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Old July 27th 10, 05:17 PM posted to rec.models.rc.air,rec.aviation.homebuilt
Morgans[_2_]
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Default What size propeller for a 36 V DC motor?


"John Doe" wrote in message
...
I have a Bosch 36 V lithium-ion hammer drill motor with batteries
and charger. What sort of propeller would be appropriate to stick
onto the shaft of that? Would a powered paraglider propeller be
too big? I just want to get a rough idea of how much air that
motor can push. Any experienced/educated guesses would be
appreciated.


After I looked at your question again, I see there is one answer I can give you.

A powered parachute prop is made for around 30 some HP and up,. probably. Your
drill motor is less than one HP. So no, a powered parachute propeller would be
about 36 times too big. On top of that, that drill motor is probably designed
to turn many more RPM's that a PP motor, so that would make it even more
mismatched.

You need to find some articles to read on model airplane electric motors,
something that talks about the numbers a motor is rated for. I don't remember
what those numbers are named, since I don't do electric...

You can get two motors that put out the same HP, and draw the same number of
watts, but one is designed to turn 3500 RPM's, while the other is designed to
turn 12,000 RPM's. The slow one could have a regular two bladed prop mounted
directly on the motor. The one that turns 12,000 would be designed to turn a
ducted fan. (imitation fighter turbo-jet engine) Yet, they still put out the
same power. The ducted engine would be only good at low amounts of thrust, but
allow the jet to go really fast, while the prop plane would be able to take off
in a shorter distance and climb steeply, but would cruise at much slower speeds.

There is a lot to read online to help understand these subjects, if you look a
little bit. It sounds like you would be interested. Look in places that talk
about remote control airplanes, because that is what even the man carrying
experimental airplanes are borrowing knowledge from, on the subject of electric
flight. It is just at larger scales.
--
Jim in NC