Step 1: Prepare.
To do this the way I did, you'll also need the following:
- one bike
- one cooler. I think this is what I used: http://www.rubbermaid.com/rubbermaid/ecommerce/product.jhtml?prodId=HpdProd200006&catId=HpdCat190071
- one steel right-angle bracket
- an electric drill and various bits
- something to attach the cooler onto the frame: I used the kind of brass bracket that slide bolts (for doors) slide into: see http://www.lowes.com/lowes/lkn?action=productDetail&productId=73299-1277-SP1271for example. You could also use the kind of copper bracket they use to hold copper pipes against the wall.
- various bolts, screws, and bits of chain
- you might find it useful to have zip ties to temporarily hold the cooler in place while you try it out.
Step 2: Drill the hole in the angle bracket
Step 3: Attach the bracket to the bike
Step 4: Position the cooler
Step 5: Make a hole for the nut
First mark where it's going to go with a sharpie. You can probably figure it out just by marking the approximate position of the bracket on the side and putting it in approximately the right place. Then drill your hole.
Step 6: Attach the top bracket to the vertical tube
Now you're going to attach a piece of metal around your vertical support and use bolts to hold it onto the cooler. Again, I used the kinda piece of metal that slide bolts slide into. Seen in profile, it's shaped like this: _n_ and has a hole in each one of the flat sides. Mine's brass, but that's only because that was what was lying around. You also find similar copper ones used to hold pipes in plumbing. You could also just use a strip of metal and bend it in shape.
So first mark on your cooler where it's going to go. Then drill both your holes through the cooler all the way to the inside, and put in one side of the bolts loosely. Then hold your cooler up against your bike, put your bit'o'metal around the vertical support, and slip the bolts through the other side, through the cooler, and tighten them up.
Before you tighten them all the way, slip three or four screws into the bottom of the cooler through the bracket. Then tighten up. That'll make sure that everything's where it's supposed to be once it's all installed.
Step 7: The final holding strap
After trying a bunch of solutions, I've finally decided that it's useful to have a bike rack in place on your bike. Then you can simply attach a bolt to the far corner of your cooler and tie that to your bike rack. It's possible to do it without, but I wouldn't recommend it. Then again, unless you're me, if you're planning on having a cooler on your bike then you probably already have a bike rack.
So you know the routine by now. Drill through the cooler; put in a bolt. In this example I used an S-hook on the bike rack, some lightweight chain I had lying around, and a bit of old brass toilet seat hardware to provide something for it to attach to. No, this is not the classiest solution.
Nor is it the best; I think putting in some kind of turnbuckle would be much nicer and let you adjust tension and the like. Then again, I've used this for a few months now and it seems in pretty good shape.