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Issue #200 March 2007
Inertial Rolling Robot
by Jeff Bingham & Lee Magnusson
Start | Electronics | Drive Motor | Servo Motor | Pressure Sensor | Software | DC Drive Motor Control | Servo Motor Control | Mechanical Components | Manufacturing | Assembly | Findings | Sources & PDF
ASSEMBLY
Once the mechanical parts are manufactured and the circuit has been built,
you can assemble the components and finish the robot. Assembly is relatively
straightforward. After examining the exploded view, drawing it should
be an easy task to determine how the pieces fit together (see Figure
7).
The only difficult part of the assembly process involves inserting the mechanical parts in the rubber ball, because some assembly must take place inside the ball. We recommend fully testing the electromechanical assembly before attempting to place it inside the ball.
It is easiest to start by assembling three sides of the pendulum subassembly (M1, M18, and M26). The flanged bearings (M17) can be loosely fitted into the front and back plates, while the back plate spacer (M2) and servo motor can be tightly secured to the back plate. The servo arm is near the bottom of the pendulum. One end of the servo pushrod can be attached to the servo arm at this time and the other end can be attached to the servo pushrod-bracket (M25).
The motor subassembly can be put together by attaching the motor to the motor plate (M22) and the motor plate to the sliding plate (M27). Next, a flanged bearing is loosely installed. Then the bore reducer (M8) is inserted on the motor shaft, a washer is placed on it, and the power sheave (M23) is pressed and tightened onto the bore reducer and motor shaft. After checking that the motor is free to rotate, the flanged bearing can be tightened down. The motor subassembly is attached to the pendulum subassembly by loosely connecting the slide plate (M27) to the pendulum front plate (M18).
The next step is to attach two bearing blocks and the electrical housing (M16) to the universal joint plate (M29). As an additional step, you might want to preassemble the miter gears (M20), drive shaft (M15), and gear shaft (M19) to check the tolerance of the gears and set the alignment of the bearing blocks. Once clearances are checked, the assembly can be returned.
The pendulum subassembly can be finished by attaching the remaining side plate (M26). In addition, one of the bearing blocks can be attached to the back plate (M1) by using the support shaft (M28) with two washers and two collars. Another bearing block can be attached to the front plate (M18) with one miter gear (M20), two washers, the driven sheave (M14), and the gear shaft (M19). Attach the battery boxes with Velcro. The belt (M7) can be placed on the pulleys and tensioned. Then the slide plate (M27) can be tightened down.
Any electrical connections can be made and the pendulum subassembly can be inserted into the ball by slightly stretching the opening. Then the universal joint assembly can be inserted and the drive shaft with the miter gear can be attached. At that point, the universal joint plate can be connected to the bearing blocks on the pendulum along with the servo pushrod bracket.
The final step is to insert the rubber gaskets and the flanged ends of the drain bowls into the ball and bolt the driveshaft to the sink drains with lock nuts. Next, tighten the sink drain lock rings firmly to the ball and apply Teflon tape to the sink-drainpipe connections. Finally, flip on the power switch with a screwdriver, tighten both end caps, inflate the ball, and stand back! (Drawings of each step are posted on the Circuit Cellar FTP site.)
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