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Old Mar 12, 2012, 03:58 PM
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Silent Quadrotor - Has anyone built one using belt driven tailrotors?

Hi All

I would love to build a quadrotor, but I can't stand the "swarm of angry bees" noise they make. After seeing ( or hearing rather) the belt-driven modification of a Multiplex Funcopter, and the variable Pitch Quadrotor from MIT, I'm inspired to make "silent" quadrotor.

My idea is to start with four belt drive tail kits. I would replace the blades with larger diameter ones, and power them with a single high-power, low speed brushless motor like the one in the funcopter. This seems deceptively easy. Has anyone tried this approach? If so, can you offer any words of warning?
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Old Mar 12, 2012, 04:05 PM
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Belts and their gears will make quite a bit of noise, also, it would the craft have way too many moving parts..
What kinda noise do you mean?
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Old Mar 12, 2012, 04:06 PM
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Been done. Well, kind of, this was a gear linkage.

http://www.openpilot.org/op-member-b...ad-using-a-cc/
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Old Mar 12, 2012, 04:27 PM
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Originally Posted by wizprod View Post
Belts and their gears will make quite a bit of noise, also, it would the craft have way too many moving parts..
What kinda noise do you mean?
The piercing, beating noise that comes from four high-speed props travelling at slightly different rpms. (I have the same problem with gear-driven tailrotors like the stock funcopter tail, I guess I'm overly sensitive)

I know there will be more moving parts than the typical quad, but it should still be less complex (and easier to pilot) than a single rotor heli. Besides, I'm a mechanical engineer - this sort of thing is my bag.
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Old Mar 12, 2012, 06:11 PM
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Quote:
Originally Posted by bsimons View Post
The piercing, beating noise that comes from four high-speed props travelling at slightly different rpms. (I have the same problem with gear-driven tailrotors like the stock funcopter tail, I guess I'm overly sensitive)

I know there will be more moving parts than the typical quad, but it should still be less complex (and easier to pilot) than a single rotor heli. Besides, I'm a mechanical engineer - this sort of thing is my bag.


I'm having a hard time picturing the benefit of what you're after. What could be more simple than four props direct driven straight from the motor shaft? How is adding belts and pulleys to the system going to quiet anything down?

Ok, maybe I didn't pay close enough attention. You are wanting to replace 4 motors with a single motor which controls 4 varaible pitch props instead of 4 fixed pitch correct? That makes more sense.

Still not sold on any sound reduction though. At least not enough to make a huge difference, but maybe I should check out some of those links and maybe be enlightened.
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Old Mar 12, 2012, 06:21 PM
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Quote:
Originally Posted by bsimons View Post
The piercing, beating noise that comes from four high-speed props travelling at slightly different rpms. (I have the same problem with gear-driven tailrotors like the stock funcopter tail, I guess I'm overly sensitive)

I know there will be more moving parts than the typical quad, but it should still be less complex (and easier to pilot) than a single rotor heli. Besides, I'm a mechanical engineer - this sort of thing is my bag.
Have you tried listening to a multirotor with 13" or 14" props?

t sure is less complex than a single rotor heli, however it's much more complex than a normal multirotor. The gears will be point of failures, and you'll lose energy there as well.

It'll be a fun build, but not a very energy effective one.

With your background I'm sure you have considered all this already.
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Old Mar 12, 2012, 07:35 PM
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go for it but be prepared to find out why everyone else doesn't build multi's like that
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Old Mar 13, 2012, 11:40 AM
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Also keep a computer science major nearby. You're going to have to change the code running on the FC in order to compensate for for controlling pitch and not RPM.
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Old Mar 13, 2012, 02:58 PM
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Also keep a computer science major nearby. You're going to have to change the code running on the FC in order to compensate for for controlling pitch and not RPM.
Good point. I wonder where the code will be different. Instead of changing the PWM signal to the ESCs, I'd be changing the PWM signal to the servos. That, and I have to figure out what speed to run the one motor at. It sounds like a fun challenge though.

(I also have to see if a double-sided belt will fit into a standard heli tail tube so that I can get two of the rotors turning backwards)
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Old Mar 13, 2012, 04:17 PM
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Try to find 3 or 4-bladed props with less pitch. Buy good quality motors with less rpm, high voltage and build as light as you can and you will get e pretty silent copter. I just saw (and hear) today a hexa with 9" 3-blades instead of 8" 2-blade. It was a significant difference.
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