Twin EDF Help - RCCanada - Canada Radio Controlled Hobby Forum
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Old 02-27-2016, 05:23 AM   #1
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Twin EDF Help

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A few years ago I stumbled across an article where another modeler had converted a Combat Models A10 kit from the recommended .46 nitro pusher into dual electric fans. Being a big fan of the A10 I acquired a few of these kits cheap. As rumored the kits are often short parts which explains their demise. I came out of it with 3 complete kits and spare airframe parts. These kits get glassed so the appearance and durability is better than a typical foam model.

I have two Wemotec Midi fan units with Arc 36-55-2 motors. The original article had the same basic fan units with brushed motors, two NiCad packs in series through a single speed controller and parallel motor hook up. These fans and motors are capable of 11 lbs thrust and 50,000 rpm each which is pretty overkill for an 8 lb model. The motors are 1380 Kv and 30,000 rpm should be more than enough thrust from the pair. That puts me at 22 volts.

Question: Can brushless motors be run in parallel through a single speed control?

It may make sense to change the motors with a higher Kv. Any thoughts?

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Old 02-27-2016, 08:17 AM   #2
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Re: Twin EDF Help

No. Brushless need their own ESCs
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Old 02-27-2016, 08:18 AM   #3
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Re: Twin EDF Help

Never ran a dual EDF setup, but this is what I found even with props:

It is impossible to do as you request. Instead of internal mechanical timing through the brushes and commutator for the DC brushed, these are 3-phase AC with no contact between the fixed and rotating cage.

Each brushless needs to run only one motor since they read feedback through the phases for timing the output. Two motors would throw them for a complete loop.

There are a few other concerns, as well. These I do have experience with:

You are usually limited to keeping the ESC battery leads the original length and extending the ESC/Motor wires. If absolutely necessary to lengthen the batt leads you should look into adding capacitors to prevent the ESC from damage.

If each ESC has a BEC you need to disable one, (usually by removing and insulating one red wire from the ESC throttle channel lead) and only use a single BEC to power your flight system. Worst case you can run an external BEC. It can be sourced from the same battery for the motors or run from a secondary. In a lot of cases the BEC is eliminated from higher current ESC setups due to electrical switching noise.

You do need to keep all negatives tied together to minimize noise anyway.

To answer your final question, normally as the input voltage climbs the motor Kv rating drops to maintain within peak RPM and efficiency.
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