Brushless ESC question

[chuck chesney]

I have been running a brushless motor and it's ESC for a few months...love it, but have a question regarding running two brushless motors.

If I were to run two identical brushless motors in parallel, for instance in a Revell Gato, can they both be run with a single ESC? Of course, the ESC would have to be capable of handling the combined amperage.

Thanks,
Chuck

[tsenecal]

sensorless brushless motor/esc setups must

sensorless brushless motor/esc setups must use one ESC per motor.

[chuck chesney]

Thanks very much for the

Thanks very much for the quick response...It would have been nice, but no such luck.

[tommydeen]

Yes!! brushless is the way

Yes!! brushless is the way to go!! and for anybody thinking about putting a
brushless in in your boat. the combo we have been using is E-flite 400/740kv outrunner
momba speed controller
and hobby lobby has a nice collection of gearboxes for brushless motors.
and all run silent!!
Tom

[duke]

Hello Chuck, Tommy, All,

I noticed

Hello Chuck, Tommy, All,

I noticed your post about using a brushless motor and ESC in your sub propulsion. I have never tried a brushless system. I have gathered the impression from reading articles here and there that a brushless system was not recommended for slow running because the ESC would heat up too much. Is this a false conception?

Thanks,

Duke Rouchell
Daphne AL

[u-30304]

Hi & Greetings from Nordic

Yes,

Hi & Greetings from Nordic

Yes, partially it is correct, that BL ESC´s get hotter on partial throttle than
full power. This due their operation on on "closing and opening" fet´s in partial throtte vs full power, when fet´s run all time open. This closing and opening makes them hotter on partial power settings.

But, like I said, only partially. If your Esc is correctly "overlimited" compared
to used amperage, it should not be any issue, or together with proper cooling,
which in sub installation are maybe more difficult. I could not see any dramatic problems on that in sub´s, as amps are not in the level like in large size faster scale or competition surface boats.

BR & Merry Xmas!

[duke]

Thanks Nordic,

I think I will

Thanks Nordic,

I think I will stick to the old fashioned brushed motors for my next sub. I was simply surprised to hear about brushless motors in subs. But now that you explain, I can see a careful setup (water cooling, gear box for low current, etc.) would make them feasible.
Thanks and Merry Christmas
Duke
Daphne Alabama

[u-30304]

Hi,

well, yes , I could

Hi,

well, yes , I could not see that really big benefits in subs with Bl´s, and fact is, that brushed motors are more accurate in throttle handling (except sensored BL´s)

Once high power is needed, BL, definately yes, otherwise brushed are in some ways better than BL´s, depending on application.

Watercooling with BL´s in subs is a bit overkil, and like said before, a bit over
powered ESC compared to needed amp level, does not need any cooling with Bl

BR,

[aeroengineer1]

There is an inaccurate perception

There is an inaccurate perception that has come from the aviation side of modeling that brushless motors are used only to increase power, when this is not the only reason for using brushless. Now if you are going to build a speed boat, then brushless is a must, but the reason that brushless motors are producing more power is that they are more efficient. Typically they are 1.5 to 2 times more efficient in this size range, and will allow for increased run times and less electrical noise. As for the cogging issues, it is a non issue because with a gear box the typical cog will come about every 2-5 degrees, and with the water acting as a damper, this is not a problem at low speeds. Inrunners will improve this as the cog effect is lessened. As for the throttle ability, that is based upon the controller, the little experience that I have with the mamba has shown that it has great control, and it gets even better when I have a variable rate programmed into the transmitter.

Adam

[Guest]

If brushless motors are sensored,

If brushless motors are sensored, they are capable of being just as accurate as a brushed motor. They also have the added advantage of requiring virtually zero maintenance.

The main disadvantage is the high cost of reversible controllers, although they are steadily getting cheaper, no doubt a result of more and more RC car owners converting to brushless power.

The other disadvantage is that most of the motors on the market are aimed at flyers or car owners, and typically have a fairly high RPM per volt.

This means using a gearbox, which for me wipes out one of the great advantages of brushless motors- their high torque. I hate gearboxes with a passion!

Outrunners are better in this respect, but these don't tend to come equipped with sensors.

Some modellers in Germany have made their own motors, wound specifically for the speeds needed for marine use.

For my purposes a good quality industrial grade, brushed motor (Maxon, pittman, buhler etc.) will last a very long time, provide efficient power (efficient enough anyway) and the multi-pole commutators give negligible interference. They're cheap too, and can usually be run direct drive.

When they wear out, I'll upgrade, but I have a sneaking feeling that I will be the one to wear out first!

Andy

[scott t]

Since brushless motors do not

Since brushless motors do not need the mechanical connection
through the brushes, has anyone tried to build a brushless motor
where the rotor is outside the water tight compartment while the
field coils are in the WTC? Possible example might be a submersible
pump. This would remove the need for water tight seals.

-Scott

[Guest]

I've considered this, and I

I've considered this, and I believe that Cord Schroeder, in Germany, has already done something like this with his Deep Rover model.

I would think some protection of the armature coils, possibly dunking them well in epoxy resin, would be advisable. The magnets will be fine as they are usually plated, and shouldn't corrode- in fresh water at least.

I think a lot of in tank fuel pumps for modern day fuel pumps work on a similar principle.

Andy