Senior Design Update

So I thought I would give a quick update about my Senior Design project. For those of you who don't know, I am involved in a year long project that incorporates most of what I have learned in my mechanical engineering program. My project involves the design, fabrication, and testing of a machine that measures the thrust generated by an aircraft valve.

We are at the end of our fabrication process. I must say it really is rewarding to see something you have spent hours on designing and creating computer models. Seeing it physically there is cooler than I imagined. Well... I guess that depends on your definition of cool.

One part that was kind of interesting to make was a bearing assembly which allows a lever on our design to freely pivot and swing. Below is a computer model I made of this during the design process with the arch on the far left.


We have very tight tolerances on many of our parts so it was a challenge to implement this design. We purchased the swivel bearing, needle bearing, and carbide pin. We made the bushing ourselves and it was a careful process of machining and measuring, making sure both sides were just right to fit the other stuff in. It is a little stressful because if you take to much off while machining you have to start over!

A really good example of this challenge was fitting the entire assembly you see above into our arch which is on the far left. It was designed to fit with a "light press fit". What this means is that it doesn't really fit but you will force it in. To accomplish this you must have extremely tight tolerances. The circular hole in the blue arch on the far left must be 0.0005" smaller than the entire bearing assembly you are putting into it. To get a reference for how small we are talking about the average thickness of a human hair is about 0.003". So we are talking about 1/6th of a human hair!

Once you have carefully machined this you then put the arch into a machine (press) which puts so much force on the bearing assembly that it forces it into the smaller hole in the arch. Below you see Alex and I using this press.


And below you see the finished product with the whole bearing assembly fit into each other and then press fit into the arch.


It went well! And I am glad that is over. The rest of the machining went well also. We are almost finished and ready for testing. Below you can see the computer model I created of our design. Then a comparison of this model with our built design. Last is a picture of our built design by itself.

We have a few small issues to troubleshoot before we begin testing of the actual valve in about 2 weeks. But things are looking good and we are encouraged by the results so far.