Installed motor test run!

With a good friend, we did a few test runs of the installed motor & power system.  

Here is a very short run just to show you it spins.

Firstly, it is quite scary sitting that close to a spinning motor putting out 4.5kW.  Wearing a helmet helps, but it's just a LOT of power super close to your body.  Neither of us ran beyond 100A and we both kept our feet on the ground out of the plane of the propeller ... just in case.

At about 60-70A, there is a slight structural resonance in the nose tube assembly.  It's not present on either side of that RPM, so we just tried to avoid that.  Balancing the propeller would help.  Tightening things up more should help too.  Most of the play appears to be in the nose down tube connections, at either end, so I probably will start with getting the proper length bolts everywhere and snugging things up.  Replacing the nose tube with an aero strut would probably make a difference.

The throttle in the end of the control stick did not work for some reason.  It moves a servo just fine, but did not move the ESC.  I suspect the ESC calibration needs to be done using the same throttle driver.  For this test, I used a different servo driver that was the one used to set up the ESC in the first place.

The batteries and the ESC and the wires all were quite cool to the touch, even after a 60s run.  Rough math suggests about 10min run time at 4.5kW.

I did try balancing on the wheel to see if the thrust would roll Goat forward.  The ground is pretty soggy and the tire was partly flat, so there was no forward motion.  Howe er, it was a definite feeling of being pulled nose-down.  This is not surprising given the high thrust-line and low pitch rotation axis (here: the wheel axle), but it was nice to feel thrust as an external force, if that makes sense.

There is a fair amount of air movement along the structure, most visible in some vibration of the inboard edge of the flaps.  There was a little drumming of the lower wing skin covering.  The rudder tended to center up with the airflow, but the elevator had enough bungee that it mostly sat stationary.  Nothing was scary.

Also, a weight check with a bathroom scale came in at 158lb including motor & batteries.  The motor itself is 5.6lb, so I am clearly below the Part 103 glider 155lb weight limit without the power system.  Adding propulsion essentially ups the legal weight limit to 255lb, so I'm also clearly below that.  Super.

 

What improvements are on the short list?

• Fix the throttle knob --- having throttle in the stick would be much nicer
  
• Improve the throttle wiring --- need a second look at the throttle wiring & battery location
• Tachometer --- having RPM would be really nice
• Move the wattmeter display? --- it was awkward looking down to the right for power readings
• Larger propeller --- the 30x10 just looks teensy.  May have to couple this with re-winding the motor for a lower KV, which is a much larger project
  

I'm also getting some hangar rash in the covering from strut or jury strut bolts poking into the covering.  Some of these looked avoidable.

Gap seal for the control surfaces is a necessary next step.  I really don't want to fly without gap seal.

Strut fairings is on the semi-short list.  It will fly fine without them, but I know the drag is unhelpful.

A trim color along the leading edge would be sweet too :-) 

Here's the battery tray installed.  It works.

Here is how the motor tube mounts.  It's sturdy in itself, but the nose tube seems like what is vibrating.