Andrew Burks

Design

This summer I have had access to the waterjet at NREC where I had my internship.  The current pedal design calls for a series of 2-dimensional parts that I knew I could cut on the waterjet very easily (it can cut through stuff faster than 10 inches/minute, so it’s preferable to a CNC for this application).  Unfortunately I put off cutting these parts until the last week of my internship.  At 10PM on the last Tuesday night of the summer, I realized that I needed to prepare the .dxf files (files that define the shapes of a 2-dimensional part) I would need to cut some parts out after work.

When I went to make the .dxf files, I realized that I could make the entire pedal assembly out of welded steel plates cut from the waterjet.  That night I started making a new version of the pedals (version 9) and had the rough outlines of all of the key parts by the time I went to bed at 3AM.  I also never made the .dxf files I wanted for the next day.

Wednesday night I made the .dxf files I needed for the old pedal design, then spent the rest of the night optimizing the brake pedal assembly for weight.  Here are some renders of the design, as well as some FEA results:

Stress Plot

Factor of Safety Plot

An Exploded View Animation of the Assembly Process

Fabrication

On Thursday night I stayed after work to cut my parts on the waterjet off-hours.  It took about 5 hours to cut three sets of parts for the old design and two sets of the experimental pedal.  Though the brake pedal hasn’t been welded yet, the tabs were easy to press together to get a good sense of what it will look like in real life.  I was really impressed that I could go from concept to completion in only 48 hours, thanks to SolidWorks, NREC, and the waterjet.  Mike was kind enough to take some glamour shots of the final product:

A completely axially symmetric vibraphone robot would be awesome.  We decided to move away from a big row of keys and towards a round plate of keys.  Here is a quick render of the key mounting structure and how it incorporates the ball retrieval and distribution system:

Structure

The large round plate is actually a 30-gon not a circle.  It is inscribed in a 32″ circle, and is 1/4″ thick.  There are 60 unique (thank you design tables!) plastic supports that slide onto notches in the aluminum.  Each plastic support has to be unique because of the awkward hole spacing in the individual keys.

There are already notches in the plastic for clips that should hold it into the aluminum plate (aka “Megaplate”).  However, depending on the design of the ball deployment mechanism, the retaining clips for the plastic plates should be incorporated into the support for the mechanism.  Here is a close up of the plastic supports:

Distribution

Finally, here is a close up of Mike Ornstein’s ball collection and sorting mechanism.  It uses brushes from the bottom of doors to pull balls up an archimedes screw into a paintball-style hopper.

Overview: We are officially crazy

Animusic is a group that makes great computer animations involving “impossible” instruments playing great music.  While considering actuation mechanisms for the RobOrchestra Vibraphone project, somehow we decided it would be a good idea to do something similar to the instrument that takes center stage at 1:07 in Animusic’s “Pipe Dream”:

Details

Right now, 3/8″ diameter stainless steel balls are looking very promising.  Mike Ornstein, Dan Shope and I have subconsciously split up the work into 3 sections.  Dan is working on the mechanism to take the balls and dispense them onto the keys quickly and with a short reload time.  Right now, it appears that this will be accomplished with a group of DC motors.  Mike is working on the mechanism to lift the used balls back up and dispense them to queues leading into Dan’s mechanism.  This is most likely going to be done with an Archimedes screw and a paintball gun style dispenser.  I have been focusing on the structure of the whole mechanism and collecting the dispensed balls and funneling them to Mike’s mechanism.

The biggest problem I am facing with this design is the awkward hole arrangement in the keys.  I basically have two very awkward hole lines I need to support for both the naturals and the sharps.  A string pulled taut needs to go through the holes in the keys and the supports to hold up the key and let it vibrate naturally.  My initial concept involved about $60 of waterjet-cut 1/8″ ABS.  Here is a render of this initial design:

This concept was that with angled plates in front of the keys sloping back toward the keys, as well as slopes over top of those angled toward the center, I could funnel all of the ball bearings into a channel between the two sets of keys.  Unfortunately it takes up a whole sheet of plastic.

Future Concepts

Moving forward, I want to find a way to eliminate all of the unnecessary material in all 32 of those vertical supports.  A bar or two mounted along the path of the key mounts could allow me to build much smaller plastic mounts for each key.  Look forward to another post with more designs, and watch my friend’s blogs for updates on their portions of the project!

My new workstation is now humming along perfectly.  To review, the specs are:

• Intel i7 920 Quad-core @2.66GHz (currently not overclocked)
• ASRock X58 Motherboard
• Nvidia FX Quadro 580 workstation graphics card
• 6GB RAM
• 1TB Samsung HDD
• 650 Watt Corsair Power Supply
• CoolerMaster Hyper 212 CPU cooler
• CoolerMaster 335 Case

Build Observations

Putting together a computer was quick and easy.  Everything went super smoothly and was very straightforward.  I never really had to read the directions (although Mike Ornstein was guiding me heavily).  The hardest part was making sure all of my components were designed to work together.  I spent more time researching individual parts than I did assembling the whole system.

Overclocking seems unnecessary right now.  I have Solidworks running in RealView, and I can spin large models with no lag.  The biggest improvement is my rendering ability.  1920×1080 renders of complex geometries in Photoview used to take more than an hour, or just crash my laptop.  On the new computer, it takes only four and a half minutes.  This makes sense, considering that my Windows 7 Experience index raised from a 3.1 (Limited by graphics score) to a 6.9 (Limited by HDD score; Graphics and processor are highest – tie at 7.9).  I successfully played an HD movie over the weekend, and am very pleased with the results.

Software

With one computer that i use in my room (or remote into) and another I take around with me, it is important to make sure they play nice.

I found a file synchronization tool, FreeFileSync, that I really like.  I have a “SYNC” folder on each computer, with everything I want to have available to me on any computer (School/Project/Personal files, Music, etc).  FreeFileSync matches this folder from each computer against a backup I set on my external hard drive.  So I have three sets of identical data in three separate places.

I was having trouble syncing my iTunes playlists.  The way iTunes handles its playlists and libraries is very weird.  I decided to convert to Windows Media Player, and I’ve never been happier.  All of my music (4-5GB) and playlists are synchronized now.  However, because WMP playlists are just xml data with absolute mp3 file locations, syncing the playlists would make it not work on one computer.  I solved this problem by drawing on my 15-123 PERL skillz and writing a quick script to convert the absolute file names into relative file names in the playlists (which are identical between computers) and now my playlists can synchronize too!

I have set up remote desktop and have given my friends an account so they can render on my machine.  I’m curious to see if i start remoting into my workstation when I’m on campus, or if I’ll just keep using my laptop most of the time.

I look forward to installing Synergy which should allow me to control the workstation with the keyboard and mouse on my lenovo (which I love) as well as using my laptop and workstation screens side by side, as if they were one computer.