First off I go to art school in San Francisco. The school provides shuttles that go to all the school buildings, but are quite slow, thus I ride my bike all the time.
Last semester I lent my bike out to my roommates friend for 2 days (I know, bad Idea). He returned everything, but the ulock key, and mini pump. Oh yeah I forgot to mention that he left the ulock locked on my bike frame. Long story short, he never returned the stuff, so I began to look for a new lock.
I browsed online and read that chain locks provided some of the best security, but i found them to be quite spendy ($20-65, yes $20 is spendy, I'm in college :P). So I sought out to make my own chain-lock for cheap!
This build is so easy it's pretty ridiculous and should cost you less than $12. Let's get to it!
Step 1: Getting the Right Chain
This part like the rest of the build is simple. Go to the hardware store, buy the thickest chain you can (within reason). You want a heavy duty thick chain for the obvious reason that they are hard to break.
I don't recall the exact specs of the chain I bought, but it was about $3 per foot. I got 2 feet which Is enough to at least lock the frame to a post. I think 3ft or 4ft would be ideal. You can make it as long as you want within your budget, just keept in mind you have to lug it around.
On to step 2!
Step 2: The Lock
This step is as easy as the last one, and like the last step it's all a matter of preference.
The Lock I am using now is just a hardened padlock I had lying around.
I prefer combo locks for bikes and lockers, because you don't have to fish around in your key ring for the right key.
It really is up to you. Just remember to try to find a lock with about the same shackle thickness as the chain obviously.
A good heavy duty lock can start from around $4 to $15. A good place to look is ebay, Amazon, and I bet craigslist wouldn't be bad either.
Step 3: Finishing Touches
Up to this point your done, but as you probably have guessed the chain might be hard on your bike frame. Don't worry this is easy to fix.
At my School Apartment, right after I bought the chain, I found my reusable grocery bag that had ripped on a prior grocery bike run. So, I cut up the bag and made it into a sleeve for the chain.
It's pretty easy I just cut the bag into a strip and wrapped it around the chain. Then I used a rubberband at each end of the chain to stop the sleeve from sliding off. After that If I were you I would use some gaffer's tape (you can use duct tape, but it ain't as good) and tape the sleeve. You don't have to cover the entire thing in tape, I just taped mine up like a coil.
Step 4: Your Done Baby!
Congrats you have just made a super cheap n' easy chain lock. Mine is a bit crude, but Ideally I would tape it again with gaffers tape and tape the ends of the sleeve and probably choose better colored rubberbands.
This has worked fantastic for me, and for coming to only $7.60 or so, You can't beat it. Tough it may be more expensive for you depending on if you have to buy a padlock or not, but it still is cheaper than the brand name and works just as good.
Hope that helps you guys and saves you some cash too!