Building an F450 Quadcopter – Day 7 – A very low first flight

Having seen one too many videos where the quad flips over on takeoff I was understandably nervous about trying our new baby out.  It seemed that at every turn there were little details that needed to be checked and re-checked.

For example, we checked the rotation of the motors and S. then fitted the props according to their direction.

Later I noticed that we had the exact opposite of what was shown on the APM website.  Our props should have looked like this but were not. So, when S. wasn’t looking, I switched them.  

Fortunately I had woken up that morning with an idea that would allow the quad to fly a little, but not enough to flip over if things go wrong.  It didn’t take long before I had it lashed to our table tennis table and we were ready to try her out!

With S. videoing the first test was a spectacular non-event.  I powered up and slowly increased the throttle until full throttle was reached.  We had plenty of noise but absolutely no lift at all!  Then I realized.  S. had been right all along and I had switched the props which were now pushing it DOWN!

A quick switch of the props and we were back in business.  This is when I thanked my lucky stars that I didn’t trust myself to try it without a safety net.  Every time it lifted up it would go wild and try to flip over.  Fortunately the string kept it in place, but it was all over the place and none of the controls made any sense!  See for yourself!

I checked things over again and realized my mistake.  I had plugged the motors into the APM board with output 1 going to motor 1, output 2 going to motor 2 etc. in a clockwise pattern.  However, as you can see from the diagram above, the ONLY motor I got right was number 1!

Switching the connections on the flight controller had us finally up and running.  It now behaved, didn’t try to flip anymore, and I could lift it up and move it backwards, forwards, left and right.  Forward and backwards was reversed because for some reason the APM sets it up to expect the ELE control to be backwards.  No problem, it just took 30 seconds to change that on the transmitter.

While it seemed to be working it was very twitchy and super sensitive to the controls – nothing like my Phantom which was very docile.  

I posted the video on the quadcopters FB page and our good Samaritan made a comment about how twitchy it seemed. I then found out that the latest version of the Mission Planner software has a sliding scale from 1 to 100 where the higher the number the faster it responds.  Guess where mine was set…yup…100!  I backed that off to 80 which seems to have calmed things down nicely without taking all the fun out of it.

One last thing.  Remember I said that my motors were the exact opposite of the picture on the APM website?  I was under the assumption that it didn’t matter as long as they the same rotation was on the opposite corners.  Turns out that is incorrect and that not having it the right way around is going to cause problems with yaw (spinning on its axis), and possibly more.  So, after some gentle teasing by my friends about not knowing how to fit props, I switched the bullet connectors so that they now all spin the right way.

After all those changes I put it back on the “test rig” and what a difference!  It was beautifully smooth and easy to control.  See for yourself.

So, that it is.  There are still many tweaks to do, such as setting up the battery failsafe and adding LED lights, but really the next big step is to wait for a clear day and take her out.  I can’t wait!!