How to connect twin electric motors

[Smurphboy]

I'm looking for some advice. I'm building a Goolie - great model but I've got a problem. 

 

The plane has twin electric motors that you need to wire up to two ESCs and in my case a v-tail mixer. I know that I need to remove the red wire from one of the ESCs so that I don't blow my recevier and I know that I need to wire the battery to both ESCs. The question I have is what is the best way to do it.

 

I've seen (on another forum) that some people have extended the ESC to Battery lead and mounted the ESC next to the motor (having chopped the ESC to motor wiring right down) but it isn't clear if they have made the T-piece near the battery or further down or if that even matters? The instructions recommend this method but I've read that you shouldn't extend the ESC to battery wires and I'm not feeling too confident about wiring the motor wires direct onto the ESC.

 

The other option is to keep the wiring between the ESC and the motors and mounting the ESC on the fuselage - but that still leaves the wiring of the t-piece at the battery end.

 

A long question I know - but hopefully that makes sense??? 

[Craig Carr]

Hi Smurphboy,

 

Generally thought best to extend the wiring between the motor and the ESC and not the battery to motor as this can cause interference and in the long term damage the input capacitors.

 

All I did on my DC3 was to make 2 smallish "y" leads , one for the 2 positives and one for the 2 negatives.  Had the "Y" end at the ESC.

 

Im sure when Timbo comes on he can find the thread on not extending battery leads and give us the link....  (BTW I recently built a 4 engine multi and made this error but so far no issues have arisen despite extensive ground testing and (to date) one flight).

 

Craig  

Edited By Craig Carr on 18/08/2009 09:05:25

[Tim Mackey]

Hi Smurphboy. I have had a go on one of the goolies - great fun !!

It is only a small model, and I wouldnt worry about extending the wires either way TBH as the lengths involved are quite minimal. The reason to disconnect one of the ESC BEC +ve leads is more to do with protecting the BECs than the Rcvr - two BECS both fighting to supply one Rx as it were can sometimes prove problematic. Simply remove the red lead pin from the ESC Rx plug on one ESC and tape it back out of harms way - that way it is still available later if needed in another model.

Its true that generally speaking extending any power cables is frowned upon, but where unavoidable the ESC to motor wires should be extended, rather than ESC to battery. Problems can occur with long battery leads causing the input capacitors on the ESC to fail ...and sometimes this happens after a period of time rather than immediately.

I wouldnt worry in this case, just do what suits the layout best

[Doug Ireland]

How do you connect two ESC's to the throttle channel? Is this where the "Y-lead" comes in?

 

If you had the means to "slave" two channels together (as with the DSX9) would you still need to cut one of the ESC red wires off?

[Tim Mackey]

Yes.  Yes. ( see above explanation as to why )

The reason to disconnect one of the ESC BEC +ve leads is more to do with protecting the BECs than the Rcvr - two BECS both fighting to supply one Rx as it were can sometimes prove problematic. Simply remove the red lead pin from the ESC Rx plug on one ESC and tape it back out of harms way - that way it is still available later if needed in another model.

[Smurphboy]

I'm using a v-tail mixer to mix the rudder and throttle together (you can't do this on a Spektrum DX6i due to a firmware bug) so that throttle controls both motors and rudder introduces a differential speed between the two motors.

 

Thanks for all the advice so far. I think I'm going to stick with the plan and extend the ESC to Batt leads. This should leave a neater wiring layout overall. 

[Tim Mackey]

That mix problem is a new one on me   Firmware "bug" ...says who ??

[Smurphboy]

Posted by Timbo - Moderator on 18/08/2009 12:01:21:
That mix problem is a new one on me   Firmware "bug" ...says who ??

 My understanding (see link) is that you can't have the throttle channel as a slave on a mix on a DX6i so you can't mix rudder and throttle together to get differential throttle. Hence I've got a v-tail mixer.

 

RC Groups post on DX6i Throttle Mix problem 

[Tim Mackey]

Interesting...never knew that one Smurphboy - thanks for the link

Seems odd that this formware limitation exists, after all, a channel is a channel is a channel surely? Oh well

[Smurphboy]

Posted by Timbo - Moderator on 18/08/2009 12:24:00:

Interesting...never knew that one Smurphboy - thanks for the link

Seems odd that this formware limitation exists, after all, a channel is a channel is a channel surely? Oh well

If you hunt around in the "other place" - there is another thread (I can't seem to find it at the moment) with a reply from Horizon acknoledging the fault - and stating that they don't intend to fix the firmware to address it. I assume its a bug and not intentional as you can use all the other channels as a slave to a mix. If the DX6i had three mixes then it could be worked around but as you are limited to just the two then it isn't possible without allowing the throttle as a slave.

 

SM