This week Miles figured out that a single 6-32 bolt with 3 threads of engagement would not be sufficient for the battery terminals. each connection and disconnection would further wear out the weak aluminum threads.
We brainstormed many solutions including tapping a much larger hole (1/2″) and putting a set screw into it as the terminal. We realized that the threads would still be very weak and the terminal would be prone to rotate.
After playing around with janky ideas about connecting the cable using several bolts, miles came up with the idea to make a terminal block that could house a bolt to be a wear part for cyclic use.
I realized that with this design, the clamping force to connect the cable to the terminal would not be put through the weak aluminum threads, but through the large block of aluminum. This design ensures that we won’t have to worried about damaging threads with repeated connections and disconnections from the batter terminals
connecting the terminal with four 6-32 bolts quadrupled the amount of mechanical load the system could take before being damaged.
I started designed and started machining the terminals on Monday, finishing the first on Tuesday and the second on Wednesday. Miles drilled and tapped the holes in the battery, the holes in the terminal being clearance holes. When we went to connect the terminal to the battery we realized that none of the bolts we had would be the correct length. Using washers to fill the space would not leave enough room for the cable’s connector, so I had to shorten the terminal to allow the use of smaller bolts.
I shortened the terminal on the bench grinder as it was far faster to set up than the mill. Miles used the rotations to count the number of effective threads tapped into the battery. He found this number to be 2.5 – 3. So I ground down the terminal until that many threads were exposed.
This had some unforeseen consequences, with the grove no-longer being deep enough to hold the head of the primary bolt. to solve this, I ground down the head of the bolt.
I forgot to clean up after making the second terminal.
When I returned on Thursday there was a threatening note on my desk saying “if the mill is left like that again, you will lose access to it.” Jonas received a similar note about the lathe.
In my defense I had only left one fly-cutter, a mallet, and a calculator on the mill. The other tools I assume had been left there by Mr. L on Tuesday.
Still, in fear, Jonas and I spent nearly the entirety of Thursday deep cleaning the mill and lathe respectively.
I completely totaled 4 rags with grease, dust, and grime. I spent 2 hours meticulously cleaning every surface on the mill, including those on top which I needed a ladder to access. Large parts of the mill looked like they hadn’t been so much as dusted in the past 15 years, because they probably hadn’t.
In this process I discovered a Z-axis power feed.
