learning the ropes

So I goofed — maybe. When I modeled the pulleys earlier this week, I somehow messed up the dimensions. I drew the model too small — and only caught the mistake after I purchased my materials. Remember measure twice — cut once? Well, I didn’t cut yet, but I definitely didn’t measure twice.

I was not thrilled about correcting my mistake, as it will take some time to correct it. Further complicating matters is that obtaining the correct material dimensions will become more difficult, too. I will need to go to Dimension Lumber to get a custom piece milled — and I prefer not to do that now because of the time involved. I was also somewhat concerned about the aesthetics of the pulleys, but maybe the smaller pulley looks nicer. It’s going to be hard to say without seeing it build. The point of these remaining weeks is to develop my performance — not to sweat mechanical details.

I’m going to sleep on it, consider the feedback I’ve received from friends, and then decide in the morning.

Today has been another marathon CAD session.

I created the electronic compartment cover (which is subject to change depending on the final contents). I’m waiting to hear back about milling the parts before I make any more changes. I expect that there will be some finessing to do once I build up another encoder board. Although it is tempting to start pushing towards ready-built solutions like those found at Acroname or switching over to an optical mouse encoder system, it’s too late in the game to try new stuff that might not work even if it might ultimately make my life easier. I have a working system now that will serve me until the next phase of this project.

Alibre Design Xpress is powerful and pretty easy to use. One of the coolest features is the way “assemblies” work. One I sketch individual parts, there are tools for “gluing” and aligning the parts together so the form an assembly.

Unfortunately, it is also easy to get lost in the miles and miles of faces and edges. Also, it is a tool that, at least for the present. has “obsession potential” for me. I was like this with Google Sketchup, too, when I was learning it. My tendency is to become obsessed with figuring out how to do something when I run into an obstacle — and ignore time limits I might place on my work. This is something I must avoid falling into in these final weeks, when the focii are going to be the performance, the presentation, and the paper.

Yesterday, I alternated between programming and 3-D modeling. I’ve assembled most of the components for the pulley supports. It has taken probably 8 hours in total to build this 3-D model. I ended up recreating the assembly this morning because some of the constraints I created on the previous assembly prevented me from moving the pieces around.

In some ways, this looks pretty similar to the mode I drew in SketchUp almost two months ago; however, this model has 3-D models of actual parts that I will purchase this week and the dimensions are exact.

I still need to create a design for the housing that covers the encoder, but that is a job for this afternoon/evening.

I now have a 60 meters of used rope to build my next units. Special thanks go out to the great folks at the City Climbers Club. Once my final mechanical designs are done this week, I will be building again.

Here’s video of my midterm presentation.

I’ve also been working on mounting systems this week. After the testing I did with Martha Mason and Wendy Richmond last weekend, I’ve been trying to improve the mounting system and and the pulley supports so that the rope stays on the pulley. Martha pointed out that a dancer needs vertical space to work in as well as horizontal space. By opening the pulleys into a triangular formation, I was able to give her the vertical space she longed for.

I bought some pulleys from the hardware store and tried mounting them to the Super Clamps. Mounting them was easy, but as I discovered today, the pulleys are not right for my system. They introduce far too much friction and acoustic noise. They really take something away from the quality that the system had before.

I also experimented with ways of mounting the pulleys that allow me to adjust them easily. While I liked the way the pulleys look when they’re mounted with the pipe running through them, this will be difficult to construct. For now, I think I’m going to stick with the super clamps.

I want to be able to work with two pulleys simultaneously, so I’m adding the rotary encoder to wooden pulley I started building last week. The PS/2 mice have turned out to be quite a clever hack because each one gives me two rotary encoders and three switch inputs in exchange to two pins on the Arduino. I’ve started thinking a bit more about multiples — and while this may be a little premature, I want to work out a bit of the technical end of this before getting too heavily into final fabrication.

I’ve invested rather heavily in this for the past two days. Perhaps because this is more comfortable for me than other things that need to get done now — like preparing for the mid-term presentation.

What this does mean, however, is that I have the pieces for a much more modular system. I’m envisioning a hub that I can plug each pulley into using a single CAT-5 cable. This makes the performance setup clean — and won’t require any soldering.

Today I worked on fabricating another two pulleys out of wood. I finished drilling well-aligned shaft holes in the side pieces and made new pulleys out of particleboard and plywood. The most time-consuming part of this process was cutting the circles out of with the bandsaw. I remembered that there is a jig for cutting circles, but didn’t want to spend time figuring out how to construct it in order to cut six circles. I first started by cutting around the contour of the circle, but ended up just making tangent cuts and then sanding away the excess. I was really trying to have another pulley finished by Saturday so I could test two of them with Wendy and Martha, but that doesn’t seem to be realistic at this point. I still have to make the encoder structure.

The completed wooden pulleys:

I constructed another P2/2 Connector Breakout Board so I can attach another pulley to my performance system. This time, I’ve annotated the photos in Flickr so the next time I construct one of these I don’t have to think how to build it again.

It felt very good to spend much of the day in the shop working with my hands. Much of the week, however, was spent struggling with how to make progress on the materials/form of the rope&pulley and also struggling with what I am producing.

Earlier in the week, I was researching materials. There are two directions I am considering: natural wood (mahogany, maple, walnut, cherry, etc) or recycled parts. The natural wood direction comes from my appreciation for naturally finished wooden instruments: electric and acoustic guitars, pianos, etc. The recycled direction relates more closely with one of the themes of the project which is, in a way, the recycling of musical content and the loop-based music metaphor.

When I got stuck researching, I tried to work a bit with the form. I started with raw sketches and then tried to work material in Google Sketchup.

I spent too much time trying to manipulate the materials in Sketchup, though, and became frustrated. A breakthrough occurred when I realized that I could use foam to quickly work through ideas. My previous prototype was cardboard, which is durable, but not easy to work with quickly.

Pretty in Pink: A photo essay about my process today. Click on the individual pictures for notes.

I made three new prototype shapes today and I’m looking for feedback on them.