Living in the Machine Shop

It seems like the perfect time to write a quick update. We’re entering the third week of the term and things are well on their way. We’ve spent the past few weeks chugging along in the machine shop and the robot is finally coming together. Eric took a photograph of a single half of the chassis attached to the welding fixture. With the welding fixtures done, our hope is to complete the welding at some point this week with the assistance of Inky down in Facility Operations and Management.

We’ve also made progress on the logistics front and have located at least one company that is willing to anodize the pieces of our robot. The plan is to anodize the aluminum chassis with a black hard-coat impregnated with Teflon, which will provide the chassis with additional strength and make it look downright sweet. In the words of the technical engineer at the metal treatment company, if the entire robot were to disintegrate, the Teflon shell would still be standing.

On the electronics front, we’ve also had major progress. Kevin got the computer up and running yesterday and was able to take input from a button and turn on an LED when the button was pressed. We also finally have the correct cables for the GPS radio and are currently working on the communication between the computer and the GPS radio.

After a brief scare with the motors and the motor controllers, we now have the motors up and running with the UltraLife batteries. The gearboxes were also finished by Neugart and are currently in the mail on their way to Dartmouth. Once we have the gearboxes, we can finish the keyhole cuts in the hub components and begin fitting everything together for the final assembly of the robot.

It's coming together

We began fabricating the chassis with prodigious speed last week. The beginning of this week we'll be working on setting up the weld fixturing, and we'll hopefully be ready to weld the chassis by early next week. After an afternoon of scavenger hunting across campus, following rumors, tips, and people's vague recollections, we tracked down a guy named Inky, who we've heard is the best welder around. We had a brief chat with him in the FO&M shop, and it sounds like he knows a lot more than we do about heliarc welding so we're hoping he'll help us out.

One of the most significant lessons we've learned is the degree to which Murphy's law holds true. I won't bore you with the details, but dealing with a project this size make me appreciate how absurdly difficult it must have been to land a man on the moon.

Leonard Parker, our relentlessly heckling machine shop guru, has taken a serious interest in our project and has helped us out immensely. He's become interested in seeing the project succeed and has saved us with freakishly timely assistance, saving us from ourselves and supplementing experience for improvisation. Without him on board it's hard to see how we'd be able to finish on time with a well-constructed robot.

Leonard


We began fabrication last week by milling the gusset plates that are welded to the square tubing on both sides of the chassis. All of the main chassis components have welds somewhere on them, so we decided to use marine grade 5086 aluminum. This alloy combines decent yield strength with weldability and machineability. We were concerned about using 6061 since our robot will be deployed in temperatures cold enough to make the aluminum more brittle. The 6061 also loses much of its strength after welding, so we paid a little more and made the upgrade.

We spent many hours in the shop this past week just machining piece blanks from larger stock material. The motor housings were designed with 1/8" walls but we could only find 1/4", which means that each piece has to be laboriously turned down for three and a half hours on the lathe. It's a good thing we have a couple team members to tap each other out. We've found that there is a limited number of 25-minute lathe cuts one can perform before you want to clamp the chuck down on your head.

Our square-bar stock was .3 inches too short (from a 5-foot piece) so we were forced to order another segment. When that arrives tomorrow, we'll begin machining our chassis tubes and will be closer to getting everything welded.

We'll update on the electrical and control side of stuff tomorrow or tuesday.

Fabrication and Testing Schedule

We've updated the schedule for getting stuff done. You can see our timeline broken down by the Electrical and Mechanical portions of the project.


Electrical Components


Mechanical Components

We're Back

The team got back from break and started classes this past week. We've sat down and broken out everyone's individual responsibilities and we're rapidly coming to appreciate how much fun we have ahead of us.

All of the main components have arrived, so we began the process of figuring out how everything works. Mike started playing with the GPS and the Radio Modem to see what kind of signals we'll need to pass between these parts and our processor. Kevin has started playing around with the processor board and was disappointed to learn that in required a little more assembly than we initially thought.

I'm working on getting our motors from EAD to work with our motor controllers, and once this is done we'll be testing the motor controllers with signals from the processor.

Gus is currently designing a power housekeeping board that will take the 48 V from our batteries and step in down to 12V, 5V, and 3V as required by our various sensors and other electronics. After we design the schematic, we're planning to lay out the circuit and send out for a custom printed circuit board.

Scott and I are working to finalize the design of the chassis components and get the drawings sent off to Pete in the Thayer school machine shop, who will be helping us with the CNC machining.

Drew is working on contacting companies to get out chassis anodized. We've found that most companies don't have the capability to anodize parts this big, so we are continuing to look for alternatives. Drew is also looking for competent Aluminum welders so we can set up our fixturing and assemble the chassis.

We'll be updating this at least twice a week so check back regularly for updates.