Friday, July 26, 2013

Project Introduction - Tricopter

I was over at Boise State University flying my tricopter when I decided that I need to actually post on my blog if I have one. Since I got back from my Houston trip I have been working on a couple of projects. The tricopter project has the greatest chance of bodily injury with its whirling blades of death and its habit of falling from the sky. So, I figure it is the most interesting one to talk about.

The frame I'm using currently is the second mock-up frame I have built. The first one was much larger and far more fragile. I have crashed this frame a dozen times and have been able to rebuild it in a couple of hours. The frame is built from some scrap plywood that is about 3/8 inch thick. The frame isn't nearly as heavy as I expected it to be and the entire tricopter in flight configuration with a 5800 mah 3s1p battery strapped to it weighs just under 2.4 pounds (1088g.)  The frame is assembled from just four pieces and only the tail boom has more than one fastener. Many tricopter designs allow for the arms to give in the event of a crash. My first frame design had three fasteners holding each boom. I broke both of the booms within the first few flights. I remounted them with nothing but friction holding them in and they lasted through a few more crashes.

The current motor configuration consists of two hexTronic DT900 motors in the front (counter-rotating) and a single hexTronic DT700 on the tail boom. I bought three DT900s and three DT700s. I had DT900s on my first frame and destroyed one of them in what some call a "creative landing." One of my DT700s burnt out while hovering. It looks like it shorted internally. Other than these issues, they seem to be tough little motors. One thing I noticed is that if you just throw a prop on them with a nut the shaft will pull up through the bell housing and put friction on the C-clip and the washer and bearing at the bottom. Currently I have three nuts on each motor. The first prevents the tightening of the upper nuts from pulling and causing binding. The second is a normal nut that holds the prop firmly down onto the first nut. The outer is a lock nut that helps prevent the previous nut from coming loose. I could save a small amount of weight by using a threadlocking compound but I break props so often that it would be a pain.

I will grab some images when I fly it here in a bit.

In other news (pun intended) I was in the paper today.
But they said I went to an entirely different state... Not the best quality article.

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