Hi John and Dan!
Many emails as arrived lately so I dont remember if I have replied to them all..!
Thanks Dan for the clearification regarding gear reduction. Yes, I will use an inboard unit with fixed shaft. (And I think I understood what you meant about reversing rotation direction for a gear that is made for one motor-direction only..)
Thanks for the links to the planetary gears. Much easier to install than a belt drive. I will certainly consider a planetary gear!
John: When studying the formulas used in the Excel sheet, I see that the efficiency is calculated from input power (P=U*I) and output power (torque*speed), and I think we must expect that the torque figures are truly the torque produced by the motor being tested. Thus the efficiency must be for the motor only.
Nice calculator for eBike. I might use this if I do a eBike conversion later;-)
The 200-127 (which I got the graphs on) is suitable for my boat. I read on their homepage that the 127D is more powerful thatn the 127, but the 127 is powerful enough for my boat I think.
Regards
Bendik
On Thursday, August 25, 2016 7:27 AM, fitloose <no_reply@yahoogroups.com> wrote:
Hi Bendik,
I'd forgotten about those sheets. The 127 200 series is not the D version. The D stands for double magnets. Worth remembering the sheets are a motor driving a generator at constant voltage from a power supply so no voltage sag like a lead acid battery. Also the efficiency is the product of the motor and generator as I recall so if a motor at a given steady voltage and load (generator) then say one is 93% efficient and the other the same it is 0.93 X 0.93 = 0.86
Think I have that right without more than a glance at sheets. The trick though with props and gearboxes is to figure out a good voltage and load (amps) combination that will give you efficiency at the thrust you need. I learned by doing sums then proving those with practical experiments.
Here's a fun calculator for electric bicycles which kind of gives you insight playing with motors etc.
John R
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Posted by: Bendik Vignes <bendik.vignes@yahoo.com>
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