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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.

i

Table of Contents

Table of Contents ........................................................................................................................................... i

Table of Figures ........................................................................................................................................... iv

Table of Tables ............................................................................................................................................. v

1. Introduction ........................................................................................................................................... 1

a. Team Members ................................................................................................................................. 1

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

2. Project Initiation .................................................................................................................................... 5

a. Research ............................................................................................................................................ 5

b. Computer Aided Design (CAD) ....................................................................................................... 5

i. Initial ............................................................................................................................................. 5

ii. Final Design .................................................................................................................................. 6

iii. Finite Element Analysis (FEA) ................................................................................................. 7

3. Components .......................................................................................................................................... 8

a. Component Selection Method ........................................................................................................... 8

b. Donations .......................................................................................................................................... 8

i. Team SolarCycle ........................................................................................................................... 8

ii. Team Maneuver Mobile (2002/2015) ........................................................................................... 8

c. Purchased Items ................................................................................................................................ 9

4. Calculations ......................................................................................................................................... 10

a. Approach ......................................................................................................................................... 10

i. Motor........................................................................................................................................... 11

ii. Batteries ...................................................................................................................................... 12

ii

5. Design Construction ............................................................................................................................ 13

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

6. Final Product ....................................................................................................................................... 23

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

7. Business Plan ...................................................................................................................................... 31

a. Cost Estimate .................................................................................................................................. 31

8. Conclusion .......................................................................................................................................... 33

9. Acknowledgements ............................................................................................................................. 34

10. Team Resumes .................................................................................................................................... 35

a. Thomas Brown ................................................................................................................................ 35

iii

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

iv

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

v

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

1

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

2

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.

3

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.

4

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.

5

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

.

6

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

7

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.

8

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.

9

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

10

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.

11

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 was set to be 0.8, and the rolling drag coefficient was set to be

0.04, and the density of air was set to be 0.0765 lb/ft3. is the friction force between the vehicle

and the ground, and 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

12

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.

13

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

14

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)

15

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

16

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 A-

arms 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

17

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

18

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.

19

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.

20

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.

21

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.

22

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.

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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

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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

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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.

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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.

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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.

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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

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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

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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.

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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

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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.

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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

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10. Team Resumes

a. Thomas Brown

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b. Garrick Hershberger

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c. Jee Myung Kim

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d. Andrew White

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11. Appendix

a) Energy, Speed and Force Calculations

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b) Motor Specifications

Figure 11-1. Motor Specs

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c) Motor Controller Schematic

Figure 11-2. Controller Layout

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d) Complete Electrical Schematic

Figure 11-3. Full Schematic

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e) Frame Cut List

Volts-Wagon Frame Cut List

Pipe # Length (in) 1st End 2nd End Location

1 90.75 Flat 45 Base Left

2 90.75 Flat 45 Base Right

3 91.25 Flat Flat Base Center

4 39 45 45 Base Rear

5 8 45 25 Base Front Left

6 8 45 25 Base Front Right

7 23.5 Flat Flat Base Front Center

8 18 Flat Flat Base Horizontals







15 24.75 Fish Fish Base Diagonals









24 15 45 45 Front Cube

25 15 45 45 Front Cube

26 15 45 Flat Front Cube




30 40 45 45 Roof Back

31 68.75 45 45 Roof Left

32 68.75 45 45 Roof Right

33 71 Flat Flat Roof Center

34 23.75 20 20 Roof Front Center

35 8 40 20 Roof Front Left

36 8 40 20 Roof Front Right

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37 34 30 30 Roof Support -

Front

38 34 30 30 Roof Support -

Front

39 45 Fish Fish Roof Support - Mid

40 45 Fish Fish Roof Support - Mid

41 45 Flat Flat Roof Support - Rear

42 45 Flat Flat Roof Support - Rear

43 17 Flat Flat Dashboard






49 23.5 Flat Flat Dashboard top

50 8 Flat 20 Dashboard top

51 8 Flat 20 Dashboard top

52 17.2 20 80 Cube Brace

53 17.2 20 80 Cube Brace

54 39 Fish Fish Seat Back - Front

55 39 Fish Fish Seat Back - Rear

56 39 Fish Fish Rear Box - Back

57 50 Flat Flat Seat Vertical




61 12.75 Flat Flat Seat Horizontal




65 6 Flat Flat Seat Corner




69 25.75 Flat Flat Rear Seat/Box Top

70 25.75 Flat Flat Rear Seat/Box Top

71 17 Flat Flat Rear Box Vertical

72 17 Flat Flat Rear Box Vertical

final report 2014-2015 team 4 calvin college engr340 ... · calvin college engr340 senior design...

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