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Old Sep 25, 2010, 05:58 PM
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Scott C's Avatar
United States, GA, Peachtree City
Joined Aug 2000
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Question
old MEGA motor and new lipo question

After being out of flying since 2002, I have started flying my SR Cutie behind my house on the golf course after hours of course. I also have an SR AcroPro waiting to be fitted with a new motor, however the slower Cutie is my main ride now.

Back in 2002 I installed a MEGA motors 16/5/6 motor powered by 8 x 1300scrs and turning an APC 8x4 thin electric. Last few weeks I have been flying this combo again. The nicads initially cycled well, but they are now showing their age. I ordered some Blue Lipo 3S1P 2100 packs and a new lipo friendly esc. I am looking forward to the increased performance and loosing significant total weight. With the new packs, the new weight should be around 25-26 oz.

I have tried a few online electric calculators with the little MEGA and Lipos. Most show that this combo with a full throttle will be right at the max 18-amp limit to the motor. I thinking that propping back to a 7x4 might let the motor run cooler.

Any input appreciated.
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Old Sep 25, 2010, 06:31 PM
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Dr Kiwi's Avatar
Chattanooga, Tennessee, United States
Joined May 2003
27,199 Posts
Many people will try to convince you that Mega motors are under-rated... and they may well be correct... but I'd start with a 7x4... if the plane has enough power stay with that... if it needs more power try the 8x4 but monitor motor temperature carefully... given the rugged Mega reputation, it is probable that it will be perfectly happy at 18A or so.
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Old Sep 26, 2010, 08:31 AM
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scirocco's Avatar
Australia, ACT, Kambah
Joined Feb 2001
3,097 Posts
I see you already have 3S, but you might also consider 2S with a 9x6. This should give you about the same static thrust and pitchspeed as your original 8 cells with the 8x4, at around 17-18A static, and lighter still. Also about the same static thrust as a 7x4 on 3S but a bit lower pitchspeed, maybe a bit more akin to the Cutie's slower nature.
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Old Sep 26, 2010, 09:56 AM
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Scott C's Avatar
United States, GA, Peachtree City
Joined Aug 2000
1,136 Posts
Thanks for the help. I am thinking that a Super Tigre 400 or .10 might make a good replacement motor if needed. It should go easy vertical on the .10, not that this is the objective. I have an AcroPro in the waiting.

I am starting to have the perception that if one takes a pre-liop and pre-outrunner electric airframe and add a 3S and an outrunner it should go vertical without breaking a sweat!!!
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Old Sep 26, 2010, 11:49 AM
Registered User
Hemet, California, United States
Joined Aug 2001
2,607 Posts
Hi,

My Cutie has a Mega 16/15/6 in it on an APC 8X4E prop. I have run 3 2100 packs in it with no problem. These are 20C packs. You will find yourself a little tail heavy.

I have not flown my Cutie for awhile. If I were going to put her back in the air I would look for a heavier pack to help with the balance.

Good luck! Mickydee
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Old Sep 26, 2010, 12:14 PM
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gotboostedvr6's Avatar
USA, NJ, Mt Laurel
Joined Oct 2007
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The 8x4 is a bit much for the /6 running at 20 amps

At that power level your losing 50 watts of efficiency
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Old Sep 26, 2010, 08:28 PM
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Scott C's Avatar
United States, GA, Peachtree City
Joined Aug 2000
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Quote:
Originally Posted by mickydee View Post
Hi,

My Cutie has a Mega 16/15/6 in it on an APC 8X4E prop. I have run 3 2100 packs in it with no problem. These are 20C packs. You will find yourself a little tail heavy.

I have not flown my Cutie for awhile. If I were going to put her back in the air I would look for a heavier pack to help with the balance.

Good luck! Mickydee
Good to hear. I made some mock-packs from fishing weights to check the balance. If the venders give accurate weights, then I should balance with no problems. I initially targeted the 1750 mah packs, however they were too light.

I still cannot believe how cheap the brushless motors are nowadays. I am still tempted to put a Supre Tiger .10 in the firewall. It appears to be lighter than the mega 16/15/6!!!
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Old Oct 04, 2010, 01:37 PM
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Scott C's Avatar
United States, GA, Peachtree City
Joined Aug 2000
1,136 Posts
Well I finally got to fly the Cutie with my new 2.2 Lipos. With a takeoff weight of less than 26 oz, it went fairly vertical. I believe that the 8x4 prop will be just fine; I’ll try to rig an amp meter to it later. Anyhow, over a minute full throttle the Cutie will either be out-of-sight or possible control surface flutter with the excessive speed.

Half throttle with some emergency war power is just fine for me.
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