Final Testing
Controlled testing to ensure the system works as intended.
| Weight (lbs) | Speed (ft/s) | Free Fall Speed (ft/s) |
|---|---|---|
| 0.35 (combination lock) | 7 ft / infinity = 0 | 21.223 |
| 1.10 (combination lock, stapler) | 7 ft / 120 s = 0.0583 | 21.223 |
| 1.20 (water bottle) | 7 ft / 120 = 0.0583 | 21.223 |
| 1.95 (stapler, water bottle) | 7 ft / 90 s = 0.0778 | 21.223 |
| 2.94 (lock, stapler, water bottle, umbrella) | 7 ft / 120 s = 0.0583 | 21.223 |
The lightest object we decided to test with was a lock.
We noticed that the system did not go down with the weight. However, the subsequent tests using heavier objects did allow the system to go down, and therefore we concluded that the system has a minimum weight that it must hold in order to work.
The speed is therefore 0 ft/s.
This aligns well with our initial unscaled design plan that the system was not meant to be used for people lighter than 50 lbs.
In order to increase the weight, we added a stapler. The whole system did move down, although much slower than expected.
The speed is approximated to be 0.0583 ft/s.
We then used a filled water bottle to test. With a similar weight to the lock and stapler, the water bottle and system fell slowly as expected.
The speed is approximated to be 0.0583 ft/s.
In order to increase the weight, we added a stapler with the water bottle. Again, the whole system came down slowly, which suggests that this sytem is weight-independent as we intended it to be.
The speed is approximated to be 0.0778 ft/s.
Our heaviest weight was composed of a combination lock, stapler, water bottle, and umbrella. Although the weight is approximately one pound heavier than the last test, the speed calculated was the same. Therefore, this confirms that this system is weight-independent.
The speed is approximated to be 0.0583 ft/s.
However, the speeds that have been seen in all of our tests are much slower than our initial design of
3 ft/s, which could be due to the scaled design and lack of modified friction calculation for this revised
system. Therefore, we propose a few modifications:
1) use a different brake pad with a lower coefficient of friction
2) use a lubricant
3) use a different rope
We did design the unscaled initial system so that it will not fall down without an initial force, which we planned to add using a lubricant in the previous semester. Therefore, this system is actually working as it should, and any movement that occurs in the tests could be considered a byproduct of impact force from the weights being dropped initially.