Instructables
Picture of Bike Lock Key Holder
A simple project that allows a bike lock key to be always to hand when you're using a Chrome or similar messanger bag - it means you can stow your main bunch of keys at the bottom of the bag when you're out for the day and not worry about losing them.
 
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Step 1: Stuff You Need

Picture of Stuff You Need
- One of your lock's spare keys.

- Some Polycaprolactone granules. Also known by the trade-names "Shapelock" and "Polymorph", it's the polymer that becomes soft at 60 degrees C. 

- Some elastic cord.

- Two neodymium magnets, bought from an on-line specialist in high-power magnets. One is a .75" disk. The other a .5" disk with a countersunk hole. Though I'm fairly sure a plain, smaller magnet would've worked just as well.

 - A thick split-ring salvaged from an key-ring.

Step 2: Cut Plastic From Key.

Picture of Cut Plastic From Key.
First thing, shave down the size of the key by removing some of the plastic handle. Don't remove it all! Leave enough to transmit the twisting force of locking and unlocking into the metal shaft of the key.

Step 3: Making the Key

Picture of Making the Key
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What we're aiming for. The split ring attaches to the back and the magnet to the side of the key, they're held on by a glob of shapelock that makes the new key handle.

By using a neodymium magnet with a countersink hole, a conical plug of shapelock in the hole is sure to hold it firmly in place. If you can't find one, try a more-common disk magnet, making sure it's completely covered in the glob of plastic . After all, you can always warm it up and disassemble it to try again.

Important!  Neodymium magnets may loose their magnetism at 80 degrees Celsius. Polycaprolactone only softens at 60 degrees Celsius so you've got to keep the polymer within the 20 degree temperature window when making this. I just put some granules of the plastic in a metal dish and carefully used a hot-air paint stripper to give them the absolute minimum of heat neaded to soften the plastic. Luckily, the stuff goes from white to clear the moment it's ready to use.


Lewis72067 months ago
I made something a while back like this...
I called it a 'pocket'...
Joking aside, this is a really useful yet simple design :)
CaseyCase3 years ago
If you did not want to use Shapelock, you could use an epoxy putty repair stick--just another option.
katsmeat (author)  CaseyCase3 years ago
True.
Although shapelock is easy to rework if you get it wrong - jusy heat it up.
OrangeFu4 years ago
With my Chrome bag I found it lacked areas to latch/thread things into it. On the shoulder strap (where you've placed a key holder) I installed a grommet so I could hook my keys onto it. For the longest time I would use a velchro loop to hook my keys/camelback valve, but I was always scared heavy keys would break the velchro.
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katsmeat (author) 4 years ago
Yep... Kryptonite New York. Not as good as a Kryp. Fahgettaboudit, or the top-of-the-line ABUS. But I'm not in an especially high-crime area.
fireraisr4 years ago
Is that a kryptonite key? it kinda looks like it.