Power train

Last week I have mounted the Power 90 motor, which basically just screws on:

The speed controller required the use of tie wraps, as it does not have any mounting brackets, which is a pity. Anyhow, this works as well I guess but I’m a little afraid the wraps might wear the housing of the ESC. Then, there’s the on / off switch for the controller. A nice feature that’s not present on most speed controllers I know of. However, the prepared opening for a switch (behind the covering, used for the gas or glow option) was positioned too far from the controller and it also was too large. For a moment I thought about cutting a hole in the fuselage, using the black covering to hide the switch, but then I saw these tabs for the cowling: bingo! Easy to mount, easy to operate and it doesn’t show in flight. The final ESC installation:

Then I drilled out the prop hole to 10 mm with my drill press (the precision hole was 9.5 mm and the center section 1/4″). I drilled from the front with a high quality metal bit and with a bit of filing I think I got the best possible result using this technique. Using a reamer wasn’t an option, as the reamers I found only go up to 9.5 mm. I am still in doubt whether to use this prop or not, but decided to do a test run to validate my result (before balancing). Here’s the Christen after its first test run of the power train:

The motor and motor box do not vibrate at all, so that is a good sign. I did a few low throttle tests and eventually powered it up to almost full throttle. I was astounded by the power of this setup! Wow!

Drilling the spinner didn’t work out very well by the way. It’s off center by only 0.2 mm, but it makes the motor vibrate even on low throttle. This is my biggest challenge on the whole build… maybe I can find a spinner with a 10 mm prop hub hole (aluminum?), but it’s hard to find one, especially since most sites and resources do not include this figure in their specs. So for the moment I can only run without the spinner.

While fitting the cowl, the ESC switch proves to be perfectly hidden, great spot for this little handy fellow:

And with the cowling fitted, the fuselage is finished!