UAV help

[@Eric]

I need to make an UAV like homework, and I need a little help
I have two 3v motors and one 6v motor, I bought a powerfull 6v battery, but it still on the floor, I was thinking about a kind of air compressed cylinder to help the aircraft. Anyone built an UAV that can help me?

[macdad-]

The 3V motors are running at what RPM? What kind of propeller are you using on the motors?
Can you provide a picture of your design?

If your having trouble getting it off the ground, a number of factors could attribute to it.

• Weight
• Rotation Speed of the Motors
• Aerodynamics of the Body/Wings

Workarounds for the factors:

>Weight
 A.Use lighter materials(Balsa wood, Carboard, or look at hobby RC Plane materials).
 B.Depending upon the weight of your battery, you should go with a NiMH or Li-Poly battery.
 C.Downgrade the weight of the payload(Control Circuitry, Camera).

>Rotation Speed of the Motors
 A.Increase the speed by using higher voltage motors.
 B.Increase battery voltage(But not too high to where you damage the motors).
 C.Decrease the weight of the propellers.
 D.Increase the torque of the motor to compensate for the weight of the propellers.

>Aerodynamics of the Body/Wings
 A.Use hobby RC Airplane wings or body.
 B.Build your own wings by using aircraft wing designs
 C.Most Challenging and Extreme but cuts down on weight, design a lifting body(Google it)

Hope this helps,
Nick(macdad-)
 

[@Eric]

All right, here is the propellers, I have 3, and one I didn't install yet.

 And here is the design of the aircraft,:




I'll leave the battery on the ground, just the aircraft will get off the ground with a thin wire plugged in the 6v battery
and I built it on styrofoam reinforced with fiber glass. About the motors and the propellers, I dont know if will be necessary to increase some torque.  My major mistake was to have me more concerned with details than with the objective of the aircraft  
I don't care if I'll need to build it again, but I need to make it perfect because I wanna be an aircraft engineer, it's my future and I have to impress  
and the last thing, he will get off the ground vertically, like a helicopter  


I dont know if you can see these pictures, but I can send it to your email. just tell me if it will be necessary

[random robots]

may i suggest something? http://www.hobbyking.com/hobbyking/store/uh_index.asp it has cheap motors, props, and other things for a uav. here is a link for the products im deciding to buy http://www.hobbycity.com/hobbycity/store/uh_showCart.asp?idproduct=9470&lasturl=/hobbycity/store/uh_viewItem.asp?idProduct=9470. i would suggest buying motors and props instead of using ones found around the house.

hope this helps,
Patrick
edit- can i have the weight of the plane and trust of the motors+props? thanks

[@Eric]

of course, any kind of help is great
this is site is very interesting. but I found a perfect 6v motor in a old RC car, and it's perfect because is small and powerfull for what I want, and I found two 3v motor with the same size of the 6v motor, this is good because the equilibrium, but I can't find others 6v motors like the other, so i'll need to use the 3v motors, =/ and the motors was the only thing that I use around the house 
thanks for the site 

[random robots]

can you weigh the motors and give data on how much force they give with the props?

Patrick

[@Eric]

the motor :about 65g
one motor + prop : about 85g  sorry 
and I dont know exactly how much force they give with the props ,sorry,  

[Razor Concepts]

That is waay too heavy. Are you sure a motor is 250 grams?? That must have been one monster of a RC car. If it really is the true mass, your UAV will have to be very big to make up for the heavy powerplant.

I also recommend hobbyking, $15 could get you a ~100 gram powerplant that can fly a plane with a 48 inch wingspan

[random robots]

i have an idea for how to measure thrust. make a rolling rig, add the motor and prop onto it, weigh it, and then test with different weights when the would starts going slower than the speed you want, weigh the highest weight you measured that didn't go slower than your wanted speed, add that to the weight of the rig, and you have the motor+prop thrust.

hope this helps,
Patrick

[@Eric]

its really a good idea, I have a rolling rig, and I'll check it out, thanks
and about the air compressed cylinder, do you think that it's a good idea to get it off the ground for a instant?

[random robots]

im not so sure about the cylinders... im pretty sure all they would really do is add a lot of weight to the plane. they aren't likely to work well as rockets. a homeade uav shouldn't be very large and heavy, so don't use them if you want it to be small or medium sized.

[@Eric]

ok, and do you think that i'll need to increase torque of the motor?
thank you again

Eric

[random robots]

adding motor torque? that isn't necessary unless the motor can't move the prop at the wanted rpm.

Patrick

[chelmi]

I found a perfect 6v motor in a old RC car, and it's perfect because is small and powerfull for what I want

Well it's obviously no powerful enough because it does not provide the necessary lift...

[@Eric]

chelmi:
so what do you think necessary voltage?


Oh, I was thinking to use a Brushless Motor, if it will be necessary, what do you think? 

[Razor Concepts]

Voltage really isn't the thing that determines power. These motors below are excellent and are actually designed for flying craft:

may i suggest something? http://www.hobbyking.com/hobbyking/store/uh_index.asp it has cheap motors, props, and other things for a uav. here is a link for the products im deciding to buy http://www.hobbycity.com/hobbycity/store/uh_showCart.asp?idproduct=9470&lasturl=/hobbycity/store/uh_viewItem.asp?idProduct=9470. i would suggest buying motors and props instead of using ones found around the house.

hope this helps,
Patrick
edit- can i have the weight of the plane and trust of the motors+props? thanks

As for measuring thrust, you have a scale, so zero out the scale while the motor is on the scale, run the motor and see how much it "weighs" to get the thrust

[random robots]

you should use brushless motors for flying 'bots

[@Eric]

As for measuring thrust, you have a scale, so zero out the scale while the motor is on the scale, run the motor and see how much it "weighs" to get the thrust

So the weight that the scale is showing while the motor is running is the necessary to get the motor off the ground?

[Razor Concepts]

Kind of.. its just the thrust produced. For helicopters, that number is definitely the maximum weight your craft can be, but you have to have it weigh a little less to actually climb up into the air.

For planes, your plane can be heavier than the number, and the plane just uses the wings to produce the lift instead of only the motor and prop like a helicopter.

[random robots]

As for measuring thrust, you have a scale, so zero out the scale while the motor is on the scale, run the motor and see how much it "weighs" to get the thrust

So the weight that the scale is showing is the necessary to get the motor off the ground?

no, its the amount of weight the motor can lift

[@Eric]

ok, and.. I'm still having problems with the 3v motors, they really cant get off the ground =/, I'm thinking to use only the 6v motor, decreasing my project.. but, making it fly. anyway, i'll see the ways.. and I dont know if you can see the pictures that i put here, just tell me who wants to see it, and i'm going to send trough the e-mail

Thanks  

[random robots]

now can you give me thrust data?

[@Eric]

I dont have a balance now  

[random robots]

what about the rolling rig idea?

[@Eric]

...add the motor and prop onto it, weigh it...

sorry man, i dont have a balance  

[random robots]

ok, i have two ideas. one, use the rolling rig idea without the rolling rig, so you won't have weigh anything. or, you can use a newton scale to measure the force of the motor. then you change the measure in newtons to weight it can pull.

Patrick

[@Eric]

Ok, but look. I cant test the motors with different weights, if the motor dont get off the ground yet, I need to ''increase'' more ''power'' in the motors, and when the motors will be able to get off the ground quietly, i'll increase different weights, did you understand me? my principal goal now is to make the motors sufficiently powerfull to get them off the ground, and later test with differents weights, I'm not sure if I understood your idea.. but i need to make my principal objective first , to understand your idea. I dont wanna be unbred, just telling you my situation 
Thanks

[MechHead]

With random robots last idea the motors don't need to leave the ground, if it's on some rolling rig thing the force it makes with be sideways and use the newton scale to measure how hard it pulls.  With this you wont need to add weights or whatever, you will know the exact force it is capable of exerting.

[Razor Concepts]

Eric is saying if the motors alone cant lift their own weight, its pointless to test them since nothing will fly anyways since just a motor won't work.

This is the kind of stuff where if you just spend a little money you will save weeks of work. It isn't worth it to develop your own flight power system. Just $15 gets you a complete brushless motor, matched prop, and speed controller.

An entire UAV is going to cost a few hundred dollars, basically the cost of a RC airplane, but with autonomy added to it. Remember that to make your UAV legal you must have a radio that can take back manual control.

[random robots]

i think you should put on a bigger prop