Many of us harp on users (old and new alike!) to constantly check the vertical alignment of your motors. There are a few techniques for doing this, but whatever method you use, do it religiously. I recently saw some data that drive this home. I am transitioning to a medium/heavy lifter in a coax/X8 configuration. As I’m constantly assembling/disassembling things, I have to constantly keep things aligned. Here is an example of two current/temp readouts from my MK’s GPX files. One before I aligned the motors, and one after. Can you spot the flight with the improperly-aligned motors? And mind you, 4 of my motors were probably less than 2° out of alignment. FLIGHT 1Motor1: 0.0 4.0 7.2 A Motor2: 0.0 4.2 7.0 A Motor3: 0.0 7.3 11.9 A Motor4: 0.0 10.0 16.3 A Motor5: 0.0 9.1 15.2 A Motor6: 0.0 9.1 14.3 A Motor7: 0.0 1.3 3.7 A Motor8: 0.0 4.4 7.5 A FLIGHT 2Motor1: 0.0 7.5 12.0 A Motor2: 0.0 6.3 11.1 A Motor3: 0.0 5.7 10.2 A Motor4: 0.0 5.8 10.9 A Motor5: 0.0 6.8 11.4 A Motor6: 0.0 5.2 9.0 A Motor7: 0.0 5.0 9.1 A Motor8: 0.0 7.2 11.6 A Mind you the motor currents are not totally even on Flight 2’s data, but they’ll rarely be perfect, even in still air. These flights were made in 10-15mph winds. This is an actual safety issue: it’s quite simple for these imbalances to result in current overloads, which can lead to a BL failure in flight. So it’s very important to keep an eye on this. IMHO this level of data is Yet Another Reason I Like MK.
A quick, but not quite so accurate way, is to hand turn the motors so that the prop tips from adjacent motors as close as possible to each other and check to see that they are the same level, then turn both motors 180 degrees and check the other prop blade. Why not so accurate? The prop blades could be bent up or down slightly. What I find to be the most accurate is to fly the copter, bring it up to eye level about two or three meters away from me -- and then just look at the edges of the visible "discs" formed by the props as they spin. I find you can easily see when one disc is canted over even a very small amount. You will need to yaw the copter through a full 360 to inspect each motor so, for safety's sake, I put the copter on AH and PH for this exercise just in case there's a gust of wind -- and I'm very conscious of the fact that I might need to throttle up suddenly if the copter starts coming towards me -- but my hand's on the left stick anyway to make it yaw. Andy.
I purchased a bubble level that comes with a 1/4-20" thread on it. It's very close to M6. Most of last year I used it with the 1/4-20 thread on it and it never damaged the prop adapter threads. Since then I installed a M6 insert. Using this bubble level has never let me down. http://forum.freeflysystems.com/ind...otors-and-checking-for-runout.334/#post-13296
Excellent idea, Dave. As you have a bubble, you can easily check the copter. Regardless, you'd see common drift on all the motors that couldn't be explained by boom axis.
I checked my Cinestar 8 HL the other day and noticed the props were out slightly. After fixing it now flies much better and I get and extra 1-2 minutes of flight time! Incredible...
I use that Whacky and overpriced laser level that Mike McVay suggested and it makes a MATERIAL difference on the X8. -m