike_Then's Avatar
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Originally Posted by tlh101 View Post
I bet that 13" pitch 3-blade APC on 6s would be a real good set-up.
See, I was thinking that 6s wasn't going to be enough power for a 12 lb. warbird on a 15" prop. I know the plane doesn't need 200 watts/lb. as it's not a 3D airplane, but due to the prop limitation I figured it would have to be at least 8s.

Buzz, thanks for the links!

Brandon, we'd just have to try it. It's easy enough to buy a few props, bolt that motor to a test stand, and see what we get as far as amps goes.
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Old Dec 27, 2012, 09:40 PM
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Brandon, we'd just have to try it. It's easy enough to buy a few props, bolt that motor to a test stand, and see what we get as far as amps goes.
Exactly.
I flew an 14+ lb 80" AT-6 on a 245Kv Power 160 on 6s with a 20x15 prop. Plenty of speed and thrust. With your higher Kv and 13" pitch, your pitch speed will be similar. The 3 blades will help with thrust, as long as amp draw is not too high. That model only had about 70-80 watts per lb.
Here's a vid:
Electric Midwest AT-6 (3 min 41 sec)
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Old Dec 28, 2012, 07:18 PM
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I ran the motor, prop, battery combo, 15.75X13.

It warns "* Prop may stall -> static thrust may not be reached! (see Prop Stall Thrust) *"

It might not be a problem at flight speeds

Using the 16X10 3 bladed prop, it says it will pull 59 amps, burst is 65 amps.

Looks like a test stand and a pile of props for a weekend test is in your future.

Buzz.
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Old Dec 29, 2012, 08:08 AM
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Most of the calculators said the AT-6 above would not fly.
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Old Dec 30, 2012, 09:07 PM
I hate waiting for parts
Mike_Then's Avatar
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Quote:
Originally Posted by blvdbuzzard View Post
I ran the motor, prop, battery combo, 15.75X13.

It warns "* Prop may stall -> static thrust may not be reached! (see Prop Stall Thrust) *"

It might not be a problem at flight speeds

Using the 16X10 3 bladed prop, it says it will pull 59 amps, burst is 65 amps.

Looks like a test stand and a pile of props for a weekend test is in your future.

Buzz.
I think that's exactly what we're going to have to do. The other big problem is figuring how the heck to get batteries into that thing but we're not worried about that until we know we've got a good motor/prop combo. He swapped out air retracts (finicky and problematic) with some nice electric retracts so that should help things out a bit since there's no longer a big air tank.
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Old Dec 31, 2012, 10:04 AM
It's electric Boogie woogie
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I will swing by the local hobby store to see if they have 16x10x3 on the way back home Tuesday
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Old Dec 31, 2012, 09:04 PM
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Good luck and try not to let the magic smoke out. If it gets away, things do not work any more.


Buzz.
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Old Jan 02, 2013, 06:40 PM
It's electric Boogie woogie
bstussie's Avatar
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Local Hobby shop did not have the 16x10x3 in stock so I have ordered that prop from Tower so over the next few days I am going to build a quick test stand and get things mounted up so when the 16x10x3 comes in I will be able to give it a spin to see how it does.

I did go through my collection of E Props and do have a good selection of 2 blades to get some #'s on as well

16x12e
16x10e
17x8e
17x10e

Dont think I will have clearance with the 17" but will give it a shot
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Old Jan 02, 2013, 07:16 PM
I hate waiting for parts
Mike_Then's Avatar
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Quote:
Originally Posted by bstussie View Post
Local Hobby shop did not have the 16x10x3 in stock so I have ordered that prop from Tower so over the next few days I am going to build a quick test stand and get things mounted up so when the 16x10x3 comes in I will be able to give it a spin to see how it does.

I did go through my collection of E Props and do have a good selection of 2 blades to get some #'s on as well

16x12e
16x10e
17x8e
17x10e

Dont think I will have clearance with the 17" but will give it a shot
Good deal. I've got a 15x10 that I'll bring with me. I think the 16x12 is gonna be the ticket on 8s. But that's what testing is for.
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Old Jan 07, 2013, 07:39 AM
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Brandon and I ran some props on Saturday. Unfortunately his 3-blade prop won't be here until today but we ran up some 2-blade props. I think we found the winner but wanted to post them here for more opinions:
  1. 16x12 = 46 amps, 1200 watts
  2. 17x10 = 39 amps, 1050 watts
  3. 16x12 (9s) = 57 amps, 1700 watts

I really think the ticket is going to be the 16x12 on 9s. We weighed the plane and with a glow engine and fuel (he had forgotten to drain the tank ), it was just about 14 lbs. So let's overestimate and say it will be 14 lbs. with an electric motor and a 9s 5000 mAh pack. With 1700 watts, that's about 121 watts/lb. Not a crazy amount of power but should be fine for a trainer-type warbird. It obviously won't have a high wing loading like fighter-type warbirds so I think this should be fine.

Thoughts? Opinions?
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Old Jan 14, 2013, 02:23 PM
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We tested the 16x10x3 prop yesterday and got pretty much the same numbers as the 16x12 2-blade prop. So the conversion is definitely doable; it's a matter of hacking up the plane to fit batteries.

The amps and watts might be the same but the efficiency of the 3-blade prop will be less. If he converts the plane, it will be a simple matter of flying it with each prop and see which setup he likes best.
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