Saturday, February 9, 2008
On making bear guards for camera traps
Our first bear guard design. When Bruin paws the hinged treadle the canary (a $1 security alarm) screams. The terrified and paw-pricked bear never touches another camera trap. Well, that's the theory, anyway.
I finally repaired the camera trashed by the bear. I dried it above the wood stove for a few days, and last weekend I resoldered the torn wires. When I turned it on for the walk test the controller and camera communicated like a charm.
I'm a little smarter now and not taking chances. Many camera trappers have no problems with bears at all, but I am not one of them. Now I only put cameras in the woods that are equipped with homemade bear guards. I have more camera traps than bear guards, however, so it was time to make some more.
I don't use junction boxes or spiked collars for camera traps any longer. Though functional, this set up was too much work to get to the camera.
Neighbor Richard and I have come up with several designs for bear guards, and all of them work. Any spiked metal frame attached to the camera case deters curious bears, but it took several designs to arrive at the quick-set bear guards seen below. If bruin used only his claws he might be able to disarm a camera case of its bear guard, but bears are ham-handed and lose interest as soon as they get pricked.
Richard improved the bear guard design with the addition of angled clamps which make it very easy to attach and remove the guard from Pelican cases. The guard is made of 3/4 x 1/8 inch angle iron. The clamps are excellent fasteners, but you have to cut off the strap slot on the top of the Pelican case. You can find pdf instructions for building it here (registration is free).
The fixed clamp of the bear guard grips the ridge on top of the Pelican case. The adjustable clamp uses a wing nut on a 1/4" threaded rod to grip the ridge on the bottom of the case.
Richard suggested making a more light weight version of the bear guard using 1/8 x 3/4 inch angle aluminum, instead of angle iron. It differs in a few details from the angle iron version described in the pdf. The joints are mitered rather than lapped, and the spikes are made of galvanized nails glued in place with J-B Weld. The iron version used sheet metal screws as spikes (which do not have to be glued--much easier to make).
To cut the aluminum accurately I made a cutting jig for the table saw (top photo, below). After drilling holes for the nails, the 4 pieces of the frame were clamped for welding (middle photo, below). Then the nails were glued in place and allowed to cure for 24 hours (bottom photo, below).
Excess J-B Weld was ground off with a Dremel tool, and the inner surface of the frame was coated with soft polyurethane to minimize scratching the Pelican case. Three pop rivets hold the top clamp in place, and the 1/4" x 20 nut for the bottom clamp is threaded and glued in place.
The cost of materials is about $12 for one, and I bought enough materials to make three. I'm lucky to have a neighbor like Richard who can build practically anything and always offers a helping hand.
I spray painted them this afternoon, and they'll be ready for use tomorrow.