Hannu Venermo, Thank you for your patiently explained run down on motors, My initial trial motor
has been selected, the first criterion, my budget concerns, was met....($105 on ebay). if it works out,
it, great! if not it, i will grab a more powerful hi rpm motor and rig a reduction transmission for it and
get larger motor controller (and probably go over budget)
I am a "rigger" and always on a tight budget...I look for hi quality stuff at a low price
that is surplus that I can cobble together for my projects and try to do it with flare...
so anyway this motor is from a large self- propelled (and battery run) floor scrubbing machine,
the kind used to clean big box stores. These ride-on machines cost over $25,000., they are like a
Zamboni for asphalt tile... so the motor is top notch hi-quality, industrial, built for continuous duty
and efficient for extended hours of battery powered operation. It is rated at 36volts, but runs great
with hi torque on 12v, and I bet will do fine at 48v. The best thing is it comes with a HD gear box and
puts out 300rpm at 36v....that is just perfect, hi torque/low speed. it is rated at 1000watts, which is
approx 1 1/2 hp at 36v, but could be considerably more run at 48v. (I'll monitor temperature closely)
The right angle drive is a used Nascar midget racer part, 3inches in diameter, good gears running in grease, 3/4 inch shafts in burly bronze bushings ($25. each, I bought two, one for a spare trany)
my prop is huge for the sailboat hull it will be pushing. its a big wide bladed bronze prop 18 inches in
diameter, at 17inch pitch, 300 rpm will give me 5mph if it doesn't slip much, I will be posting photos
of my propulsion contraption soon. it is built for whimsy, humor, perhaps a little showy in a
purposefully eccentric way...but hopefully it is also well engineered in a "mad max" sense.
The motor controller I purchased was a pulse wave mofit thingy from china also purchased on ebay for under $15....it seems to work, it has on off and a potentiometer dial, we will see how well and for how long under load, but its wattage/amperage rating is high enough for this motor. This motor reverses if one simply reverses polarity, I am hoping that the motor controller works ok if I switch plus to minus and minus to plus with the reversing switch I also bought ($6.00, you-guessed-it..on e-bay) If you know anything about this type
motor, which I think is a permanent magnet motor with brushes and whisper quiet, let me know if I can run
+ and - backwards through the mofit pulse wave controller when throwing it into reverse, If I can't I guess Ill get another $14 dollar controller for reverse.
thanks again for the help/advice
---In electricboats@yahoogroups.com, <gcode.fi@...> wrote :
Modern motor controllers are extremely efficient at almost any speed.
An example is brushless servo motors.
They are about 1/4 the size, and 1/10 the mass, of my old 3-phase 1/2 hp
Bridgeport motor.
The Bp is 18 kg, for 0.5 Hp continuous output.
Its made in maybe 1950 (? 1940), and is near silent.
The 750 W == 1 Hp AC brushless servo motor is 3 kg, at 1/3 the size, and
will output 750 W forever.
Near silent, longevity == 10.000 work hours.
The 2.5 kW servo is ==8 kg, and equally good.
The electronics have fan cooling, unlike the smaller 750 W ones.
VFD-driven 3-phase motors (ie industrial motors) == servo motors, these
days, of different (electronic) designs.
Depending on the design, boat motors may or may not be as efficient.
Mostly, they are not, and thus need cooling.
There is no engineering reason for this, just that the boat market is so
small, most stuff does not come from industry, today (yet).
Usually, where you get lots of amps, heat becomes a factor.
Thus, higher voltage == tends to equate to "better".
Price has no bearing on the matter.
Some servos I use (750) cost 590€ for the motor, controller, everything.
Some others (yaskawa,Siemens) cost about 1500 for the electronics,
alone, and 3000€ for everything.
A 3-phase VFD motor from surplus center, for example, can cost 1500$ for
10 Hp, and 2500$ for 150 hp.
Some controllers for brushed motors need cooling at higher powers.
A well known respected KBIC controller is an example.
Thus, it will be "less efficient" - and this is mostly seen in that more
modern, brushless, designs tend to be better in terms of torque,
efficiency, longevity, maintenance etc.
All above may or may not be relevant -
As for those buying a kit, there are only a relatively few options, and
price + other considerations tend to dictate what you can choose.
For those making their own set from scratch -
Its neither hard not easy - somewhere in between.
The motor and controller is the easy part - and anything modern and
industrial meant for harsh duty/service will work well.
It just needs to be coupled to a suitable driveline.
A boat motor and controller is just about the easiest thing there is,
technically.
Similar to a conveyor belt.
Heavy varying loads for an extended time.
An example is brushless servo motors.
They are about 1/4 the size, and 1/10 the mass, of my old 3-phase 1/2 hp
Bridgeport motor.
The Bp is 18 kg, for 0.5 Hp continuous output.
Its made in maybe 1950 (? 1940), and is near silent.
The 750 W == 1 Hp AC brushless servo motor is 3 kg, at 1/3 the size, and
will output 750 W forever.
Near silent, longevity == 10.000 work hours.
The 2.5 kW servo is ==8 kg, and equally good.
The electronics have fan cooling, unlike the smaller 750 W ones.
VFD-driven 3-phase motors (ie industrial motors) == servo motors, these
days, of different (electronic) designs.
Depending on the design, boat motors may or may not be as efficient.
Mostly, they are not, and thus need cooling.
There is no engineering reason for this, just that the boat market is so
small, most stuff does not come from industry, today (yet).
Usually, where you get lots of amps, heat becomes a factor.
Thus, higher voltage == tends to equate to "better".
Price has no bearing on the matter.
Some servos I use (750) cost 590€ for the motor, controller, everything.
Some others (yaskawa,Siemens) cost about 1500 for the electronics,
alone, and 3000€ for everything.
A 3-phase VFD motor from surplus center, for example, can cost 1500$ for
10 Hp, and 2500$ for 150 hp.
Some controllers for brushed motors need cooling at higher powers.
A well known respected KBIC controller is an example.
Thus, it will be "less efficient" - and this is mostly seen in that more
modern, brushless, designs tend to be better in terms of torque,
efficiency, longevity, maintenance etc.
All above may or may not be relevant -
As for those buying a kit, there are only a relatively few options, and
price + other considerations tend to dictate what you can choose.
For those making their own set from scratch -
Its neither hard not easy - somewhere in between.
The motor and controller is the easy part - and anything modern and
industrial meant for harsh duty/service will work well.
It just needs to be coupled to a suitable driveline.
A boat motor and controller is just about the easiest thing there is,
technically.
Similar to a conveyor belt.
Heavy varying loads for an extended time.
On 10/03/2015 13:06, billhopen@... [electricboats] wrote:
> I've a question about your motor efficiency, when you run your motor
> at lower power, does the motor itself get inefficient? I've seen
> power charts for certain motors that seem to indicate that at lower
> speeds, half the electric power is wasted, but at high output they are
> 90% efficient
--
-hanermo (cnc designs)
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