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Old Jun 21, 2001, 10:57 AM
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Ontario, Canada
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Approx. AMP draw for two Sp400 6V on 8 cells??

Can anyone who had experience and had wattmeter, please tell me how much amps will two Sp400 6V motors either Graupner or Multiplex permax will draw with 8 cells, motors connected in parallel and using gunther puch on props.

And with 7 cells.
And with 7 cells and 7.2V motors.
This will be to see if an FMA mini 30 will be suitable for a Twinstar.
Thanks in advance.
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Old Jun 21, 2001, 11:12 AM
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Austin, Texas USA
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The S400 6V will be the hottest combo, and right about 30 amps max. Everything else would be less.
I would also ask about the FMA 30 ESC you plan to use. Nothing against FMA or any other manufacturer, but some 20 map ESCs work better than other 30 amp ESCs. That number printed on the package is just a number. I used a 35 amp in my Twinstar with twin 480s and stock props with no problems. But it was a Kontronik Sun 4000 which is a very robust ESC. FMA has a good rep in general, so I would think that you would be fine, but on the edge.

Shawn
<a href=http://www.eflightpower.com>Eflightpower.com</a>



[This message has been edited by sf_247 (edited 06-21-2001).]
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Old Jun 21, 2001, 01:49 PM
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Thanks SF_247
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Old Jun 22, 2001, 12:32 AM
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Agree with Shawn
30a ESC would be stressed to its limit.

I just measured a single 6V 400 with Gunter prop on new plane today (with Astro meter)
15a with fresh charged R500 8 cell pack

Dave
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Old Jun 22, 2001, 08:49 AM
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So, I'll recommend the guy for 6v motors and 7-cells. This will be better for him, as he has a 6-cell pack and will have to add only one more cell.
Actually, I was using 40 Amp ESC, so I had no problems with 8 cells, but the guy who I sold it to, only had 30 AMp, so just wanted to be safe. Thanks alot guys.
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Old Jun 22, 2001, 10:33 AM
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The Twinstar flies well on 7 cells from what others say. I have only tried 8 cell packs in mine, but considering the power with 8, I am sure the 7 cell packs are fine.
The guy can always upgrade later and have something to look forward to if he wants. Or he may be pleased with the way it is.

Shawn
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Old Jun 23, 2001, 12:30 AM
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Andy W's Avatar
Marietta, GA
Joined Jun 1999
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What sf said.. My mini30 is stuttering @ around 20A - works great (and a nice size) for single speed 400 use, but not for a twin or larger motor.
Get a Castle 40A controller, or a Jeti 350..
..a
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Old Jun 23, 2001, 12:52 AM
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I have run twin 6 Volt 400 motors in all my 5 twins I have designed so far.
My first was a twin Mustang.It ran 8-800 cells, and used a 20 amp FMA esc,wired motors in parallel.Even though it was on the edge, it never faultered.Part of the reason is that I use APC 5x5 props,and the motors draw under 10 amps each this way.

All of the following twins(Me 262, Neptune,Whirlwind)have used the same setup without so much as a glitch.My Sportwin was built with an FMA 30,only because I planned to sometime try other , higher performance motors.It , too, has never faultered.These all use 8-800 cells, or 8-1250 cells.I would think 1700 or larger might be pushing it, as they have a little less resistance, and more power getting through the ESC.

To be on the safe side, use an FMA Mini30,and use APC 5x5 props or smaller.Ask anyone who has built a SPortwin if this works, and they will say yes.

I cannot say anything bad about the FMA product.They perform flawlessly!


The reason some of these guys say that setup is pushing it is because they are drawing more amps with the Gunther props,more than the APC's will pull.

MR
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Old Jun 23, 2001, 08:12 AM
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I am running a turbo 450 with a 6.5x4 prop on 800AR's. The ESC cuts power to the motor if you hit full throttle on launch (when the pack is fresh). Current draw never exceeds 20A (and this ESC is rated 30A).
..a
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Old Jun 23, 2001, 02:48 PM
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Thanks guys, I have advised the guy to use 7 cells and 6V 400s, I hope it'll be fine. I have to do the test flight for him any ways, I'll check it on the ground thoroughly before I take off. Twinstar has pretty good vent locations, and I mounted it at a place for good air going over it, so hopefully, it'll be fine.
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Old Jun 23, 2001, 03:41 PM
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Andy, what type of esc is that?If its an FMA, send it back and get a new one.It HAS to be faulty!Mine are being used right to the limit of the reccomendations, and have NEVER failed,even for a second.


MR
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Old Jun 23, 2001, 08:48 PM
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How about wiring 2 4.8vs in series?
-fish
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Old Jun 23, 2001, 09:05 PM
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Fisher-
From what I understand, the 4.8V motors need 5 cells to start performing well. Most are even used with 6 or 7 cells! But with high amp draws, of course. This would require 10 cell packs with 5 cells per motor.
It sounds like we are giving advise to someone who is giving advise to the Twinstar owner, second hand. Wiring the motors in parallel seems to be the best choice long-term to keep it simple.

Shawn
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Old Jun 25, 2001, 09:47 AM
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You are right Shawn, I am giving advise to someone who bought the Twinstar from me. And I did say that in a previous post. I was using a Pico Duo 40 AMp ESC, but he only had the FMA MINI 30, so I thought before he messes up anything, I should double check with the experts. Thanks.
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