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My first Tricopter build...

#1
I have been into the RC thing for a long time... but always ground based. Some nitro monster trucks, some buggies... my last toy was a RC Crawler, but a buddy of mine got into helicopters and after seeing a few Quad's and such I was sold. After weeks of reading and researching, I have decided on doing a Tricopter. My first thought was to build a Quad, but that is just too simple and they all end up looking like large flying blocks.

I think a tricopter will fly with more style, and should end up being alittle cheaper since I am not buying 4 Motor's and ESC's, only 3. I watched a few video's and realized building a Tricopter frame wouldnt be any easier. The rear Yaw pivot seemed to add a challenge, but I knew i had the parts needed to do it. So I went digging through a couple boxes of spare RC parts, and came up with something that should do the trick.

Here is my first setup:


Its from an old buggy frame, the front steering knuckle on its side. I figure I should benefit from the double ball bearing setup. Here's some quick video of its basic operation...
https://picasaweb.google.com/lh/photo/RUnTAmARdVm37NLklQ7uttMTjNZETYmyPJy0liipFm0?feat=directlink

After jumping that hurdle, it was off to Home Depot to get some Aluminum square for my frame. I opted for 3/4" square tube, and picked up some 90 degree aluminum stock as well for various brackets and such. For the body I got 2mm lexan. It only took a few minutes to cut the arms to length, and fit my rear yaw mechanism.





I used the other steering arm, and cut the horn off, and trimmed the hub with a dremel to make it fit snug into the hollow aluminum. I then marked where some of the original holes lined up, and ran screws through both sides to secure the assembly inside the frame. Also at the bottom I drilled a 3rd hole and placed a 2.5mm screw in place as an extra precaution. Video of the assembly in operation can be viewed here: https://picasaweb.google.com/lh/photo/lA6LUBddjO7glY0JjW-GNdMTjNZETYmyPJy0liipFm0?feat=directlink

For the body I used RCexplorers .pdf but just made straight edges instead of curves. This would be my first attempt at cutting with my new saw, and I didnt want to try anything fancy. I increased the size by 30% to compensate for my larger arms.





At first I wanted to use rivets to hold the body plates to the arms. But after securing the tail, and then each wing, I realized it would be best to just use 4mm bolts and run them through the entire assembly. So I drilled out the rivets and am now at a stand-still, waiting for some parts to come in that I have ordered.

Which brings me to the good stuff!! the internals. This is what my HK order consists of:
KK2 Flight Controller - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=24723
DT750 Motors - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6247
Turnigy Plush 30A ESC's - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=2164
8x4 Propellors - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11331
HobbyKing 939MG Servo - http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14458

And also a few other goodies like the Programming card for the ESC's, low voltage alarm, 2200mah 20c 3s lipo's (two) and a USB connector so I can use my Turnigy 9X in Realflight and crash on the PC instead of real life!

So yeah... I guess this is the first step. The next step is to wait for my parts to come in so I can setup the KK2 position along with my RX and battery etc.
 

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#2
So as I wait for my parts to arive, I thought I would continue to progress on the rear yaw design. Now that I have the movement down, i need a way to secure the motor. I found some spare plastic that I shaped, and used as a spacer to offset the uneven steering knuckle. Then cut some spare Plexan that I used for the body, and used Gorilla Glue to hold it all together. Once the glue had cured, I then used a drill bit and drilled some holes through the entire assembly on each side of the axle it pivots on. Once the holes were drilled, I used a couple aluminum sleeves I had from some unknown RC setup, and pressed them into the Lexan, so my screws do not wallow through the plastic and oval my holes.





Afterwards I used some allen head screws and locknuts and ran them through the entire assembly and bolted it solid. I had to dremel the underside to fit the locknuts evenly, but in the end everything came out exactly as I planned.





The entire assembly is very solid, and there is no free play at all. The shaft that the rear motor pivots on, is supported by 4 ball bearings. Two in the motor mount, and 2 in the frame. The only slop is in the connecting rod between the mount & servo. I took a couple video's of it in action:
https://picasaweb.google.com/lh/photo/0qQI33FTExcYHVM2431CENMTjNZETYmyPJy0liipFm0?feat=directlink & https://picasaweb.google.com/lh/photo/HkWPoVklrfJj4wP991MucdMTjNZETYmyPJy0liipFm0?feat=directlink

I ordered 4x30mm bolts, and locknuts with washers for my frame, and as soon as those show up I can re-drill the body plates & find places to secure everything. The next step is to come up with some vibration dampening mounts for the KK2 board. I have some fuel line and PC Motherboard spacers to play with and try to come up with something :D