What size propeller for a 36 V DC motor?

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.
Thanks.
Reply to
John Doe
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You need to know some more things to be able to guess.
Need to know how many RPMs it turns.
Need to know how much amps it pulls at what HP level. You can make a dynamometer by putting the motor on a stand that has a lever on it that will lift some weight a certain number of degrees, which will allow you to measure torque. Put a dummy prop on it that will put a reasonable load on it.
Lacking that info, or a motor number, NFI.
Reply to
Morgans
These guys are experts in R/C electrics.
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would be interesting to see what they come up with.
Reply to
Anyolmouse
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.
Reply to
Morgans
...
I will consider that when simulation flying.
Flight of the Phoenix (2004) :D
I tried researching the printed numbers on the motor, but got nothing.
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?
Reply to
John Doe
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.
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.
Reply to
Tim Wescott
Very good point. The bearings do take all of the load, called thrust, and it depends on the type of bearing whether it can stand the end load. Most likely that motor would not do well. It would be best to use a geared adapter to turn the prop, and that will remove the thrust load from the motor. Check model supply places for a suitable gearbox.
I seriously doubt that you are going to get more than 8 pounds of thrust out of that motor, even with the ideal gearbox and prop. Probably not going to do well to move a person on skates.
Reply to
Morgans
I hadn't realized this was part of the whole skater thing.
You'll do much better to drive the skate wheels with the motor -- driving a vehicle by pushing on the air is just not efficient, it makes little sense to do so if you can drive a wheel.
(For obvious reasons you can't make an airplane go by driving the wheels -- hence, propellers).
Reply to
Tim Wescott
...
How about a "thrust bearing"? "Handles thrust loads, also called an axial or side load, which is a load parallel to a shaft. Facilitates smooth rotation between surfaces like other rotary bearings, but their design supports higher thrust loads. Choose from plain and ball bearing designs. "
Reply to
John Doe
...
Right... Just depends on how easy it is to try. But maybe I can get a feel for what sort of electric motor would do. Propeller powered inline skating has been done with small gasoline/petrol motors.
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The first clip is on topic after the cool hang gliding introduction.
But I would not want to use a noisy gasoline motor.
Thanks.
Reply to
John Doe
I believe that, but how come you never see a real airplane standing on its tail? Looks like that would be a neat way to simulate a Harrier landing, and takeoff.
Reply to
John Doe
Actually you can do it. It is just too expensive and dangerous.
As for your project. The best is to experiment with it. As a starter, you should calculate the power that you need. Power is a function of battery, not motor. The motor rated power is the sustained power that the motor and windings can withstand for along time.
the motor power is defined by rpm x torgue. rpm is proportional to voltage
How much rpm can your motor stand for a short time, mechanically.
torgue is proportional to current. How much current can your motor stand for a short time. Current creates heat so the limit is heat. If you can put cooling system to this motor you can operate it at high torgue, at least for a short time.
Propeller theory. Propeller is just like a screw. How far does it go per RPM. At low speed, the air need not travel so fast, so low pitch is desirable. In order to increase the thrust, you need high volume running at low speed. Long propeller.
You don't need maths. Just a sense of balance.
So adjust the pitch and diameter of the propeller to match the voltage and current rating of your electric motor.
You can exceed these ratings, but take special precautions, such as cooling the coils. In fact I like to experiment with overcurrent and its effects. Over RPM is dangerous because it is mechanical. Over current is just heat which we can control.
Reply to
Ir. Hj. Othman bin Hj. Ahmad
| "Morgans" wrote: | |> 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. | | I believe that, but how come you never see a real airplane | standing on its tail?
Because you don't look in the right places?
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Ultimately, yes, for electric flight, most of the innovation is happening with models and UAVs because that's where it's more practical. Once you get into planes large enough to carry humans, the cost difference between electric and internal combustion becomes huge. For example, for a powered parachute, somebody mentioned a 30 hp engine. You could have that engine for a few hundred dollars, perhaps a thousand, but a comparable electric setup would cost way more, and something that will keep you up for an hour or two will weigh way more than the equivalent gasoline powered setup and cost even more.
Full scale electric planes do exist, and I would expect more work in that area, but it's not going to really be practical for most uses until battery or fuel cell technology gets a lot better (or at least cheaper.)
And also, if your model fails, you've got a pile of sticks to fix up. If your full scale plane fails, you might be dead.
But good ideas certainly do flow in both directions.
| Looks like that would be a neat way to | simulate a Harrier landing, and takeoff.
Yes, though the examples I gave had massive problems. The first was never even taken off vertically!
Reply to
Doug McLaren
"Doug McLaren" wrote
Yes, it did. Another interesting feature (that I read somewhere) of the Lockheed XFV you linked to was the fact that the pilot's seat was designed to pivot close to 90 degrees during landing and takeoff operations, so the pilot would stay level, or close to it.
I would love to see how the engineers had all of the control linkages designed, and the instruments placed so they would be useable.
Reply to
Morgans
I should have worded that better, for clarity.
I meant to say, yes it did have massive problems, _not_ that it had never taken off vertically.
Reply to
Morgans

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