Handmade Cycle Fenders Class @ Techshop

Yesterday afternoon I attended the Techshop class How to make Aluminum Cycle Fenders on the English Wheel. This was my first Techshop experience and as such, I had some mixed feelings, though overall the experience was great. I did learn a good bit about making bicycle fenders from scratch, and brought home a decent sample as proof. Overall, it was a worthwhile experience, and I am planning on returning to Techshop for more classes in the future.

I'd first heard about Techshop through a mention on the Framebuilders list (thanks Alex!). It's been a life-long dream of mine to have access to a machine shop, so I was shocked to learn that Techshop has been active just a short drive away at their Menlo Park, California location since mid-2006, and I was only now discovering it! On their website I read about the large, well-equipped facility and about Techshop's origins. I envisioned a tidy, energetic place, bustling with creative activity. However, when I arrived for my class, I entered a mostly quiet, somewhat-shabby environment that was fairly devoid of people. As I pulled into the parking lot, I saw a guy ride up on a titanium fixed gear bike -- I instinctively knew he'd be in my class and that I'd be in good company. As I entered the building I was greeted by the receptionist, who (after guessing my name) informed me that there were only two students registered for the class, and had me complete and sign a waiver. I inquired about the usual class size, and learned that the maximum number of students per class was five -- I'd expected that it'd be three or four times that!

We met our instructor, who gave us a quick tour of the building's mostly-empty rooms. We first passed through the general project area -- a space containing about twelve large work tables with general-access parts/scrap storage shelving along one wall. Techshop members are encouraged to clean out the junk/scrap/excess from their home workshops and contribute to this community parts pool. If I remember correctly, there was only one individual working on a project when we passed through this area. At the opposite end of the large room is a lounge/kitchen area with a few scattered tables and chairs, and a bank of computers along one wall. I didn't ask, but presumably these PCs are for people to use when they visit Techshop -- I noticed several computer-graphics books next to one computer. Behind the lounge area is the main machine shop, featuring several milling machines, lathes, and other large machine tools. Most of these machines were silent: there were two guys working on a couple of the mills, but I couldn't see what they were making. Down a hallway, past some administrative offices, we saw the tool storage room where small hand tools, safety gear, and other equipment is housed. We stopped in at the paint room and saw their small vent-hood system as well as the powdercoating system. I asked how much it might cost to powdercoat something there, specifically wondering about paying for the powder I might use, and was told that small, one-off jobs in stocked colors were included in the normal Techshop membership fee -- but if I wanted to do a production run or needed special colors, I'd be responsible for covering that. Next door to the paint room is the laser-cutter room, where one person was engraving a photograph into a mirror to make a psuedo-three-diimensional portrait. The final room we visited was the metalworking and welding room, which is where our class took place. There were a few more people in this room finishing up a welding class, and they left shortly after our class started. One side of this area held MIG, TIG, and OA welding equipment plus a large computer-controlled plasma cutter; the other side of the room housed a sheet metal brake, cutting tools and a rotary stamping press, a work table, tools for bending, shrinking, and stretching sheet metal, and a small English wheel and an air-powered planishing hammer mounted on a shared pedestal. After my class was over, as I wandered around searching for the restrooms, I passed many more dark and empty rooms: a sewing room housing industrial sewing machines, a few rooms marked "Private" or "Project in progress", and a retail area with some books, small parts, and tools on display.

Our instructor started our class with a quick overview of the tools we'd use to make cycle fenders: delrin hammers and leather bags, the English wheel, the sheet-metal shrinker, and the planishing hammer. He used the power shear to cut some sheet aluminum into samples for us to work on, roughly 2x8 inches in size. To curve the leading and trailing edges of the fender, we used a scribe to trace around the bottom of a soup can and then cut the arc using metal shears. We gently filed the cut edges of the piece to debur them. Next we used the delrin forming hammer and the leather sand bag to rough in the compound curve. The spherical end of the hammer stretches the metal when struck against the bag, and the soft surfaces insure that no work-hardening of the metal takes place, which can lead to cracking during later forming stages. Once the compound curve is formed, the ridges and imperfections in the part are smoothed using the English wheel -- this tool has flat upper and curved lower wheels which you pass the piece between. The gap between the two wheels is adjusted by a large screw, which you tighten as you work the material back and forth through the tool. It's important to keep the part pressed against the curved lower wheel so the material adopts its shape. After the part was smoothed, we moved on to the shrinker tool to curve the sides of the fender inward even further. The shrinker has two sets of plier-like jaws which grasp the material and then squeeze together sideways incrementally, forming little ripples in the material. (The stretching tool, which we didn't use, does exactly the opposite -- the jaws clamp the material and then move apart). The final forming step was the air-powered planishing hammer, which works like a miniature jackhammer driving a flat hammer against a domed anvil, and imparts the characteristic dimpled appearance onto the material. The planishing hammer mainly smoothes the surface, although it also stretches, thins, and forms the material as well. The lower anvil can be swapped for other shapes to acheive different results and/or depending on the size of the part being formed. The air pressure driving the hammer can be adjusted, ours was set at 20-25psi depending on the thickness of the aluminum sheet. Finally I used a beading tool to roll the long edges of the fender inward, to simulate the shape of Berthoud fenders.

Although Techshop wasn't exactly what I'd expected, I had an enjoyable experience. I imagined a bustling hive of activity (what self-respecting DIY'er wouldn't want to play in a machine shop all weekend?!) but, perhaps because it was a Sunday afternoon, the facility was fairly empty and quiet, save for the occasional machining noise. The instruction I received was quite loose and informal -- I would've preferred something a bit more structured and comprehensive -- but given that it only cost $30 for nearly three hours of facetime it's a good bargain. I learned a lot about hand-fabricating bicycle fenders (and now have renewed appreciation for Honjos and Berthouds!) and I might attempt to make an actual set of fenders at some point (if I can find material to work with), although frankly given that you can buy a set of quality metal fenders for $40-50 these days, it's certainly not a good investment, time-wise. I definitely want to return to Techshop in the near future for more classes to learn the basics of TIG welding, using the Bridgeport mill and the lathes, and other exciting DIY topics!

Postscript for those in the SF-Bay area: I asked the instructor about local sources for aluminum sheet and other metals -- he recommended Metal Supermarket @ 2999 Spring Street in Redwood City, CA (650) 299-9856. From their website, it appears they have other locations throughout the USA and Canada as well. I'd never heard of them so I wanted to pass this along...

Update: Here's another source for many of the tools used in this class: http://www.eastwoodco.com. They have a video demonstrating the shrinker/stretcher tools (requires Quicktime).