Final Report
2014-2015 Team 4
Calvin College ENGR340 Senior Design Project
Thomas Brown ME,
Garrick Hershberger ME,
Jee Myung Kim ME,
Andrew White EE
May 13, 2015
Copyright © 2015 by Calvin College and Team 4 Volts-Wagon.
All rights reserved. No part of this book may be used or reproduced, stored or transmitted in any manner
whatsoever without written permission from the publisher, except for the inclusion of brief quotations in
review
Abstract
The decline of fossil fuel reserves calls for research and development of alternate energy sources.
To prepare for the future, Calvin College will need to obtain and maintain vehicles powered with such
alternative energy sources. This project proposes to offer a remedy to this problem in the form of a small
electric vehicle for on-campus use that will replace a standard gasoline-powered golf cart.
The Volts-Wagon is a four person electric vehicle with a maximum speed of 15 miles per hour
(mph). This vehicle is designed to travel on campus paths, and it will travel a minimum distance of ten
miles with fully charged batteries. It has the capability to travel forward and backwards, with maximum
steering angle of 30°. It is mounted with four 12V batteries which are charged by a standard 110V outlet.
The batteries are wired to a 15 horsepower (HP) electric motor which will power the vehicle. One inch
outer diameter steel pipe with 1/8” wall thickness was used to build the frame for durability, and the body
panels were cut out of 1/8” sheet aluminum. Chains and sprockets were used in two applications on the
vehicle: A drive chain to transfer power from the motor to the rear axle, and a second chain to drive the
steering mechanism from the steering wheel.
This report details the progress of the project, starting from the initial client consultations to the
final deliverable.
Table of Contents
Table of Contents ........................................................................................................................................... i
Table of Figures ........................................................................................................................................... iv
Table of Tables ............................................................................................................................................. v
Introduction ........................................................................................................................................... 1
1.
Team Members ................................................................................................................................. 1
a.
i.
Thomas Brown .............................................................................................................................. 1
ii.
Garrick Hershberger...................................................................................................................... 1
iii.
Jee Myung Kim ......................................................................................................................... 1
iv.
Andrew White ........................................................................................................................... 2
b.
Team Picture ..................................................................................................................................... 2
c.
Client ................................................................................................................................................. 2
d.
Project Definition .............................................................................................................................. 3
e.
Requirements .................................................................................................................................... 3
f.
Design Norms ................................................................................................................................... 3
Project Initiation.................................................................................................................................... 5
2.
a.
Research ............................................................................................................................................ 5
b.
Computer Aided Design (CAD) ....................................................................................................... 5
i.
Initial ............................................................................................................................................. 5
ii.
Final Design .................................................................................................................................. 6
iii.
Finite Element Analysis (FEA) ................................................................................................. 7
Components .......................................................................................................................................... 8
3.
a.
Component Selection Method ........................................................................................................... 8
b.
Donations .......................................................................................................................................... 8
i.
Team SolarCycle ........................................................................................................................... 8
ii.
Team Maneuver Mobile (2002/2015) ........................................................................................... 8
Purchased Items ................................................................................................................................ 9
c.
Calculations......................................................................................................................................... 10
4.
Approach ......................................................................................................................................... 10
a.
i.
Motor........................................................................................................................................... 11
ii.
Batteries ...................................................................................................................................... 12
i
Design Construction............................................................................................................................ 13
5.
a.
Frame .............................................................................................................................................. 13
b.
Steering System .............................................................................................................................. 14
c.
Axle ................................................................................................................................................. 15
d.
Suspension ...................................................................................................................................... 16
i.
Front ............................................................................................................................................ 16
ii.
Rear ............................................................................................................................................. 17
e.
Motor............................................................................................................................................... 18
f.
Batteries .......................................................................................................................................... 18
g.
Accelerator ...................................................................................................................................... 19
h.
Brakes ............................................................................................................................................. 20
i.
Parking Brake.................................................................................................................................. 21
j.
Front and Rear Running Lights ....................................................................................................... 21
k.
Underbody Lighting ........................................................................................................................ 22
l.
Circuit Overview ............................................................................................................................. 22
m.
Seating......................................................................................................................................... 22
Final Product ....................................................................................................................................... 23
6.
a.
Pictures............................................................................................................................................ 23
b.
Steering Angle ................................................................................................................................ 24
c.
Actual Weight Capacity .................................................................................................................. 24
d.
Actual Vehicle Weight .................................................................................................................... 24
e.
Actual Speed ................................................................................................................................... 25
f.
Run Time ........................................................................................................................................ 25
g.
Charging Time ................................................................................................................................ 25
h.
Control Panel .................................................................................................................................. 26
i.
Paint ................................................................................................................................................ 26
j.
Vehicle Testing ............................................................................................................................... 27
Business Plan ...................................................................................................................................... 31
7.
a.
Cost Estimate .................................................................................................................................. 31
8.
Conclusion .......................................................................................................................................... 33
9.
Acknowledgements ............................................................................................................................. 34
10. Team Resumes .................................................................................................................................... 35
a.
Thomas Brown ................................................................................................................................ 35
ii
b.
Garrick Hershberger........................................................................................................................ 36
c.
Jee Myung Kim ............................................................................................................................... 37
d.
Andrew White ................................................................................................................................. 38
11. Appendix ............................................................................................................................................. 39
a)
Energy, Speed and Force Calculations ........................................................................................... 39
b)
Motor Specifications ....................................................................................................................... 41
c)
Motor Controller Schematic............................................................................................................ 42
d)
Complete Electrical Schematic ....................................................................................................... 43
e)
Frame Cut List ................................................................................................................................ 44
iii
Table of Figures
Figure 1-1. From Left to Right: Andrew White, Jee Myung Kim, Garrick Hershberger, Thomas Brown ... 2
Figure 1-2. John Britton ................................................................................................................................ 2
Figure 2-1. Initial Design .............................................................................................................................. 5
Figure 2-2. Final Design of the Frame .......................................................................................................... 6
Figure 5-1. Steering Assembly.................................................................................................................... 14
Figure 5-2. Rear Axle ................................................................................................................................. 15
Figure 5-3. 2 Front Shocks.......................................................................................................................... 16
Figure 5-4. Shock Position .......................................................................................................................... 16
Figure 5-5. Leaf Springs ............................................................................................................................. 17
Figure 5-6. Leaf Spring Position ................................................................................................................. 17
Figure 5-7. Motor Mount ............................................................................................................................ 18
Figure 5-8. Batteries Mount. ....................................................................................................................... 19
Figure 5-9. Accelerator and Brake Lever.................................................................................................... 20
Figure 5-10. Accelerator and Brake ............................................................................................................ 21
Figure 5-11. Front Lights ............................................................................................................................ 22
Figure 5-12. Front and Back Seats .............................................................................................................. 23
Figure 6-1. Final Product ............................................................................................................................ 23
Figure 6-2. Final Product with Lighting ..................................................................................................... 24
Figure 6-3. Control Panel ............................................................................................................................ 26
Figure 6-4. Vehicle in Paint ........................................................................................................................ 27
Figure 11-1. Motor Specs ............................................................................................................................ 41
Figure 11-2. Controller Layout .................................................................................................................... 42
Figure 11-3. Full Schematic ......................................................................................................................... 43
iv
Table of Tables
Table 3-1: Purchases ..................................................................................................................................... 9
Table 4-1: Control Variables ...................................................................................................................... 10
Table 4-2: Power Calculation ..................................................................................................................... 11
Table 8-1. Total Manufacturing Cost per Vehicle ...................................................................................... 31
Table 8-2. Total Annual Profit .................................................................................................................... 31
v
1. Introduction
Calvin College Engineering Department provides a two-semester sequences of senior design
project courses. Engineering 339, which is provided in the fall semester, focuses on the initiation of an
original major design project. Engineering 340 in the Spring Semester places emphasis on the completion
of the project that was initiated in Engineering 339. Students are divided into teams of four to accomplish
the project. The course was instructed by the following four professors: Professors Mark Mitchmerhuizen,
Ned Nielsen, Jeremy VanAntwerp, and David Wunder. The team gathered every day to design and build
the project. All documents and records such as test results, major reports, presentations, budget, pictures,
etc. are kept in the Calvin College Engineering senior design server.
a. Team Members
i.
Thomas Brown
Thomas is pursuing a Bachelors of Science in Engineering with an International Mechanical
Engineering Concentration at Calvin College. He is from Grand Rapids, MI and works for Calvin
College’s Student Activities Office organizing student events based around video games, which he enjoys
playing when he has the time. After graduating in May 2015 he will work for Grand Rapids Chair
Company as a project engineer.
ii.
Garrick Hershberger
Garrick is pursuing a Bachelors of Science in Engineering with an International Mechanical
Engineering Concentration with an international distinction at Calvin College. He is from Nashville, MI
and works for Calvin College Physical Plant in the Transportation department. He enjoys playing rugby
for Calvin’s Men’s Rugby team in his spare time. He has accepted an offer from Bradford White in
Middleville, MI as a combustion engineer.
iii.
Jee Myung Kim
Jee Myung is a senior at Calvin College pursuing a Bachelors of Science in Engineering with an
International Mechanical Engineering Concentration and a minor in mathematics. He was born in South
Korea and lived in China for half of his childhood before coming to the United States for his college
education. He enjoys playing tennis and listening to music and works for Calvin College’s Engineering
1
Department as a grader. After graduating in May 2015 he plans to find a job in his field of Mechanical
Engineering.
iv.
Andrew White
Andrew is pursuing a Bachelors of Science in Engineering with an Electrical and Computer
Engineering Concentration at Calvin College. He is from Howell, MI and in his free time he enjoys
ballroom dancing, singing, and playing piano. After graduating in May 2015 he plans to find a job in
Research and Development, Troubleshooting, or Manufacturing.
b. Team Picture
Figure 1-1. From Left to Right: Andrew White, Jee Myung Kim, Garrick Hershberger, Thomas Brown
c. Client
Figure 1-2. John Britton
The direct client of Team Volts-Wagon is John Britton, the Associate Dean of Campus
Involvement and Leadership, and the Director of Orientation at Calvin College. He is also the head of the
Student Development Office, which heads up Passport, the freshmen orientation program, Buck Fridays,
and Nite-Life, the Friday night events program.
2
d. Project Definition
Calvin College currently maintains a small fleet of gasoline powered golf carts which are
expensive to purchase/rent, maintain, and fuel. The aim of this project is to create a lightweight,
inexpensive, and sustainable vehicle that could be used in place of Calvin College’s current golf carts,
thereby providing transportation for faculty and staff around campus.
Our client is looking for a vehicle that is more sustainable and attractive than the standard Calvin
golf carts and can be used as a promotional tool for Calvin’s Engineering Department and the college as a
whole when it is being driven around campus. The team has consulted him on multiple occasions for
feedback regarding the vehicle’s design.
Given that this vehicle will be used on campus on a daily basis, it represents an excellent way for
Calvin College to demonstrate the comprehensive scope of their engineering program as well as the
capabilities of the program’s current students to prospective students, alumni, and donors.
e. Requirements
The Volts-Wagon will be powered by an electric motor that will be supplemented with charging
equipment, thereby providing the ability for the batteries to be charged from a standard 110V wall outlet.
The Volts-Wagon will be user-friendly, intuitive, and have a single forward and reverse gear to facilitate
movement in all directions. It will have front lights and rear lights to ensure the safety of both passengers
and pedestrians while operating within low light environments. The vehicle will be sized and outfitted to
comfortably accommodate one driver and three passengers and operable year round per request of the
client. The vehicle should also have underbody lighting and a roof, at the customer’s request.
The Volts-Wagon must have a minimum travel distance of ten miles on a single charge at a
maximum speed of 20 mph. The vehicle is required to have a charge time of 9 hours or less, therefore
giving the vehicle the ability to be charged overnight and ready to operate at the start of the next day.
f. Design Norms
Trust:
The vehicle must be trustworthy and dependable. It should be constructed to go beyond its design
parameters ensuring its reliability. This product will be used on a regular basis by college staff
and should be designed and constructed to the highest standards.
3
Integrity:
This project must be carefully designed and constructed to be ergonomic, comfortable and useful
in order to make the staff’s jobs easier. It must also be intuitive to use and accomplish its task
with a minimum amount of effort from the user.
Caring:
This product must be pleasurable and take into account the method and effect of recurrent use.
The final design will be helpful and not harmful to those who not only use the vehicle, but also
maintain it.
4
2. Project Initiation
a. Research
The research for this project was limited in scope and was mostly restricted to researching
information about the various parts that were donated and purchased, an example of such research being
finding the specifications of the front shocks and rear leaf springs.
b. Computer Aided Design (CAD)
i.
Initial
The initial design that the team thought of included the beginnings of a basic frame which
remained largely unchanged. However, after running a Finite Element Analysis (FEA) on the frame, it
was found that this iteration of the design would be unable to support more than 1500 lbs without
plastically deforming. This was deemed unacceptable by the team as this weight was the equivalency of
only six 250 lb passengers. Under overloading conditions, the team anticipated more weight/people on the
vehicle.
Figure 2-1. Initial Design
.
5
ii.
Final Design
In the second meeting with the client, he specified that he would like the vehicle to have a roof.
The design was modified to incorporate a roof, which changed the stiffness of the vehicle. It increased the
stiffness to a degree of safety that fell within the vehicle’s safety factor of eight people. Also, more
support was added to the floor of the frame, in the form of diagonal cross-beams, to increase the stiffness
of the frame. This gave the vehicle the ability to withstand much more than the required weight capacity.
This was done by adding diagonal cross bars in each square on the frame base. Details are in Section 2bi
below.
Figure 2-2. Final Design of the Frame
6
iii.
Finite Element Analysis (FEA)
Figure 2-3: 4000 lbf FEA Model
The vehicle was designed to seat 4 people. However, for the analysis, a weight of 4000
was
distributed to the four seating locations on the frame. This amount was chosen because it was four times
the number of people the vehicle was designed to fit. Assuming each person weighs 250 lbs, 4000 lbs is
16 people. This extreme case was tested in order to account for the possibility of unexpected overload,
such as the vehicle being loaded with as many passengers as possible and taking an impact of similar
magnitude comparable to driving straight off of a curb. Under this extreme case the maximum deflection
of the vehicle was just 0.058 inches, well within the elastic deformation range of the steel.
7
3. Components
a. Component Selection Method
The team decided early in the project that the vehicle could very easily go over budget if all the
necessary parts were purchased new. The decision to reuse the parts and equipment already owned by the
team or the Engineering Department was made providing that the installation of said parts would be safe
and would not interfere with the design or the customer specifications. Keeping in mind that all parts and
components contain embodied energy from their manufacturing, it seemed evident to the team that the
best way to maintain sustainability would be to reuse any available components and purchase all others
that could not be found or replaced by suitable replacements.
b. Donations
i.
Team SolarCycle
Team SolarCycle (2013-2014) kindly donated their vehicle as it was not fully functioning. The
following five components from the motorcycle were reused for this project:
1. The throttle potentiometer
2. Mars Electric ME0708 Motor
3. Four 12V VMAX Charge Tank SLR60 batteries
4. EVDrives SPM48400 Motor Controller
5. Two Kyocera Shocks from a 1986 Honda Nighthawk
ii.
Team Maneuver Mobile (2002/2015)
Team Maneuver Mobile (2002) took the rear axle off a Club Car golf cart and used it for their
vehicle. Team Maneuver Mobile (2015) removed this axle from their vehicle to replace it with hub
motors. They then offered it to Team Volts-Wagon, who had been planning on custom making a rear axle
and buying a differential. The axle mounts were perfect size for the Volts-Wagon, which was designed to
be standard golf cart dimensions, and the axle had built in differential and drum brakes. This differential
contained a 7:1 gear ratio that would slow the speed of the motor down to a comfortable top speed. The
analysis done by the team showed that a 6:1 gear ratio would give the vehicle a top speed of 28 miles per
hour, which would meet the customer’s request of a top speed of 20 mph. A 7:1 gear ratio would bring the
vehicle to a top speed of just 20 mph, but given that the customer requested a maximum speed of 20 mph
and not a minimum, this new speed was deemed acceptable. The axle, unmounted, can be seen below in
Figure 3-1.
8
Figure 3-1: Rear Axle Unmounted
c. Purchased Items
Many items were purchased for this project because they could not be made at Calvin. The full
list is shown below in Table 3-1: Purchases.
Table 3-1: Purchases
Total Spent
Cost
Tire and Axle Hubs
$224.00
Steel, Aluminum - Frame and body
$0.00
Heim Joints - Joint rod ends
$26.32
Rivet Nuts and Castle nuts
$33.15
Electrical Components #1
$47.34
Pitch 40 Master and Half Links
$14.40
Electrical Components #2
$51.04
Pitch 40 Master and Half Links
$19.45
Wiring and Motor Parts
$214.38
Universal Joint
$19.95
10” Steering Wheel
$21.99
Steel Ball Joint Rod Ends
$26.32
TOTAL
$698.34
9
4. Calculations
a. Approach
It was proven by Team Solar Cycle that the motor, the batteries, and the controller were able to
work together while simultaneously not bothering the other components. Thus, Team Volts-Wagon
decided to go backwards in the feasibility calculations, starting by receiving the specifications from the
motor and running the calculations to verify the strength of the vehicle, instead of working from the
specifications required to drive the vehicle and sizing the perfect motor for it.
The following control variables were used for the feasibility calculations. More calculations can
be found in Appendix A: Energy, Speed and Force Calculations.
Table 4-1: Control Variables
Control Variables
Values
[
]
[
Distance
]
[
Weight
]
[ ]
[
[
]
]
20 [mi/hr]
The frontal surface area was calculated on the CAD design. The distance per travel was set to be
5 miles because the team considered it to be a reasonable distance to travel within the campus in one trip.
The vehicle was weighed to be a little less than 750 lb. Assuming each person weighs 200 lbs, the
maximum weight the vehicle can hold was set to be 1550 lb. This weight capacity was used for the
calculations to follow. Note that for the FEA, as specified before, a weight capacity of 4000 lb was used
to provide extra room in the calculation. The maximum velocity was set to be 20 miles per hour on the
motor controller as specified by the client. This value was selected so that the driver would not be
required to get a legal license to drive the vehicle.
10
i.
Motor
In order to verify that the motor was strong enough to drive the vehicle, the team found the force
required to move the vehicle by using the equations below.
The drag coefficient
0.04, and the density of air
and the ground, and
was set to be 0.8, and the rolling drag coefficient
was set to be 0.0765 lb/ft3.
was set to be
is the friction force between the vehicle
is the force against the air flow. The power draw required to overcome both
forces was calculated using the equations below.
The constant g is the gravitational constant. The results are shown in Table 4-2: Power Calculation below.
Table 4-2: Power Calculation
Variable
Values [HP]
9.977
5.294
9.421
11
Because the maximum power value of 9.97 HP is well beneath the 15 HP maximum capacity of
the electric motor, the motor is more than capable of driving the vehicle. For detailed work, refer to
Appendix A: Energy, Speed and Force Calculations.
ii.
Batteries
Next, the calculations were run to see if the four 12V batteries were enough to provide sufficient
power. As indicated in Error! Reference source not found., a single trip was defined to be 5 miles in
distance, and 20 minutes in time. Considering the facts that this vehicle will only be run on Calvin
campus, and the farthest distance from one end of the campus to the other end is less than 0.5 miles, the
amount of energy in battery terminology was calculated using the equation below where
and
.
The result showed that the four batteries will be able to hold approximately
Next, calculations were run to see how much energy a single trip would draw from the batteries. The
following equations were used:
The result of this calculation showed that each trip will draw 4,737
of energy from the battery. This
meant that each full charge will operate the vehicle for approximately 2.2 trips, which is equivalent to 11
miles of travel or 45 minutes of non-stop traveling time. This exceeds the specification that the vehicle be
able to travel 10 miles on a single charge.
12
5. Design Construction
a. Frame
The frame was designed so that all the stresses and forces were transferred to the center beam of
the vehicle. The frame is made of 1" ID, .875" OD cold rolled steel and is welded at all of the joints. This
material was chosen because it was easy to acquire and the strength and lightness that it will provide is
comparable to solid or square stock. The frame was modified to make room for the differential after some
initial testing was done. When the suspension bowed due to weight, the center bar hit the differential. The
center bar was cut out and replaced by two bars, one on either side of the differential.
The pipes were cut out for the frame by using the master cut list. This list, which can be seen in
Appendix E: Cut List, contained all of the pipes, their lengths, and the angles for each end. We originally
thought that we would need 146 feet of pipe but after choosing to raise the roof so that taller people could
sit more comfortably, we found that we needed 165 feet. The cut list was updated to reflect the new pipe
lengths.
Figure 5-1: Construction of the Body Frame
13
b. Steering System
The steering system utilizes two horizontal extension bars connected to two pivot arms that move
the control arms. This system was created to eliminate all bump steer from the vehicle. Bump steer occurs
when the suspension compresses due to excessive weight and the control arms are not allowed the
freedom to move in parallel with the A-arms, thus pivoting the wheels outward. The steering system
works like a rack and pinion system, but without either a rack or pinion. The horizontal extension bars
transmit the motion of the pitman arm (the vertical bar in the center of the cube in Figure 5-1)
horizontally, acting like the rack, and the pitman arm rotates, acting like the pinion. The steering shaft is
connected to the pitman arm shaft via a sprocket and chain, which are used to achieve an offset that is
desirable to the driver. The chain that connects the steering wheel to the steering mechanism is #40 pitch
Roller Chain, and the steering arms were custom machined out of 1/2” steer bar and threaded on both
ends so that they could be easily adjusted. The heim joints (colored gold in Figure 5-1) that make the
steering possible were all ½ inch ID to ensure ease of replacement and continuity.
Figure 5-1. Steering Assembly (Left Side Only)
14
Figure 5-2: Steering System
c. Axle
The axle that was chosen for the Volts-Wagon is a standard Club-Car rear axle with a built-in
differential. This axle was chosen because it was donated to the team and because of the ease of use in an
application that is identical to its previous use. The power is transferred from the motor to the axle, which
utilizes a 5/8 bore, 5/8 pitch, 12 tooth gear, using a #50 Roller Chain. The frame of the vehicle was
designed to have the same dimensions as a standard golf cart, and this resulted in the axle’s mounting
brackets lined up perfectly with the edges of the frame. The differential on the axle has a 6 in ground
clearance when paired with the wheels used on this vehicle. The aluminum body mounted to the
differential housed the main drive shaft, which is kept straight by a single 203PP bearing. The front
wheels were attached with a 6.25 inch long, 1 inch OD threaded rod on each side. The bearings used in
these wheel hubs were A14 bearings, two on each side.
Figure 5-2. Rear Axle
15
d. Suspension
i.
Front
The Kyocera shocks on the vehicle were taken from the 1986 Honda Nighthawk used by Team
Solar Cycle. Using experimental testing the shocks were found to have a spring stiffness of 540 lbs/in.
These shocks were mounted with 5/8 inch bolts onto double A-arms using a bridge of square tubing to
keep the angle of the shocks as close to vertical as possible, allowing the shocks to work most efficiently
by reducing the mechanical advantages. Below are the pictures of the front shocks. The design of the Aarms had to be revised multiple times due to the team’s unfamiliarity with A-arm suspension. The initial
designs for the shape, angle, and size of the arms were poor and resulted in bump steer and the steering
system lockage when turning.
Figure 5-3. 2 Front Shocks
Figure 5-4. Shock Position
16
ii.
Rear
The rear suspension was made from two standard Club-Car leaf springs that held the rear axle
beneath the vehicle. Below are the pictures of said rear leaf springs which were donated from Maneuver
Mobile 2015 along with the rear axle. In order to provide a flat surface for mounting the leaf springs,
there are four pieces of 1.75 inch square steel tube welded to the round frame.
Figure 5-5. Leaf Springs
Figure 5-6. Leaf Spring Position
17
e. Motor
The original design called for the motor to be attached to the frame rigidly, along with the
batteries. This design proved unfeasible as the compression of the suspension would create slop in the
motor chain which allowed the chain to jump off the sprockets. This made it necessary to mount the
motor directly to the axle at the differential. The team machined a plate of ½ in thick aluminum so that the
motor and differential could be rigidly attached to each other, which can be seen in the figure below.
When completed, the chain was still able to move laterally, so an idler sprocket was also mounted to the
mounting plate. The idler was designed so that it could be tensioned against the chain, therefore
eliminating the slop that was originally there. It was made from a third sprocket gear that was bored out
and had a bearing press fit into its center. The drive chain is ANSI #50 5/8th pitch.
Figure 5-7. Motor Mount
f. Batteries
The batteries were rigidly mounted to the frame by making a bracket to hold them in place and
held them medially while two bars held them laterally. In this way they were prevented from moving in
any direction away from the frame and were rigidly attached to it. This can be seen below in Figure 5-8.
18
Figure 5-8. Batteries Mount.
g. Accelerator
The team initially designed for a pedal system to actuate the accelerator and brake but after
completing the frame and mocking the seats it was found that the frame had not been designed as
ergonomic as originally thought. It quickly became apparent that the front seats would be somewhat
cramped and therefore rendering a pedal system difficult and uncomfortable. The team decided to
approach the vehicle from a different perspective and find a pedal-free way to operate the vehicle. This
approach led to the decision to use a double lever throttle/brake combination. The two levers would
control a throttle body taken from the SolarCycle with a circuit kill switch with one, and the brakes with
the other. This setup was chosen so that the vehicle would shut the motor off completely when the lever
was released. After some thoughtful consideration, it was determined that a modification to add a second
spring to the throttle body would allow the two levers to be combined into one. This final design was
deemed appropriate, and placed on the vehicle. When the lever is pushed forward, the potentiometer turns
and tells the motor controller to send current through the motor. The farther the lever is pushed, the more
current is allowed through. When the throttle is released, the first spring brings the lever back to the
upright position (referred to as the lever’s neutral position). The second spring is tensioned so that when
the throttle lever is in the neutral position the kill switch is engaged. This second spring is extended to
pull the lever backwards and brake the vehicle, but also brings the lever from braking back to the neutral
position. Because of the spring which brings the throttle back to neutral, it takes a constant 1.5 lbs of force
to keep the throttle engaged. If the throttle required more force to keep engaged it would be strenuous on
the driver to maintain speed. The lever can be seen below in Figure 5-9.
19
Figure 5-9. Accelerator and Brake Lever
h. Brakes
The brakes on the vehicle are drum brakes built into the axle. They are actuated by lever arms
attached to 3/16 in. braided stainless steel cable (maximum tension of 840 lbs) that can be pulled by the
throttle/brake lever. This lever, described above, allows for both the throttle and the brakes to be actuated
by a single input. Normally the throttle body would not allow the lever to be pulled backwards in order to
brake, as this motion is outside of the range of the potentiometer, so this created the need for the
installation of the second spring, allowing for more motion. In order to brake the vehicle, 10 lbs of force
on the top of the lever is needed. Given that the length of the lever is 17 inches long above the vehicle and
5 inches long below, the total force actuating the brakes was found using the Law of the Lever. This brake
force was found to be 34 lbs to each brake.
20
Figure 5-10. Accelerator and Brake Finished
i. Parking Brake
The parking brake was designed so that the brake would be held in the engaged position. This is
accomplished by having a hook that will only slip through a hole when the brake is fully engaged with 15
lbs of force acting on the lever.
j. Front and Rear Running Lights
The front lighting of the vehicle includes two halogen headlights and two taillights. This is a
result of the lights being wired up in such a way so as to connect ground and power through the DC-DC
converter. The front lights purchased were a set of two Harbor Freight Clear Lens Halogen Lights, SKU:
37349 and the rear lights were Red Rectangular Trailer Clearance Side Marker Lights with Reflectors
from etrailer.com. The front lighting can be seen in Figure 5-11 below.
21
Figure 5-11. Front Lights
k. Underbody Lighting
The client specifically requested underbody lighting for the project. This does not serve any
functional purpose, but does add to the style and image of the vehicle. The lighting purchased was a Red
HML 72W 5 Meter 300xSMD 5050 635 – 640nm Water Resistant Flexible LED Strip Light. This was
wired into a separate circuit to the other lighting so that the electrical draw of the vehicle could be
minimized by the operator keeping as few lights on as needed.
l. Electrical Overview
The way the vehicle is electrically wired it directs the current through the controller to the engine
with the current flowing in one direction or another determined by the polarity. The controller determines
whether or not the motor will run based on the signal sent to the relays. A majority of the parts that were
used for the electrical circuit were necessary for the vehicle to run, including the controller, the batteries,
the motor and the 1/0 cables to connect the batteries together. The team determined this would be the best
course of action in order to save money and time. The reason the team used a DC-DC Voltage converter
was to equally drain all four batteries for use of the headlights and taillights as opposed to draining just
one battery and ruining the circuit. See Appendix D for the full electrical schematic of the vehicle.
m. Seating
The seats were kindly donated by Grand Rapids Chair Company (GRC). The team gave GRC the
size of the seats needed and they made two custom bench seats for the vehicle. The backs and bases of the
seats are the same dimensions, 36x18in.
22
Figure 5-12. Front and Back Seats
6. Final Product
a. Pictures
These photos represent the final vehicle as it appeared on testing day, May 7, 2015.
Figure 6-1. Final Product
23
Figure 6-2. Final Product with Lighting
b. Steering Angle
The maximum steering angle for the vehicle was set to 30°. This was chosen as the maximum
angle due to the tires being unable to grip at angles steeper than this. This was confirmed during the
testing phase of the vehicle. If the steering angle was sharper than 30° the tires would slide on the thin
layer of gravel that covers Calvin’s paths and cause excessive wear on the tires. Therefore, the steering
angle was limited with hard stops, pieces of steel welded on the right and the left sides of the pitman arm
to prevent it from moving the wheels beyond 30°.
c. Actual Weight Capacity
During the tests the vehicle was loaded until the suspension bottomed out, which occurred at
1100 lbs. This is above the specified limit of 1000 lbs set by the team to account for four passengers. It is
however below that of the minimum 1500 lb. limit that the frame was designed to hold. This means that
the weight capacity of the vehicle is limited to just 1000 lbs, and that the suspension will run out of
completely depress before the frame deforms.
d. Actual Vehicle Weight
Using the Gaston Crane Scale in Calvin’s Engineering Building the vehicle was weighed,
unloaded, at 752 lbs. This is very close to the calculated weight for the project proposal which was 746.7
lbs. The calculations for this can be seen below in Figure 6-3. The team believes that the majority of this
24
discrepancy comes from small electrical parts, rounding, and the failure to account for the weight of the
frame paint in the calculations.
Figure 6-3: Initial Weight Calculations
e. Actual Speed
The speed of the vehicle was tested using the Gear Drive Plus app on Android Lollipop. This
gave the velocity of motion with an error of +/- 1 mph. The app gave a consistent reading of 15 mph with
the engine at maximum rpm. This was less than the predicted value of 20 mph based on the speed and
torque of the motor and the team believes that this is due to frictions that were unaccounted for.
f. Run Time
The team attempted to confirm the calculated the run time of 11 miles, but was interrupted due to rain and
could not be completed. The team attempted twice more and the test was interrupted by rain on both
attempts.
g. Charging Time
The charging time was estimated at 8.5 hours in the original proposal using a 12v charger wired
to the batteries in parallel. However, the final vehicle used the batteries in series, so this charger could not
be used. Instead, a SCHSE-1072 Series Charger Schumacher Electric Golf Lead Acid Battery Charger
was used, resulting in a charge time of just 4.5 hours.
25
h. Control Panel
The control panel, which can be seen below, was first designed by the team and later,
independently tested to assess the usability of the layout. The first iteration of the design had the
directional lever (on the right) orientated vertically. This made the direction images difficult to see, so the
testers were asked which orientation made the most sense between up or down. One tester remarked that
it would actually be better orientated left, as this would make “forward” be ‘up’ on the lever, and “reverse”
be ‘down’. The team deemed this orientation the best and incorporated it into the final design, which can
be seen on the vehicle’s control panel below in Figure 6-4.
Figure 6-3. Control Panel
The layout of the toggle switches was also influenced by the testers, who asked that the toggle
switches be laid out in the order of most to least used, left to right. The toggle switches were chosen for
their multiple feedback methods; audible, haptic, and visible.
i. Paint
The vehicle frame was painted in Calvin College’s Physical Plant’s paint booth using black gloss
paint. The vehicle was painted top and bottom with the floor mounted so that the vehicle would be
uniform in color. The color black was chosen because the customer requested it and was donated by the
Physical Plant.
26
Figure 6-4. Vehicle in Paint
j. Vehicle Testing
The vehicle testing was completed by having the team test the vehicle and by having two
independent testers drive the vehicle. The testing was completed in Calvin College’s Parking Lot #7, as
this lot is often empty. The first tests completed were those of basic vehicle handling
1. Top Speed Testing
This was completed by giving the vehicle space to drive so that the top speed could not
only be reached, but also maintained, to confirm that the vehicle did not slowly accelerate to
a higher speed. The value that was consistently found was 15 mph.
2. Half Speed Testing
After confirming the top speed of the vehicle, it was necessary to test the half speed
toggle switch. When active this would force the motor controller to limit the throttle output to
the motor at 50%, resulting in half speed. This resulted in 8 mph as the velocity at half speed.
Given that top speed was 15 mph +/- 1, 8 mph is accurate for top speed.
3. Coast Stop
To test the friction of the vehicle and the ability of the motor controller to use
regenerative braking, a coast stop test was also completed. The vehicle was brought to top
speed and then stopped, allowing the motor to spin freely against the natural electrical
currents and slow the vehicle. This test resulted in a stopping distance of 130 ft +/- 2 ft.
27
4. Braking Test
To test the worst case scenario the braking test was done from top speed just after a
rainstorm, leaving the pavement damp. This test resulted in a 15 mph-0 mph deceleration in
45 ft., and while this was more than the calculated value of 30 ft, it is believed that this
discrepancy was due to the dampness of the pavement.
5. Turning Radius
This test was completed to know how sharp the vehicle could actually turn based on the
maximum wheel angle of 30° and the wheelbase length of 8.5 ft. The test was completed by
turning the vehicle at low speeds 180° and dividing the distance between the starting and
stopping position by two to change radius into diameter. The final value after multiple tests
was 20 ft.
6. Acceleration Time
The time from start to top speed was tested next. The calculated time to top speed was 4
seconds for 20 mph. However, the team anticipated reaching top speed of 15 mph in less than
4 seconds. The test, ran multiple times and averaged, showed that the vehicle was able to
reach top speed in just 3.5 seconds, confirming the hypothesis originally anticipated by the
team.
7. Top Speed Turn
To ensure that the vehicle was safe at any speed this test was conducted. The vehicle was
brought to top speed and the wheels were turned their maximum of 30°. This test showed that
although the body of the vehicle does shift positions, all four tires remain in contact with the
ground, and the maintains stability, drivability, and safety.
8. Fully Loaded Running
The vehicle was also tested for ride comfort level with the 4 passenger maximum limit.
This test involved running over uneven ground in Calvin’s North Field with 4 people in the
vehicle. The test showed that the vehicle maintains a relatively smooth ride even under
maximum passenger load.
9. Blind Testing
28
This test was the most involved test completed. It was completed twice, with a different
tester each time. One tester was male, and the other was female. The testers were unaffiliated
with the project, were not STEM majors, were not allowed to speak to or see the other tester,
and were not given any instructions or information about the vehicle. The test was three-fold:
First, a tester was invited to look at and walk around the vehicle. They were asked to
describe it, explain what they liked, did not like, and what they thought of it.
Second, the tester was invited to sit inside the vehicle and describe it, explain what they
liked, did not like, and what they thought of it.
Third, they were asked to drive the vehicle. The vehicle started out completely off and it
was up to the tester to figure out the controls and how to turn the vehicle on.
This test had many intriguing results with respect to usability, intuitiveness, and customer
satisfaction. During the first part of the test the testers both used word like ‘cool’, ‘classy’,
and ‘unique’ to describe the vehicle.
During the second part of the test they both said that the vehicle was easy to get in and
out of but that the vehicle did not have enough leg room in the front or the back. Both
disapproved of how low the seating was. However, they also both described the vehicle as
safer, due to the walls that surround each seat. When asked if they considered it safer than a
golf cart, both agreed they felt safer in the Volts-Wagon, despite one tester verbalizing
dismay that there were no airbags. Both testers also agreed that the underbody lighting was a
very ‘cool’ feature and that the seating was ‘comfy’. One remarked that in bright sunshine the
reflective hood could blind the driver. Both found that the parking brake, painted black and
partially hidden beneath the seat, was difficult to find.
Finally they were both asked to drive the vehicle. One was able to work out the controls
on the dashboard and the operation of the lever in just 37 seconds. The other was flustered by
the lack of pedals for gas and brake and took 2 minutes and 21 seconds to figure out the
driving mechanism. Both found that the vehicle was easy to operate once they knew what to
do, but agreed that the steering was a little stiff. Interestingly enough, both of them intuitively
29
knew that the throttle lever must be the brake if pulled back. This was their first reaction after
realizing the lever was the throttle.
The results of this test show that the vehicle is very user friendly, not very ergonomic,
and decently intuitive. Both of the testers took longer to realize the function of the
throttle/brake lever than expected and this demonstrates that the design is not as intuitive as
the team intended. It was decided that repainting the parking brake to a brighter color, yellow,
would make it stand out among all the black painted objects around it. If the team had more
time the seating would be modified to make it more ergonomic. Namely, more legroom
would be allowed, and the seating would be raised higher.
30
7. Business Plan
a. Cost Estimate
The cost of manufacturing the vehicle is considered for large scale production and marketing. It
was assumed that total of 10 vehicles are produced per year, and all are sold. The cost for producing a
single vehicle is shown below in Error! Reference source not found..
Table 7-1. Total Manufacturing Cost per Vehicle
Description
Price [$]
Frame
150
Motor
450
Controller
350
Batteries
400
Charger
150
Wheels & Shocks
260
Steering
20
Headlights / Taillights / Underbody
70
Design
1000
Labor
2000
Total
4850
The price is far less than the price of similar gasoline golf carts in the market, which range from
$6000 to $7000. Table 7-2. Total Annual Profit shows the annual profit assuming that all 10 vehicles are
sold. The expense was calculated by multiplying the raw material cost by the number of vehicles to be
sold.
Table 7-2. Total Annual Profit
Description
Amount [$]
Selling Cost
5000
Income
50,000
Expense
18,500
Profit per Year
31,500
31
32
8. Conclusion
The vehicle is in working order and is in the process of being delivered to the client, Mr. John
Britton. All of the requirements by the client were met. The team was satisfied with the design and
construction of the vehicle and relished the opportunity to learn how to apply engineering principles to a
long-term project. The team plans to speak with the client, at intervals, to confirm his satisfaction with the
vehicle. The team was very satisfied with the frame of the vehicle and the vehicle’s ability to be modified
by later design teams. If there was more time the ergonomics of the seating would be improved and the
steering system would be changed so that it would require less effort to move.
33
9. Acknowledgements
The team would like to thank the following people.

Team SolarCycle for donating their senior design project and documentation.

Team Maneuver Mobile for donating the rear axle.

Professor Ned Nielson for his wise council and expertise.

Professor Ren Tubergen for his help in 3D modeling and Finite Element Analysis.

Professor Yoon Kim for his help with researching solar panel integration and electronics.

Professor Mark Michmerhuizen for his help in electrical diagrams and wiring.

Mr. Phil Jasperse for his knowledge and expertise in machining and so many other things.

Mr. Chuck Holwerda for his knowledge and expertise in electrical circuits and willingness to help
whenever possible.

Grand Rapids Chair Company for the donation of the vehicle's custom seating.

Families and friends for supporting with prayers and encouragements
34
10.
Team Resumes
a. Thomas Brown
35
b. Garrick Hershberger
36
c. Jee Myung Kim
37
d. Andrew White
38
11.
Appendix
a) Energy, Speed and Force Calculations
39
40
b) Motor Specifications
Figure 11-1. Motor Specs
41
c) Motor Controller Schematic
Figure 11-2. Controller Layout
42
d) Complete Electrical Schematic
Figure 11-3. Full Schematic
43
e) Frame Cut List
Volts-Wagon Frame Cut List
Pipe
#
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
Length (in)
90.75
90.75
91.25
39
8
8
23.5
18
18
18
18
18
18
18
24.75
24.75
24.75
24.75
24.75
24.75
24.75
24.75
24.75
15
15
15
15
15
15
40
68.75
68.75
71
23.75
8
8
1st End
Flat
Flat
Flat
45
45
45
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Fish
Fish
Fish
Fish
Fish
Fish
Fish
Fish
Fish
45
45
45
45
45
45
45
45
45
Flat
20
40
40
2nd End
45
45
Flat
45
25
25
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Fish
Fish
Fish
Fish
Fish
Fish
Fish
Fish
Fish
45
45
Flat
Flat
Flat
Flat
45
45
45
Flat
20
20
20
Location
Base Left
Base Right
Base Center
Base Rear
Base Front Left
Base Front Right
Base Front Center
Base Horizontals
Base Horizontals
Base Horizontals
Base Horizontals
Base Horizontals
Base Horizontals
Base Horizontals
Base Diagonals
Base Diagonals
Base Diagonals
Base Diagonals
Base Diagonals
Base Diagonals
Base Diagonals
Base Diagonals
Base Diagonals
Front Cube
Front Cube
Front Cube
Front Cube
Front Cube
Front Cube
Roof Back
Roof Left
Roof Right
Roof Center
Roof Front Center
Roof Front Left
Roof Front Right
44
37
34
30
30
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
34
45
45
45
45
17
17
17
17
17
17
23.5
8
8
17.2
17.2
39
39
39
50
50
50
50
12.75
12.75
12.75
12.75
6
6
6
6
25.75
25.75
17
17
30
Fish
Fish
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
20
20
Fish
Fish
Fish
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
30
Fish
Fish
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
20
20
80
80
Fish
Fish
Fish
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Flat
Roof Support Front
Roof Support Front
Roof Support - Mid
Roof Support - Mid
Roof Support - Rear
Roof Support - Rear
Dashboard
Dashboard
Dashboard
Dashboard
Dashboard
Dashboard
Dashboard top
Dashboard top
Dashboard top
Cube Brace
Cube Brace
Seat Back - Front
Seat Back - Rear
Rear Box - Back
Seat Vertical
Seat Vertical
Seat Vertical
Seat Vertical
Seat Horizontal
Seat Horizontal
Seat Horizontal
Seat Horizontal
Seat Corner
Seat Corner
Seat Corner
Seat Corner
Rear Seat/Box Top
Rear Seat/Box Top
Rear Box Vertical
Rear Box Vertical
45