How BLDC motor and Propeller hold together

Hey guys,

Please excuse me if this topic has already been discussed before and please do let me know if someone did.

The subject says it all. And I'm talking about the motors(Motor A2212/6T 2200kv for instance) used in RC aircrafts generally.

I do understand that the shaft and prop assembly holds on to the motor shaft tightly but i don't understand how the resultant system keeps itself attached even under heavy motor loads, and at the same time i can easily 'peel' away the shaft and prop assembly from the motor shaft when the motor isnt running.( Answer lies in the question itself? Centrifugal forces?

The prop adapter should not come off when the motor is stopped. If so, it will come off under load.
There are various different prop adapters. Most for this motor have a nut at the front. Turning the nut pushes the prop back towards the motor. This pushes the baking plate back and that backing plate squeezes the adapter against the motor shaft.

Its a reverse collet.

Thank you so much for the response.

You're right about the fact that the adapter shouldn't come off at all.

Honestly, even i thought of the same reason at first but didn't convince me enough considering what we are dealing with :expressionless:

So can the backing plate be replaced with another propeller of same hub dimensions, so that we can have a 4 blade propeller without compromising the motor performance and operational safety significantly?

Just a thought...

The backing plate is part of the prop adapter. The same backing plate should be used with any prop you are putting on.
A 2 bladed prop or a 4 bladed prop should not make any difference to the prop adapter.

I understand what you're saying but unfortunately i asked whether if it's logical to replace the backing plate with another prop, such that there would be 2 propellers attached together in cascade form. I thought of doing this to create an equivalent 4 bladed prop as i have propellers with only 2 blades each.

Thank you once again. =)

Is there room? I doubt that there is.
Why not just get a 4 bladed prop?

Also, why do you want a 4 bladed prop?

If you mismatch the prop to the motor you risk overloading the motor (burning it out or
burning out the ESC), or getting less efficient system. Its best to match props to motors
using any of the online calculators available.

@vinceherman -

"Is there room? I doubt that there is."

Yeah there's plenty of room for the second prop if the backing plate is removed. I haven't actually tested this setup but it does hold together just as it should. The only concern is that the hub of the prop is not made of metal unlike that of the backing plate.

"Why not just get a 4 bladed prop?"

I could go for a 4 bladed prop but i would like to see how this tandem rotor config. performs in comparison with the conventional 4 rotor prop. I know this is a really bad idea on the whole(burned motors, wear and tear) but I've been really keen to experiment on one since long. It's just that I didn't have experience setting up propellers onto bldc motors myself in the first place. Guess I may have to wear a helmet and grab a fire extinguisher ready before firing it up. If this works then I would try with 2 4-bladed props soon.

"Also, why do you want a 4 bladed prop?"

Like I said earlier, I just wanted to note the characteristics, such as it's speed, current, thrust, inertial effects to say the least. Again, I know it isn't a brilliant idea at all. But I love to see how it performs within it's specified limits.

Btw, thank you very much for the advice :slight_smile:

@MarkT -

True that but I'm just conducting an experiment on it. This setup may not be as beneficial as I thought yet I really wanted to know how truly it performs. :slight_smile:

747Sachin_S_K:
"Also, why do you want a 4 bladed prop?"

Like I said earlier, I just wanted to note the characteristics, such as it's speed, current, thrust, inertial effects to say the least. Again, I know it isn't a brilliant idea at all. But I love to see how it performs within it's specified limits.

The relative performance of 2, 3 and 4 blade props is pretty well known. The more blades the less efficient the prop is. Generally 4-blade props are used when there is not enough room for an equivalent 2-blade prop (which for the same power will have a greater diameter). Putting on a 4-blade prop of the same size as the working 2-blade will increase the power the motor takes...people have burnt motors out trying that trick.

But if you want to conduct your own experiments by all means go for it. But be very careful putting 2 props together as you describe. You may find you have bits of prop flying all over the place at high speed and getting a blade in your eye won't do you any good at all.

Of course none of this has much if anything to do with Arduinos.

Steve

Sorry for the late reply.

Thanks a lot @slipstick for the info and support.

Fortunately I do know how things can go technically wrong when dealing with motors. It's just that I'm totally new to hobby sized hardware.

And yes I do wear a full-face helmet before trying something unusual everytime. :slight_smile:

Hopefully I would post some results in some other forum in the near future. Thanks again. :slight_smile: