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Motors too close together

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Motors too close together

Postby Stevolution » Thu Mar 08, 2012 1:34 pm

Hi all

What is the thinking when mounting a pair of motors in a WTC... very close (basically nearly touching). Surely the magnetic fields in each motor affect their performance :?

I would upload pics.... but their isn't a pic upload from my laptop facility.

The pair of 385 motors are certainly repelling each others magnetic fields.
My only other option is to mount one further back than the other. Problem is that wastes a lot of space I don't have to spare.

Mmm
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Re: Motors too close together

Postby Chuck Chesney » Thu Mar 08, 2012 2:38 pm

Don't worry about it. I've run motors in very close proximity to each other for years, without problems. Your looking for ghosts that don't exist.
A bigger potential problem would be heat build-up, but even that is unlikely to be much of an issue in your boat.
Chuck

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Re: Motors too close together

Postby JWLaRue » Thu Mar 08, 2012 2:50 pm

I agree with Chuck....while there may be some ever-so-minor interaction of the magnetic fields, in terms of practical application there is not impact or negative effect from having the motors close to each other.

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Re: Motors too close together

Postby Stevolution » Fri Mar 09, 2012 5:14 am

I ran both motors apart with ammeters on them and then brought them together, the amps only increased by 0.3A on one motor and 0.2A on the other.

Not looking for ghosts, I was just suprised how much they opposed each other.

As for heat. They don't run that fast, so I think I all will be fine.

I assume to post pics I need to upload to Flickr or something and then carry across.
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Re: Motors too close together

Postby JWLaRue » Fri Mar 09, 2012 10:04 am

...try rotating one of them to see if aligning the magnetic fields makes any difference...

-Jeff
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Re: Motors too close together

Postby Stevolution » Fri Mar 16, 2012 12:20 pm

Anyone had issues with a pulsing ESC?

Got my two motors connected across the ESC - 15A rated. As I push away from neutral the ESC itself makes a squeaky/squawk sound and then the motors start to turn (is that normal? - never used a ESC before).

Full speed is fine, but at the lower speeds the motors slightly pulse - making the amps they draw pulse up and down by about an amp.

Doesn't appear to be the driveshafts causing it.

Shouldn't be the suppressing capacitors should it? (0.22uF across the motors and 0.1uF from each connection to chassis - standard MFA suppression kit)

Mmmm :roll:
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Re: Motors too close together

Postby Sub culture » Fri Mar 16, 2012 1:08 pm

Some ESC's make the motor windings 'sing'.

It's all to do with the chopping frequency the ESC uses to pulse power to the motors, some ESC's use a very low frequency e.g. 50hz which isn't audible, others use a very high frequency, which again isn't audible. Some ESC's use a chopping frequency of 1 or 2khz, which you can certainly hear.

Most people aren't fussed one way or the other, but some find it irritating.
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Re: Motors too close together

Postby Stevolution » Sun Mar 18, 2012 1:50 pm

How do you guys charge your battery packs? Do you have a watertight charging 'point', or do you have to open the WTC to get to your batteries?
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Re: Motors too close together

Postby Sub culture » Sun Mar 18, 2012 1:54 pm

You should never charge batteries inside a sealed container.

You don't have to remove them from the cylinder completely, just remove an endcap and hook them up. Some designs have the batteries in the wet space, so you don't need to touch the cylinder.
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Re: Motors too close together

Postby Stevolution » Sun Mar 18, 2012 3:05 pm

:roll:

Oh... never thought of that. Thats a real pain in the backside - having to open the WTC for every 'sailing'.
Especially as I have built mine with a set of side rails to hold the end caps in place, and it is also a tight fit.

I wonder if I could add a 'screw' lid seal onto the end of the WTC (Assuming I can find room), so that it acts as a vent and a charging point?
You shouldn't need much ventilation ... surely just enough to ensure the escape of any gas build up.
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Re: Motors too close together

Postby Sub culture » Sun Mar 18, 2012 4:59 pm

Some sort of vent should be okay.
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