Home Made U-Lock Bicycle Lock




About: Tim Anderson is the author of the "Heirloom Technology" column in Make Magazine. He is co-founder of www.zcorp.com, manufacturers of "3D Printer" output devices. His detailed drawings of traditional Pacific...

Make your own bicycle lock.
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

The "Modern" U-style lock is pretty old. Here's a patent for one from 1925.
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

Many patents for bike locks come from the Boston area.

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

My Dad never stole because my Grandfather gave him a lecture on the subject: "Stealing is easy."
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

The cardboard lock seemed about right, so I scavenged some stainless steel to make the real one. I wanted some heavy stainless that would actually be hard to cut through, but all I could find was this stovetop. As long as the finished thing looks fairly solid that's probably enough. I bought a four-pack of padlocks all keyed the same for $15, and it's time to cut metal. I marked the cuts and folds on the metal with a permanent marker. The little rectangles in the lower right corner are the cuts and folds to make the guard box around the padlock.

Step 5: Cut Out the Parts

I clamped it in a vise and used a sawzall with a hacksaw blade to 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

The metal edge had some curves I didn't want so I flattened it with a hammer.

Step 7: Make the Slot for the Crossbar

Drill a row of holes. That's the first step to cutting the slot.

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

I'm fortunate to have friends that grind my screwdrivers sharp so they make good chisels.
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

There are two slots in the U part of the lock.
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

Clamp, fold, pound. Repeat.
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 used old stainless steel bicycle spokes as welding rod and a TIG welder.
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

I thought I made my hasp guard too deep, so I sawed it shorter.

Step 13: Grind Slots in the Hasp Guard

Keep reshaping the hasp guard until you can get the padlock to fit in it properly.
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!

Here's the finished lock in use. It looks and acts like a real lock, at least well enough for running errands.
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.



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    48 Discussions


    3 years ago

    at first glance I thought you were suggesting the cardboard version!


    8 years ago on Introduction

    "As Henry Ford said "You can have any color you wanted, as long as it's black."" is a misquote, the first few generations of Fords were not even available in black.

    5 replies

    Reply 7 years ago on Introduction

    "As Henry Ford said "You can have any color you wanted, as long as it's black." is not a misquote i can't remember what model of car it was for but he did famously say that


    Reply 7 years ago on Introduction

    Ford wrote in his autobiography that he told his management team in 1909 that in the future “Any customer can have a car painted any color that he wants so long as it is black”.
    From 1908 to 1914, the Model T was not available in black but rather only grey, green, blue, and red. Green was available for the touring cars, town cars, coupes, and Landaulets. Grey was only available for the town cars, and red only for the touring cars. By 1912, all cars were being painted midnight blue with black fenders. It was only in 1914 that the "any color as long as it is black" policy was finally implemented.
    The model changes were not designated by a new letter but frequently under the banner of Model-T which was also seen more recently with the VW Beetle that change dramatically over the couples of decade they were built although they kept the same name and styling. 


    Reply 7 years ago on Introduction

    That was the whole point you could only buy the car in black and I have since researched what model car this was and it was the Model T in 1909

    weldor2 stroke

    Reply 8 years ago on Introduction

    Depending upon the thickness and type of stainless steel used it can be quite a chore to cut through with snips. Stove tops are typically a 300 series ss which is not as hard ad the 400 ss. It is typically tougher (this is what makes ss such a pain in the rear to work with). The wider the strap the more trouble it will be to get through.
    The lock in the pic is a Masster Lock. Although typically a decent lock, I knopw how to destroy one in a matter of seconds. Master does make a lock that has a hex shaped shank. There are other types of locks that are harder to break as well. They typically have what is best described as a "warded" shackle. Look them up on the Maaster Lock web site. There are other companies that make good locks as well. Some of the knock offs are pretty stout as well. I would recomend using a lock that is stainless as well- no rusting and all but impossible to cut with a torch as well as a real pain in the keister to cut with a saw.

    Any thief with a bolt cutter could have most bikes in a few seconds. Most bike locks are meant to prevent the casual/semi casual thief (just walking around, and steals a bike without intending to do so that day, or similar variants). If there's a gang of thieves driving in a van with power tools or even a bolt cutter, Your bike is pretty much gone, unless you have a bunch (10+) of insane strength locks.


    Reply 8 years ago on Introduction

    Stainless steel will not break by bending it back and fot\rth as you suggest. However, it will proceed to getr hotter and hotter until you burn your fingers. JUst ask anybody who works with metal for a living.


    8 years ago on Step 12

    Funny to see your gloved hand on the handle and the bare one near the blade.


    8 years ago on Introduction

    i found most of the time when you buy a lock from a bike lock exclusive company, they're usually more than happy to reimburse you for the bike