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Electric Stunt => Gettin all AMP'ed up! => Topic started by: paul winter on November 25, 2012, 11:22:06 AM

Title: info about twin and electrics
Post by: paul winter on November 25, 2012, 11:22:06 AM
it is long but worth watching


http://www.youtube.com/watch?v=JXx0ZlSszEI&feature=plcp
Title: Re: info about twin and electrics
Post by: jjorgensen on November 25, 2012, 03:02:27 PM
Great video Paul. When you use a single battery with two motors does each motor get the same voltage or is it one-half the voltage? In other words, if you use motors that are limited to 3 cells, can you use a 4 or 5 cell battery, or are you still limited to 3 cells but you just double the mah?
Title: Re: info about twin and electrics
Post by: John Cralley on November 25, 2012, 03:06:51 PM
Nice job showing how it is done!!!
Title: Re: info about twin and electrics
Post by: John Cralley on November 25, 2012, 03:08:32 PM
Jim,  Each motor gets the full battery voltage.
Title: Re: info about twin and electrics
Post by: Igor Burger on November 26, 2012, 01:13:45 AM
Be carefull with that paralel run 2 esc on one battery. In case that battery dischrges during flight (should not happen, but I saw guy who started and forgot to charge battery) one ESC will cut the power and the second will see "enough" because the other does not take any current. The result is long flight with only one motor running waht can cause "troubles"  ;D

... btw how you controll landing gears in such emergency?  ;D
Title: Re: info about twin and electrics
Post by: paul winter on November 26, 2012, 03:02:11 PM
hi there
the escs have a 10% cut off built in i think !!!!

also when you loose any power the eflight retracts come down
pw
Title: Re: info about twin and electrics
Post by: Tim Wescott on November 26, 2012, 03:41:55 PM
hi there
the escs have a 10% cut off built in i think !!!!

also when you loose any power the eflight retracts come down
pw

Ahhh, but:

The ESCs have to measure the voltage, and no two devices are going to measure the voltage the same way.  So one ESC will always cut out first.  When that happens then the current drain on the battery will drop to 1/2, the battery voltage will recover somewhat, and the other motor will just keep on truckin'.

And the eFlight retracts may come down when you lose all power, but probably not when you lose some.

This is an interesting problem.  You could make a timer that would account for all of this, but I don't think there are any that currently do.  You'd pretty much need a special timer; one that monitors voltage like Kieth Renicle's does, but that controls rectracts based on both time and voltage.
Title: Re: info about twin and electrics
Post by: paul winter on November 27, 2012, 06:05:20 AM
hi Tim
it like crashing lets hope it never happens  lol

paul
Title: Re: info about twin and electrics
Post by: Howard Rush on November 28, 2012, 01:05:21 AM
That's one way.  Reckon there's a market for a monitor that puts the gear down and stops the second motor and maybe stomps on the rudder? 
Title: Re: info about twin and electrics
Post by: paul winter on November 28, 2012, 03:54:26 AM
hi Howard
how r u ?

miss flying in the US but theres always next year

i have had 20 flights with a test bed plane with retracts and  a twin electrics ,no problems SO FAR

The thing i find when the horizontal cg is almost perfect ,as there is no u/c hanging down or a heavy motor ,is that the model turns so much better and trimming is almost non existent .

the only thing will add  is don't get complacent with the electrics otherwise something will come back and bite you .
PW