This will be the last installment on the boat project. Today was D-Day (well, actually tomorrow is the real D-Day but today it was due). So of course, as I noted in last night’s post, he was working on it until late last night. We left off yesterday’s blog with the new prop, with the blades pointed in the right direction, on the printer.
The new prop finished printing a little after 11PM. It was bigger than the first one (which had the boat going in reverse) but looked like it would work. Except for the axle. The center hole in the old axle fit like a glove on the motor shaft – snug enough to operate without any glue. This axle had a smaller hole that didn’t fit on the motor shaft.
First attempt was to drill it out a little with a drill bit that was about the same size as the hole. Thinking it might clean it out just enough, it was worth a try. But it wasn’t enough. The next drill bit didn’t seem that much bigger but the result was a hole bigger than the motor shaft. We were going to have to glue.
We knew glueing was final and part of Ben’s design included a piece to steady the axle. This piece was printing on the printer right after the new prop and axle. (Radius and Diameter killed me on setting up circles on the printer – the axle holder needed a 9mm diameter circle, but it was late, I was tired and I did a 9mm radius creating a holder that was way too big. Reprint) So while the axle holder was printing, we used a piece of the old axle, taped to the new, to do a bathtub test (at close to midnight). Although the tape job caused it to wiggle a lot, it worked otherwise!!
With things moving in the right direction (literally), we mounted the axle guide and glued the axle to the motor shaft. Ben also wanted to elevate the switch so he glued a block to the front and then the switch to the block. In the morning, everything should be ready to go.
I was up early to feed the dogs and decided to check on the boat. I first tried to turn the axle and it wouldn’t budge. The glue had set along the end of the axle against the housing of the motor. It was stuck. I took an Exacto knife and worked to cut away the glue. After a few minutes of work, it freed up enough to make it turn but was still stuck to the point the motor would barely turn. So I continued to cut and eventually got it freed up.
I then tried to turn on the switch. The glue Ben had put down must have been a little too thick and oozed into the switch itself. It wasn’t budging.
So I got a little wire and tried to bypass the switch. I was able to create a small spark so I knew I had juice from the battery but the motor didn’t move at all. Either the glue had made it into the motor or we burnt it out at some point or one of the capsizings from our early design had finally taken its toll.
Ben went into emergency mode. He worked with his project partner and secured another motor. We setup a new prop and axle to print and got that to him at school (Josh was getting his license this morning so he went to school late and was able to deliver the prop that finished printing after school started). Per Ben’s report tonight, he worked throughout classes today to get the prop mounted and everything in place for the presentation and real run in his last class of the day.
I am not sure of all the details but at some point he glued the motor to the motor holder and realized that wasn’t helping. So he had to cut and peel apart the motor mount to get it back out. In the end, it sounded like he and his teacher were able to get it to complete the distance, in the water filled trough, with manually wiring it to a new battery and holding the wires in place (since the switch was still shot). It completed the course, slowly, and per Ben was the first 3D printed boat to not sink or capsize during the event.
This was a great project. Ben learned a lot about engineering and project management (or sometimes the lack thereof). It required thinking, planning, reworking and paying attention to balance, measurements and many other technical skills that he will have a chance to tune in college. I hope he also learned that expecting everything to work perfectly rarely happens and not leaving yourself enough time to manage when things go wrong really reduces your options. And perhaps he even learned a little about time management, planning and commitment. Once can dream.