Test Results

Results from Initial Testing

To determine the reliability of the Grain Bin Rescue System, and to determine the weakest parts, a testing procedure was developed as follows:

1. Suspend the rescue system a minimum of 6 feet off the ground.

2. Attach a weight (> 30 pounds) to the rope and drop from the bottom of the rescue system.

3. Record if the pawls caught. If so, how many and which ones caught? How far did the weight travel before being caught?

4. Repeat this test 50 times.

From this testing procedure, data was obtained and recorded. A summary of this data can be seen in table 2, below. Fifty tests were completed by dropping a 50 pound mass from distances of 4 to 13 feet (one-foot increments) below the rescue system. The testing at each height was repeated 5 times. During these 50 tests, 11 jumps were recorded, and the average fall before engagement was 8.45 inches. Jumping refers to the pawls engaging, and then disengaging due to an elastic collision occurring when the teeth and pawls collide. This typically occurred when the distance was changed to a point not yet tested. The new, un-stretched rope acted as a spring, causing the mechanism to engage, jump, and then re-engage. Once the rope had stretched, and if adequate weight was applied, the collision between the pawls and teeth became inelastic. With jumping, the maximum distance the mass fell before being caught was 14 inches.

Fifteen tests were completed at three different heights (5, 10, and 15 feet) with a 100-pound mass. During these tests, no jumping occurred, and the average fall was 8.4 inches. Five tests were completed with a human subject weighing 175 pounds at 8 feet from the bottom of the rescue system. During these tests, no jumps were recorded, and the average fall was 9.3 inches*.

For all tests conducted, the rescue system never failed to engage. All pawls were engaging consistently, however, only one pawl typically engaged at a time. There were a few exceptions when two pawls engaged simultaneously. Typically, the pawls located at the bottom left or right of the mechanism at the time of engagement were the ones that engaged. When jumping occurred, the secondary engagement typically occurred at the pawl located in the top left of the mechanism.

Below is the finished product that has been improved through testing, and caught two of our group members:

Below is the raw file of testing data.