Advanced Manufacturing 

MasterCAM/CNC Machining Project

Please consult with your Project Outline on D2L to
see what exactly you will be getting in your parts kit.
 Note: Parts may be substituted, depending on what's in the Mech office supply cabinet

1/4" dia. X 12" wooden dowel = 6g


Paper Clips
3-3/4" long when stretched out
wire is 0.035" dia.



Rubber Bands
3" when not stretched
will safely stretch to 12"
K= 1/2 lbf/inch or K= 0.8 N/cm
coefficient of friction on tile floor about u=0.9


Wax birthday cake candle
approx. 2-1/4" long


Medium Density Fiber (MDF) board
(MDF is a wood pulp product)

Boards - 7"x4"x1/4" thick (nominal) = 96g


#6-32 x 3.4" long machine screw with nuts 2.4g

Not shown:
Sheet of 8.5 x 11" white paper

Power Sources

Constant Force Spring
5 lbf - weight = 36g
5/8" wide, 1.13" OD
McMaster- Carr #9293k337

constant force spring


Small DC electric motor (previous year)
motor dia. = 0.730x0.950"
motor body length (not including shaft) = 1.360"
shaft dia. = 0.081"
shaft length from motor  = 0.385"
Specs: no load 10,000rpm @ 12V
no load: 100mA and 1.2W
stall (0rpm): 3.6A and 43W
Torque at stall = 0.02Nm
(you must make your own MDF or rapid prototyped pinion gear)

Power must be applied to the two "sockets",
so allow space for wires as shown below:

DC motor

SolidWorks File

solidworks cad model

SolidWorks Part file of the motor

Fitting Parts Together

The milling machines you will be using are accurate to within a few thousanths of an inch.
Generally, if you need a 0.250" dia. shaft to rotate in a 0.250" hole, draw a 0.250" hole in AutoCAD,
bring the drawing into MasterCAM, generate G-code and the machine will cut an exactly 0.250" hole. If you want a press fit, machine a hole 0.002" smaller, if you want a loose fit, machine a hole 0.002" larger. Keep in mind, the dowel's dia. changes with temperature and humidity.
Remember, small holes can be filed (or sanded) larger.  You can't make a big hole smaller!

Mounting the Motor

The motor can be press fit into the body.
Machine a hole in your car body for a press fit.
motor in car

Close-up of motor mount.
motor hole

Designing Gear Trains

Please go to my Cycloid Gear Page

Devin's Steam Car

Prof. Chan's Catapult

The 4x4 Track

Prof. Chan's Rubber Band Car

Devin's Rubber Band Car

Page created: Jan 5, 2001,  Updated Sept. 19th, 2016 by: Vincent Chan, Associate Professor, Department of Mechanical Engineering,
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