Mechanical Design

The mechanical aspect of the horse racing game consists of two identical race tracks. We will describe the design for one of the tracks here.

Track

The track is made of two 7.5’ X 3” X 1.5” boards spaced four inches apart. It is attached at the ends by smaller lengths of the same board type. This track allowed for the mounting of two pairs of IR beam-breaking sensors and a motor. There is a one-inch diameter PVC tubing running along the top of each board. The tubing is attached to the board by brackets made from sheet metal.

Side view of the track

Horse Mount

The horse mount is made of several pieces of sheet aluminium, bent and riveted together. It is designed to slide along the top of the PVC piping. There is also a vertical piece designed as a holder for the photodiode-radio frequency transmitter circuit and the paper horse.

Horse mount with photodiode-radio frequency transmitter circuit and paper horse

Pulley System

A loop of wire runs between the boards and is attached to pulleys at both ends of the track. One of the pulleys is free to move, the other is attached to the drive shaft of a brushed DC motor that is mounted at the end of the track (near the starting line). The wire is also attached to the horse so that when the wire winds around a pulley, the horse is pulled backwards or forwards depending on the rotation of the motor shaft.

A loop of wire attached to the pulley which is driven by a brushed DC motor

The pulley was machined on a lathe. It was drilled and tapped for a set screw that tightens the pulley to the motor shaft so it will not slide off when the motor rotates.

CAD drawing of the pulley

Conclusion

This design worked very well. We considered using wheels for the horse, but the cost of at least four wheels per horse and the additional effort needed to mount them were unnecessary given the small weight of the horse. There was considerable friction in the system acting against motion of the motor; however by testing, we found that most of the friction came not from the horse sliding on the track, but from the cheap-store-bought pulleys at the end of the track (near the finish line). The actuation would have been smoother and had higher top speeds if the those pulleys were of better quality.


Introduction	Mechanical Design	Electrical Design	Programming	Results
Mechanical Design The mechanical aspect of the horse racing game consists of two identical race tracks. We will describe the design for one of the tracks here. Track The track is made of two 7.5’ X 3” X 1.5” boards spaced four inches apart. It is attached at the ends by smaller lengths of the same board type. This track allowed for the mounting of two pairs of IR beam-breaking sensors and a motor. There is a one-inch diameter PVC tubing running along the top of each board. The tubing is attached to the board by brackets made from sheet metal. Side view of the track Horse Mount The horse mount is made of several pieces of sheet aluminium, bent and riveted together. It is designed to slide along the top of the PVC piping. There is also a vertical piece designed as a holder for the photodiode-radio frequency transmitter circuit and the paper horse. Horse mount with photodiode-radio frequency transmitter circuit and paper horse Pulley System A loop of wire runs between the boards and is attached to pulleys at both ends of the track. One of the pulleys is free to move, the other is attached to the drive shaft of a brushed DC motor that is mounted at the end of the track (near the starting line). The wire is also attached to the horse so that when the wire winds around a pulley, the horse is pulled backwards or forwards depending on the rotation of the motor shaft. A loop of wire attached to the pulley which is driven by a brushed DC motor The pulley was machined on a lathe. It was drilled and tapped for a set screw that tightens the pulley to the motor shaft so it will not slide off when the motor rotates. CAD drawing of the pulley Conclusion This design worked very well. We considered using wheels for the horse, but the cost of at least four wheels per horse and the additional effort needed to mount them were unnecessary given the small weight of the horse. There was considerable friction in the system acting against motion of the motor; however by testing, we found that most of the friction came not from the horse sliding on the track, but from the cheap-store-bought pulleys at the end of the track (near the finish line). The actuation would have been smoother and had higher top speeds if the those pulleys were of better quality.