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TINY HOUSE TRAILER DYNAMICS
Analysis of Trailer Sway Phenomenon and Design Improvement
A Thesis
Presented to the faculty of the Department of Mechanical Engineering
California State University, Sacramento
Submitted in partial satisfaction of
the requirements for the degree of
MASTER OF SCIENCE
in
Mechanical Engineering
by
Aurelien Andre Biwole Meke
SPRING
2020
ii
© 2020
Aurelien Andre Biwole Meke
ALL RIGHTS RESERVED
iii
TINY HOUSE TRAILER DYNAMICS
Analysis of Trailer Sway Phenomenon and Design Improvement
A Thesis
by
Aurelien Andre Biwole Meke
Approved by:
__________________________, Committee Chair
Dr. Rustin Vogt
__________________________, Second Reader
Dr. Troy Topping
___________________________
Date
iv
Student: Aurelien Andre Biwole Meke
I certify that this student has met the requirements for format contained in the
University format manual, and this thesis is suitable for electronic submission to the library
and credit is to be awarded for the thesis.
_____________________, Graduate Coordinator ___________________
Dr. Troy Topping Date
Department of Mechanical Engineering
v
Abstract
of
TINY HOUSE TRAILER DYNAMICS
Analysis of Trailer Sway Phenomenon and Design Improvement
by
Aurelien Andre Biwole Meke
Trailer Sway is a phenomenon observed when a towing vehicle reaches a certain
speed, due to the different forces acting on the trailer and resulting in a side to side motion
of the trailer. There is a very high possibility to lose control of the trailer, making this a
very dangerous situation. The problem is to prevent such an issue by figuring out the exact
causes behind it and ways to prevent it.
In 2012, the Department of Mechanical Engineering at Sac State collaborated with
Sacramento Municipal Utilities District (SMUD) to develop a self-sustainable tiny house,
which was going to take part in multiple competitions. The dimensions of the house allow
it to be trailed by a small duty chassis, such as a Ford F250. During multiple trips, the house
was subject to the sway phenomenon as the towing vehicle was reaching speeds over 45
miles per hour. This makes it the perfect candidate for our analysis, with the goal to
understand the reasons behind the phenomenon and improve the design.
vi
The first part of this thesis is demonstrating how factors such as center of gravity
location of the trailer can increase or mitigate the impact of sway.
Moreover, we will focus on determining stress points with the trailer assembly to
understand the phenomenon observed. A 3D model of the hitch was designed in
SolidWorks, and an FEA analysis was used to determine stress points. This helped us
determine where to locate strain gauges for data collection during our experiment. Hand
calculations were also utilized in that regard. Finally, the data was analyzed to determine
factors behind sway phenomenon. The next step would be to observe the trailer behavior
while on the road at speeds of 45 mph or over.
Finally, we will discuss opportunities to improve the hitch system design in that
regard. The analysis of data collected will help us provide immediate solutions and
theoretical basis for future design.
_____________________, Committee Chair
Dr. Rustin Vogt
_____________________________
Date
vii
ACKNOWLEDGEMENTS
I would like to thank Dr. Rustin Vogt for allowing the use of the Tiny House for
the sake of this research. His valuable knowledge was very helpful throughout the entirety
of it. I would also like to thank Dr. Troy Topping whose guidance was valuable throughout
the entirety of my Graduate program. He aided in multiple areas from class choice to thesis
writing.
I would also like to thank my parents who have always provided their full support
and their advice to the best of their abilities.
Finally, I would like to thank my fiancée who was a backbone to this project,
supporting me through it all and pushing me to stay motivated.
viii
Table of Contents
Acknowledgements ..................................................................................................... vii
List of Tables .................................................................................................................x
List of Figures .............................................................................................................. xi
Chapter
1. INTRODUCTION .............................................................................................1
2. BACKGROUND INFORMATION AND LITERATURE REVIEW ..............3
2.1. Motivation ..........................................................................................3
2.2. Sway Phenomenon .............................................................................3
2.3. Sway Control Methods ......................................................................4
2.3.1. Passive Methods.................................................................................4
2.3.2. Active Methods ..................................................................................5
2.4. Tiny House Characteristics ................................................................6
3. PRE-TESTING ANALYSIS OF THE HOUSE AND HITCH .........................9
3.1. Tiny House Center of Mass ...............................................................9
3.2. Trailer Hitch Specifications .............................................................12
3.3. SolidWorks Modeling of the Trailer Hitch ......................................13
3.4. Finite Elements Analysis on the Trailer Hitch .................................17
4. TESTING PROCEDURE ................................................................................20
5. DATA ANALYSIS ..........................................................................................22
5.1. Tongue Weight Calculation .............................................................22
ix
6. FINDINGS AND INTERPRETATIONS ........................................................23
7. DESIGN IMPROVEMENT: ACTIVE HITCH...............................................24
7.1. Concept Overview ...........................................................................24
7.2. Dynamic Modeling ..........................................................................25
7.3. Results [2] ........................................................................................29
8. DISCUSSION AND CONCLUSION .............................................................31
8.1. Future Work .....................................................................................31
Appendix A – Solidworks and Working Model 2D Features [13] ..............................33
Appendix B - Working Model 2D Features [14] .........................................................34
References ....................................................................................................................35
x
LIST OF TABLES
Tables Page
1. Forklift Test Results ……………………………………………………………22
xi
LIST OF FIGURES
Figures Page
1. Representation of Side Forces Creating Sway ............................................................ 3
2. 3D Model of Anti-Sway Bars [4]................................................................................ 4
3. AntiSway Hitch Layout .............................................................................................. 5
4. Tiny House Front and Side View................................................................................ 7
5. Inside Layout of Tiny House ..................................................................................... 7
6. Tiny House Working Model 2D ................................................................................ 9
7. Tiny House Working Model 2D in Free Motion ..................................................... 10
8. Tiny House 3D Free Body Diagram ........................................................................ 10
9. Center of Gravity Calculation via Forklift Test ........................................................ 11
10. 2" BulletProof Hitch Specifications ......................................................................... 12
11. Extrude Boss 1 for Hitch Modeling .......................................................................... 13
12. Extrude Boss 2 for Hitch Modeling .......................................................................... 13
13. Extrude Boss 3 for Gusset......................................................................................... 14
14. Extruded Cuts for Mounting Holes ........................................................................... 14
15. Extruded Boss 1 for Insert Design ............................................................................ 15
16. Extruded Cut 1 for Insert Design .............................................................................. 15
17. Hitch Ball Design ...................................................................................................... 15
18. Insert Final Design .................................................................................................... 16
19. Chassis Receiver of Towing Vehicle ....................................................................... 16
xii
20. Hitch Assembly for FEA .......................................................................................... 16
21. Assembly Fixed Geometry ...................................................................................... 17
22. External Loads Acting on Hitch .............................................................................. 18
23. Mesh Setup............................................................................................................... 18
24. Stress Chart ............................................................................................................... 19
25. Working Model 2D of Towing Vehicle and Tiny House ......................................... 20
26. Active Hitch Layout .................................................................................................. 24
27. Class III Hitch; Used on a Chevrolet Equinox SUV ................................................. 25
28. Actuator Assembly.................................................................................................... 25
29. Hitch Assembly Mounted on Towing Vehicle ......................................................... 26
30. Boundary Conditions on Finite Element of Linkage Arm ....................................... 26
31. FEA Stress Chart....................................................................................................... 27
32. 3D Assembly of Active Hitch ................................................................................... 27
33. Hitch Assembly mounted to Towing Vehicle ........................................................... 28
34. Test Trailer ................................................................................................................ 28
35. 2011 Chevrolet Equinox with Testing Sensors ......................................................... 29
36. System Response to Steep Steering Input - Active vs Standard Hitch .................... 29
37. Resonance created for a sinusoidal driver input of ± 1°. ......................................... 30
1
1. INTRODUCTION
In 2012, the Department of Mechanical Engineering at Sacramento State
collaborated with Sacramento Municipal Utilities District (SMUD) to develop a self-
sustainable tiny house, which was going to participate in competitions such as the Solar
Decathlon in 2015, or the Living Building Challenge. Once built and operational, the house
had to be transported in different locations, including out of state to participate in the
competitions mentioned above. However, during those different trips, unusual behavior
was observed as far as the trailer’s motion. The most noticeable and concerning being
trailer sway. Different reasons such as center of gravity location can be behind such
behavior. Determining a way to prevent such unpredictable behavior is crucial for safety
and reliability reasons. The purpose of this research is to investigate such dynamic
inefficiencies, which mainly occurred at towing speeds above 45 miles per hour. This
project will consist of analyzing the design of the towing assembly, which includes the
hitch and trailer. The first step will be to analyze the hitch assembly via Finite Elements to
determine high stress points. The testing portion, using a sensor device to help us gather
data such as trailer motion and wheel displacement. From the data collected, proceeding to
some calculations and comparing the results to our assumptions will be the next step.
Due to recent extended confinement measures in relation with the Coronavirus,
field tests were not performed. Therefore, theoretical analysis was emphasized for the
purpose of this report. Existing documentation was used to predict the behavior of the
house trailer and make assumptions used for design improvement suggestions, as well as
2
laying out following steps for future work. The design improvement chapter will focus on
a less common method for sway control: the use of “Active Hitch”.
3
2. BACKGROUND INFORMATION AND LITERATURE REVIEW
In this chapter, we will present all relevant information regarding this project. This
entitles the motivation and impact of this research, discussing existing knowledge on sway
phenomenon, as well as presenting analysis previously done on the house.
2.1. Motivation
Sway is a phenomenon known to happen often while towing a trailer. Having a decent
size trailer such as the tiny house is a great opportunity to test, evaluate and predict different
behaviors the towing assembly can display, and therefore come up with solutions to
mitigate this phenomenon. There is an opportunity for a safety win and more important a
reliability win in that regard. According to the Federal Motor Carrier Safety Administration
(FMCSA), a good portion of highway traffic accidents are related to trailers [1]. The results
of our research will help raise awareness on the impact of weight distribution at a bigger
scale, with immediate reduction of traffic accidents associated with towing vehicles.
2.2. Sway Phenomenon
Sway occurs when side forces operating on the trailer cause it to deviate from traffic
direction and move side to side behind the towing vehicle.
Figure 1: Representation of Side Forces Creating Sway
4
These transient oscillations create dynamic forces transmitted to the towing vehicle,
resulting in decreased handling ability from the driver. Therefore, handling characteristics
of the towing vehicle cannot be used to predict or avoid it. These forces also affect the
heading angle of the trailer.
In addition to the side forces, the location of the towing point relative to the center of
gravity of the trailer plays a role in the frequency of oscillations. Finally, there is a
correlation between tongue weight and trailer stability. The ideal tongue weight is about
“6-8% of trailer weight” [2].
2.3. Sway Control Methods
Existing sway mitigation methods can be classified in two categories: Active and
Passive methods.
2.3.1. Passive Methods
The most common passive method is the use of anti-sway bars. The earliest models
consisted of friction bars attached to the trailer’s frame and the towing vehicle. This helps
by creating more resistance that the trailer would have to “overcome in order to sway”.
They also help with turning and passing, as they “give the trailer more maneuverability”
[3].
Figure 2: 3D Model of Anti-Sway Bars [4]
5
More recently, it has become more frequent to use anti-sway hitches, which are based
on the same principle of added resistance. The system includes anti-sway bars being
attached directly to the hitch and to the far most rear axle of the trailer. This helps stabilize
the trailer by “transferring the trailer’s weight to the rear of the trailer and its rear axle” [3].
Below is a representation of such a system:
Figure 3: Anti-Sway Hitch Layout
Item 1 on the representation above is the insert which gets attached to the towing
vehicle; item 2 is the hitch ball. Item 5 represents a set rotating links which facilitate the
movement of the anti-sway bars. Item 4 is a set of frame brackets which connect to the
trailer’s rear axle. Item 3 are the anti-sway bars. They are equipped with a spring system
which facilitates weight distribution. They also add resistance to the articulation of the
trailer and therefore reduce its motion due to side loads caused by the wind, or to the road
conditions. [5]
2.3.2. Active Methods
As far as active methods, a noticeable one is Direct Yaw Control (DYC). Its basic
principle is applying a reaction force, usually a braking force or a tractive force depending
on the yaw instability detected. This provides immediate stabilization on the vehicle-trailer
6
assembly [6]. DYC Systems consist of sensors monitoring inertial changes in the trailer’s
behavior and based on this data send an independent signal, a braking command to the
trailer brakes, providing the stability expected. DYC “has been extremely popular in many
vehicle systems due to its ability to generate large external moments, and its ability to function
outside the typical working region of the tires” [2]. According to a research on electric
drivetrains and friction brakes, “continuous direct yaw moment control allows significant
“on-demand” changes of the vehicle response in cornering conditions and to enhance active
vehicle safety during extreme driving maneuvers.” [6]
2.4. Tiny House Characteristics
In their paper labelled “The Effect of Longitudinal Center of Gravity Position on the
Sway Stability of a Small Cargo Trailer”, Michael Gilbert, Daniel Godrick and Richard
Klein explain the “effect of front to rear load position on the stability of a trailer by
measuring its dynamic response to a variety of steer inputs at several different highway
speeds.” [7] They highlight the importance of the center of mass location and weight
distribution. We will need to determine the location of the center of mass of the tiny house
to determine to what extent it influences its behavior.
The tiny house is a 184 square feet [8] tri-axle trailer, see picture below:
7
Figure 4: Tiny House Front and Side View
Looking at the figure above, we can see the axles are not located in the axle of
symmetry of the house. Before making any calculation, we can assume its center of gravity
is not based on its geometry. The inside layout of the house also plays a role in the
asymmetry of its center of gravity. In fact, several irregular loads part of the house structure
can explain this. Items such as the plumbing system, the bathtub and other bathroom items
fall in that category, per the layout below:
Figure 5: Inside Layout of Tiny House
8
Taking these elements in consideration, we can estimate the location of the longitudinal
center of gravity as being to the right of its geometric center of gravity.
9
3. PRE-TESTING ANALYSIS OF THE HOUSE AND HITCH
In this chapter, we will proceed to all calculations and analysis relevant to our testing
procedure.
3.1. Tiny House Center of Mass
Using software Working Model 2D, dynamic modelling of the house was made, as well
as assumptions, on the center of gravity location to evaluate weight distribution.
Figure 6: Tiny House Working Model 2D
With this location of the center of mass, free motion results in weight shift towards the
front with reactions as follow:
10
Figure 7: Tiny House Working Model 2D in Free Motion
The Free Body Diagram below shows a 3D visual of the house with the assumption of
its center of mass forward of the axles, as well as the different forces acting on the trailer:
Figure 8: Tiny House 3D Free Body Diagram
11
The main forces acting on the house are the tension force from the hitch, the drag
force, gravitational force, the normal reaction force on the ground and the road friction. As
mentioned above, we assume its center of gravity might be more towards the front.
This assumption is verified by weight analysis performed on the house. A forklift
test was performed to determine its center of gravity:
Figure 9: Center of Gravity Calculation via Forklift Test [9]
Assuming equilibrium at a zero-lift angle, we can write an equation summing
moments around reference point G (aligned with center of gravity) equal to 0, see below:
Σ𝑀@𝐺 = 0 → 𝑵𝟑𝑳𝟑 + 𝑵𝟐𝑳𝟐 + 𝑵𝟏𝑳𝟏 − 𝑭𝑻𝑾𝑳𝟒 = 𝟎
For a lift angle different than zero, the equation becomes:
𝑵𝟑𝑳𝟑𝒄𝒐𝒔𝜽 + 𝑵𝟐𝑳𝟐𝒄𝒐𝒔𝜽 + 𝑵𝟏𝑳𝟏𝒄𝒐𝒔𝜽 − 𝑭𝑻𝑾𝑳𝟒𝒄𝒐𝒔𝜽 = 𝟎
We will present these results in the following sections.
The next step would be to measure the reaction forces on each axle, which will allow us to
make calculations and determine the longitudinal center of gravity location.
12
3.2. Trailer Hitch Specifications
The tiny house is trailed using a Class IV [10] BulletProof hitch. It includes a 2” solid
steel hitch shank with a full-length gusset, and an insert consisting of a solid steel platform
on which 2 hitch balls are welded, enabling maximum strength and stability. The hitch has
a 3000lbs tongue weight capacity and a 22,000lb maximum towing capacity with the
specifications below:
Figure 10: 2" BulletProof Hitch Specifications [11]
The Bulletproof hitches are designed to exceed the SAE-J684 testing requirements [12].
The 2” Ball is rated to 12,000 lbs and the 25/16” Ball is rated to 22,000 lbs. The house
weighing approximately 12,000 lbs, this hitch is appropriate for towing.
13
3.3. SolidWorks Modeling of the Trailer Hitch
Before starting the sensor test, we need to determine where to mount the strain gauges.
We performed a Finite Elements Analysis of the hitch assembly to determine areas of high
stress. A 3D model of the hitch was generated in SolidWorks, using the following steps:
• The square tube portion of the hitch shank was modelled using a boss extrude using
the manufacturer’s specification
Figure 11: Extrude Boss 1 for Hitch Modeling
• Using a reference plane perpendicular to the hitch shank, we extruded the U-
shaped channel of the hitch:
Figure 12: Extrude Boss 2 for Hitch Modeling
14
• The gusset was inserted via another extruded boss feature with the sketch below:
Figure 13: Extrude Boss 3 for Gusset
• Finally, insert holes were modeled with an extruded cut and a hole wizard for the
square tube portion:
Figure 14: Extruded Cuts for Mounting Holes
The design of the 2-ball insert was as follow:
• An extrude boss/base in H-shape for the base part as follow:
15
Figure 15: Extruded Boss 1 for Insert Design
• A couple of extruded cuts to define the shape of the insert:
Figure 16: Extruded Cut 1 for Insert Design
• A revolved boss base in the midplane for the 2-ball:
Figure 17: Hitch Ball Design
16
The final layout for the insert is as follow:
Figure 18: Insert Final Design
Using similar extrude boss/base and cut features, a 2” receiver tube was modelled
representing the towing attachment on the truck to be used for the experiment:
Figure 19: Chassis Receiver of Towing Vehicle
We finally created an assembly mating all three parts, see below:
Figure 20: Hitch Assembly for FEA
17
3.4. Finite Elements Analysis on the Trailer Hitch
In order to determine appropriate location for our strain gauges, a stress analysis of
the hitch assembly is needed. The points of high stress concentration are expected to be
around the pinpoints on the U-shaped channel. To proceed with the simulation feature in
SolidWorks, the square tube portion of the hitch was set as fixed geometry:
Figure 21: Assembly Fixed Geometry
Finally, we applied two loads, one vertical worth the tongue weight and the other
horizontal worth the trailer weight, see below:
18
Figure 22: External Loads Acting on Hitch
A mesh was created with the parameters below:
Figure 23: Mesh Setup
The simulation is performed and the results in the chart below:
19
Figure 24: Stress Chart
As expected, the area of high stress concentration is around the pinpoints of the U-
shaped channel and the gusset. This area will be indicated to locate our strain gauges for
the testing procedure.
20
4. TESTING PROCEDURE
Trailer sway can be determined by “measuring the trailer articulation response during
repeated, pulse steer tests” [7]. The tiny house will be attached to a light duty truck using
the 2” hitch presented previously. The Working Model 2D below gives us an idea of the
setup, with the speed of 792 in/sec equivalent to 45mph, which is a speed at which sway
phenomenon is likely to start happening:
Figure 25: Working Model 2D of Towing Vehicle and Tiny House
It will be important to collect observational data such as frequency of the trailer sway,
or the motion of the three-axle suspension. Cameras will be used and located near each of
these crucial points. Based on the results from the previous analysis, we can narrow down
location points for our strain gauges as follow:
• On each axle of the trailer, which will allow us to determine the reaction forces
• On the hitch around the pinpoints
• On the suspension
21
In order to get diverse, yet accurate data, an impulse steering input might be needed from
the driver. The goal will be to collect the displacement, as well as observing the
suspension in case of any malfunction that could affect the trailer stability.
22
5. DATA ANALYSIS
As mentioned in the introduction, limiting circumstances prevented data collection on
the field. We will therefore proceed using existing research and compare the assumptions
made and verified regarding our project.
5.1. Tongue Weight Calculation
Using a scale, the team previously involved with the tiny house analysis measured the
tongue weight at different angles above the horizontal. The results were as follow:
Data Points Angle
(Degrees)
Scale Reading
(lbs)
Δ Front
(in)
Δ Back
(in)
2 0 1110 15 16.59
2 -3 744 9.2 21.5
3 3 1966 23.6 9.375
4 2 1322 18.75 13.125
Table 1: Forklift Test Results [9]
Further data analysis could not be conducted as the testing part of the project could
not be performed and data could not be collected.
23
6. FINDINGS AND INTERPRETATIONS
This chapter’s content will need to be revisited as complete data could not be collected
nor analyzed. The next chapter will be focusing on an existing study and based on the data
and results, draw some conclusions and verify the veracity of our assumptions.
24
7. DESIGN IMPROVEMENT: ACTIVE HITCH
Based on the previous assumptions and data analysis and interpretation, we can
confidently say mass distribution and trailer oscillation are related. Several studies discuss
methods to reduce or mitigate sway phenomenon. We will discuss a study focused on
“Active Hitch”.
7.1. Concept Overview
A Canadian study discusses the use of an “Active Hitch” as anti-sway method. An
active hitch uses a “planar linkage that changes the lateral position of the hitch ball to
introduce changes in the trailer heading angle” (pp. 10-11) [2] The lateral motion of the
hitch changes the heading angle of the trailer, countering the effects of side forces
responsible for sway. The single-track design below shows a representation of the assembly
motion:
Figure 26: Active Hitch Layout
To verify this theory, developing a dynamic model was necessary. Such a system would
be set with limited sensing and “be robust to changes in tractor trailer lateral dynamics”
[2]. The sensing apparatus is to be incorporated in the hitch design. An essential factor to
take in consideration is the trailer angle: as it changes, it would create an error signal that
would trigger the hitch lateral motion to counter its effects. The starting point of the trailer
25
would be considered the “zero point” and every data point collected would be relative to
the initial conditions. The data collected was the lateral position of the hitch ball, as well
as the rate of change in these positions, and the yaw angle relative to the towing vehicle.
7.2. Dynamic Modeling
A single-track system, similar to a bicycle handling model was used for the simulation.
This system should meet the experiment requirements, as the goal is to observe the
system’s reaction to “steering inputs” [2]. The test will be performed on a 4-wheel towing
vehicle, but the sensors and data will be collected on one side of the vehicles. Below are
the components used in the design of the active hitch:
Figure 27: Class III Hitch; Used on a Chevrolet Equinox SUV
The linkage system allowing hitch motion consists of a linkage arm, a 1500psi rated
hydraulic cylinder (actuator) and a support bracket, see isometric view below:
Figure 28: Actuator Assembly
26
The towing apparatus once mounted to towing vehicle is represented below:
Figure 29: Hitch Assembly Mounted on Towing Vehicle
In the pre-testing analysis of the tiny house, we established the importance of
performing Finite Element Analysis on the tiny house hitch, to evaluate if it can withstand
applied loads and stress. A similar approach was used for this study: the active hitch system
was, with the boundary conditions below:
Figure 30: Boundary Conditions on Finite Element of Linkage Arm
27
The simulation was done with both positions of the actuator, with the following result chart:
Figure 31: FEA Stress Chart
The maximum stress levels being lower than the yield strength of the material, it was safe
to proceed with the experiment. The complete active hitch system, including sensors and
hitch couplers is modeled below:
Figure 32: 3D Assembly of Active Hitch
28
Figure 33: Hitch Assembly mounted to Towing Vehicle
The test trailer consisting of a single axle assembly, made of structural 4” X 7.25” channels,
was worth 650 kg (1433 lbs) and is represented below:
Figure 34: Test Trailer
Finally, the towing vehicle was a 2011 Chevrolet Equinox, equipped with sensors on the
Curbside, per the representation below:
29
Figure 35: 2011 Chevrolet Equinox with Testing Sensors
7.3. Results [2]
Based on the data collected per the previous test, the following charts were put together
comparing the trailer behavior using a standard hitch versus an active hitch:
Figure 36: System Response to Steep Steering Input - Active vs Standard Hitch [2]
30
We can clearly see a change in oscillation rate with an active hitch versus a constant
oscillation for a standard hitch. Moreover, in a situation of sway, the natural response for
a driver would be to steer the towing vehicle trying to counter the side to side oscillations,
adding therefore some force to the system. The data collected with that configuration at a
1°-degree yaw angle input helped put the charts below:
Figure 37: Resonance created for a sinusoidal driver input of ± 1°.
Again, it is noticeable that a higher stability is observed with the use of an active
hitch versus a standard one.
31
8. DISCUSSION AND CONCLUSION
Road safety is a serious matter which can be ensured different ways. As mentioned in
the previous paragraphs, there are several accidents related to trailers. Trailer sway can be
responsible for these accidents, which makes it an important topic to study. There are
several ways to mitigate sway, such as the use of anti-sway hitches. The goal of this thesis
was to establish a relationship between mass distribution in the trailer and its likelihood to
experiment sway. Considering its configuration, the tiny house happened to be perfect for
an experiment in that regard. Via theoretical analysis, assumptions were made on the
location of its center of gravity, as well as its role on the house behavior while trailed.
Previous work used a forklift test to gather data relevant to center of gravity calculations.
Unfortunately, due to the current events, the orientation of our analysis had to be modified,
as further tests could not be pursued to determine whether our assumptions were correct or
not. However, the second part of the research focused on an existing study related to the
use of an active hitch to mitigate sway. This research focused on design and
There has been very little work on active hitch method and its effectiveness, which
made it relevant to study in parallel with our project. The results of this study do confirm
our assumption on the tiny house behavior being related to its mass distribution. The results
of the active hitch test show a significant reduction in sway behavior even for a “very
unstable trailer configuration” [2].
8.1. Future Work
The following steps of this research would be to perform field tests. The expectation is
for all our assumptions to be confirmed. We would then need to evaluate what the best
32
method to mitigate sway would be. Throughout this study we discussed different methods
to mitigate sway. We will base our analysis on the different parameters collected from the
suspension behavior, to the oscillation frequency to determine which would be the better
method for the tiny house configuration.
33
Appendix A – Solidworks and Working Model 2D Features [13]
A. Extrude Boss/Base Feature
Extruded Boss/Base allows to add thickness to a 2D Sketch. The end condition is the parameter
that causes the extrusion to stop. SolidWorks’ end conditions are blind, up to vertex, up to surface,
offset from surface, up to body and midplane. The blind and mid plane require depth distance. All
the offset end condition’s options must specify the offset in the model.
B. Revolve Feature
Revolve Boss/Base allows to create a 3D solid by revolving a 2D sketch along an axis. The
axis of revolving should be included on the 2D sketch as a construction line. The end condition is
the parameter that causes the extrusion to stop. SolidWorks’ end conditions are blind, up to vertex,
up to surface, offset from surface, up to body and midplane. The direction is the amplitude in
degrees of the revolving profile; this direction must be defined for blind and midplane end
conditions.
C. Extrude Cut Feature
Extruded Cut allows to remove parts of a solid model from a 2D sketch. Mainly used to create a
hole. The end conditions and options are the same as those of the two previous features.
D. Loft Feature
The Loft Feature creates a solid between different 2D profiles. The profiles must be closed. On the
profile tap, the different profiles need to be in order. Used the down and up arrows to obtain the
correct order of sequence.
E. Create Plane
It is possible to create planes in any part of the model. Planes could be used for sketch or a simple
view of the model.
F. Mates Feature
A mate is a geometrical relationship between two solids in an assembly. On the mate tab, select the
geometry features involved in the mate, and the type of mate: coincident, parallel, distance, tangent,
concentric or perpendicular.
34
Appendix B - Working Model 2D Features [14]
A. BODY PROPERTIES & FEATURES
• Body types: circle, box, polygon and smooth (b-Spline edges) • Mass, density, geometry, center
of mass, moment of inertia, velocity and angular velocity, electrostatic charge and more • Track
the motion path of a body • Automatic collision detection and response • Automatically applied
static and kinetic friction
B. CONSTRAINTS • Pin, rigid, slot, keyed slot and curved slot joints • Rods, ropes, pulleys
and gears • Linear and rotational spring/ damper
C. MOTION DRIVERS
• Motor • Actuator • Force • Torque Constraints and drivers can be defined by numeric or
equation input in the formula editor, or with tabular data. UNITS SYSTEMS & FORMULAS •
SI, English, CGS and user-defined
D. MEASURABLE PARAMETERS
• Position • Velocity • Acceleration • Momentum • Angular momentum • Constraint force and
torque • Gravity, electrostatic and air force • Kinetic energy, gravitational potential energy and
power Record and display simulation data in real-time with graphical and digital meters.
SIMULATION CONTROL • Run, stop, reset, single step, or pause the simulation at any time. •
Control the accuracy of your simulation by modifying integration and animation steps and
configuration tolerances. • Superimpose multiple simulations.
E. INTERACTIVE CONTROLS
• Connection to Excel and MatLab • Complete “Visual Basic” style scripting language with built-
in debugger • Menu and script buttons • “Player” mode for content creation
F. VISUALIZATION
• Track the motion path of a body or its center of mass • Attach graphics to bodies • Images on
bodies rotate • Display system center of mass • Multiple, moving reference frames SCRIPTS •
Optimize • Create constraint • Document model • Zoom to extents • Measure distance between
points • Flip polygon • Multiple file run • Pin friction • Slot friction • Slot damper • Flexbeam
• Shear and bending moment
G. OUTPUT
• AVI video files for playback • Meter data from simulations to tabular data file PRINTING •
Print an image of your simulation or meter data
35
References
[1] United States Department of Transportation-National Highway Traffic Safety
Administration, Quick Reference Guide to Federal Motor Vehicle Safety Standards and
Regulations. February 2011 [Online]
https://www.nhtsa.gov/sites/nhtsa.dot.gov/files/fmvss-quickrefguide-hs811439.pdf
[2] Sykora, Connor “Trailer Sway Control Using an Active Hitch”. 2017
[3] Sharpe, Kimberly “RV Anti Sway Bar Basics” March 21, 2018 [Online]
https://traveltips.usatoday.com/rv-anti-sway-bar-basics-101624.html Accessed on
04/18/20
[4] GrabCad Community, AntiSway Bar 3D Model [Online]
https://grabcad.com/library/rear-anti-roll-bar-swaybar-1
[5] Hensley Manufacturing “How to Eliminate Trailer Sway”. 2011 [Online]
https://cdn2.hubspot.net/hub/18997/file-13377555-
pdf/docs/how_to_eliminate_trailer_sway_v1.1.pdf
[6] L. De Novellis and A. Sorniotto, “Direct yaw moment control actuated through
electric drivetrains and friction brakes: Theoretical design and experimental assessment”,
Mechatronics, vol. 26, no. March 2015, pp. 1-15, 2015. [Online]
http://epubs.surrey.ac.uk/853199/1/Trailer%20control%20through%20vehicle%20yaw%
20moment%20control%20-%20VoR.pdf
[7] Gilbert, Michael; Godrick, Daniel and Klein, Richard “The Effect of Longitudinal
Center of Gravity Position on the Sway Stability of a Small Cargo Trailer” Paper No:
IMECE2008-66022, pp. 295-305. August 26, 2009
36
[8] CSUS Tiny House Information [Online]
https://www.csus.edu/news/articles/2016/10/10/Hitch-up-the-tiny-house-Students-head-
to-big-competition-.shtml Accessed 01/21/2020
https://inhabitat.com/student-built-solar-powered-tiny-home-represents-new-vision-for-
the-american-dream/sacramento-state-tiny-house-3 Accessed 01/21/2020
[9] Iqbal, Lailaa; Contreras, Andre; Fanning, Angelia; Perez-Hughes, Katiria and
Castro, Fernando, “Tiny House Dynamics”. Senior Project Report. 2018
[10] Different Classes of Hitch and Capacity [Online]
https://www.drawtite-hitches.com/learning_center/general-towing-classes Accessed on
04/18/2020
[11] Bulletproof Hitch Specs. [Online]
https://www.bulletproofhitches.com/collections/heavy-duty-hitches/products/2-0-heavy-
duty-6-drop-rise Accessed 02/07/2020
[12] SAE-J684 Testing Requirements [Online]
http://popupbackpacker.com/wp-content/uploads/2017/01/B3-2-SAE-J684.pdf
[13] Solidworks Features [Online]
https://help.solidworks.com/2017/English/SolidWorks/sldworks/c_Features_Top.htm
Accessed on 01/12/2020
[14] Working Model 2D Features [Online]
http://workingmodel.design-simulation.com/Documents/WM/wm2denglish.pdf
37
[15] GMC, “Tongue Weight: Why It’s the Key to Safe Towing” [Online]
www.gmc.com/gmc-life/trucks/why-tongue-weight-is-important-for-safe-towing.
Accessed on 01/12/2020
[16] J. Darlin; D. Tilley and B. Gao “An Experimental Investigation of Car-Trailer
High-Speed Stability”. January 8th, 2009
[17] F. Sorge, “On the sway stability improvement of car–caravan systems by
articulated connections” International Journal of Vehicle Mechanics and Mobility, vol. 53,
no. 9, pp. 1349-1372, 2015.
[18] Husky Towing Products - MV Weight Distribution System with Friction Sway
Control [Online]
https://assets.rigidhitch.com/hitch_instructions/32215.pdf
[19] Deng, W. and Kang, X. “Parametric study on vehicle– trailer dynamics for stability
control”, SAE paper 2003-01-1321, 2003.
[20] Fratila, D. and Darling, J. “Simulation of coupled car and caravan handling
behaviour. Veh. System Dynamics”, 1996, 26, pp. 397–429.
[21] "CURT Class 3 Trailer Hitch #13591," Curt Manufacturing, [Online].
Available: http://www.curtmfg.com/part/13591 Accessed on 04/19/2020
