Test Stand Rollout
This is the third part in a series about UB SEDS rolling out our test stand to support our in-house propellant program. In this part we test the test stand’s structure.
- Part 1 – Smoke Test
- Part 2 – Backboard Test
- Part 3 – Structural Test
- Part 4 – Electronics Test
- Part 5 – Final Check Out
If you just want to skip to the end and see the test stand page, you can find that here.
If you want to find out more about our propellant mixing, you can find that here.
Design and Construction of the Test Stand
Test Stand cross section (Not to scale)
The design of the test stand consists of three support legs welded to a central tube. At the base of each support leg there is a small tab allowing for the placement of a spike to secure the test stand to the ground. Each leg is also braced to the other two legs.
The central tube’s inner diameter is slightly larger than 58mm to allow us to place 58mm motors inside it for testing. This central tube acts both to guide proper placement of the motor but also as a safety measure. Radially, it is a quarter-inch thick, and designed so that a failure would cause it to shred instead of fragment.
A second sleeve of the same material was made with an outer diameter of 58mm and an inner diameter of 38mm. This sleeve could be inserted into the main guider tube to adapt it for use with 38mm motors. This increased the combined thickness of the central tube to be about half an inch. This added thickness increases the safety of the test stand. At the bottom of the guider tube there is a wooden wedge that focuses the force from the motor onto a force sensor. The force sensor is held in place by a cup mounted on a cross brace. All permanent connections between metals were welds.
Test Plan
The plan was originally to test out both the structural, and electrical components of the test stand. Unfortunately, the weather was misting when we began the setup for the test. Because the electronics were not yet finalized, they were not weather proofed. We wrapped most of the electronics, aside from the force sensor and laptop, inside a plastic shopping bag. This protected it from most of the moisture. Unfortunately, we did not have a bag large enough for the laptop and once the track pad got wet, it became impossible to use. We did not bring a mouse and decided to hold off testing the electronics until the weather got better.
This mist did not stop the test in its entirety, it just reduced the scope down to purely a structures test. We left the force sensor and electronics in place for the structures test, removing only the computer. The force sensor was placed in the cup under the wooden wedge. The test stand was staked into the ground using rebar stakes that were about 8 inches long.
Test Conclusion
This test was a complete success. The test stand kept the motor in proper position at all times. There was no wiggle in the components when we placed the motor into the inner sleeve. After the test there still was no wiggle between any of the components. No components appeared to have shifted position. All legs and cross braces appeared without any deformation. The test stand did not appear to move, and all the stakes were still snug in the ground. All electronics appeared to be in their original places and undamaged. Once we went back inside, we tested the force sensor and it performed as before.
This photo was taken on 2017-04-01 (yyyy-mm-dd)