# Thread: making a motor lift on its own

1. How much rpm do the cd rom motors provide??
Also, how much rpm is necessary to generate necessary lift??

As there are Rs 1500 helicopters available in the market, it shouldnt be that difficult to generate lift, should it??

2. If those are heli's like Airhogs, then they just use a very tiny DC motor coupled with a large reverse gear ratio- meaning 1 turn of the motor results in several turns of the propeller. They also have a foam body and a stabilizer propeller at the rear.

Again if you search rcgroups in the multi-rotor forum forum, you will get info for CD-ROM motors.

3. Moving bodies are are weird; rotating bodies are absolute Magic. Not for nothing that we have Statics and Dynamics as separate topics of Motion Physics.

The behavior of a body is governed by forces acting on them. The question is whether it is moved by something or it moves by itself.
The following is a jist of motion facts relevant to this discussion:

1. A Rotating body is not governed completely by Gravity.
If you rotate a sphere at some angular velocity, it will move away from the gravitational pull ie., it is now governed by centrifugal force which will try to negate gravity. This is how the planets and other stuff stay up in space.

2. If the body is rotated by , say a motor, Newtons III Law will show up by rotating the body and the Motor in opposite directions.
When a motor drives a body, for all practical and sane purposes, one of it should be fixed. Fix the motor, the body will turn. fix the body, the motor will turn. Suspend the motor by its wire, it will lift itself with the body that it is turning and the entire system will rotate in the horizontal plane around the wire. This is the Gyroscopic effect.

Now, consider the body to be a Propeller.

The propeller is shaped so that it pushes the air as it rotates in a particular direction, when static ( it acts as a fan). If it is free , then the air remains static and the propeller will move, but in the opposite direction. It moves through the air in a helical, screw-type movement.
How much it moves depends upon the amount of air it can push per unit time. Simple design is to twist it at an angle; more the twist more the air pushed in time. At some RPM & degree of twist, it will over come gravity due to Newtons III Law.
The propeller can be designed to produce huge amounts of power with some trick engineering. These tricks use Bernoulli's principle, Coanda effect etc.,
Now the power delivered by the propeller is Thrust. It depends on speed.

Flight is a balance between different forces- Weight , momentum and thrust. These are aided by Aerodynamics and inertia for stability.

Your toy propeller flies because it is the only component that rotates. It generates lift due to its rotation and the shape of its blades. The thrust generated is quite high and makes it rise up quite fast.

4. ## making quadcopter

hey ice i am building a quadcopter as my final yr BE project need some help frm u.....

5. can u plz tell me is it possible to design my own ESC?...coz i have budget of around rs10k....n if not CDROM motors; then other high rpm brushless cost abt RS1300 and i am designing my own transmitter and receiver circuit...

6. it is possible to make an ESC, buti would recommend you buy one, it will be cheaper and consume less footprint, and weigh much less than when you make it.

http://indianhobbies.com/shop/index....=index&cPath=8

the link will give you an idea of how much things cost. Its just for an idea, and not a recommendation, as i have not purchased anything from them other than a couple of BLDCs. So I do not know how these ESCs perform.

7. thnx for replaying buddy....these indianhobby guys have shop in mumbai..i have visited them but at tht time they wr nt having enough components so am planning to visit thm again......where can i get brushless outrunners with speed sensors(hall sensors in built)?....is every outrunner is sensored?...and is thr any diff ESCs r available for sensored ones?....n can i interface a wired joystick wid ASK transmitter....as i said i am building my own wireless controller for quadcopter...plz help

8. Its better to go sensorless. I have made speed control for both types, and thats why i said its better you buy them if you want to put them in something that goes up in the air.

Sensorless is better. less wires and less mess. There ARE speed controllers available for sensored ones, but the ones i have and know about are heavy, and will not suit your purpose. and there is this site i browsed http://rotor.co.in/ ., i have not purchased anything from them, but i thought it might be useful for you.

:idea:
ask/PM docel. He will be able to guide you well.

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