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STUDENT HELP

#21
I think we are probably still missing some info on the rules.

We know you are limited to a motor and a craft that fits into a 24 inch circle (i wonder if a flying wing would make the best use of this space).

Are you limited in battery? Is one specified in the rules?

Are there rules on how long it needs to fly carrying the cargo?

I think sticking to the simple pinion gear setup and optimizing the prop is the best option. More complex gears setups will likely be heavier and add friction to the drive system.
Wow, I'm impressed. So what is the goal? Carry the most weight? Longest flight? Most efficient? What will the winning plane need to do?

@DamoRC makes a good point, a planetary gear system may be just too complex and heavy for the task.
successfully make two lap and carry as most weight asap in 8 minutes
 
#22
I think we are probably still missing some info on the rules.

We know you are limited to a motor and a craft that fits into a 24 inch circle (i wonder if a flying wing would make the best use of this space).

Are you limited in battery? Is one specified in the rules?

Are there rules on how long it needs to fly carrying the cargo?

I think sticking to the simple pinion gear setup and optimizing the prop is the best option. More complex gears setups will likely be heavier and add friction to the drive system.
Do you have a selection of props to try out?
yes and no I am currently looking for props. I want to try bigger prop yet I want to test if smaller one will get the most power out of the gearbox. Idk any recommend on prop. We use a 7inch 4.7 sf which we test with a thrust measure tool. We test with some prop like different pitch and inch but that was the best one. We never test the smaller one and slightly bigger one.
 
#23
Hrmmmm... i would think more along the lines of the dormiers. Run a long solid shaft so you can prop the front and rear of the plane with one motor.

Find a happy reduction gear that can turn two props (most likely lower pitch or even smaller size)
That is very interesting and how do you do that. Will the motor be too weak to lift up or even do better than one motor one prop.
 
#24
This is how the challenge work. No battery is being attach to the plane due to "too complex for some student"(i didnt write that). This challenge the power source is being attach to the plane by some alligator clip(to control, you add the voltage for more power or reduce for less power). The plane is being tension by the electrical wire from the power pole. The team will then have 8 minutes to fly and carry as much weight as possible. The minimum is 20 cm above the ground (count from the landing gear down to the ground)
*i will try to find some pics
 

Merv

Legendary member
#25
The plane is being tension by the electrical wire from the power pole.
So you are flying in a circle, like this guy. That is similar to what we call that control line. The handle he is holding has 2 wires, they are used to control the elevator. By changing the angle of his wrist. In theory these wires could be used to supply electricity to the plane. Not sure if anyone has done this, I’ve never seen it done.
 
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Merv

Legendary member
#26
This challenge the power source is being attach to the plane by some alligator clip(to control, you add the voltage for more power or reduce for less power).
So you have unlimited power? As much power as the motor can tolerate without burning up the motor? Any possibility of controlling the elevator, like control line?
 
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#27
So you have unlimited power? As much power as the motor can tolerate without burning up the motor? Any possibility of controlling the elevator, like control line?
yes, the power source is frok 9volt to 12volt. The idea is the same but I cant not use any surbo. The only "mechanic" part is motor and prop. I will try to get a video up here just isnt the best quality. The idea of flying in the circle is exactly the same just smaller scale and a pole instead of a human.
 

DamoRC

Elite member
Mentor
#28
I'm beginning to like this challenge more and more. What's the radius of the circle that the plane flies around (length of the power wires).?
 

Merv

Legendary member
#29
yes, the power source is from 9volt to 12volt. The idea is the same but I cant not use any servo. The only "mechanic" part is motor and prop. I will try to get a video up here just isnt the best quality. The idea of flying in the circle is exactly the same just smaller scale and a pole instead of a human.
I’m thinking you need to max out the amp draw on the motor. It would be helpful if you have any specifications on your motor, how may amps can it putt without burning it up. If you don’t have any specs on the motor we will need to sneak up on it. Test a prop for a minute or two to see if the motor gets hot, if not hot try a larger prop. You are looking for the motor to get hot enough you can comfortably hold for while but not so hot you have to immediately let go.
 
#30
I’m thinking you need to max out the amp draw on the motor. It would be helpful if you have any specifications on your motor, how may amps can it putt without burning it up. If you don’t have any specs on the motor we will need to sneak up on it. Test a prop for a minute or two to see if the motor gets hot, if not hot try a larger prop. You are looking for the motor to get hot enough you can comfortably hold for while but not so hot you have to immediately let go.
Alright, do you think gearbox will be a critical piece? Lot of good teams use them.
 

buzzbomb

I know nothing!
#33
He's limited to an eighty's style dc motor rated at 6 volts DC. He's got twelve volts DC available. The airframe doesn't even have to be an airplane. It has just has to haul a heavy load through the air and last for eight minutes. No control surfaces, just throttle and tethered to a post.

A frackin' blimp! Holy cow, build a blimp with some down thrust.
 

Merv

Legendary member
#34
Alright, do you think gearbox will be a critical piece? Lot of good teams use them.
I don’t have enough experience to say for sure. I think a gearbox would be beneficial. I also think you could have too much gear reduction. I'm thinking something in the 2-4:1 ratio, I don't think the answer will be 10:1. Others with more experience may have different advice.

I'm not sure if the limiting factor will be wing area or power from the motor. Here is my thinking for the plane, more air speed = more lift. So the question is how much airspeed will you need to achieve maximum lift with the wing area restrictions given. Can the motor supply enough thrust to achieve that airspeed. OR Will the motor wimp out before we reach the maximum potential of the wing area.
 
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#36
I don’t have enough experience to say for sure. I think a gearbox would be beneficial. I also thing you could have too much gear reduction. I'm thinking something in the 2-4:1 ratio, I don't think the answer will be 10:1. Others with more experience may have different advice.

I'm not sure if the limiting factor will be wing area or power from the motor. Here is my thinking for the plane, more air speed = more lift. So the question is how much airspeed will you need to achieve maximum lift with the wing area restrictions given. Can the motor supply enough thrust to achieve that airspeed. OR Will the motor wimp out before we reach the maximum potential of the wing area.
Yeah, I am currently using a 5 ish: 1 ratio cant remember right now. But the motor is very weak if you put a spinner and a big prop on it, it will burn out very quickly. This is the reason use a gearbox.
 
#37
Hey,
I wonder if a pusher airplane will able to carry more weight compare to a pull airplane( conventional airplane). Just a thought I had and waiting to know.
 

Hai-Lee

Old and Bold RC PILOT
#38
Hey,
I wonder if a pusher airplane will able to carry more weight compare to a pull airplane( conventional airplane). Just a thought I had and waiting to know.
Sadly not! The fast airflow from the propeller will be providing a fair bit of lift that you will not get if the design is a pusher!

Have fun!
 

buzzbomb

I know nothing!
#39
Hey,
I wonder if a pusher airplane will able to carry more weight compare to a pull airplane( conventional airplane). Just a thought I had and waiting to know.
Nah. From what I've read, pushers use more power to do the same thing. I don't know why.

I wanted to mention that you handled my initial outburst like a pro, though. I misunderstood what I was seeing and reading and you managed to push me aside with respect. That was very well done.

My next idea was helium bladders. Nope. I read the pdf. dang.

Keep in mind, my knowledge of aerodynamics is from my own schooling, and that was a long time ago. I get confused with RC because of what the power to weight ratio is capable of and the fact that my aerodynamics knowledge is so very basic.

You need lots of lift. Lifting surfaces cause drag, and that drag means you need more power. You were looking to the gearbox to get that extra thrust. OK.

Ratio. Back in my motorcycling days, I swapped out the rear sprocket for one with one more tooth. That little change meant I had less torque, but I pulled fewer RPM's at speed, got better gas mileage (I commuted on the thing, it was important) and generally stressed the drive train less.

I can kind of see it, but not quite. Does that give anyone any ideas?
 

PsyBorg

Wake up! Time to fly!
#40
I think I would try gutting a metal gear servo and use that gearing to drive the fattest slow fly prop it could turn.

Slow fly requires less rpm and more torque. Sounds like servo gearing to me....

Just my not had coffee morning musing so get others thoughts on this.