Kirk's point about arcing in brushed systems gives some people the willies when it is mixed with a gasoline-powered generator and/or propane stove/oven in the cabin. If there is a fuel leak, the heavier than air fumes gather in the bilge and a brushed electric motor, if not ignition protected (such as an air cooled, open frame), can make sparks which can ignite the fumes.
Needless to say, there are thousands of Atomic 4-powered boats out there as well as who knows how many propane stoves in boats today that operate in relative safety. But we also hear/read of occasional explosions of boats, mostly due to exactly these causes.
Your boat, your money, your decision.
There are fume detectors and bilge blowers available and insurance companies will require that these be installed in order to insure. Awareness of potential problems is the only way to be able to avoid them.
Mike (of Bianka) has a brushed motor (Thoosa 9000) on his boat as well as a gas-powered Honda 2000 generator and after reading his installation history on his blog, I would have no qualms whatsoever about stepping aboard his boat. Hell, I'd even bring a case of beer for the privilege of seeing his setup in operation .
So as to avoid a potential lively debate, I will say that much has already been said on this topic in this forum. Use the forum search tool on the yahoo website to read those posts. There are people on both sides of the brushed/brushless is better fence. This is unlikely to change. If anything, it fosters competition in the market place and benefits us consumers by keeping prices of systems collectively lower. Choice is good.
Cheers,
/Jason
--- In electricboats@yahoogroups.com, Kirk McLoren <kirkmcloren@...> wrote:
>
> A DC Brushless Motor uses a permanent magnet external rotor, three phases of driving coils, one or more Hall effect devices to sense the position of the rotor, and the associated drive electronics. The coils are activated, one phase after the other, by the drive electronics as cued by the signals from the Hall effect sensors, they act as three-phase synchronous motors containing their own variable frequency drive electronics.
> BLDC Motor Pros
> * Electronic commutation based on Hall position sensors
> * Less required maintenance due to absence of brushes
> * Speed/Torque- flat, enables operation at all speeds with rated load
> * High efficiency, no voltage drop across brushes
> * High output power/frame size.
> Reduced size due to superior thermal characteristics. Because BLDC has the windings on the stator, which is connected to the case, the heat disipation is better
> * Higher speed range - no mechanical limitation imposed by brushes/commutator
> * Low electric noise generation
>
> BLDC Motor Cons
> * Higher cost of construction
> * Control is complex and expensive
> * Electric Controller is required to keep the motor running. It offers double the price of the motor.
> ________________________________
>
> A Brushed Motor has a rotating set of wound wire coils called an armature which acts as an electromagnet with two poles. A mechanical rotary switch called a commutator reverses the direction of the electric current twice every cycle, to flow through the armature so that the poles of the electromagnet push and pull against the permanent magnets on the outside of the motor. As the poles of the armature electromagnet pass the poles of the permanent magnets, the commutator reverses the polarity of the armature electromagnet. During the instant of switching polarity, inertia keeps the classical motor going in the proper direction.
> Â
> Brushed Motor Pros
> * Two wire control
> * Replaceable brushes for extended life
> * Low cost of construction
> * Simple and inexpensive control
> * No controller is required for fixed speeds
> * Operates in extreme environments due to lack of electronics
>
> Brushed Motor Cons
> * Periodic maintenance is required
> * Speed/torque is moderately flat. At higher speeds, brush friction increases, thus reducing useful torque
> * Poor heat dissipation due to internal rotor contsruction
> * Higher rotor inertia which limits the dynamic characteristics
> * Lower speed range due to mechanical limitations on the brushes
> * Brush Arcing will generate noise causing EMI
>
>
> Â http://www.dynetic.com/brushless%20vs%20brushed.htm
>
> "Happiness is a perfume you cannot pour on others without getting a few drops on yourself. â€
> â€" Ralph Waldo Emerson
>
>
> ________________________________
> From: Carter Quillen <twowheelinguy@...>
> To: "electricboats@yahoogroups.com" <electricboats@yahoogroups.com>
> Sent: Sunday, November 20, 2011 11:14 PM
> Subject: Re: [Electric Boats] Re: new lithium battery breakthrough?
>
>
> Â
> Where's the fun in that? One man's conspiracy theory is another man's reality.
> Â
> Don't get me wrong, staying on topic is fine too, we're all here to share our ideas, knowledge and experiences with electric boating but there are bigger pictures items that are obliquely relavant so what's the harm in discussing them. And I don't recall any talk of "nebulous technology" by anyone, except maybe Kirk with his perpectual motion machine, but hey, why not? This is for fun, isn't it?
> Â
> So before we abandon free thinking and for all the republican yachtsmen out there I'd just like to say:
>
> Climate change is really happening, global warming is not a left wing conspiracy to promote a socialist agenda,  unbridled greed and mankind's self absorbed passions are poisoning this world for future generations. This is a fact, not a paranoid delusion. Humanity really is rapidly changing the chemistry of our planet for the worst and I personally believe that the development of efficient electric boating technology is just one of many small steps in the right direction, that's why I persue it.
>
> But if getting a little philosophical here is forbidden by the thought police then lets get back on topic.
>
> Could someone please explain why, or if, Â brushless motors are so much better than brushed motors?
>
>
> ________________________________
> From: Ed Bachmann edbz <edbz@...>
> To: electricboats@yahoogroups.com
> Sent: Sunday, November 20, 2011 10:54 PM
> Subject: Re: [Electric Boats] Re: new lithium battery breakthrough?
>
>
>
>
>
>
>
> Could we get back to electric boats and skip discussions of distant and nebulous future technologies, land-based power generation and conspiracy theories?
> Â
> Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Ed B
>
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