Here's my contribution to the Homemade Cargo Bike revolution!! :) Used an old Mountain Bike frame from a great junk bike store close by. I basically followed the instructions from this guy: http://www.instructables.com/id/build-a-2-wheel-cargo-bike/
with a few of my own modifications. The bike is functional, but not done at this point. I still have to engineer and build a kickstand, install the brakes and shifters etc, and decide what kind of platform or box I would like to have.
Note, I brazed the entire frame, which I have never done before, but since I didn't have a working TIG welder I went with this because of better control than with MIG or standard oxy-acet welding. The joints are not all pretty, but they are strong and beefy!!
Materials used: Mountain bike frame, 2 BMX frames (used for the steerer tube and the 20" fork). Cost: $20
Some scrap steel tubing, I used various cutoffs from the local steel yard. Cost approx. $30
Bike components: had a bunch lying around from my various bike projects over the years, bought some others. Cost: depends on how high end you want to go.
Step 1: Frame Extension
Next I used some thin walled 1 3/4" diameter steel tube for the main frame extension off the front. Figured this would be nice and stiff since I'd seen lots of variations where people tried to engineer multiple tubes together to add stiffness. This worked great. This also allowed enough clearance so I could keep the entire length made from 1 piece of steel instead of 2 separate pieces.
Harbor Freight Tube Notcher was a great investment (with some slight modifications to make it more accurate: http://www.youtube.com/watch?v=Ty915Z0GrJo
Step 2: Head tube setup
The hardest part was getting the front steerer tube and fork aligned and the correct height so that everything would end up level with the wheels installed, and there would be the correct clearance for the front wheel to the frame. Took multiple tries, and I had to recut these pieces of tub several times before I was happy with everything.
Step 3: Disc brake mount
Figured, while I had the paint off, why not go for disc brakes!! I have no experience with disc brakes as they weren't invented back when I was working on bikes, so it took some figuring out to position the mount!!
I also ended up switching to a different fork because the fork I started with didn't have clearance for the brakes.
Step 4: Front Wheel
Took a break from opening presents on Christmas Day to lace up and build the front wheel.
Step 5: Assembly and trial ride
First attempt at connecting the steering rod. I ended up cutting the connectors down so they didn't stick out as far. This was based on looking at various manufactured bikes like the beautiful CETMA Cargo: http://cetmacargo.com
WORD OF ADVICE!! I used some seriously old random frames for the steerer tubes etc. and ended up with some really hard to fine headset sizes. You might want to check the headset sizes used on your frames before you start. Especially old BMX frames.
Step 6: Kickstand
Here's the kickstand in process. Again, I based it on the nice design of CETMA's model. He has a really extensive Flikr page with tons of details and closeups just waiting to be copied!!
Note: I have since gone back and shortened the "U" connector between the 2 legs of the kickstand. When it was up, it would scrape on the ground if I rode from the street up my driveway.
Sorry for the poor photo quality of some of these, I have a horrible cell phone camera.
Final note: the kickstand has the problem of flopping down when I ride over a big bump !! I think the solution would be to raise the spring peg on the frame end so there is more force holding it up. I also would increase the angle when it is down, of course I wish I had realized both of these issues before I had painted the frame!!
Step 7: Stays/ Supports
Finally attached diagonal stays to the main body.
Ok, so I had planned on finishing and riding the bike all summer, but turns out my time off was taken up with other more pressing projects like the birth of our 2nd!! But now that school is back in session I can resume some work on the bike!!
Here I've added pics of machining cable housing stops for the shifter cables. The cable routing for the shifters is all thrown off because of the added front extension tube, so I had to be a bit inventive. You can order these parts on line, but the shipping for small parts is ridiculous so I just made some. Love having access to the jewelry dept.'s mini metal lathe!! (One of those tools no students even know exists, and I'm pretty much the only person who's used it in 10 years).
Step 8: Color!!
Finally managed to take the frame fork and kickstand to be powder coated!!! Yay, now to reassemble!
I highly recommend OLYMPIC Powdercoating if your in SoCal/OC as they seem to be bike enthusiasts.