It can be lighter, cheaper, and much more fun than any lock you can buy.
Here's one made of cardboard!
It's perfect for use in Japan and other nice places where people don't like to steal.
I live in the United States where lots of people steal things.
So we'll make a stainless steel one from an old stove.
Step 1: The Ancient U-Lock
It's designed to fit over the spoked wheel of an automobile.
Back then lots of cars didn't have locks.
As Henry Ford said "You can have any color you wanted, as long as it's black."
So people accidentally taking the wrong car must have been a problem.
Step 2: Boston Massachusetts, 1974
That's because North Korean submarines loaded with ninja spies go there to steal bicycles.
There are about fifty colleges within ten miles of each other. All those students are
1) Easy to steal bikes from, and
2) Easy to sell stolen bikes to.
When I lived in Boston I had the lock made from these patent drawings. It was great. It was a bit unusual, so the North Korean training camps didn't bother teaching people how to break them open.
This excellent but simple lock is the inspiration for this whole project. The drawings shown here explain all you need to know about how it works. To keep boltcutters from reaching the hasp of the padlock, there is a sort of box around the padlock. The crossbar has lumps to keep it from pulling through the U.
Step 3: The Japan Compatible Bicycle Lock
He was Swedish and didn't like talking very much.
Forinstance there was the famous Anderson Family Sex Lecture: "There's not much to that."
or the one on the importance of communication: "I never talked to MY parents."
My point is that cultural differences exist. One can take them into account when designing bicycle locks.
I was just in Japan for a few weeks. I lost my bike lock so I just tied my bike to the rack with a plastic bag. Of course it was still there when I got back.
North Koreans don't steal many bikes in Japan. I hear they run Pachinko parlors instead.
Step 4: Make a Model and Gather Materials
Step 5: Cut Out the Parts
Stainless steel workhardens quickly and conducts heat poorly.
That means you need to use a sharp blade with a slow deep cut.
The other way is use a dull blade and just melt your way through it.
Step 6: Pound on It
Step 7: Make the Slot for the Crossbar
As you can see I've already done one of the bends for the hasp guard.
That's easy, just clamp it in the vise, fold it over, and pound on it to make a nice corner.
Step 8: Chisel Between the Holes
Use something like that to chop out the metal between the drill holes.
When the slot is big enough for a saw blade you can saw the slot bigger.
Step 9: File the Slot Smooth
This is the longer one at the end away from the padlock.
Keep filing until your crossbar fits easily in the slot.
Step 10: Fold the Hasp Guard
Repeat until it's the shape you want and your padlock goes into it easily.
Step 11: Weld the Hasp Guard and the Blob on the End of the Crossbar
I'm not showing any of the details of welding because it's hard to photograph and the info is abundantly available elsewhere.
Most people don't have a TIG welder. Use whatever you've got.
If you don't have a welder use solder, rivets, glue, string, or chewing gum.
The goal is to make it look like a bicycle lock or at least like something a normal person wouldn't want to touch.
The crossbar looks just like the cardboard one except it's metal.
The blob at the end can be welded, folded, or any combination.
Step 12: Saw Down the Hasp Guard
Step 13: Grind Slots in the Hasp Guard
I probably made the "ears" on mine too short because of too much coffee.
The grinder blasted lots of crap into my face, so I was glad I had safety glasses on.
Step 14: Lock Your Bike!
It's lightweight and not very strong, but there isn't any lock that would keep this particular bike safe in any American city for more than a day.
I'm scavenging materials for heavier locks that would be harder to cut.
You can never have too many bike locks.