Hardware

Introduce hardware blah blah blah

Chasis Construction

Before beginning to build a chassis, you need to understand that this must be the sturdiest part of your lego bot. Because you will only build from here, an unstable chassis makes an even more unstable robot, only adding to natural drift problems and other unavoidable problems with motors and programming. The fist step to avoiding this is when securing Motors, make sure they are snug. If they aren't securely surrounded by legos and pins, they will wiggle in turn causing the wheels themselves to be unreliable and unpredictable. On the opposing side however, if legos are too tight, they may snap apart at anytime including while running the bot. It is a tricky balance, but the idea is to secure the motors, not strangle them.

Secondly, for beginning teams, it is advisable to stick with mounting motors right next to each other. If you are bold enough to venture into mounting wheel motors separated, you mush make sure that each motor is level (use an actual level to make sure they are even) and both are extremely secure. A good rule of thumb to follow is that there should be a lego on each side of the motor to secure it.

Creativity

Besides making sure that the motors are secure, the rest is a free rein for creativity! For beginning teams, follow the KISS motto (Keep It Simple, Stupid); follow the chassis built from the demobot diagrams or use the chassis model attached. For more advanced teams, still keep in mind the KISS motto, but try out a new way of mounting. Try mounting the motors vertically instead of mounting them horizontally, or mount them separated from each other. You must keep in mind though, that there are only a finite amount of pieces available in each years botball kit, so if you use too many legos in while building the chassis, you won't have enough parts to continue building claws and other such attachments.

You also have to keep in mind what the bot is being used for. For example, if you are going to attach a giant claw to it, you may need to leave space (or put an extra lego) so that a counter weight can be attached to the back or add a skid somewhere near the front (or the side where the claw will be attached) so that it doesn't topple over. If you are building a "garage door" attachment (something that just plows over tribbles in order to collect them and then deposit them) or any other attachment that will be on the floor, you need to be mindful of building out far enough so that you can properly attach the chassis and the actual attachment. Whatever the function of the bot is, should ultimately control what the chassis includes.

Testing

Testing your bots is probably the scariest part as a builder. For builders, there are two main ways to test your chassis (or entire bot in general) and neither is less nerve racking: the drop test and the stair test. The Drop test consists of dropping your chassis or bot (for the Bot make sure you take off both the CBC and any claws or attachments so it is the main structure) from about 3 to 3½ feet in the air drop it on the ground. If the chassis or bot stays relatively intact (you may need to re-attach a bushing or liftarm thin or two), you have a sturdy reliable bot that shouldn't cause any structural problems in the future. The second methods, the stair test, is this more or less same test, but instead of dropping it make sure it can safely travel down 4-5 stairs with minimal damage. Again, you may need to retighten where legos are attached with pins, push down any loose bushings, etc.

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Foam Ball Grabbing Claw

When designing a claw to pick up the large foam balls, two key points need to be considered; stability, and weight. The claw does not need to be complex to complete its task, but the more advanced teams can get creative and have very unique designs. The claw needs to be reliable and consistent because the possible 30 or even 90 points for a water ball needs to be scored every time for the team to do well.

Planning

The claw has to be designed to each teams specifications. Some teams will have minimal room to work with, so the claw will have to be smaller; but, other teams may have the claw as the main aspect as their robot and will have plenty of room to work with. Another thing to consider is making the claw slightly oversized to help ensure the ball is in the claw every time. The mechanic also has to consider the ability of his or her programmers and whether or not they will be able to find the ball accurately enough for the claw. A bigger claw can help compensate if the programmer can not be that precise.

Design

There are two main aspects to the claw, the lift and the grab. The simplest method to raise and lower the claw is by just screwing a lift arm to the servo arm and having the serve rotate the arm. The more complex teams could utilize a geared lifting, or even a parallelogram design. The other aspect is in the grab itself. There are two main options for this, the more complex parallelogram system, or the simpler pincer type. Both have advantages, the parallelogram can fold in and be fit into very small spaces, but it can be very challenging to build for new teams. The pincer is good because it is very simple to build and it is easy to repair if it breaks during a run. The key to the design is to make sure it will work before it is built. It is a hassle to build the whole claw to discover it won't lift, or it is too small. These all have to be tested before the final build.

Testing

The claw needs to be rigorously tested before put into use in the game. It needs to be tested grabbing the ball in many different places in the claw. It also has to grab it at different heights and lift the ball to different heights. Another option not highly considered is closing at a different speeds. Sometimes closing the claw slower (utilizing the technique in the programming article on servos), can help to secure the ball in the claw. The tests of the claw need to be successful and can pick up the ball every time before it is put into action on the robot itself.

Solidworks

Here is an eDrawings of a basic water claw.

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Gears and Chains

Whenever, you make a robot mechanism, you almost always need a power source. Whether it is motors, servos, rubber bands, or controlled gravity. In many instances, the simple output of the power source must be 'modified" or "moved" in order to accomplish a task (claw, bin, arm, self destruct switch). In this article, I will be discussing how you can do this is through gears and chains.

(The first few paragraphs cover the basics, later paragraphs may cover more advanced topics, like differential drives, alternating gear shifts.)

Gears

Gears are simply discs with teeth, almost attached to an axle to produce rotation. Gears vary by the number of teeth and their diameter (size). This difference of size is usually referred to as a "ratio". Using gears of various ratios, you can do many useful things.

"Ratio Gear Chains"

By using ratios, you can do two things, you can increase either the speed or the "strength" of the motor, also known as "gearing up" and "gearing down" respectively. In these examples, you will be referring to two gears, the "power gear" and the "wheel gear". The power gear is attached to a motor, while the wheel gear is attached to... a wheel.

"Gearing Up"
- Increase speed
- Decrease strength (torque)

By using a big power gear and a small wheel gear, you can increase the speed of the wheel. When the large gear makes one rotation, the small gear makes multiple. The wheel gear spins faster then the power gear, making your robot move faster (ignoring acceleration, weight, center of gravity, etc). However, the force of the motor is "spread out" on the large gear, making the strength lower.

pic of gearing up

"Gearing Down"
- Increase strength (torque)
- Decrease speed

By using a small power gear and a big wheel gear, you can increase the strength of the wheel. When the small gear makes one rotation, the large gear makes a partial rotation. The wheel gear moves slower than the power gear, making the robot move slower. However, the force of the motor is "more concentrated" on the small gear, making the strength higher.

pic of gearing down