[...]... in Inches Max Working Load, in Pounds Average Tensile Strength, in Pounds 25 1 /4 1/8 0.31 140 1,050 35 3/8 3/16 0 .47 48 0 2 ,40 0 40 1/2 5/16 0.65 810 4, 300 50 5/8 3/8 0.79 1 ,40 0 7,200 60 3 /4 1/2 0.98 1,950 10,000 80 1 5/8 1.28 3,300 17,700 TABLE 6-1 Standard Chain Size and Load Specifications I 115 116 Build Your Own Combat Robot chain-link spacing and subsequent uneven loading on one of the two chains,... battery that could result in fire, smoke, and a dead robot FIGURE 7-5 Schematic of a one-direction relay control system with braking 133 1 34 Build Your Own Combat Robot Driving with an H-Bridge Relay control gives you only two speeds—full speed or stopped Some weapon systems require that you reverse the direction of the motor, and the motors of your robot s drive train will also need to be reversible... speed reducers using the 56C NEMA standard face size 123 1 24 Build Your Own Combat Robot Planetary and Harmonic speed reducers are the most expensive forms of a gearbox For low- to medium-power robots, one of the most cost-effective methods of obtaining a planetary gearhead is to pull one out of a cordless drill But when doing this, you will have to build a special mount for the gearmotor because these... batteries from the rest of the robot For safety purposes, a disconnect switch should be placed in all combat robots You do not want the robot to be accidentally turned on by you or another person while you’re working on the robot; and sometimes a short can occur during maintenance, which will cause a motor to turn Many robot contests, such as BattleBots, Robot Wars, and Robotica, require that a manual...112 Build Your Own Combat Robot Location of the Locomotion Components Most combat robots are fairly simple, internally They consist of a power source, a set of batteries; motors for the wheels; a radio-controlled (R/C) system receiver; controllers to take an R/C signal from the receiver and send power to the motors; and a weapon system’s actuators, if they’re required in your design Other... long length of chain and wrap it around both sprockets, holding the two ends in your hand Then you cut the chain at the appropriate place, apply the master link, and possibly use an idler sprocket to take up the slack Figure 6-8 shows a sprocket FIGURE 6-8 A typical 12-tooth ANSI #40 sprocket 117 118 Build Your Own Combat Robot B elt Drive Systems In addition to chain drive systems, a belt drive system... amount of voltage that goes to the motors and the direction in which the motors turn in your robot Without an ESC, you cannot control your robot The ESC is probably the most critical component in the entire robot, so you must select it carefully An improperly selected controller will usually result in a short life for your robot and can damage the motors or the batteries If the ESC fails during a competition,... speed reduction The common methods consists of spurs gears, planetary gears, helical gears, worm gears (shown in Figure 6-10), or some combination of these gears FIGURE 6-10 A worm gearbox attached to an electric motor Note the screwtype gear in the center of the gearbox 121 122 Build Your Own Combat Robot Mounting Gear Assemblies Now that we’ve covered gear assemblies and methods of gear reduction, we... together Motors for combat duty can draw from a few amps (for weak motors) to several hundred amps for major weapon or drive motors in the larger weight classes Relays for your robot should have high-current capacity, and they should be compact, durable, and easily available Many relays used in robotic combat are the automotive surplus type, which typically have 12-volt DC or 24- volt DC coils and contacts... physically One of the cheapest and easiest ways to mechanically actuate a switch is to simply use a standard hobby radio-controlled (R/C) servo to throw a switch 135 136 Build Your Own Combat Robot FIGURE 7-7 Standard Futaba FP-S 148 R/C servo Radio-Controlled Servos The R/C servo discussed here is the same type of servo that is commonly found in R/C model airplanes Figure 7-7 shows a photograph of . 0 .47 48 0 2 ,40 0 40 1/2 5/16 0.65 810 4, 300 50 5/8 3/8 0.79 1 ,40 0 7,200 60 3 /4 1/2 0.98 1,950 10,000 80 1 5/8 1.28 3,300 17,700 TABLE 6-1 Standard Chain Size and Load Specifications ■ 116 Build Your. use a coefficient of friction greater than 1. 6. 14 6.12 6.13 112 Build Your Own Combat Robot Location of the Locomotion Components Most combat robots are fairly simple, internally. They consist. used for. For high-powered robots, careful design of the components and mounting lo - cations will be needed to minimize shaft misalignment. 1 14 Build Your Own Combat Robot FIGURE 6-5 Direct-drive