The new propellers was a success

Last night I tried out the new 8 inch propellers along with a fresh motor to replace the last faulty one. The x550 now spins like a cat and flies like a bird. I trimmed the flight controller for the new propellers, which wasn't all that much to change and it's very stable.

After the basic trimming I started working on navigation and RTL (return to launch). These also has a set of P, I and D parameters for navigation. There is a good guide over at the ArduCopter wiki. However, I didn't have much success in trimming the RTL and the x550 always overshot or navigated wrong. Once both batteries were drained, I figured out that I'd trimmed using wrong parameters, dooh! I had been trimming the HLD_LAT/LON instead of LOITER_LAT/LON. Will have to do this at some other point where I can find a good field to try it out at.

Link to the guide: https://code.google.com/p/arducopter/wiki/AC2_loiter_PID

Packages packages, more packages and washers

 

This came in the mail today. It's the order for new motors and 8 inch propellers. Having smaller propellers also eases the torch on the motors, which should lessen the overheat.

Now I might have come to a conclusion why my motors are failing. Due to the nature of aluminum, its quite weak. Now as the screws that hold the motor in place slightly bends the aluminum inwards, the top of the screw seem to get scewed too far into the motor and may cause a short circuit.

To counter this condition, I've bought some washers. These washers are used both to protect the aluminum from bending too far and also to put some distance between the top of the screw to the motor. I also bought some locking washers to keep the screws in place keeping them from coming loose due to vibrations.

This is the end result, now only time can tell if it works or not. Will try this out tonight along with the 8 inch propellers.

Ultrasonic range finder and stuff

My trials with the ultrasonic range finder shows that it doesn't get too much interference from the other electronics that are located close by. I still made the rookie mistake by connecting the Echo and Trigger cable the wrong way around and spent much time trying to figure out what was wrong until I figured it out. I've also tried to activate AltHold while having the range finder activated. Didn't see much difference in it's behavior but it'll be essential for automatic landings.

Also, yet another motor has started showing signs of problem. It's slaming back and forth before spinning up but doesn't seem too big of an issue with that. However, after running for a while, 5-7 minutes, it gets really hot while the other three motors stay cool. I'm wondering why I'm having these problems with the motors all the time :(. Therefore I've made another order for more spare motors and I also threw in some more propellers. This time 8 inch x 4.5 propellers. Will try and see if these propellers are more suitable for the quads weight.

Maiden flight flipped over

Today I flew my quad for the first time. It left the ground and within less then one second flipped over..

It seems as if one of my motors isn't running correctly. Each electric motor, as most people know, consists of a number of magnets that are energised in sequence in order to turn the propeller. However, if one or more of these magnets are faulty, the propeller will not turn as intended. This is something that the motor early on indicated as the propeller seemed as if it didn't start up as early as with the other motors. I choose to ignore that and drove up the throttle, which then made the propeller turn and accelerate as the others. This then made the quad to flip over each time I tried to fly.

As this blog states, I tried to keep my budget low and to buy cheap parts. The motors I'm using are branded Turnigy. That brand is a cheap Chinese pirated copy of another brand, which also makes it less reliable. I was then also early on recommended to buy a few extra motors while ordering to be able to coupe with one of them to be broken on delivery. That I never did. So, today, I've ordered two extra motors plus two ESC's as I actually don't know if they may be faulty as well.

Another thing, I tried to mount the prop savers to the engines today to be able to save the propellers if I'd crash only to figure out that I'd ordered prop savers with the wrong dimension of the propeller shaft. Ordered 4mm prop savers now also instead of the old 3mm.

Schematic drawing

This is the way that I see that my quad will be hooked up. As I'm new at this, I will keep this drawing up to date as well over time.