Going to put together a list of what I would need to build a quad rotor that can do some lifting. Quad built using motors on each corner.
Inspired by the stability of this quad. Video showing AP stability shown here.
LED Strips from HK to light the 4 corners.
Motors (listed in this post) Turnigy 2209. Going with this 20L-22 motor
Turnigy 18A speed controller from HK.
3.5mm plugs from HK
Body:
HK450 heli tail booms. Carbon Fiber ones, and Aluminum ones.
Props. Get them here?
Some more details.
I’ve began watermarking my images that get out on the web.
Here’s a script that watermarks right out of bibble.
I will convert my script to work in bibble as per that post.
I’ve decided to use William’s tricopter controller boards for my own copter.
Reasons being that I’m using 3 rotors, and that the code is written in basic, so that will be easy for me to edit.
I don’t plan on starting with the full IMU cube. Just 2 gyros will do for a start, and I will add on later. Probably a bad idea not to use the whole cube… should just bite the bullet, and make my life simpler, since the development of this copter is secondary to the platform I am after.
Also Will’s code will not dirrectly work on my machine, since I will be adjusting the pitch on the 3 corners, not the motor speed. And the servo that he controlls, will be used by me to control the main motor speed.
These modifications will be made to the code when I get to that stage.
After starting a few threads on RC Groups forums, and giving the design some thought, I’ve decided that the way I will be starting is with a quadcopter (was tricopter).
Change to a quad was dictated by the design of the frame. I couldn’t come up with an elegant and simple solution to design a body using few fabricated parts. A quad design uses much fewer fabricated parts. So far I only have to drill some holes in some aluminum angle. Simple enough.
I will use 3 tail rotors (HK-500GT Metal Tail Holder (Align part # H50073)) since they are pretty cheap, at $13. That’s about the cost of one good prop.
Using HK450 tail units instead of the hk500 tails. The 450 has cheaper components.
One central motor will drive the whole system, which will be located in the center of the craft, and will drive the rotors using the belt system that comes with the tail rotors.
No rotation mechanism will be used on the rear rotor, as I will use a few vanes, and adjust their angle to direct the thrust. This should simplify my build considering, and it won’t interfere with the belt drive system.
I will eventually duct the props, for increase efficiency, and safety (so failed blades won’t kill anyone). Speaking of ducting, there a great thread here on construction of a ducted propeller build. Need to finish reading.
Found some interesting info on propsizes and thrust produced here. Need to give it a look.
Interesting: variable pitch heli tails not as efficient as a prop…here.
Another interesing post to read here, regarding variable pitch rotors.
Another Hong Kong shop for heli parts, here.
Forum post on SAFE lifting weight of different sized RC helicopters. Did a plot, and the trend seems to be exponential.
No 205mm blades, but from this, I’d estimate a safe lifting weight of 0.42lbs (190g). Not quite what I expected.
Servo choices: I looked at the recommended servos for a 250 and 450 sized helis. They seem to recommend similar size servos for both copters. 1.8Kg-cm servos seem to be recommended. So 3 servos should be able to put out 5.4Kg-cm of torque. I am also looking for a digital servo, so that raises the price a little, but I think I found a 3.5Kg-cm digital servo at just over $11. Less torque, but I think should be adequate.
I should use this servo torque calculator to estimate a torque, to see if my choice is correct.
Torque tube upgrades: Tarrot Torque tube upgrade
Very interesting thread.
http://www.rcgroups.com/forums/showthread.php?t=567290
Excellent and lengthy article on the use of everything that is milling machine.
For the version 3.0 of the copter, I am planning on getting 3 sets of the HK-T250 CCPM Electric Helicopter Kit which are only $30 each.
I will need 9 servos (3 servos per rotor swash plate) , and these look great value at $9 per pack and had great reviews. Turnigy 1800A SERVO 8G/1.7KG/.10SEC (3-PACK)
The microcontroller will have to control the speed of 3 motors, as well as 9 servos. Initial thoughts on this seem to tell me I may need 1 processor per rotor (controlling one rotor motor and 3 servos).
So 3 processors (one per corner) and then a 4th processor collecting data from IMU, and giving instructions to the other 3 controllers.
Or maybe use an ATmega1280 (Arduino Mega) which has 54 I/O channels, 14 of which can drive PWM. I would only ned 12 PWM channels.