Mechanical Design and Dimensioning

 

Overall Structure

The main structure was constructed from ½” foam core and hot glue.  The bowling alley ramp was made with an angle of 2.7° by making the front supports 1.5” taller than the back supports.  The angle was chosen so that the pennies would not curve too much, as a larger angle would have made them curve toward the middle of the ramp.  The majority of the indicators were mounted in the display panel above the end of the ramp.  The bowling pins were also mounted to this panel.  The start button and the difficulty selector are mounted in their own panel on the front right side of the ramp.  The prize dispenser is underneath the bowling alley ramp near the front panel.  A trap door was included in one of the side panels to allow access to the components underneath.  The main circuit boards, microcontroller, and power supply were also underneath the ramp.  The circuit board for the seven-segment LEDs is supported on a ledge behind the display panel.  The substructures of the game are described below.

     

Bowling Alley Ramp Dimensions

 

Side Panel Dimensions

 

Front Panel Dimensions

 

Display Panel


The start button and the difficulty selector

 

Trap door to allow access to components

 

Stepper motor circuit board for Prize Dispenser

 

Main circuit board

 

Seven-segment LED displays for score and timer circuit boards

 

Behind display panel

 

Launch Mechanism

The launch mechanism consists of a foam core ramp, a foam core penny insertion slot, an optointerruptor, an aluminum guiding ramp, a wood dowel for an aiming handle, and a solenoid with a gate attached, all supported on a cardboard disk.  The optointerruptor is mounted directly behind the penny insertion slot and in front of the guiding ramp so that the penny will be detected and then roll into its starting position.  The guiding ramp has a milled lengthwise 0.1” slot (slightly larger than the width of a penny).  Near the top of this ramp is milled an additional slot for the solenoid gate to block the penny from escaping.  The bottom of the guiding ramp touches the bowling alley surface so the penny will release smoothly from the launcher.  The solenoid gate is constructed from small pieces of cardboard and is hot glued onto the solenoid shaft.  The solenoid is supported by pieces of foam core to raise it to the appropriate height.  All of these components are mounted onto the foam core ramp, which gives the penny a large starting angle so it will gain enough speed to hit a bowling pin.  This ramp is glued to the cardboard disk, which is connected to the bowling alley surface with a pivot.  The wood dowel is glued to the disk to allow the user to easily aim the ramp at the correct bowling pin.

Penny launcher

 

Foam core penny insertion slot

 

Top view of penny launcher

 

Bowling Pins and Their Sensors

The eight bowling pins are cut from cardboard, and are mounted to the display panel with Ύ” wide hinges.  A small cardboard tab is affixed to the back of each pin to block the optointerruptor when the pin is hit.

 

The original idea for detecting a “hit” was to use an array of switches mounted to the top of the bowling pins that would be closed when the pin was hit.  However, the team was unable to find switches that would activate with the small force provided by the penny.  Since optointerruptors were readily available, we devised a way to use these instead.

 

An array of eight optointerruptors is mounted directly behind the bowling pins on a foam core strip.  To make sure the bowling pin tabs were precisely aligned with the optointerruptors, the optointerruptors were placed first, and then the correct location for each tab was determined.

Dimensions of bowling pin

 

Prize Dispenser

The prize dispenser uses a stepper motor to give out Skittles based on the number of motor rotations.  The original dispensing idea was a vertically mounted wheel with grooves cut into its circumference.  Skittles would drop one by one from a reservoir into these grooves as the wheel was rotated by the motor, and then drop into a prize collection area.  The problem with this idea was that the opening in the reservoir needed to be much larger than the thickness of the wheel in order for the Skittles to drop, so there was little control over where they would go.

Vertical prize dispenser wheel

 

We modified this concept by attaching the motor to a horizontal wheel with four holes cut into it.  The Skittles reservoir was placed right above the wheel, and as the motor turns each hole passes by the reservoir outlet and Skittles fall through the hole and into the collection area.

Horizontal prize dispenser wheel

 

The reservoir is made from a large empty Gatorade bottle, cut to the right height.  The horizontal wheel is foam core, and the holes are lined with PVC pipe to create a smooth, uniform surface.  The collection area consists of a cardboard ramp that guides the Skittles from the horizontal wheel to the bottom surface of the game, and a horizontal cardboard surface flush with the bottom of the game.  The horizontal surface has tall cardboard walls so that the Skittles will remain in the area until the user collects them for their prize. 

 

Reservoir with skittles and horizontal foam core wheel

 

Ramp to guide skittles for prize collection

 

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