A simple project that throws a ball.
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This Ball Thrower Bot was highly inspired by Baseball pitching machines and Cricket ball Bowling machines. It uses a flywheel assembly to throw the ball out of the contraption.
The Ball Thrower Bot test videos can be viewed here. Overall, I have a very satisfied puppy. She loved the build, though she still needs to learn how to use it properly. Since that is a lengthy process and is not very relevant, I will not be including that here.
Ruler, Drill, Drill Bits, Hacksaw, Glue Gun, Wire Strippers, Soldering Iron
Pencil, Utility Knife, Multitool
Glue, Insulated Wire, Toggle Switch, Barrel Adapter, Cello Tape, Masking Tape, Glue Sticks
2 inch Wood screw, Machine Screws, 10mm Wood screws, RS 775 Motor Bracket
5V Power Supply, Electrical tape
70mm x 40m wheels, RS 775 Motors
For this project you will need:
1. Tools
2. Materials and Electronics
Circuit diagram
Motor Wiring
Since we are using a pair of flywheels to toss the ball across the room, we need to have them spinning in opposite directions such that the ball is pushed out of the middle. Hence we wire the motors using opposite polarity so they spin in opposite directions. following the diagram shown above, wire your motors in a similar way. Adding a toggle switch on the live wire helps too, since I have found that the contraption is kind of noisy and sometimes needs to be connected to the power even when not in use. A barrel adapter is added so that the 5V power supply can be used.
After you have made all connections and tested that the circuit works, solder it together. Make sure to use electrical tape to insulate it after.
Motor Mount and Support
Wood screw used to fix the motor brackets
Wood screw used to fix the motor mount to the support
Frontal support
Necessity of the counterweight
Counterweight (*NOT* the ball that is used in the contraption) and box
Now that the motors are wired properly and have been soldered, we need a way to hold them in the right position for the ball to pass through. We will use a plywood scaffolding to hold the motors in place.
The distance between the motors depends on two factors, the diameter of the ball and the diameter of your flywheels. Here, I am using 70mm wheels for the flywheels and a 65mm ball, so the distance between the two shafts of the motors should be 35+65+35=135mm. Make your calculations accordingly, and mark the plywood for the motors.
To mount the motors we will be using a RS 775 motor bracket. The width of this bracket is 42 mm, hence the center lies at 21mm. Adding 21mm on either side of the motor shafts we have 135+21+21=177mm. This is the final length of plywood I require. It is also a good practice to reduce the distance between the two motor shafts by a millimeter or two so that the ball may be gripped better.
Using a motor bracket as a template, mark the points where you would need to drill holes in the plywood. Use a 3.2mm drill bit to drill about 10mm into the plywood. Then use a screwdriver and 4mm screws to fix the motor brackets to the plywood. Then mount the motors (without using screws) and check if they are at the required distance.
Once this is done, we will make the rest of the scaffolding, namely the support. If you had measured out the distance between the two motor shafts, mark the midpoint using a pencil. Take a new piece of plywood, and drill a hole in the center lengthwise. The hole should be about 3/4th the length of the wood screw, in my case 1.5 inches deep. Now, drill a hole at the base of the plywood, as shown in the picture above (pic 3). Finally, use a wood screw to attach the two pieces of plywood. If you feel that the attachment is unstable, use a little bit of glue while putting the screw in.
Now, for the final frontal support. I ended up freestyling it, but you may use any method you please. I screwed in two wood screws in a small scrap of plywood I had left over, and covered the heads on hot glue to prevent damage to surfaces, then hot gluing the scrap to the assembly.
Since my build was top heavy, I ended up having to glue a small box to the back so that it wouldn't topple over.
Mukundan Chariar
dearuserhron
Johan R. Botha
John Leeman
Andy