My first adventure in flight... a Tricopter Build - RC Groups
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Aug 02, 2012, 02:48 PM
we dont NEED roads!
AcroFPV's Avatar
Build Log

My first adventure in flight... a Tricopter Build

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...

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:

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 -
DT750 Motors -
Turnigy Plush 30A ESC's -
8x4 Propellors -
HobbyKing 939MG Servo -

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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Aug 02, 2012, 03:04 PM
we dont NEED roads!
AcroFPV's Avatar
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: &

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
Aug 02, 2012, 04:22 PM
8x4 props are a bit small for those motors. 10/11x4.7 would be best.
Aug 02, 2012, 04:36 PM
we dont NEED roads!
AcroFPV's Avatar
Thanks. I was worried I went with too small of a prop, but I followed another build list and ended up choosing different motors than he did.

thanks for the suggestion
Aug 02, 2012, 04:42 PM
really nice frame, though
Aug 02, 2012, 11:45 PM
we dont NEED roads!
AcroFPV's Avatar
Thanks Sir. I took your advice, and contacted Hobbyking. I had them remove the 8x4 props from my order, and add 2 sets of these 10x4.7 props ( )

I thought about getting the 11x4.7 but my frame is not going to be that large. Each arm only extends 12" outside of the body.
Aug 03, 2012, 12:08 AM
we dont NEED roads!
AcroFPV's Avatar
If some sort of Moderator sees this, can they move it to the Scratchbuild area?? I didn't realize there were 3 subforums for Multirotors.


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