Wednesday, July 4, 2012

Raspberry Pi Model B Case

I hadn't taped it yet, hence the rubber bands.

Today I got around to making a case for my Raspberry Pi. I liked the idea of still being able to see the circuit board and components, so I wanted a transparent case. The most conveniently available, viable, transparent material I had lying around was transparency film.

I got going on the footwork of building my case, the most obvious part of which is to make it fit! I looked up the dimensions online, and whaddya know, I found them on the website of the Raspberry Pi itself. "The Raspberry Pi measures 85.60mm x 53.98mm x 17mm, with a little overlap for the SD card and connectors which project over the edges." is explicitly stated on the FAQs page. But just to make sure, I got out my ruler. I have no idea where those dimensions came from, but they don't belong to my Raspberry Pi Model B. Maybe they're for the not-yet-produced Model A? Anyway, I measured to the best of my ability. For small schematics and technical layouts like this, I usually just use Inkscape, my favorite vector graphics editor. I'm very familiar with it, and it's usually sufficient for tasks like this (plus, I don't have to leave Linux and boot into Windows to use Solidworks :D).

Judging lengths by eye with my meager  plastic ruler turned out (predictably) not to be very accurate. Too bad I don't have callipers lying around. Needless to say, I had trouble jamming the Raspi into the first case, and the second revision was still troublesome. Finally, I got something that fit perfectly, and went on to slap some fancy connector labels on there.

I've made the final product freely available, and open source. You can download the US Letter version, or the A4 version.

The project page is here. Have fun building your cases, or customizing your own. I'd love to see what anyone does with this!
All of it's beautiful insides visible.

Friday, July 29, 2011

First Fixed Gear Conversion: pt II, Deciding What to Do with It

The first step in any project is to plan it. With this conversion, it's deciding which parts I'm going to keep, which will be replaced, and what other restoration may need to be done.

The frame does have a couple small scratches with rust. Also, basically all the "Raleigh" and "Grand Prix" decals have been worn off, or at least to a point where they don't look good. Naturally, it needs a paint job. I'm leaning towards powder coating for the improved durability.

I'd like to keep as many parts as possible, so as to keep costs down. All I'll be replacing is the back hub and chain (at least for the time being; I'll probably replace the cranks later). I'll replace the back hub with a flip-flop hub and a 1/8" cog, as I've heard the full bushings used in 1/8" chains make them much more durable, though it sacrifices flexibility (not needed on a single gear). Until I replace the cranks, I can ride the 1/8" chain on the 3/32" chainring. I would replace the chainring and keep the cranks, but the chainring is permanently connected to the drive-side crank, rather than bolted to the spider, as with modern cranks. I'm keeping the rim, so I'll need to find a 36-hole hub (as opposed to the more popular 32h nowadays) and a new set of spokes.

I'm going to remove the rack, water bottle cage, shifters and shift cables, but I will keep the brakes for the time being, despite of it frowned upon by some "hardcore" fixie riders. I may (probably will) remove them eventually.

I would like to do as much work as I can to keep costs down, and because I enjoy working on projects. I may need to go to a bike shop to pull the cranks, but I've read about some other makeshift tools for a lot of the work. More on that later.

So far, here's the procedure:
  1. Go to bike shop for quotes on parts and work
  2. Go to powder coating shop for quote on paint job
  3. Disassemble bike
    1. Remove rack
    2. Remove water bottle cage
    3. Remove brake levers, shifters and cables
    4. Remove brakes
    5. Remove kickstand
    6. Remove wheels
    7. Remove derailer
    8. Remove chain
    9. Pull cranks
    10. Remove bottom bracket
    11. Remove seatpost and saddle
    12. Remove handlebar stem and handlebars
    13. Disassemble headset and remove fork
    14. Pull head tube and fork crown races
    15. Drill out head badge rivets and remove badge
  4. Strip paint from frame
    1. Apply paint stripper and scrape paint
    2. Remove paint from crevices with a wire brush wheel on a rotary tool
    3. Wipe down entire frame with solvent/cleaner
  5. Bring frame for powder coating
  6. Order parts
  7. Clean remaining parts
    1. Clean off dirt, grease and rust then regrease
    2. Overhaul headset, bottom bracket, front hub
      1. Replace bearings
      2. Grease
  8. Assemble bike
    1. Build back wheel
    2. Etc.

Thursday, July 28, 2011

First Fixed Gear Conversion: pt I, Aquirement of the Donor Bike

This is the first post, of most likely many, documenting my first conversion of a road bike to a fixie.

I had been looking for a good used, cheap road bicycle recently. I searched Craigslist and yardsales for weeks. Most of the ones I found were either asking too much or were so rusted out and beat up it wasn't worth it.

Finally, I found a 1976 Raleigh Grand Prix at a garage sale for $5. It's in amazing condition (considering that it's over 30 years old) with basically no rust, no dents and rode at time of purchase with no repair. As far as I can tell from research, every part is original. Its only downfall is that the front derailer was nowhere to be found.

It even has the original tensioned leather saddle stamped as a "Wright W3N"; I've found that the Wright Saddle Co. was (or is) owned by Brooks, the very well known, and possibly only existing company still making leather saddles and that the Wright W3N is basically an exact equivalent of the Brooks B17.[1]

The hubs are made by Normandy, the crankset is Sugino, the derailer's Simplex, the brakes and levers are Weinmann, and I'm assuming the rims are Sturmey Archer from research and because of the spoke protector stamped "STURMEY ARCHER". I can't identify the manufacturer of the handlebar stem, other than a logo with "CB" or "GB" imprinted on it.

Four of the remaining five gears shift, though not smoothly or quietly, and the chain hops off the front chainring every once in a while (hopefully onto the smaller ring). The bad back shifting is probably due to the back derailer pulleys being worn close to smooth. The slipping front chainring is probably due to every tooth on the chainring being rounded off. I guess I can't complain knowing how old it is.

Here are some pictures:
First Fixed Gear Conversion: pt I, Aquirement of the Donor Bike

1. ^ Bregan. "Wrights Saddles." The Brooks Blog. Brooks England Limited, 22 June 2011. Web. 23 July 2011.