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Old Jul 15, 2011, 04:29 AM
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United States, WA, Sumner
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Question
Electric Motor Choice for a Roedelmodell 4.2M ASK-21

Wracking my brain trying to decide a nose mount motor/prop/gearbox combo for my 4.2M Roedelmodell ASK-21 which I'm converting to "E" power.

Weight around 10 to 14 lbs. I have plenty of 6S 30C 5000mah packs I can use and also series the 6S into 12S if necessary.

I would appreciate any suggestions for a system regardless of cost but a nice inexpensive system would be favorable.

Cheers!
Perry
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Old Jul 15, 2011, 08:29 AM
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North Yorkshire UK, on a big hill facing the prevailing wind. Coincidence?
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Hi Perry,

Assuming the 14lb weight includes drive train, I'd aim for about 1200 - 1300W input power, so I reckon 6s would be fine pulling a relatively modest 60Amps.

Your 5000mAh 30C packs are a great size too, giving plenty of duration and a nice safety margin for max. current.

As for motors/props etc, Kontronik motors + gearboxes are very popular in Europe with the advantage that the slimmer gearbox means you can use a smaller and shorter spinner. Much cheaper and simpler is a brushless outrunner direct-driving a big prop, but you may have to chop off nearly 3" of nose(!) to get a big enough firewall. Or if you have the skills/tools you can extend the outrunner prop shaft with a bearing right into the nose. Hmmm. Your choice.

Please let us know how you get on - I'm going to do the same to my similarly-sized 4.2m Rodel Ka6 someday. You can do my alpha-testing!

Cheers,
Rog

P.S. Nice model!
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Old Jul 15, 2011, 08:31 AM
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North Yorkshire UK, on a big hill facing the prevailing wind. Coincidence?
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Sorry, didn't answer your question - I've used a few Turnigy motors and found them fine providing you work well within spec, and you can almost afford to take a chance at the price providing you flight-test them carefully.

R
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Old Jul 15, 2011, 11:55 AM
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Hi Rog,

I made an "E" conversion on one of my large woodies with an outrunner with extended shaft. And even though it worked, it was pretty challenging to set up and get the extended shaft in the correct position.

Assuming the 14lb weight includes drive train, I'd aim for about 1200 - 1300W input power, so I reckon 6s would be fine pulling a relatively modest 60Amps.

Yes. The weight is AUW.

So on this conversion I would like to opt for the inrunner with the gearbox option and keep the nose area small as you mentioned.

I've done this mod before with a smaller sailplane but on this thread I am looking for posts on what specific brand of equipment others have used or are currently using on their ships of this class.

Looking at Neu motors right now. They have a good selection of inrunners with gearboxes. I'll check Kontronik as well.

Thank you.

Perry
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Old Jul 15, 2011, 12:28 PM
aka Schleppmeister
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Also very efficient & powerful:

http://www.aero-model.com/Hacker-Sai...ors-12lbs.aspx
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Old Jul 15, 2011, 02:39 PM
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This is a cleaner installation. You don't have to desecrate the sailplane's nose.
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Old Jul 15, 2011, 04:24 PM
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That's a neat job Mario. What did you use for the front bearing?

Rog
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Old Jul 15, 2011, 04:48 PM
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Quote:
Originally Posted by mario alvarez View Post
This is a cleaner installation. You don't have to desecrate the sailplane's nose.

Well done Mario!

Thank you,

Perry
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Old Jul 15, 2011, 05:25 PM
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Sorry guys, I wish I could take credit, but it's not mine. I'm working on a 4M Lunak in which I'm replicating this setup. As for the front bearing, I'm using a 6mm flange bearing bought from Boca Bearing. The driveshaft is a 6mm SS rod and the coupler was machined for me. My motor is a Hacker A50 outrunner. It's on the backburner presently since I'm trying to finish Topmodel's Fox.
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Old Jul 16, 2011, 03:30 AM
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Okay guys here's what I found.

Just made an offer for a Hacker B50-9XL motor less gearbox but will get the 5.2:1 gearbox separately for it since it does not come with this motor purchase.

If purchased as a single complete unit it would cost 440.00 from Esprit Models

http://www.espritmodel.com/index.asp...OD&ProdID=2044

Purchasing second hand and getting a new gearbox will hopefully cost me about 225.00 if the seller accepts my offer.

Here are the specs from Esprit Models site on this motor and gearbox combo.

B50 XL Series B50 9XL w/5.2:1
Kv (rpm/V) 1753
Max Power (W) 1700W
Max Amp (15sec) 70A
Max Efficiency 87%
Io (No load A) 2.22A 1.57A
Rm (Resistance) 0.098Ohm 0.152Ohm
Shaft Diameter 6mm
Gearbox 5.2:1
Motor Diameter 35.8mm
Motor Length 94.8mm
Motor Weight 395g
Built in Fan N/A
Max Rpm 60,000
Poles 2
Case Smooth
ESC Timing 0-5 deg
ESC Switching Freq. 8KHz


Model type Model name Motor Controller Cells Prop
Pattern 60 GP Venus 60 B50 9XL 5.2:1 Phoenix ICE 100 EM3700 6S Li-Poly 16x10 APC-E

Aerobatic/3D 60 H9 Frenzy 100 B50 11XL 5.2:1 Phoenix ICE 100 EM3700 6S Li-Poly 19x8 APC-E

Fun-Fly 60 Diabolic 3D B50 11XL 5.2:1 Phoenix ICE 100 EM3700 6S Li-Poly 19x8 APC-E

Warbird 60 H9 P-51 Mustang B50 11XL 5.2:1 Phoenix ICE 100 EM4500 7S Li-Poly 17x10 APC-E

Scale 90 GP PT-19 B50 11XL 5.2:1 Phoenix ICE 100 EM4500 7S Li-Poly 16x10 APC-E

I have the batteries, prop, prop adapter and spinner, and ESC. So this should be the ticket.

Sorry Mario. Going to cut the nose on this one. I will make a replacement nose if I decide to aerotow so not a big deal.

Perry
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Old Jul 16, 2011, 12:43 PM
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I have several motors for sale right now. There are a couple of them that may be just right for your sailplane:

http://www.rcgroups.com/forums/showthread.php?t=1472248

Bob
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Old Jul 16, 2011, 06:54 PM
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Got the B50-9XL from the fellow Ezoner.

Anyone have the 5.2:1 gearbox for a B50-9XL they want to sell, PM me.
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Old Jul 16, 2011, 09:04 PM
formerly soaringbird
mount dora, florida
Joined Jun 2006
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don't do it keep it as a pure sailplane and sell it to me......lol
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Old Oct 17, 2011, 03:08 AM
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Conversion completed. Ready for her maiden!

Here are her specs.

B50-9XL 5.2:1 gearbox
Castle ICE 100 ESC
Aeronaut carbon 16x10 folder
Turnigy NanoTech 6S 45-90C 5000 mah pack

Motor test with a one year old with several runs Turnigy 6S 30C 5000 mah standard lipo pack showed an amp draw at 70 amps at full throttle and 1400 watts.

Motor test with a brand new never run Turnigy Nano Tech 6S 45-90C 5000 mah high discharge pack showed an amp draw at 90 amps at full throttle and 2000 watts!

AUW with battery pack is at 13 lbs.

She pulls really hard and I wouldn't be surprised if she couldn't be hand launched. My 11lb electrified Merlyn launches effortlessly out of my hand with the same type of pack but with an outrunner motor.

Flight report and possible video coming.
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Old Oct 17, 2011, 04:15 AM
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North Yorkshire UK, on a big hill facing the prevailing wind. Coincidence?
Joined Oct 2007
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Good luck with the first flight. Certainly the numbers look promising. I'm amazed at how much power difference between the two battery packs assuming you kept everything else (prop size etc) the same.

Self launch may be an option assuming you're a fast runner and there's a headwind to get the wings working + you're ready for a big torque roll from that poweful setup.

Thanks for the update.

Rog
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