Another one bites the dust

 

There has been a few days since I last wrote. To that, I can only say: laptop + morning coffee = less blogging and even less field testing of quad.

Today was however the first time since the resurrection that I've done some serious testing. I wanted to try out the RTL (return to launch) function that went AWOL last time I tried.

The first thing that happened today once I fired up the quad and was lifting off was that after 30 meters or so, one of the blades of the front left propeller broke off. I didn't realize this at first but what happened was that I heard a ill sounding noise as if something broke followed by a ill sounding motor engine. The quad then slowly started banking towards left and at that point, I couldn't stop it from flying further to the left. I made a controlled crash landing as I couldn't stabilize the quad. Once I located it again I quickly realized why it behaved as it did; it had close to no lifting power on the left side and therefore, I couldn't stop the motion towards left.

This is one of the 8x45 propellers I recently bought and from the breaking point it looks like it might had been delivered with a defect. I am no expert in this field but you can examine the picture for your self. Anyhow, these are cheap propellers and I guess I buy more as they may break. The positive outcome from this accident is that I now know that a failing propeller isn't an instant fatal crash but very recoverable.

I've considered buying these carbon fiber propellers instead of the plastic propellers I've been using until now but they are fairly pricy and I think I need more practice and less close calls to fund these. Carbon fiber propellers won't take any small nudges without splintering into pieces nor will the plastic once but the plastic once are six times cheaper..

RIP zippy

 

The last casualty of the crash is the battery. I tried all last night to revive it using all sorts of Jedi mind tricks to the charger according to instructions. The force wasn't with me this time and as I feared it felt it might catch fire due to the heat and the fact that it started expanding, I stopped my attempts. This must be the single most expensive loss of this crash but still nothing compared to rebuilding the whole quad.

RTL fly away...

Yesterday I went away to find a field large enough to do some serious RTL (return to launch) and navigation testing. This requires space without trees too close. I found some nice fields and started testing. I successfully tested both RTL and three way point navigation before my last RTL went sour...

I flew quite far away as I previously had done and hit the RTL. The normal procedure then is for the quad to gain height to 15 meters, which is default. Then head to its home position and descend to about 3 meters and loiter. This time, instead of turning towards home, it started drifting to the left. I quickly intervened to save the quad by counter steering rightwards. The quad then rotated 90-180 degrees making the direction impossible to see from this distance and disappeared behind those trees according to the drawing. I then ran towards the highway and never saw it again.

I've since then been covering the grounds around the point where it disappeared for about 8 hours in total, checking trees and the ground where it might have crashed without result.

It might have kept going in that direction ending up on the other side of the field as the program does not include anything about landing, but keeping 15 meters until the destination has been reached. It might also have taken a short trip on the field, then turned around ending up somewhere else. I still think the highest possibility is that it sitting in one of those trees along the highway.

Later today or tomorrow, I'm going to print posters asking people to contact me if they find my quad. Hope that gives some results. At this point, I don't think I can afford a new one, which leaves me with a pile of spare parts that will not be used..

One motor down..

Yesterday, I started trimming the AltHold function that relies on any altitude sensors. The sensor I have so far been using is the barometer, which is very noisy. That means it's less then perfect at holding it's altitude, but works +/- 1-2 meters.

Today, I thought of doing some more testing, maybe even try the AutoLand function as the AltHold seemed to work. However, after a few minutes of flying this happened..

 

One of the motors came off upon takeoff and took a piece of the radio antenna with it. The motors are fastened with two screws at the bottom and it seems as it came unscrewed, possibly due to vibrations. This seem to be the case for one other of the motors when I checked them all. It seems as checking the screws before going flying is a bullet on the pre-flight checklist.

Now, I only found one of the screws, which means, I have to get another somehow. Not sure if I should order a whole new frame as spare part or if I should try to find one in a local utility store. I'm going to try the second option tomorrow to see if they have any thing available that would work as a substitute.

Yes, there will be more videos. I have two that I filmed yesterday when doing some trimming but I haven't uploaded them to YouTube yet as my bandwidth is limited and the amount is not unlimited at the moment.

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.