Sunday, November 27, 2011

Even More Power!

OK, I decided that I need more power.  I went online to my favorite hobby store site and purchased a new battery (2200mah, 3C), brush-less outrunner motor, and speed controller.  They actually came in some time ago but I just got around to installing and setting everything up.  A few things I had to take care of first like charging the battery and figuring out how to setup the speed controller.  I connected the battery to my charger and topped it off.  Then I checked the battery with my voltage checker and each cell read out very close, just the way I like to see it.  Now I needed to check out the speed controller as it usually requires a programmer to set it up.  I found out the speed controller could also be programmed to the default setting (which happen to be what I want) by using the transmitter.  This is done by powering up with the throttle in the full position and waiting for a certain number of beeps, returning the throttle to the off position and waiting for the required beeps, and then putting the throttle back to full and waiting for beeps again and then put the throttle back to the off position.  After all of this, it works just fine.  So, I setup the receiver, speed controller, battery, and  motor and checked everything out with the transmitter.  All worked as expected.

Now it was time to figure out how I was going to mount everything on the plane.  I started by removing the old motor and speed controller.  This required loosening the hot glue I had added to the motor, cutting the wires, and pulling on it until it came out.  Then I pulled out the wires from the speed controller, removed the power switch, disconnected from the receiver, and then completely removed it.  Now everything is out of the way and I can see how it will all fit.

I had already held the motor up in position next to the original and marked the nacelle.  I mounted a three blade prop that I had on hand just for reference.  So now was the time to start cutting.
I cut out a big chunk of the nacelle and made sure the surface was level.  I cut out a piece of hardwood to use for a firewall.
I marked the piece to find the center for mounting the motor.

 Next I tried the fit and found I needed a notch for the firewall to fit better.  I also figured it would give more stability since so much foam was cut out.

Now it was  time to dry fit all the motor pieces before permanently installing anything.  Everything was laid out to make sure I have everything I needed.  Since the screws to attach the motor to the aluminum mount would be hidden and not easily accessible, I made sure they were locktited in (reddish purple tube).  I decided to use wood screws with lock washers on the firewall since I would not be able to get to the back side if I used bolts with nuts once all was glued in place.

Here is the aluminum mount with the locktited screws, and to the right, mounted to the firewall with wood screws and lock washers.

Now that I was happy with everything, I decided to trim the wood down for a more aerodynamic profile.  I did this by holding the firewall in place and then tracing the nacelle outline on the back side.  Then I used a belt sander to trim it down to the profile I marked out.  Next I glued it in place with hot glue.  I made sure that the perimeter and slot were glued well.  I also added a vertical line to use to align the firewall with the seams in the foam (this helped a lot for centering).

I noticed that there was still a little flex in the new nacelle and so used some tooth picks to stiffen things up.  I ran two strait down on either side of the seam and then two more at an angle from just behind the wood to the front of the nacelle.

Now I screwed the motor back on being careful to make sure the wood screws went right back into the threads they cut during the dry fitting.  This I know will ensure the best performance and least chance of failure.  I also made sure that the screws were torqued down just enough to collapse the lock washers.

Now I need to get the battery in place.  I noticed that it was not going to fit at all unless I started cutting things up.  I really wanted it to be as far forward as reasonable to maintain the C. G.  I bit the bullet and opted for major surgery and sliced off the top of the nose.  This allowed for full access to the battery compartment.  I laid the battery where I wanted it and marked what needed to be cleared away.  I then used my soldering iron with a nail in place of the soldering tip and melted the foam until there was enough room.  I like to melt the foam instead of cutting it out as I feel that it helps to retain structural integrity.  Any way, once I was happy with the space, I hot glued the top back on.  I did not use any tooth picks for support as this section will be well taped with strapping tape.

Finally I'm getting to the speed controller.  It seemed to fit well just laying it out from the motor to the cockpit opening.  The two power wires were just far enough apart (being on either side of the controller circuit board) that the cover tab fits right in between them.  Instead of gluing it down, I opted for just taping it in place with strapping tape.  There were two reasons for mounting it the way I did.  One is that this was way easier than threading the wires through the foam, and two, it would provide for better cooling if needed.  So this configuration worked great other than the power connectors having to make an awkward loop to connect.  A little tucking of wires and rubber bands to hold down the canopy and no one is the wiser.

I powered up my radio then plugged the battery in (I no longer have an on/off switch) and everything worked as expected.  I am very happy with this and cannot wait to get out and fly this thing.

Thanks for stopping by my blog and please post comments, good or bad.  Be sure to come back and check for future posts.

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