Subsystem Build & Test
Table of Contents
Team Vision for Subsystem Level Build & Test PhaseThe Goal for this phase was to complete the manufacture of subsystem level components prior to system integration.
Subsystem Build Summary
Mechanical Subsystem Build Summary
The breakdown of component manufacture was split approximately 50/50. 50% of the components were manufactured by Tom Skudlarek and the other 50% were completed by the staff of the Mechanical Engineering shop. The Components were predominantly made using the 3-Axis CNC Mills in the shop.
Machined Mechanical Components
Other than the surface finish on some of the components, the parts came out great. In order to save time in constructing and assembling the prototype, a finish pass was never run. A huge thanks goes out to the RIT Mechanical Engineering Machine Shop!
Composite Subsystem Build Summary
To build the toilet seat, the initial layers and foam core were cut to size using a laser cut template. The template was the exact size and dimensions of the desired seat. With all the shapes cut, the surface was prepped for layup.
- A coat of turtle wax was applied to the surface
- After allowing several minutes for the wax to harden and turn to a haze, it was removed with blue shop towels
- Steps 1 and 2 were repeated.
- The proper amounts of epoxy we mixed and painted onto the first layer of tooling fabric
- The wetted fabric was draped over the layup surface and allowed to set (stiffen slightly) prior to the additional layers.
- Following the original design of the seat, additional layers were added with the same process as in step 5.
- All layers were liberally coated with epoxy prior to layup
- The seat was then left to cure for over three days before any attempt was made to remove the seat from the polycarbonate
Test Results Summary
The original seat testing procedure as follows:Seat Testing Procedure:
- Place Toilet Seat on edge of table to simulate being cantilevered on toilet base sub assembly.
- Using C-Clamps and Carpenter's clamps, apply significant force to the seat to simulate being bolted to the toilet base sub assembly.
- Photograph seat pre-testing
- Apply a proof load of 50% the ultimate load of 500 [lb] to the seat.
- Remove load and inspect seat for signs of stress and yielding. Photograph and compare to pre-testing photograph data.
Component Test Set Up
Component TestingAs was stated in the original test plans, the seat was incrementally loaded. First, the seat was pushed on using Tom's hands to test the set ups "sturdiness". From here, one hundred pounds of mass were added to the seat which were provided by Cassandra Derr. This weight simulates 50% of the proof load of 200 pounds.
From here the seat was taken to its proof load of just over 200 pounds.
Post Testing the seat was inspected for damage or signs of stress. If the fibers had been stressed beyond its yield point, in theory, they would show signs of discoloration.
Risk and Problem TrackingLuckily, the aforementioned risks from the build and test prep page have been resolved. The turtle wax was applied in multiple coats to the polycarbonate, which, after the seat cured, allowed the seat to pop right off. The seat was also able to survive testing after very cautious load application.
The new risk to be added is that the bolt holes being hand drilled into the composite seat won't align with the machined holes in the base plate.
- Risk Mitigation: Create a drill jig to help alleviate the problem.