ASME 2014 – Loophole

Filled under: Electronics, Projects

Date posted: March 25, 2014

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Loophole: Our ASME 2014 Student Design Competition Entry.

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This year’s (2014) American Society for Mechanical Engineers (ASME) Student Design Competition is building a remote-controlled aircraft capable of navigating a few simple obstacles and dropping a payload onto a designated target.

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The flight area is a meager 5 meter by 7.75 meter indoor course. Yikes!

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The craft is required to fly through two gates.

The spirit of the competition was building a ‘lighter than air’ vehicle, however due to an oversight in how the scores are calculated there was no penalty for being heavy than air. What was a remote-controlled blimp competition turned into whomever can build the heaviest flying multirotor. Challenged accepted! The official problem statement and rules.

Having no experience in multirotor design I scoured the web for hours which turned into days which then turned into weeks. I decided the best way to approach building such a complicated craft was to build a simpler version; thus I made my first hobbiest level tricopter: found here.

Being the team leader I was able to select my own team. Luckily a fellow engineering student has also built his own multirotors and we were able to bounce  ideas off each other. The other two team members were selected for their lack of experience and eagerness to learn.

We received a grant from a local sponsor and my adviser was adamant about us spending $2000 on this project… wow, it was actually more difficult than I thought it would be to spend money on legitimate parts.

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Since the craft was restricted to size, it had to pass through a 28″ diameter hoop, the first step was laying out the major components.

We choose to maximize the amount of 12″ propellers by creating a hexagon shape with six propellers around the edge and one in the center.

Seven propellers is good, but we stepped it up by adding another set of seven propellers by pairing each one in a coaxial format. More on the this later.

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One stipulation of the competition was that major construction aspects of our craft had to be documented by photography.

The parts are in! Here is our Bill of Materials

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Here is Zach and I measuring parts to verify our layout will fit within the size restriction.

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Here I am marking the wood booms for drilling using our center bracket as a guide.

Wood  booms and wood brackets were chosen because they are decently strong, easy to machine, and that if the event of a serious crash the booms would break. Replacing a boom would be much easier than attempting to bend a metal airframe back into alignment. Also, we lacked metal and metal machining tools.

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Andy brought in is Harbor Freight drill press…. wow this little thing almost shook itself apart! But, it got the job done.

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After an hour of measuring and cutting the boom on the miter saw, everything looks ready to be assembled.

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After a quick paint job and some assembly the frame is starting to look good.

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Here you can see the motor mounts are mounting and the wiring has begun.

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Meanwhile, Andy is preparing the motors and balancing the propellers.

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Andy made a hand-held balance checker. He basically verifies the prop and motor is balanced by manually detecting vibration.

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Ethan dived in and started soldering wires to the ESCs.

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Here is Andy working with Zach on soldering bullet connectors the wire ends.

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After I finished the wiring I gave it test. It works! I added LED navigation lights to the motor mounts for the coolness factor.

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Tests revealed that an ESC had a bad solder connected, a quick fix.

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A few days later we mounted the control board, the receiver, the battery holders, and all the motors. We also added landing feet.

Here you can see the coaxial motor layout, one on top and one on the bottom. It does not generate twice the lift, but still a sizeable amount to warrant the extra complexity.

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A last minute change to the rules added the requirement that all craft have the blades protected by a shroud. We made our shroud out of pool noodles. They worked decently well.

You can see we attached a multitool to a boom to balance the craft.

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Flight test! Here we are in stable flight in the engineering lab. Outside is our test gate.

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Much of our build time lasted into the night and we could not resist flying our craft. Here’s a very nice shot of our craft in the commons.

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The craft was so stable in the air I felt comfortable walking underneath it and taking a shot of it in flight.

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Here we are at Love Park in Philadelphia the day before the competition at Drexel University. I was the camera guy.

Sarah competed in the poster competition, Charles and Jade completed in the web design competition.

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Here’s is the flight area. I don’t know why the host decided on a small room for the flight area, that back wall was fatal for a few competitors!

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Here we are at weigh in.

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Our team was one of a few teams whom actually brought in a safety net per ASME rules. The director asked us to deploy our net for public safety. Ethan and I agreed and got front row seats, well stands.

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Our turn. We are at the designated lauch point performing the final flight check.

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Ready to go, but wait, let’s take a group picture first.

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We are up! Andy calmly lifts the craft into the air.

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Andy takes the craft through the first gate.

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We are past the second gate and the payload is dropped, bullseye!

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Touch down!

We placed 1st by a large margin. Only one other craft out of 18 completed the course. Our weight was around 22 pounds theirs was around 6 pounds. The competition was a blast. Some crafts could not even get off the ground, while others immediately flipped over, and a few crashed into the gates and walls.

At hover the current draw at 12.4vDC was 150 amps! Once I find the technical specifications sheet, I will post it.