I am working on my first attempt at a plane with dual motors. They are 2217/6's with 8x6e APC thin props. Has anyone had any experience with twin motors? I've done some reading on this and it has had some interesting comments.

 

Not that one. I like the price though. I got my pair of combos from RCHotdeals.com
The motor and 40 amp ESC was $35.00

http://www.rchotdeals.com/Products/rc/b ... 17-12.html Attached files

 

I've built a couple dual-brushless systems. What do you need to know?
Yes, you DO want to use TWO different ESC's. You want to read this article from Castle Creations http://www.castlecreations.com/media/ca ... ar2006.pdf (the section on multi-motor systems) because they are the guys that MAKE controllers and KNOW what they're talking about. Many of the morons on the forums haven't got a clue how stitching systems and back-EMF feedback loops work.

 

Dorsal, thanks for the link. Yes, I already have two ESC's. I'm also going to use a CC 10 amp BEC unit. I am curious as to how the RPM's match between the two motors. As the article points out, if the motor/ESCs are purchased at the same, they should be close. An RPM meter would be nice. Do you know about how much current the Dean's Ultra connectors can handle? I think I plan on using two 1500 to 1800 mah batteries in parallel connected to a single Ultra that feeds both motors. I could use the smaller size lipos on smaller planes as well. Any pictures of the dual planes?

 

Well, i have some 5000 Lipos that use a deans so I think your safe

 

I remember reading that Deans ultras are good for 80A. It's been a while since I setup a twin brushless system, but I remember it being advised to disconnect the +ve wire from one of the esc's. I also had to calibrate the throttle range of each esc with my tx independantly, this solved a sync issue I had at one point.

Si.

 

These are 300 watt motors so it sounds like the Ultras can handle the current. Thanks! With the separate CC BEC, I would think that both +ve leads on the ESCs to receiver connector need to be disconnected.

firetrappe, why and how did you calibrate the throttle range? I have an Eclipse 7 tx.

 

Yes, I agree, if you're using a separate BEC then disconnect both +ve leads from the escs.

The speed controllers that I was using required calibrating to the range of the throttle stick on the tx (for any brand). IIRC this had to be done by having the throttle stick at max when connecting the rx power, waiting for a sequence of beeps and then moving the stick to min throttle. With both escs wired together, they entered their respective programming modes at different times which made it impossible to calibrate both throttle ranges at the same time. They were identical esc's both purchased together, but the delay from connecting power to the rx and them entering programming mode differed by several seconds.

Hopefully you won't encounter this problem, but I just thought i'd mention it incase.
Oh BTW, back then I was using a GWS V-tail mixer between the escs and rx to give me differential thrust vectoring.

Si.

 

Firetrappe, that had to be kind of a nuisance to have to calibrate. Hopefully, I will be spaired that step. I'm sure I have a mixer in my cabinet somewhere too. I do like the programmable tx. The receiver I was going to use was a Hitec Neutron 6, but, I hooked it up and it worked about 15 seconds, then went crazy, and then dead. Tower Hobbies is sending a new one. That will give me time to install servos and put the covering on the saucer.

rjarois, that must have been a BIG motor/plane!! What was it?

 

They're not hideously reliable..... They do fail quite often.

Having owned a Multiplex Twinstar 1 and now two Twinstar 2's I've had more than a bit of experience of twin set-ups...

On those motors your ESC's want to be rated at 33A minimum.... Ideally more. Always pick an ESC that's at rated at least 50% above the maximum that your motor and prop combination is capable of drawing. Not only does that ensure that you won't overload the ESC's it also means that they run a lot cooler and waste less power as heat.

You're doing good so far... You're absolutely right about disconnecting both red wires on the control cable to the ESC's when you're using a separate U-Bec.. They'll only fight with each other and get confused as to which of them should be supplying the power if you don't.

In fact using a separate Switch Mode U-Bec is one of the things I'd always recommend. The BEC in the ESC's is rarely up to the job of powering the radio and more than about two servos, especially the regulated BEC's that most of them have and even more so if you're running 3S or more.

Best Regards,
Julian (Fozzy The Bear)

 

Sounds like you don't like Hitec rx. Is the Hitec Supreme IIS 8-Channel any better? What have you found to be a very durable rx?