SNARE NOOSE RELEASE DEVICE STUDIES - ACCURACY AND PRACTICALITY

By Dick Sinrud, Thompson Snares

(Editor's note- We are pleased to have Mr. Sinrud sharing his expertise on this issue. He is the grandson of Raymond Thompson, the founder of Raymond Thompson Snares. This business has been in the family since its conception in
1925. Thompson Snares has been running this business in the same location since 1947)

In the past few years there have been many changes and adoptions of snare equipment and regulations. One of the major changes occurred with the requirements of using snare noose release devices. Although there are many issues regarding snares, this article will only confront release noose systems and their validity. (These devices operate under various names, the most common perhaps is snare "break-away')

About 15 years ago Thompson Snares experimented with a neck lock that would allow a moose or caribou to free itself from a wolf snare while still being capable of holding an Alaskan wolf. This neck lock was a successful application used in Alaska where the problem of an occasional moose or caribou got their snout or leg hung up in a snare set. At that time no other states had shown interest in such release systems.

In the past several years, this concept has caught on in many states to allow the release of unwanted captures such as deer, range cattle, and protected wolf species. Now approximately 25% of the legal snare states require a noose release type snare and the numbers continue to grow.

Last year Thompson Snares, through their Research and Development Department, made a decision to follow along with this concept and began contacting various game and management officials for information on their testing procedures and who to approach for studies on release systems.

To our surprise we were informed, in almost every instance, there currently were no testing facilities, and it was assumed the snare maker tested their own equipment. Furthermore, we were told there was no current way to identify and guarantee a release type snare worked other than a visual examination. We did find the state of North Dakota was sending samples to their State University in Fargo, although they did not know how the test were conducted.

Since most states use a common break release weight requirement (either 350# or 285#), Thompson's R & D decided to make some preliminary tests using a ferrule type of release. Since we produce our own parts, we can maintain control and accuracy.

It is important to understand the relationship between cable types and various snare components. Because we use only IxI9 I.P.S. single strand cable in manufacturing our snares, these studies are limited to this cable type. Other cable types may produce different results. The materials used for these studies are limited to Thompson brand materials and parts.

Ferrule, stock was cut to identical dimensions and machine compressed to a specific thickness on various cable diameters. These snares were then attached to a measured weight at the swivel end, and the noose end was applied to a 3-inch pipe mounted on an electric forklift. The speed at which the forklift operated was calculated at 1/4-m.p.h. (6 feet. in 17 seconds.)

Through a series of samples, we calculated proper consistent dimensions for the release ferrule to fall off allowing the snare noose to open at less than 3 separate weights - 150, 285 and 350 pounds.

After we were satisfied with the results of these tests, we proceeded to make samples of 4 different cable diameters - 1/16", 5/64", 3/32" and 7/64" diameter. The maximum break point for the 1/16" cables was set at 150#, as it is designed primarily for smaller game. The 5/64" and 3/32" cables were both set to release at less than 285#, and the 7/64" cables were set to release at 350# or less.

One dozen of each of these samples was sent to North Dakota Mechanical Engineering Department where they used a Tinius Olsen Testing Machine. The testing results were returned as follows:

1. 1/16" diameter cable rated at 150#. 12 samples were taken and the ferrule popped off at the following release pound weights: 287, 360, 234, 198, 314, 165, 236,
403, 294, 332, 291, 329. Average = 286.92 / std dev = 68.48 / range = 198-403.

2. 5/64" diameter rated at 285#. 12 samples were taken and the ferrule popped off at the following release pound weights: 480, 490, 614, 553, 556, 579,462, 424, 414, 392, 496, 657. Average = 509.75 / std dev = 82.84 / range = 392-657.

3. 3/32" diameter rated at 285#. 12 samples were taken and the ferrule popped off at the following release pound weights: 216, 226, 474, 550, 457, 511, 207, 227, 321, 480, 434, 575. Average = 389,83/ std dev = 140.79 / range = 207-575.

4. 7/64" diameter rated at 350#. 12 samples were taken and the ferrule popped off at the following release pound weights: 585, 559, 576, 567, 724, 525, 695, 421, 554, 564, 660, 442. Average = 572.67 / std. dev = 89.77 / range = 421-724.

We were astounded at the gigantic difference between North Dakota's results and the results in our R & D Department experiments.

We decided to build a more accurate test procedure and built a solid beam frame for a testing platform. To this platform we mounted an 800# capacity electric winch overhead. Our next investment went towards the purchase of a digital weight counter with a "peak hold" indicator with an accuracy of I/I0-pound. The peak hold indicator stops the digital readout at the point of break.

After the completion of our testing equipment, we proceeded to duplicate the 3/32" diameter snare with a release point of 285# or less. These snares were tied to the bottom of the test frame and the noose was placed around a 2-1/4-inch pipe with a small piece of carpet attached to help give a better simulation of an animal's body. The addition of the carpet increased the diameter of the pipe to 31/4".

Test
Two separate tests were taken using identical snares on each test.

TEST "A"

Test "A" (left) was performed using a "single pull cable" creating a calculated pull speed of 8/10-mph (6 ft. in 7.8 seconds). Test A - The results of this test on 6 snares using a steady pull are as follows: Ferrule releases at 56.4, 51.0, 51.1 59.2, 37.8, 48.3 (break point in pounds). Range: 37.8 - 59.2 / Low: 37.8 / High: 59.2 Avg. dev.: 3.56 Test "B" (right) was performed using a "double pull cable" creating a calculated pull speed of 1/4mph (6 ft. in 17 seconds). Test B - The results of this test on 6 snares using a steady pull are as follows: Ferrule releases at 75.8, 74.2, 77.2, 60.0, 73.1, 67.6 (break point in pounds). Range: 60.0 - 77.2 / Low: 60.0 / High: 73.1 Avg. dev.: 2.18

TEST "B"

Test "A" was performed using a "single pull cable" creating a calculated pull speed of 8/10-mph (6 ft. in 7.8 seconds). Test "B" was performed using a "double pull cable" creating a calculated pull speed of 1/4mph (6 ft. in 17 seconds).
Test A - The rate of travel on the winch in a "single line pull" was calculated at 8/10 mph, The results of this test on 6 snares using a steady pull are as follows: Ferrule releases at 56.4, 51.0, 51.1 59.2, 37.8, 48.3 (break point in pounds).

Test B - A second test was performed using a "double line pull" on the winch. This reduced the rate of travel to 1/4-mph. The results of this test on 6 snares using a steady pull are as follows: Ferrule releases at 75.8, 74.2, 77.2, 60.0, 73.1, 67.6 (break point in pounds).

Analysis

By analyzing the last two studies, we see an approximate relationship between rate of pull and weight of break points. When the rate of pull is reduced by about 66% the rate of break point increases about 33%. (A slower pull resulted in a higher breaking point) By addition of the two variances we could sum up to approximately 100%.

My suspicions regarding the North Dakota results were confirmed when I contacted Professor Paul Labossiere of the University of Washington Mechanical Engineering Department. Professor Labossiere is familiar with (and has access to) the Tinius Olsen Testing Machine. After discussing the result variances with him, I was told the North Dakota study was achieved using a methodically slow steady pull, at perhaps I inch per hour. This type of testing is used for stress factors in cables and other devices and should not be used for test related to snare release systems. The rate of travel on the pull is a critical factor relating to the release break points.

We contacted Dr. Wayne Reitz, in charge of the North Dakota Study. Dr. Reitz confirmed what Professor Labossiere stated and sent the following letter to the North Dakota Game and Fish Biologist Department.

Jacquie Ermer, Furbearer & Wildlife Disease Biologist
North Dakota Game & Fish Dept., 406 Dakota Ave, Riverdale, ND 58565
Subject : Replicating Snare Test Environment
Dear Jacquie,
I talked with Mr. Sinrud in Washington state regarding the testing performed in Fargo versus the testing performed by his company. Mr. Sinrud has very valid point in that an animal will jerk the snare as opposed to a slow pull that was conducted here. His data suggests that a more representative test should be developed. I am inclined to agree with him at this time. Currently, if a snare passed in Fargo using a slow pull, then it would certainly pass when tested with a rapid pull. Conversely, as is the case with Mr. Sinrud's snares, failure in Fargo could be a false failure. You and I recognized from the beginning of our testing that a slow pull was less than optimal. However, cost was a major factor and using existing equipment alleviated the concern of designing, fabricating, testing, and then implementing new test equipment.
I suggest that the North Dakota Game & Fish Department be involved in developing a test that more accurately reflects the environment (rate of pull) that a large animal can exert on a snare. I would be glad to be involved; perhaps through a project involving Mechanical Engineering students (involving students minimizes costs). Ideally, the test would be standardized across many of the interested states. I would appreciate your thoughts and comments on this subject.
Sincerely,
Wayne Reitz, PhD, PE
Adjunct Prof., NDSU, Mech. Eng.
701 235 0859
701 235 6122 (f)
reitzconsulting@cableone.net
cc: Randy Kreil ­ Wildlife Div. Chief

Test Conclusion
The rate of pull speed has a significant relationship to the breaking point of the release systems. Although the rate of pull speed on the preliminary test using the forklift and the "double pull test B" were the same (1/4 mph) there was a significant difference between results. This indicates the methodology of testing is also important, Standardized and uniform testing equipment must be developed.

The current testing being done regarding release snare systems is totally inadequate and lacking in practical application. Where most states do have release snare regulations, they do not have testing available. There is no practical means of validating release systems and, therefore, no valid means of identification or enforcement.
Summary

If release systems are to be continued as a viable means of conservation, there must be an appropriate and consistent methodology implemented for their validation, Uniformity in all states is a necessary process in this issue.

Manufacturers need to be included in the standardized testing criteria. The state regulations should regulate functional requirements. The manufacturer's responsibility is to produce the equipment which meets those requirements.

Raymond Thompson spent many years creating and cultivating the birth of the modern snare. This is a heritage of Thompson Snares and we hope to continue the improvement, longevity, and prosperity of the trapping industry and conservation issues related through continued growth of this heritage,
These studies are only a beginning process in our continued effort to create appropriate and meaningful information.

David Hastings, editor - Fur Taker