Attaching a plastic crate to the rear rack of a bicycle provides a convenient place to carry small-to-medium sized items on your bike. But sometimes you may be running multiple errands and you may not want to unpack everything from the crate and carry it all with you each time you park your bike. This instructable adds a locking top lid for a bike crate that will provide some degree of security for items in the crate while your bike is parked (it will at least keep the honest people out).
Step 1: Parts List
1) A saw for cutting out the plywood parts (A table saw is probably the best option, but you may be able to manage with a skill saw or even a hand saw)
2) An electric drill and a 1/4" drill bit
3) T-handle reamer (for enlarging holes to fit the t-nuts)
4) A Welder (I used a welder to make a few custom hardware parts like the chain, but you may be able to find other solutions that do not require welding)
SAFETY NOTE: Never use any power tool without proper training.
1) You will need to make several plywood parts. Refer to the drawing on the next page.
NOTE: Plastic crates come in many varieties so the exact dimension of these parts will depend on the crate you choose. The dimensions on the drawing are for the crate I used, but you will need to make your own measurements to fit the crate that you choose for your bike.
NOTE: Bike racks also come in many varieties and therefore the method to mount the crate to the rack may need to be different than what I used for this instructable.
NOTE: For a small project like this, you can sometimes find suitable plywood scrap pieces at bargain prices at your local lumber or home-improvement store.
2) Several miscellaneous hardware items such as: 2x hinges, 15x 1/4" t-nuts, 1x 1/4" eye-bolt, 4x 1/4" carriage bolt
Step 2: Drawings for the Plywood Parts
This drawing show the plywood parts needed for the lid as well as the parts needed to mount the crate to the rack. If you already have your crate mounted, then you won't need the parts labelled "UNDER MOUNT".
Step 3: Mounting the Hinges
I used 1/4" t-nuts to mount the hinges. Test fit the hinges and mark the location of all the mounting holes. I used a drill with a 1/4" drill bit to drill the holes for the t-nuts and then used a t-handled reamer to enlarge the mounting holes until the t-nuts made a good press fit (there are probably more efficient way to do this, but that's the method I used). Use 1/4" (coarse thread) screws to mount the hinges to the top lid and the 9" square front panel.
NOTE: After I fitted the t-nut and before I mounted the hinges, I painted both the top lid and the front panel with exterior grade urethane to protect the plywood from the weather.
Step 4: Add a Handle and Lock Ring to the Top Lid
The handle is a spare cabinet handle I had lying around. It's optional, but nice to have. It mounts with the screws that came with it. The lock ring is needed for the locking mechanism (shown in a later step). The lock ring is a steel ring I had lying around that I welded to a 1/4" bolt, but here may be other easier solutions that do no require welding. The ring just need to be large enough for the locking chain to pass through (shown in a later step). The plastic clip and bungee are from a camera bag strap that I bought (for $.50) at a local thrift store. The clip is used as a quick way to secure the top when you don't need the top locked down.
NOTE: I added a strip of self-adhesive foam (left over from a home weatherproofing project) to the rear edge of the top lid. The foam strip prevents the lid from rattling around and making distracting noise when riding.
Step 5: Mount the Front Panel to the Crate
Drill and fit 2 t-nuts to the 9" square front panel. The exact location of the t-nuts will depend on the layout of your crate (as noted before there are many different crate configurations). You just need to space them so the front panel is well secured to the crate. On the inside of the crate I used a large diameter galvanized steel washers and 1/4" bolts to secure the front panel to the crate (as shown in the attached picture).
Step 6: Mount the Rear Panel to the Crate
Drill and fit 2 t-nuts to the 5" square front panel.The exact location of the t-nuts will depend on the layout of your crate (as noted before there are many different crate configurations). The upper t-nut is secured with a ring bolt which is needed for the locking mechanism (shown in a later step). And the lower t-nut is secured with an ordinary (3/4" long) 1/4" bolt.
Step 7: The Lock Mechanism
The locking mechanism consists of a chain with 2 rings welded to it. The ring on one end must be large enough so that when the chain is threaded though the ring mounted on the top lid it will anchor the chain in place. The ring on the other end needs to be small enough to thread though the ring mounted on the top lid and large enough to fit the padlock. When not in use, I keep the padlock and chain in a zippered pouch that I keep in the crate.
Step 8: Mounting the Crate to the Rear Rack
You can skip this step if you already have your crate mounted. I mounted the crate using 4x (1.5" long) 1/4" carriage bolts that go through the 12" square bottom panel (mounted inside the crate) and attach to the "UNDER MOUNT" plywood parts (#1, #2, #3, and #4). I hope the arrangement of these "UNDER MOUNT" parts is clear from the picture. Parts #1 and #2 are placed (lengthwise) perpendicular and parts #3 and #4 are parallel (to the direction of the bike).