What is mechanics? If you've ever been around a physics teacher or engineer, they are always talking about mechanics, and its seems that no one really understands what mechanics really is. Quite simply, mechanics is the knowledge of design and construction of machinery. In robotics, this translates into the physical construction of the robot. Since every game is different (thus requiring different mechanical solutions), this section will be an introduction of the different options for robot construction available to the Robotics Team through the kit of parts from F.I.R.S.T. as well as the basics of mechanical design/planning. Before we begin, it is time for the one rule:
There is only one real rule which should be followed regardless of the situation: Whatever I say is okay and whatever you say is okay. Repeat it with me: "Whatever I say is okay and whatever you say is okay."
The important thing to remember is that we are all on a team. There is not one person on this team whose ideas are more valid than another's. Every single person has the right to express their ideas and every person should respect that right. I think everyone will agree with that, so I'll stop preaching.
Where do we start?
Traditionally, robot construction proceeds as follows:
• 1. Develop and Decide on Strategy
Since every year the game changes, the primary task after the kickoff in January is planning the actual strategy for the team. This generally involves brainstorming in little groups and then presenting each strategy to the collective group. Then, pros and cons will be weighed for each strategy and then a strategy will be selected. From this strategy can be developed necessary task for our robot to execute, which leads to an actual working design of the robot.
Before we move on, everyone should understand that no one is always correct. The very nature of any engineering project (including this one) makes it impossible for a single person to design the best project. That is why it is necessary to have a lot of people brainstorming together on the same project. More people also make troubleshooting a lot easier, so it is important to not only question your own ideas, but also those of others.
Actually, please, please, please ask questions. In fact always question. There is no design which is perfect and no idea which is flawless. Continually question, dissect, take apart, stare at every single part of the robot. It is useless if we discover a flaw during the competition (i.e. faulty welds). Everyone can screw up- even engineers- and it is important to realize this and to (almost) never accept anything on faith.
• 2. Design Robot
Once the tasks have been finalized, design of the physical robot can begin. At this stage, it is only necessary to decide on a frame/chassis design and major features of the robot. It will be the job of each team to come up with the actual design of the components.
If you're like most people, you are probably stuck trying to come up with a design. I wish there could be a set of directions I could give you to solve all of your creativity blocks, but that is obviously impossible. I've included a couple pointers to help you get over those mental hiatuses common to all involved in any creative problem.
Where do ideas for designs come from? These are the most creative steps of the whole process, and inspiration can come from anything. Let me repeat that: inspiration can come from ANYTHING. If you are ever stuck on a design problem, go look at something around you. We are surrounded by mechanical marvels (and even are one ourselves), and all are potential sources for a design. For example: notice how the arm on The Doctor mechanically resembles a human arm? Coincidence? Probably not.
Another technique that seems to work well is just letting your mind wander. One day after school, Mr. Van was talking about something or another and I found myself blanking out, singing "Casey Jones" by the Grateful Dead in my head. So I started thinking about trains...and the way old trains were driven by those linking arms on the wheels...I realized how powerful and compact that system was...the grabbers needed to be powerful and compact...WHAMMO! we had our grabber design. And teachers always say pay attention during class.
These are just ideas, do not feel limited to these techniques. Say, you find eating cheese is particularly inspiring to you, by all means, do that. You probably shouldn't tell too many people about that, though.
• 3. Component Design
After the chassis has been designed, and the major components roughed in, it is time to break into teams, with one group per major component. The teams serve to concentrate the efforts of the collective team, focusing each group on every detail of their respective component. The groups will become self-evident after an overall design is decided on, and you will choose in which group you want to participate. After the groups are formed, each is responsible for creating a final design of their component, with every detail planned (including parts, motors, electronics, abilities, limitations, etc.). Then comes the fun part.
• 4. Construction
This is the good part, the heart of the project. Every group is now responsible for the construction of their component. Depending of the design, this will require hours in the machine shop, more hours in Mr. Van's room trying to get everything together, and countless more troubleshooting the stupid thing (all in good fun, of course). Once all of the parts are assembled, it is time to bring everything together.
• 5. Final Assembly
This is when all of the individual components come together and the robot is actually completed. If everything goes smoothly the components will all fit together perfectly, everything will work as planned, and the robot will be complete. Of course, that's probably not going to happen, so this is the time to complete the troubleshooting of the components, as well as the interaction of the separate components. Hopefully there will be no major design flaws and the robot will be complete. That's it!
NOTE: Since this is the mechanics section, I didn't mention the electronics or programming. That happened somewhere between step 3 and step 5, I think. The other two sections will deal with that stuff.
So your team has designed the perfect, elegant component. But you forgot one thing, the infamous kit of parts. F.I.R.S.T. provides every team with a kit of parts, which includes the robot controller, the pneumatics, the motors, and some other cool stuff. The problem is, we are limited to use only parts from the kit, the Small Parts catalogue, or the additional parts list. In this section, we are going to look at some of the different design options available for the competition.
Motors are the driving force of the robot (haha- bad pun). There are numerous different motors which can be used in a large variety of situations. And what is a motor? A motor is any mechanism that produces or imparts motion. This can be through the conversion of heat energy, chemical energy, or electrical energy into mechanical energy, but we are limited to use electrical motors (that's right, we can't strap a two stroke lawnmower motor on the robot and let 'er rip). Below is a chart with the specifications of the different motors. You are not expected to understand torque or current draw, or anything else on the chart; it is merely included as a means for comparison of the different motors.
Motor No-load Speed (RPM) Stall Current (Amps) Stall Torque (N•m)
Van Door 75 40 34-37
Fisher-Price 15,000 57 0.36
Globe 87-97 18.5 16.9
Seat 95-615 5-17 0.1-1.3
Drill 20,000 16.9-114 85.6-651
Window Lift 22-64 3-15 1.8-6
Torque 0.17 35 4