Few persons realize the unusually trying conditions under which a trap spring has to do its work, and it is safe to say that no mechanical contrivance performs its functions with greater precision than a well made and tempered trap spring.
A No. 1 spring weighs less than three ounces and will exert a force of between 70 and 80 lbs., and one of these has been known to remain under strain for over thirty years and then spring as promptly as though just set.
The jaw of a trap should have a good wide bearing surface, otherwise it will be apt to break the animal's leg bone, a calamity always to be avoided, especially in dry land trapping, for as before remarked "legging" is thus likely to follow. Anything like a sharp cutting edge or a saw tooth is especially objectionable, for our object in catching an animal is to obtain its fur and not to amputate its limbs. As a prevention of "legging" the Nos. 81, 91, 91 1/2 traps, described elsewhere, are especially designed. The pintle or end bearings of the jaws should fit loosely in the holes to allow for rusting and a little freezing, and there should also be a slight end play for the same reason.
The weight and strength of a jaw should be sufficient to prevent it from being sprung or bent enough to throw it out of its bearing when it is set or when sprung by the animal.
Much diversity of opinion obtains regarding the proportionate size of the pan or treadle. Some trappers like a large pan similar to that used in the Jump trap, but it is safe to say that the greater majority, especially among the old and experienced trappers, prefer the smaller sizes, and for obvious reasons. When an animal steps on a small pan he is caught to stay, but with a large one he may be "nipped" or his foot may be thrown out altogether. At any rate his education has been immensely advanced and it will take a trapper with a "long head" to get him into a trap next time.
The pan should fit loosely in its bearing for as is well known, rusting increases the size of a piece of iron and as there are four surfaces to rust in a pan bearing, ample room must be left.
LIMB GROWING THRU JAWS.
This trap was made about 1875 and no part had given way from the tremendous pressure.
Surely a good Newhouse.
The dog or latch should be thick and narrow rather than wide, as presenting less surface for the animal to step on. It should be curved and pointed in such a way as to hold up the pan but so as to "go off" "easy" or "hard" in proportion to the size of the animal trapped for. This is a nice point for each trapper to decide for himself and it is this susceptibility to adjustment by curving or straightening the dog that makes this old "trigger arrangement" superior to any other that has been invented. Of course, the cross and bottom pieces must be made in proportion to the other parts of the trap and the experienced trapper or inspector knows how to so bend them as to make them conform correctly therewith.