What size propeller for a 36 V DC motor?

On 07/28/2010 10:53 AM, John Doe wrote:
"Morgans"jsmorgan charterJUNK.net wrote:

"John Doe"jdoe usenetlove.invalid 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.

...

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.

I will consider that when simulation flying.

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.

Flight of the Phoenix (2004)

I tried researching the printed numbers on the motor, but got
nothing.

Those numbers are DeWalt part, inventory, date code, or (not very
likely) serial numbers. DeWalt would consider the motor specifications
to be proprietary information, so you'll not get your hands on it!

Even if the motor isn't made by DeWalt it'll still be custom made _for_
DeWalt, and the motor manufacturer would be contractually obliged not to
divulge details.

So you're kind of on your own there.

Does the forward push on an ordinary electric motor cause abnormal
wear on the bearings? Or maybe that is countered/supported by the
magnetic part of the motor?

It is _not_ supported by the magnetics. It may, indeed, cause
objectionable wear -- that depends on whether the motor bearings can
absorb the thrust of the prop (assuming you prop it directly).

For all but outrunner motors, you'd want a gear box anyway. Any
non-planetary gear box (or belt drive) will put a side load on the motor
shaft, but its much more likely that the motor is designed for that.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html