18-09-2012, 04:48 PM
Combat robots
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Combat robots come in many sizes from 75grams to 340lbs each one of them has their pros and cons. The first thing to do when thinking about building is to find the competition which you want to compete and see what weight classes are going to be there, because what is the point of building a bot you can never fight.
Large robots: 60lbs +
There is nothing like the thrill of seeing two large machines hitting each other with the force of a small car wreck. When most people think of combat robots it is these larger machines which first cross your mind. If you are fortunate to live near one of the large robotic events these machines can be fun builds, but at the same time the level of engineering required can be quite difficult. These large machines can also cost quite a bit of money. When you commit to building a machine this size you are committing at least $1000, and in many cases much more. I would estimate that your average heavy weight (220lbs) would cost a builder $4000-$5000 to build a competitive machine, and it is not uncommon to see builders spend upwards of $15,000+ on their machines over the course of a few years. In the days when combat robotics was televised there were many sponsorship opportunities which would subsidize the cost, unfortunately now as a builder you will be on your own.
Small Robot:
Building a small robot can be alot of fun but also a good challenge, with a restricted weight limit it makes every part on the machine to be critically thought about and designed. Most people are drawn to these smaller machines because of the frequency of competitions for them as well as the ability to transport them easily. While it is the common misconception that small robots are cheap they can be just as expensive as their larger counterparts. Alot of times the small electronics required for these can cost quite a bit as compared to larger components.
Choosing Components
Every bot is made up of a combination of both manufactured and purchased components. Choosing the right components is crucial for a successful robot. In this step I will step through some of the major components for small to medium robots and how you choose which is right for your bot.
Motors: The driving force behind any size robot you build. They make your robot move and in many cases power your weapons. The motors used in combat robots are DC or Direct current motors, designed for anywhere between 3 and 72 volts. Just like every other component you need to make decisions to choose the right one. The four traits to consider in on each motor is torque/speed, voltage, size, and weight. Motor torque is typically rated in oz-in or in-lbs at the "stall" area. Since dc motors produce their maximum torque with minimal RPM stall torque is only a reference point. I only use the torque as a baseline for comparison for different motors and try to get the most torque I can within my other constraints. Size and weight go hand and hand since the larger form factor your robot is the more it will weigh. When defining the size of your bot try to make it as small as possible without sacrificing functionality. Voltage is one of those things that is my last priority, most motors are 12 volts but for those that aren't you just need to make sure that your electronics all match the voltage of your motors.
Computer Aided Design (CAD)
CAD is the system used by all professionals for the creation of the products you see and use everyday. It allows you to make 3D computer renderings, seeing how things fit together on the computer before you build. This step can revel potential problems on your bot which will reduce your time and cost overall.
It is a common thought that CAD systems are difficult to use and build if you are not an engineer or have been trained to use them through some class. Recent CAD software has been shifted from even five years ago so that they are easier to build models with a user interface that anyone can pick up and learn within a few hours.
Within industry the three most popular pieces of software are Autodesk Inventor, Solidworks, and Pro-e. Each one of these has advantages and disadvantages to their own right but all are comparable for this type of design. I will not be going into how to use CAD in this instructable but there are many resources online for using this type of software.