16 July 2010

Photos from Guatemala

IMG_5147I just got back from a month long vacation in Guatemala. I've uploaded pictures.

If you just want highlights, check out Semuc Champey and Tikal.

11 July 2010

DIY Bakfiets

I don't have a car---not even a license---and so transportation is a problem for me. It wasn't a problem back in Charlottesville or in Brooklyn, since both cities offered walkable communities. But now that I live in Princeton, my grocery stores are far away. I use a bike for personal transport, but even then, I can only carry a small amount of groceries at a time. I need a better solution; I need a sport utility bike.

The spark that moved me into action was one of bike-machismo. My friend Sean-not-douche of the Cyclab asked me to help him build a tall bike. That went well, but I was embarrassed that we needed a pickup truck to transport my welder and tools to his shop. Why do we need to burn gas for a bike-geek activity!? It seemed wrong.

Sure, I could simply buy a trailer, but I don't really like trailers. I had built a trailer back in my Virginia days, but I didn't like how it affected the feel of the ride. The joint between the frame and the weight added an unsettling resonance to the ride, especially around corners. I wanted a design that offeres a more rigid ride.

The dutch have long ago perfected a design known as the Bakfiets ("box bike") for transporting cargo. These literally are the SUVs of Holland; Dutch moms even use these to carry their children to school. I thought about it, and the design seemed perfect for my needs. In short, the design is a two-wheel bicycle, with a large cargo platform between a 20" front wheel and the steering column.

IMG_4528 I ran off to lowes and bought a lot of 1" square steel tubing. The new steering column is made from 1-1/2" EMT conduit. The headset, fork and wheel were scavenged from a child's huffy. The cargo platform is made from two 1" tubes, one above the other, with 1/2" tubes supporting between them.
I didn't really measure anything---I eyeballed everything. I found out later that the angle between steering column and front half was important and incorrect. I would need to correct this later.

IMG_4529Next, my friend Hjalmar gave me a small, purple schwinn to serve as the rear half. I cut-off the headset and mitered it to fit the steering column, and added another 1" square tube from the bottom bracket. Alignment is important, but not critical. So, I used a string to aid alignment. I made a loop of string, joined by a rubber band for tension. I wrapped this around the dropouts and the headset, then tapped the steering column left or right until it was centered between the two lengths of string. Clamp, weld, and repeat until the frame is straight.

IMG_4543I achieved the steering using an offset arm. An old fork was cut and extended with a piece of plumber's pipe so it would span the steering column. At the end, I welded a bold at a 90-degree angle, and added a complementary bold on one tine of the fork. I added a length of rebar, which connects to these two bolts using univeral (aka ball) joints. I built it up, adding components and wheels, and took it for a test ride.

Honestly, the first time I tried it, it rode like crap. The bottom bracket was too low, and the pedals would strike the ground. It felt very unstable, and the rider would tire very quickly. But why? I can't say I knew enough about bicycle geometry---was the slope of the front wheel incorrect? Was it misaligned? I was lost.

Luckily, my friend Joe figured it out for me. I welded the front half to the steering column at a 90-degree angle, and the steering column met the top-tube at a 90-degree angle as well. However, the purple schwinn had a rising top tube. Effectively, the 90-degree angle caused the rear frame to tilt forward unnaturally and lowered the bottom bracket. The solution was to change the angle.

IMG_4575From what I had, the easiest solution was to cut just in front of the steering column, and then reattach at a more obtuse angle. This raises the bottom bracket, moves it forward of the seet, gives a comfortable slope to the steering column, and leveled the cargo platform. Indeed, this simple change made the bike much more comfortable.

Per Zach's suggesting, I added a triangular piece from the steering column to the cargo platform, for strength.

Next, I welded two 27"-long 1/2" square tubes perpendicular to the cargo platform. These will help to support the platform.

IMG_4583Once I had achieved a ridable frame, and could not forsee any major changes to geometry, I build a box out of scrap plywood I found in the dumpster. These three boards rest against the frame. I didn't have any hardware to attach the wood. I searched my junk pile, and found some scrap copper sheets, leftover from some roofers. I cut, bent, pierced these into brackets, and then screwed the frame tight against the frame. Copper is expensive---if you were buying it, I'd recommend you use sheet tin or steel.

IMG_4586Now the bike is done-ish. I can carry cargo. The next few things I'll do are: add sides to the box, add cable stops so I can shift gears, and also strip it all down and paint it. In the mean time, it's certainly strong enough to carry 8 bags of groceries, or a hundred-or-so pound of tools. Success.

But this is better than just a hack---this is a liberating technology. I want a life without gasoline yet without sacrificing quality of life. This machine gets me one step closer.
The whole set of photos is on flickr.