Endurance Suggestions Please

[helinewbie]

Hi, I am new to RC helicopters, but trying to learn what I can to compete in a design competition. I am interested in designing and flying a helicopter for a long length of time >30 mins. I would also like a minimal amount of useful load for a camera + transmitter. As of now, I can just put ballast where the camera would go for proof of concept. Speed and maneuverability are not really issues.

What configuration do you think is best? Coaxial, conventional, tandem, etc
What is the most efficient electric motor? Cost is not a factor
What is the best battery mA-H/oz? Cost is not a factor
What would be an efficient rotor diameter?
Variable RPM or collective lift?

Thanks for your suggestions!

[Aztek1701]

Hi,

Welcome

Interesting problem that considering how horribly inefficient the whole concept of a helicopter is lol. I cant answer your questions directly because Im no expert (maybe someone else watching can) but I can probably generally answer and point you in a direction to look...

To do what you want, in my opinion youd be best with a tandem rotor design because then 100% of the thrust is being put into lift. The downside is controlling them is a nightmare and all of the model ones I have seen need 3 gyros to make them controllable. Co-Axial is easier to control but more ineffient because the thrust from the top rotor will disturb the air that the bottom rotor is using.

Motor wise, you have to be looking at a good brushless unfortunately, I cant name names here. Maybe a hacker, platenburg, or neu will do what you want.

At the moment as far as I know Lipo is the highest energy density easily available I believe that Life (A123) batteries may be better but at the moment they are still quite new... this link might help http://www.batteryuniversity.com/partone-3.htm

The Rotor diameter is linked to the wieght of the machine you are trying to lift and the speed of rotation but from the models and real helis that Ive seen.. rotor diameter is about 1.5 times the size of the body. The key to efficency is the weight

Go for collective its heavier but more efficent becase you can "tune it" so that your power source is under least strain.

I hope this helps... Good luck with it

Azzy

[hawkman]

More than 30 minutes flight time? good luck!

I have a petrol engined heli that will do 30 mins on a tank...and can carry a camera.

To be honest if you were after a camera platform and dont mind some forward speed then maybe a plane would be the better option?

I have a plane that I use with a 'Flycam', results are very good considering the cams small size....it uses an SD card...and you can select either filming or photos at 4 second intervals...I select the mode and press record and then take off...the results are always good. I plan to use my setup for surveying old housing sites around the Islands where I live...The Heli I use will come into play as well...you can get a different perspective with a heli.

[helinewbie]

Thanks for the input. I need to go with a helicopter so that I can have hover capability inside a large room. Hence the need for electric. I had heard that brushless motors are the most efficient. I didn't realize that tandem configurations are so difficult to control. I agree about the inefficiencies of coaxial, but they are inherently stable.

[Aztek1701]

Hi Again,

Im intrigued, can you say what your application is?. What size of camera are you trying to lift?.

Take care... Azzy

[helinewbie]

I don't really know what kind or size of camera to use. I figured I would just add the equivalent weight in ballast to show that the A/C is capable of carrying the camera and transmitter. The A/C needs to be able to fly within a 20x20 room and down a hallway. Right now I am thinking coaxial would be the best configuration to fit down the hallway.

Thanks for your interest.

[Aztek1701]

Hi there,

flying in a 20x20 room and a hallway means that you are looking at a small bird. You could get away with blade CX lifting a wireless minicam (about the size of a block of Pool chalk with a 9v battery) but I dont think that you could ever get anywhere near the 30min endurance with a bird of this size, the most flighttime I see you getting is about 10-12 mins with a 1500MAh 2cell lipo and a de bodied CX stripped down to save every ounce of wieght. You might also be able to power the camera from the flight lipo to save more weight but bear in mind that the power the camera consumes will come directly from the flight time .You might get 15-20 if you dont fly the camera. The problem with this set up is that the camera isnt brilliant resolution wise and the vibration will be an issue.

Hope this helps... Azzy

[mrmuffinmanvw]

Originally Posted by helinewbie

Hi, I am new to RC helicopters, but trying to learn what I can to compete in a design competition. I am interested in designing and flying a helicopter for a long length of time >30 mins. I would also like a minimal amount of useful load for a camera + transmitter. As of now, I can just put ballast where the camera would go for proof of concept. Speed and maneuverability are not really issues.

What configuration do you think is best? Coaxial, conventional, tandem, etc
What is the most efficient electric motor? Cost is not a factor
What is the best battery mA-H/oz? Cost is not a factor
What would be an efficient rotor diameter?
Variable RPM or collective lift?

Thanks for your suggestions!

Take a step back what you want to do and the flight time you are looking for are not a reality at this point in time maybe in a few years. With the best motor and the best battery you still will never be able to get the kind of time your looking for, than even if you could flying a heli for a half hour straight would be very hard if not close to impossible.