i realize that i am dealing with multiple things at once and i am sorry about that but it is sort of one big multivariate equation so i sort of can't help myself at times
and YES and I have run across the 360ibl.... i hate to be asking about too many things at once so i decided to leave questions specifically about the 360ibl until later... but now that you mention it i do have a couple...
and YES and I have run across the 360ibl.... i hate to be asking about too many things at once so i decided to leave questions specifically about the 360ibl until later... but now that you mention it i do have a couple...
does anyone have any specific experience with this doubled up 180ibl system? are they using a single controller to address the needs of both motors? (if so a standby redundant controller would seem to be in order)
wouldn't the motors be slightly more efficient at turning battery power to motion if the belts were eliminated and the connections were directly motor to motor to propeller shaft?
i sort of asked this once before but it comes back around here.... hypothetically, if one were using one controller for each motor, set one to provide power while leaving the other in a regen setting mode wouldn't the net result be to transfer energy from one battery bank to the other while providing propulsion and losing just a bit to resistance or drag if you will?
seems like the regen function would also be able to balance battery sets through differential settings
gonna look up PMAC
From: Eric <ewdysar@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Tuesday, September 6, 2011 6:13 PM
Subject: [Electric Boats] Re: belt drives vs directly coupled motor shafts and torque
Hi Michael,
You're mixing two different issues but they can each be answered.
Reduction systems, belt and pulleys, gearboxes or chains are not significantly inefficient. My Browning greabox is 97% efficient, 2% loss to the gears and 1% loss to the seals, and it includes a thrust bearing. There are a number of belt drive systems that exceed 95% efficiency. I don't know about chains because I consider gearboxes or belt systems to be better, but some people have used them to some success.
While the torque from an electric motor is fairly constant through low RPM, the power generated is not. A motor that is overloaded will draw too many amps at low RPM and overheat. A motor that is underloaded will reach max RPM before drawing maximum rated amps resulting in an underpowered system. Using a reduction system allows one to match the motor output to the boat's resistance and the prop's ability to create thrust. For direct drives, AC induction motors are better suited for higher power at lower RPM, Solomon Technologies offers that type of solution.
Even though you didn't ask specifically, you may want to do a little research on the differences between BLDC and PMAC motors, they are subtle. Many people mistakenly believe that they are the same thing, but by correctly matching the controller type to the motor type, you should gain more efficiency than you might lose through your reduction setup.
It's good to see you coming up to speed, but for a while, you'll probably be missing something. Hang in there, it's not rocket surgery, but it is more complex than a set of oars.
Fair winds,
Eric
Marina del Rey, CA
PS. Anybody can put together a system that works, it's harder to figure out how to put together a system that works well....
--- In electricboats@yahoogroups.com, Michael Mccomb <mccomb.michael@...> wrote:
>
> aren't belt drives inherently inefficient if one compares that method of connection to a directly coupled shaft?
>
> AND...
>
> if electric motors produce the same torque at any rpm then why would one wish to gear an electric motor either up or down? wouldn't one simply want a slower revving more efficient propeller and then run a motor rated to run at 2400 rpm or more at 1000 rpm instead? i understand the cooling might be an issue with some motors due to the fans being an integral part of the motor but surely a secondary dedicated fan system could make up the difference for VERY little wattage
>
> again, am i missing something.... BLDCs do run at constant torque do they not?
>
You're mixing two different issues but they can each be answered.
Reduction systems, belt and pulleys, gearboxes or chains are not significantly inefficient. My Browning greabox is 97% efficient, 2% loss to the gears and 1% loss to the seals, and it includes a thrust bearing. There are a number of belt drive systems that exceed 95% efficiency. I don't know about chains because I consider gearboxes or belt systems to be better, but some people have used them to some success.
While the torque from an electric motor is fairly constant through low RPM, the power generated is not. A motor that is overloaded will draw too many amps at low RPM and overheat. A motor that is underloaded will reach max RPM before drawing maximum rated amps resulting in an underpowered system. Using a reduction system allows one to match the motor output to the boat's resistance and the prop's ability to create thrust. For direct drives, AC induction motors are better suited for higher power at lower RPM, Solomon Technologies offers that type of solution.
Even though you didn't ask specifically, you may want to do a little research on the differences between BLDC and PMAC motors, they are subtle. Many people mistakenly believe that they are the same thing, but by correctly matching the controller type to the motor type, you should gain more efficiency than you might lose through your reduction setup.
It's good to see you coming up to speed, but for a while, you'll probably be missing something. Hang in there, it's not rocket surgery, but it is more complex than a set of oars.
Fair winds,
Eric
Marina del Rey, CA
PS. Anybody can put together a system that works, it's harder to figure out how to put together a system that works well....
--- In electricboats@yahoogroups.com, Michael Mccomb <mccomb.michael@...> wrote:
>
> aren't belt drives inherently inefficient if one compares that method of connection to a directly coupled shaft?
>
> AND...
>
> if electric motors produce the same torque at any rpm then why would one wish to gear an electric motor either up or down? wouldn't one simply want a slower revving more efficient propeller and then run a motor rated to run at 2400 rpm or more at 1000 rpm instead? i understand the cooling might be an issue with some motors due to the fans being an integral part of the motor but surely a secondary dedicated fan system could make up the difference for VERY little wattage
>
> again, am i missing something.... BLDCs do run at constant torque do they not?
>
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