Design Project SP22
ENGR-100 Design Project Spring 2022
Overview
Your assignment is to design a gea
ox that will allow a motor to lift a 120lbf load 60ft vertically
in 30 seconds using a rope and winch system. See the ru
ic in Brightspace for grading info.
Key Dates:
● All materials must be submitted in Brightspace by 7PM on Monday, April 18th.
Deliverables:
1. CAD Model: at minimum, a basic “crayola” CAD model with gears and a backing plate.
To earn full credit, include additional detail beyond the bare-minimum requirements.
2. Overview Sheet: a single typed page that contains, at minimum:
a. The overall gear ratio for the gea
ox
. The calculated output torque for the gea
ox
c. The calculated rope linear speed
d. The part number, cost, power, speed, and continuous torque for your moto
e. Your selected winch diamete
f. The following information about each of the gears in your gea
ox
i. Tooth count
ii. Diametral pitch
iii. Pitch diamete
iv. Material
v. Tooth stress
g. Total cost of the parts from McMaster for your gea
ox (motor and gears)
h. An image of your gea
ox, with the overall dimensions and gear tooth counts
labeled.
3. Supporting Documentation: copies of all your math used throughout the design of you
gea
ox. Be sure to clearly label your steps and work, so that it is obvious what is being
done, and which iteration the math is for. If you use spreadsheets, include those files in
your Brightspace submission. Note: part of your project grade will be based on the
accuracy of the calculations for your final design.
Design Requirements:
As stated above, the gea
ox must allow a motor to lift a 120lbf load 60ft vertically in 30
seconds
1. The output torque of the gea
ox should be at least 20% greater than the load torque.
For your calculations, use the “continuous torque” rating from the motor product page.
a. Assume 95% efficiency for 2 gears, or 92.5% for 4 gears
. Note: having more torque than needed is OK.
2. The output speed of the gea
ox should be such that the rope speed is within ±0.5ft/s
of the necessary speed. For your calculations, use the maximum speed rating from the
motor product page.
a. Note: this means your system has both a minimum and maximum speed.
3. The tooth stress on each gear must be less than 1/3rd of the yield stress for the gea
material:
a. Brass: 55000PSI
. 1117 Ca
on Steel 68900PSI
c. 1144 Ca
on Steel (Hardened): 89900PSI1
d. 1020 Ca
on Steel 60900PSI
Available Materials:
● The available winch diameters are: 1in, 1.5in, 2in, 2.5in
● You may use any of the motors listed here:
https:
www.mcmaster.com/motors/face-mount-ac-motors/electrical-phase~single/voltage
~115v-ac/motor-frame-size~nema-56c/motor-enclosure-type~open-dripproof-odp-
● You may use any of the 20 degree gears listed here (don’t wo
y about gear shaft size):
https:
www.mcmaster.com/gears/metal-gears-and-gear-racks-20-pressure-angle/compo
nent~gea
system-of-measurement~inch
https:
www.mcmaster.com/motors/face-mount-ac-motors/electrical-phase~single/voltage~115v-ac/motor-frame-size~nema-56c/motor-enclosure-type~open-dripproof-odp-
https:
www.mcmaster.com/motors/face-mount-ac-motors/electrical-phase~single/voltage~115v-ac/motor-frame-size~nema-56c/motor-enclosure-type~open-dripproof-odp-
https:
www.mcmaster.com/gears/metal-gears-and-gear-racks-20-pressure-angle/component~gea
system-of-measurement~inch
https:
www.mcmaster.com/gears/metal-gears-and-gear-racks-20-pressure-angle/component~gea
system-of-measurement~inch
Math Tips
● Start by using the linear power equation to determine the motor HP rating you’ll need.
● The load torque is based on the load weight and winch radius (note radius vs diameter)
● When determining the gear ratio for your gea
ox, remember to check both the output
torque and output speed at your chosen ratio
● For tooth stress, meshing gears have the same tangential load (WT) and tip speed (V).
● If you are using a 2-stage gea
ox (2 pairs of meshing gears):
○ The tangential load (WT) and tip velocity (V) for the last gear (N4 in diagram on
the next page) should be calculated using the gea
ox output torque and speed.
○ The tangential load and tip speed would then be the same for the 3rd gear (N3).
Equations
● ?????? = ????? * ????????
● ?????? ????? = ????? * ????????????
● ?????????? ????? = ?????? * ??? * 2π60
● Gear ratio for single pair of gears:
????? = # ?????? ????ℎ# ??????? ????ℎ =
?
2
?
1
● Gear ratio for a 2-stage gea
ox:
????? =
?
2
?
1
( ) * ?4?
3
( )
● Gea
ox output speed:
?????
???
=
?????
??
?????
● Gea
ox output torque:
??????
???
= ??????
??
* ????? * ??????????
● Tooth stress (V in ft/min, Pd is the pitch, not the pitch diameter)
σ =
?
?
*?
?
?*? *
1200 + ?
1200