This is an acrylic model of a differential as found on the back end of nearly every car (except dual-engine electric cars), made from laser-cut acrylic. It should be possible to make using an ordinary desktop laser cutter able to cut 1/8" (3mm) acrylic. Photos and videos can be seen at http://mechanicalgifs.com
Overview and Background
This is a laser-cutter project, which will require a supply of acrylic sheet and a laser cutter able to cut at least 1/4" (5.6mm) acrylic. The model also requires two bends, which can be done using an acrylic bending bar or bending tool, or other suitable source of concentrated heat along a thin line. The model can be made entirely of plain clear acrylic, or various parts (noted in the plans) can optionally be made of colored acrylic.
The included dxf file contains all the cutting and engraving patterns, one layer per thickness/color of acrylic. Lines in yellow are meant to be engraved, all other colors of line should be cut. Use the speed and power settings appropriate for your laser cutter: every one is different.
The layers are split up by type of acrylic.
A3 should be cut in 1/8" (3mm) acrylic
A3A should be cut in 1/8" (3mm) acrylic, recommended to be colored amber
A3G should be cut in 1/8" (3mm) acrylic, recommended to be colored green
A3B should be cut in 1/8" (3mm) acrylic, recommended to be colored blue
A5 should be cut in 1/4" (5 or 5.6mm) acrylic (or use two copies in 3mm)
A9 should be cut in 3/8" (9mm) acrylic (or use three copies in 3mm)
A12 should be cut in 1/2" (12mm) acrylic (or use four copies in 3mm)
This model requires one post-processing step after the acrylic has been cut: The long thin strip with three holes needs to be bent in two places, forming a U-shaped piece. The "Folding Jig" layer should be cut out of 1/2" thick material (doesn't matter what it is) and used to form the U shape after the acrylic is heated at the location of the two bends.
A detailed assembly video showing exactly how to put the model together is available at https://mechanicalgifs.com/instructions
Lesson Plan and Activity
This model can be used together with the Transmission and Rack-and-Pinion Steering models to illustrate how the major mechanical parts of a car work.
(1) Approximately 8" x 10" (200mm x 250mm) piece of 1/8" (3mm) clear acrylic.
(1) Small pieces of 1/4" (6mm), 3/8" and 1/2" clear acrylic. Optionally can substitute multiple layers of 3mm acrylic for these thicker pieces.
(2) Optionally pieces of three different colors of 3mm acrylic to make the gears colored.
(2) #6 x 3" round-head machine screw (or metric M3 x 75)
(1) #6 x 2-1/2" round-head machine screw (or metric M3 x 64)
(4) #6 x 1-3/8" round-head machine screw (or metric M3 x 34)
(1) #6 x 3/4" round-head machine screw (or metric M3 x 20)
(2) #6 x 5/8" round-head machine screw (or metric M3 x 16)
(5) #6 x 1/2" round-head machine screw (or metric M3 x 12)
(18) #6 hex nuts (M3)
(2) #6 lock nuts (M3)