AUBURN UNIVERSITY “EAGLE PULLERS” 2016 FINAL DESIGN REPORT

X___ __ X_______ ______ X___ _ Dr. Tim McDonald Bud Bliss Sam Dunbar Team Advisor Co-Captain Co-Captain

14

Auburn University

Table of Contents 2

Introduction ................................................................................................................3 Target Market .............................................................................................................4 Design Overview .........................................................................................................5 Engine and Drivetrain Components .............................................................................6 Transmission Design ....................................................................................................7 Frame Design ..............................................................................................................8 Suspension Design ......................................................................................................9 Steering Design ......................................................................................................... 10 Protection Systems ................................................................................................... 11 Testing and Development.......................................................................................... 12 Safety ....................................................................................................................... 13 Serviceability ............................................................................................................ 15 Ergonomics ............................................................................................................... 15 Manufacturability ..................................................................................................... 16 Cost Analysis ............................................................................................................. 17 Tractor Specifications ................................................................................................ 18 Acknowledgments and Citations ............................................................................... 19

14

Auburn University

Introduction 3

Figure 1: 2015-2016 Quarter Scale Tractor Team (from left to

right): Sam Dunbar, Kade Campbell, Tyler Smith, Eric Vogt, Jacob

Dickie, Bud Bliss, Trey Colley, Conner Henderson, and Faculty

Advisor Tim McDonald (Not pictured: Brock Daughtry)

The Eagle Pullers are a division of the Auburn University, ASABE Chapter comprised of nine members that came together through the Biosystems Engineering Department to design, test, and build a scaled version of a tractor with specific criteria in mind. Sadly due to unforeseeable circumstances, the team was inactive from 2009-2015. A few young men decided that 2016 was the year for Auburn to once again be represented in this competition. These like-minded individuals gathered a group of dedicated students to achieve this goal of building a machine capable of pulling over two times its weight. This group of nine elite minds banded together with different ideas and designs to eventually utilize principles from engineering courses to build the “Screaming Eagle ‘16” (SE-16), for the 2016 competition. The design, the first by the Eagle Pullers in six years, produced a relatively simple machine capable of getting the job done. Being the first year back, the team decided not to push for elaborate designs, but rather focused on the rejuvenation of this program within the department. With enthusiasm and vigor, the team has been dedicated to designing and building the best quarter-scale tractor Auburn can offer. This design report will present all of the details available for this year's competition tractor. It will outline each aspect of the tractor, how it was made, and the calculations and processes used in the creation of the SE-16. While looking to the future of this highly competitive event, the team hopes to pass along knowledge and skills to younger members in order to propel the Eagle Pullers into future competitions.

14

Auburn University

Target Market 4

Figure 2: Concentration of Broiler Production in Alabama, 2010

(each dot represents 1,000 Broilers) Source: NPTC

With Alabama having the 3rd highest poultry production in the

US, we decided to design a tractor to meet the needs of most

poultry farmers within the Southeastern United States. Auburn

University has had extensive collaboration with the National

Poultry Technology Center (NPTC). A NPTC committee member

suggested that we tailor our design to meet the needs of

poultry producers, specifically in the northern Alabama region.

Figure 3: Size comparison of the SE16 to a typical poultry house

door.

With the small, yet durable design along with the easy

maneuverability, the tractor is able to travel throughout the

poultry houses swiftly while also being able to complete almost

every task the farmer needs. With the low manufacturing cost,

the sale cost is brought to a more feasible range that poultry

farmers are able to afford, rather than the average compact

tractors on today’s market.

14

Auburn University

The Design 5

Figure 4: SE-16 Design Overview

14

Auburn University

Engine and Drivetrain Components 6

Engine

The Screaming Eagle 2016 (SE-16) is powered by a Briggs and

Stratton Vanguard series engine. This Vanguard engine puts

out a maximum of 31 hp at 3600 rpm and 66 ft-lbs of torque.

Past models of the Screaming Eagle have been powered by

multiple 16 hp Briggs and Stratton Vanguard engines. In the

2015-2016 design process, the Eagle Pullers decided to run a

single engine for weight reduction reasons, manufacturability,

and for simplicity of drivetrain design. The 31 hp Vanguard will

sufficiently propel SE-16 as well as any load that it must move

under 1600 lb.

Figure 5: SE-16 Drivetrain Subassembly

Drivetrain Components

The Drivetrain of the Screaming Eagle contains the necessary

components to move the tractor as quickly and efficiently as

possible. The SE-16 transmits power from the 31 hp Vanguard

motor to the drive tires through use of a Comet Duster

Continuously Variable Transmission (CVT) coupled to a drive-

shaft that leads to the Midwest Super Cub Transaxle. The

Comet Duster 94c primary clutch, attached to the motor, is

coupled to a 90d secondary clutch via a rubber v-belt. This

clutch is supported using a box that bolts on as an extension

onto the frame. There is a two-bolt flange bearing in front of

the secondary clutch and one behind it to ensure the proper

amount of support. This clutch is held in place by a short

section of drive-shaft that sits in the two flange bearings and

then connects to a universal joint that is coupled to the main

drive-shaft. The main drive-shaft then connects a second

universal joint which connects directly to the Midwest Super

Cub transaxle, the bread and butter of the drivetrain. The

transaxle combines the aspects of a manual transmission and

a solid axle to give the SE-16 an efficient and effective way to

put the power to the ground.

14

Auburn University

7

The Eagle Pullers considered many options for the transmission

for SE-16. In years past, hydraulic and gear driven

transmissions have been used. For 2016, the Eagle Pullers

wanted a transmission that allowed SE-16 to have a full

complement of gear ratios and speeds for the various tasks

that the tractor would encounter. Transmitting the power and

torque of the motor to the tires is one of the most important

aspects of agricultural machine. With that in mind, the Eagle

Pullers elected to utilize two options, a CVT and a Midwest

Super Cub transaxle. The combination of these two platforms

allows for a greater range of gear ratio combinations than one

could not achieve with most other transmissions. Within the

transaxle of SE-16, the Eagle pullers elected to use three

forward gears and one reverse gear. For the three forward

gears, gear ratios of 89:1, 50:1, and 29:1 were used for 1st, 2nd,

and 3rd gears respectively. With these ratios, speeds of 3.3,

5.6, and 9.7 MPH were obtained. To increase these speeds

without the cost and labor changing all of the gears, a single

43% overdrive gear was specified and ordered from Midwest

Super Cub. This allowed for an increase of 6.5 in the rotation of

the gears. This increase produced speeds of 5.8, 9.8, and 16.9

MPH and gear ratios of 50:1, 29:1, and 17:1 respectively, which

was better suited for the specified applications of SE-16. For

the second half of this transmission, the CVT, the Eagle Pullers

originally decided to use the primary and secondary clutches

from a salvaged Kawasaki Mule. After running into problems

manufacturing an adapter shaft to join the primary clutch to

the motor, the Eagle pullers quickly decided on an alternative.

A primary and secondary clutch was specified and purchased,

the Comet Duster CVT that more easily adapts to the keyed

shaft of the Briggs and Stratton motor. For simplicity and ease

of manufacturability, both the primary and secondary clutches

were designed to have constant diameter, keyway slotted

bores. This allowed the Eagle Pullers to directly mount the

primary clutch to the engine and in-house manufacture a shaft

for the secondary clutch. When fully opened, the CVT gives an

additional gear reduction of 3:1 and when closed, a reduction

of 1:1.

Figure 6: SE-16 Transmission Overview

With the CVT and transaxle connected in series, SE-16 has the

ability to produce a range of gear ratios within each selected

gear of the transaxle, utilizing this setup to the maximum

extent. By adapting this system to SE-16, the Eagle Pullers

gained a seamless transition of gear ratios without the need of

a typical manual clutch. Through testing, this proved to be a

more operator friendly setup while providing the necessary

speeds and torque requirements.

Transmission

14

Auburn University

8

For the construction of the frame, the Eagle pullers considered

many options, but ultimately decided to use a C-channel

designed made out of bent sheet metal. For this construction,

16 gauge sheet metal was chosen due to its strength properties

while still being light enough to not encompass a significant

amount of weight. Cold rolled sheet metal of this thickness

weighs approximately 2.5 pounds per square foot totaling just

under 20 pounds for a completed frame.

Each frame rail was cut and bent using a hydraulic shear and

an open-ended sheet metal brake. To allow for adequate

spacing between the primary clutch mounted on the motor

and the secondary clutch, upper and lower frame rails were

made. This also allowed a flat surface to mount the engine,

steering console, and gas tank without changing the design of

the main frame rails. Prior to fabrication of these frame

members, stress analyses were performed to ensure that they

would withstand the loads that they would encounter. The

assemble frame was loaded with (3) downward forces on the

front totaling 600 pounds to simulate front end weights, a

resulting force upward of 100 pounds to compensate for the

tension of the CVT, and finally (2) downward forces of 100

pounds each located two thirds back to simulate the operator.

The analysis returned results of a maximum displacement of

0.003 inches and a minimum safety factor of 5. These results

gave us the confidence that the SE-16 would be able to

withstand the loads that may be applied to the tractor by the

customers.

Figure 7: Frame Stress Analysis - Displacement and Safety Factor

Frame

14

Auburn University

9

The Eagle Pullers decided to utilize a coil-over-shock front

suspension for the Screaming Eagle. The coil-over-shock

suspension will be a much more comfortable ride than the

originally proposed solid front axle. This suspension setup

would be better for the durability course as well because the

front of the tractor will not rock side to side as it rolls through

the course. Allowing the tractor to flex with suspension will

create a more comfortable and structurally sound design.

A-Frames

The coil-over-shocks were purchased from WorldPac and the

A-frames were fabricated by the Eagle Pullers. The coil-over

shocks were rated to be capable of handling a 600 pound force

per pair and have a length of travel of 2.6 inches. A simple jig

was constructed that allowed the A-frames to be quickly and

easily welded together after being cut from 1” round ERW

tubing. They were then mounted to the frame using a bracket

constructed by the Eagle Pullers. The suspension was mounted

to the tires on ball joints using brackets the team had from

earlier Eagle Puller teams.

Figure 8: Assembled A-Frame Suspension

Figure 9: A-Frame Arms and Steering Knuckle

Suspension

14

Auburn University

10

Figure 10: Front Suspension Stress Analysis - Displacement and

Safety Factor

Steering

For steering the team elected to use a rack and pinion systems

for its simplistic, yet effective steering. A complete mechanical

system eliminated the need of complex hydraulic or electronic

systems to control the steering of the tractor. The gearbox of

the rack and pinion was mounted to bottom of the frame rails

with the tie rods extending underneath the frame to the

steering knuckles. The connection between the knuckle and

the tie rod was made using ball joints. To control the steering,

universal joints were welded to a 0.5 inch diameter ERW tubing

that extended from the gearbox to the steering wheel

mounted on top of the steering console.

To verify the design, a simulated stress analysis was performed

using Autodesk Inventor. The front suspension was loaded to

the maximum rating of the shocks. The maximum deflection

was measured to be 0.005 inches and a built in safety factor of

3.31.

Figure 11: Front Steering Assembly

Steering

14

Auburn University

11 11 11

Protection Systems

For the SE-16, Eagle Pullers decided to fabricate in-house the

wheelie bars to save on cost as well as to have a product unique

to the team. The bars are constructed out of ¼” plate and are

made to be adjustable for ground clearance concerns for the

difference terrains of the southeast. The wheelie bars will

ensure that no matter the load put behind the tractor, it won't

rear back on the operator potentially injuring them or even to

the point of a fatality.

Figure 12: Inventor drawing of Wheelie Bars on SE-16

Along with the wheelie bars, the SE-16 can be outfitted with an

adjustable/telescoping ROPS system in conjunction with the

ASABE ROPS standards. Tractors produced post 1985 are

required to have an installed Roll Over Protection System

before exiting the factory. The Eagle Pullers thought the

implementation of this system was a vital part of the design, as

5 fatalities occur yearly for every 100,000 tractors in operation

(Iowa St. Extension article).

The design of this system fluidly incorporates the bar around

the seating area, and bolts straight into the frame. By directly

bolting the system into the frame of the tractor, the SE-16’s

weight will be amply supported in the event of an accidental

rollover.

Figure 13: Cut-away of SE-16, exposing the ROPS bolted to frame

(a) (b) Figure 14: ROPS system stress analysis with both vertical (a) and

roll over (b) loads

Stress analysis results yielded a maximum displacement of 0.04

inches on a vertical load, and 0.4 inches of distance on the rolling

over load. This system will provide substantial strength to support

the tractor and operator during a vehicle overturn.

Protection Systems

14

Auburn University

12

Dynamometer

In order to maximize performance, dynamometer tests will be

run before the team reaches competition. Our drive train

components were fabricated in-house, further enforcing the

need for extensive testing. Regrettably, both the primary and

secondary clutch were received late and the Eagle Pullers did

not have ample time for testing. Within the next month,

however, the team will use the in-house dynamometer to test

the output power from the shaft of the motor. Additionally, the

drivetrain will be assembled for testing on the same

dynamometer.

Figure 15: Dynamometer used for testing by 2015 senior design

group

FEA Failure and effects analysis were run for virtually every part, subassembly, and the overall tractor. This was a very valuable piece of the design process because it allowed us to see the direct results of forces on each component without having to spend time and money on multiple fabrications of the same

piece. AutoCAD Inventor® program was the processing

software used to generate these results. These analyses many times led to a redesign of the piece in testing, and in many ways shaped the SE-16 into the final product that will be at competition.

Figure 16: Primary Clutch Adapter Shaft for Kawasaki Mule CVT (not used in SE-16)

Testing and Development

14

Auburn University

Safety

Operator safety was a top priority for the Eagle Puller’s SE-16,

and is a vital part of the final design. If safety were not on the

forefront of the design process, all other design

considerations would be in vain. All components were

designed with the worst case scenario in mind, considering

that operators of the SE-16 may not have prior equipment

operation experience, This could lead to the use of this

tractor for tasks outside of its original intention in the poultry

industry. Therefore, the SE-16 has intuitive controls and

multiple safety mechanisms which may have increased the

cost of the model, however no cost is too large to overcome

the cost of losing a life.

Figure 17: Safety Placard and Fire Extinguisher utilized on SE-16

Safety signage, easily visible from all points of operation, and

produced in bilingual context are located in this, this, and that,

locations. Any area incurring a high safety priority has multiple,

brightly colored signage (complying with ASABE standard

S441.3). Two different pressure switches are incorporated into

the final design: the first is located under the operator’s seat

to prevent the SE-16 from continuing to run, possibly crushing

the operator in the event he or she is involuntarily dismounted

from the vehicle. The second pressure switch, will be located

on the brake pedal, requiring the operator to engage the brake

before starting the engine.

Figure 18: Brake petal pressure switch

(Source: http://giterdunn.com/id36.html)

A kill switch attached to an implement, stops the engine when

the load sled, or other implement, becomes detached from the

hitch of the SE-16; thus, preventing the sled from being left

behind. An optimized line-of-sight design, paired with high

luminosity head and tail lights give the operator of the SE-16

the most opportunity to see and divert from potential safety

hazards. In case of an emergency, a fire extinguisher is

accessible and located at the back of the seat. The fuel tank,

featuring a fuel cut-off valve, and battery are located a

substantial distance away from the operator.

13 Safety Safety

14

Auburn University

14

ROPS System

The operator seat features armrests and a seat belt to prevent

involuntary dismount from the vehicle. When the operator has

properly fastened his or her seat belt, they will be considered

in the safety zone of protection from rollover. All models of the

SE-16 have a provided ROPS protection system, the Eagle

Pullers deemed this a necessity due to possible steep gradients

around the outskirts of poultry facilities. This system is built

around the seat for optimum ergonomics, but still has

substantial strength to protect the operator in the event of an

accident. Due to low profile requirements in poultry facilities,

the ROPS system may be folded down for use inside of the

house; however, upon exit from the house the operator should

immediately raise the ROPS system again.

Figure 19: Zone of Safety for operator if seat belt and ROPS

utilized

Shielding is incorporated into the design of all moving pieces,

16 gauge sheet metal comprises the majority of the shielding

components and easily withstands the force of an operator’s

weight. Shielding is incorporated wherever any part with

rotational motion is open to possible contact with an operator.

All drivetrain components, the battery components, transaxle

gears, and steering column are encased in shielding as a

preventative safety measure. Grip tape was applied to high

contact areas of the shielding components to prevent operator

slips and falls. Wheelie bars also prevent the front end of the

tractor from raising too far off of the ground during the tractor

pull. Additionally, safety loops prevent, in case of failure, the

drive shaft components from striking the frame and other parts

of the tractor and also the operator.

Figure 20: Drive-shaft safety loop

Safety

14

Auburn University

Serviceability/Ergonomics

Ergonomics

15

Serviceability

The ability to quickly maneuver around, and replace engine

components can be an unwanted, but necessary task for

individuals in the middle of competition. To streamline the

servicing process, Eagle pullers manipulated the clutch system

in order to quickly access the motor. International

Quarterscale regulations require the engine output shaft to be

exposed within two minutes of work, the SE-16’s sleek design

easily permits this action with the loosening of one bolt.

The oil filter on the Briggs and Stratton Vanguard 31 hp engine

is easily accessed on the left side of the tractor. In addition, the

drain plug is located right below the filter. The transaxle hitch

plate can be easily removed in order to drain the transaxle fill

pan of oil. All bolt locations were designed to have ample

clearance for fastening, and unfastening.

Figure 21: Quick access to motor output shaft single bolt removal

Ergonomics

The SE-16 is optimized for poultry farmers, and other

operators, regardless of size. Ergonomics crucially affect the

success of a design; if an operator experiences any type of

discomfort during vehicle operation, product and brand

reputation will dwindle. Entrance and exits from the vehicle

are easily completed thanks to substantially supported tractor

floor. Grip tape is incorporated into the points of access and on

all handle grips. A comfortable seat complete with armrest

provides comfort, even under the roughest riding conditions.

Noise levels were significantly under the ASABE required

exhaust volume of 91 decibels, giving a user-friendly ride.

Figure 22: Coil-over shocks for front suspension

An extended shifting lever enhances the operation process by

allowing the operator access to all ranges smoothly.

Additionally, brake and clutch pedals are extended and

optimized to best fit the everyday rider. A hand set throttle is

conveniently position at the right-hand side of the operator’s

seat. The seat selected for the SE-16 is a fold-down seat from

Agrosupply®, which provides optimal lumbar support and

riding comfort.

14

Auburn University

Manufacturability

Manufacturability

SE-16 provides a final product, at low cost, that can be readily

produced by a standard manufacturing plant. In order to meet

the elusive goal of 3000 units per year, the Eagle Pullers

specifically composed multiple subassemblies of our tractor to

have easily manufacturable finished product. Each specific

subassembly is optimized for manufacturing speed, and

requires all intricate parts to be assembled before the final

assemblies. A streamlined final assembly line consisting of

bolting together these subassemblies in order to reduce labor

costs and increase profit for the Eagle Pullers.

One main initiative toward our manufacturability goal was the

use of multiple easily cut and bent sheet metal components, in

order to lower production costs. Both the frame and shielding

components were constructed from 16 gauge sheet metal for

a both lightweight and easily manufacturable design. All sheet

metal pieces produced have flat pattern plans readily available

for the manufacturer. The drive shaft, which connects the

secondary clutch to the transaxle, is comprised of 1” DOM

tubing with ⅛” thick walls with universal joint connectors at

each end. This tubular design allows the SE-16 to save weight

and money, and will provide ample rigidity for the rpm

requirement.

16

Figure 23: Manufacturing Flow Chart

14

Auburn University

Cost Analysis

Our total tractor building cost came to be

$7,527.72. This cost is over our initial

budget, however due to fundraising efforts

and minor donations, the team was able to

make up the difference. The Eagle Pullers

set the selling price for the Screaming

Eagle-16 at $13,500.00. This price is $7,169

less than a comparable John Deere 3038E,

a tractor that is often used in poultry

houses. A price of $13,500 would give the

Eagle Pullers a profit of $5,972.28 per

tractor and if 3000 units were produced

per year, the total net profit would be

$17,916,840.00 per year.

The Eagle Pullers would also like to offer an

upgraded option with a rear hydraulic kit. A

rear hydraulic kit would be used for a

variety of different implements used in

every day farming jobs, but especially in

poultry production. Adding a hydraulic

pump would greatly increase the

productivity potential of the SE-16. After

adding the required hydraulic hoses and

fittings to complete the setup, the total

cost for the rear hydraulic set up would be

$318.04, bringing the total cost of the

tractor to $7,845.76. The eagle pullers

suggest the retail price for the upgraded

tractor be set at an even $15,000.00. This

would give the team a profit margin of

47.69%.

17

Production Cost MSRP Units/year Total Income Profit/tractor Yearly Profit Profit Margin

Base Model 7,527.72$ 13,500.00$ 3000 40,500,000.00$ 5,972.28$ 17,916,840.00$ 44.24%

Market Results per Year

Section Category Purchased Fabricated Cost/Unit Quantity Cost

1 Engine System $1,468.21 $37.41 $1,505.62 1 $1,505.62

2 Transmission / Transaxle $1,634.25 $0.00 $1,634.25 1 $1,634.25

3 Drivetrain $346.06 $20.83 $366.90 1 $366.90

4 Tires & Wheels $270.19 $0.00 $270.19 1 $270.19

5 Steering and Suspension*** $391.75 $0.00 $391.75 1 $391.75

6 Frame $0.00 $203.99 $203.99 1 $203.99

7 Body $167.95 $101.78 $269.73 1 $168.96

8 Brake System*** $78.20 $64.81 $143.01 1 $143.01

9 Electrical System $34.46 $66.60 $101.06 1 $101.06

10 Fasteners*** $13.30 $0.00 $13.30 1 $13.30

11 Safety Equipment $201.40 $74.43 $275.84 1 $275.84

12 Trim*** $22.85 $180.00 $202.85 1 $202.85

13 Labor N/A N/A $45.00 50 $2,250.00

Total $4,628.63 $749.86 $7,527.72

$7,527.72

Auburn University Eagle Pullers-2016

Cost Reporting Sheet

Total Vehicle Cost

14

Auburn University

Tractor Specifications

18

14

Auburn University

Acknowledgements and Citations

Acknowledgements

The Eagle Pullers would like to acknowledge Dr. Tim McDonald,

Doc Flynn, Dr. Ken Thomas, Auburn Department of Biosystems

Engineering, and ASABE for their assistance throughout the

design and fundraising process for the SE-16. We would also

like to thank David Williams at Talladega IMS, R&D Fabrication

and Sabel Steel for assisting us in our frame and drivetrain

construction. The Eagle Pullers would also like to thank Uncle

Maddio’s Pizza and Auld and White Construction for their

generous donations that helps us to buy the necessary parts to

construct our tractor.

Citations

Schwab, Charles and Hanna, Mark. “Using Tractors with ROPS to

Save Lives – Safe Farm.” Iowa State Extension and Outreach. Iowa

State University, May 2013.

United States Department of Agriculture, National Agricultural

Statistics Service. Alabama Agricultural Statistics. Montgomery,

AL: Alabama Field Office. 2011.

http://www.nass.usda.gov/Statistics_by_State/Alabama/Public

ations/Annual_Statistical_Bulletin/2011/2011AlabamaAgricultu

reStatistics.pdf

17

19