Prototype Design

Trailer Dolly Design Proposal

Ryerson UniversityMEC 613 Machine Design

Table of Contents1.0 Problem Analysis.............................................................................................................................3

1.1 Current Situation...............................................................................................................................3

1.2 User Groups.................................................................................................................................3

1.3 Deliverables.......................................................................................................................................3

1.4 Existing Products................................................................................................................................3

2.0 Dolly Requirement...........................................................................................................................4

2.1 Design Brief........................................................................................................................................4

2.2 Design Attributes...............................................................................................................................4

2.3 Functionality......................................................................................................................................4

2.4 Design Constraints.............................................................................................................................5

3.0 Embodiment....................................................................................................................................6

3.1 Morphological Chart..........................................................................................................................6

3.2 Evaluation of the Initial Concept..................................................................................................8

3.3 Revising of the concept..............................................................................................................11

3.4 Product Assembly............................................................................................................................12

3.5 Ergonomic Factor.......................................................................................................................12

4.0 References.................................................................................................................................12

5.0 Appendix....................................................................................................................................13

Figure 1..................................................................................................................................................13

5.1 Material Selection............................................................................................................................13

5.2 Fastener Analysis.......................................................................................................................13

5.3 Shaft Analysis.............................................................................................................................15

5.4 Motor Requirement...................................................................................................................18

5.5 Hitch ball Force Analysis............................................................................................................19

5.11 Fatigue Simulation.........................................................................................................................20

5.6 CAD Drawings..............................................................................................................................0

1.0 Problem Analysis 1.1 Current Situation

1.2 User Groups

1.3 Deliverables1.4 Existing Products

Model Specification

Parkit360 “The Force” (P360HD)

- Featuring “Smart brake”, allows automatically control trailer brakes through wire harness

- 12 V deep cycle battery operated

- 4” wide tires

- Built in battery charger

- Aluminum steel

Vestil PTM-GPT

- Gas Powered Trailer Mover

- Foam filled tire does not require air

- 8.5HP gasoline engine with variable speed hydrostatic transmission

- Adjustable ball height controlled by hand lever

- Steer handle allows forward/neutral/reverse lever and integral dead-man engine kill switch

- Aluminum steel

- Powered by 3000 lb 1.1 HP ATV style Winch

- Winch brake keeps mover from rolling when power is removed

- Receiver style hitch allows different height ball mounts

- handle rotates vertically to minimize storage space

- Aluminum steel

2.0 Dolly Requirement2.1 Design Brief The objective of this assignment is to design a prototype trailer dolly to be sold in conjunction with their trailers. The niche that this dolly will satisfy is for it to fit trailers into tight spaces where a towing vehicle would not fit.

2.2 Design Attributes The final design must contain specific tributes that will allow all the various functionalities to be carried out effectively. The design attributes include:

Motor powered, however must be able to be manually operated during emergency Dolly must lift the trailer receiver to a minimum height of 20” Inhibit trailer movements at speeds beyond 2 mph Ability to stop in emergency situations, activated by user Versatile functionality on any surface

2.3 Functionality Mobility is the key functionally that must be considered in the designing the dolly. In terms of mobility, there are two major groups; first one being the ability move forward and reverse, second being the capability to steer in the tightest possible turning radius.

Figure 1. Black box describing the layout of general functionality required by the design

The purpose of this black box system was to layout the general process in which our dolly would operate and to see what components were necessary in order to complete this process. We started with the input and output criteria that were required from dolly system and then brain stormed the components we thought were necessary to transform the input into the desired output. The dashed lines in the black box represent the transfer of information, while the solid lines represent physical movement of the components.

2.4 Design Constraints The subjective design constraints of this project are as follows:

The subjective design constraints of this project are as follows: Must use a standard trailer hitch ball and be interchangeable. Motor powered, however must be able to be manually operated during an emergency Must keep the fully loaded (10,000 lbs) trailer stable without external forces applied by the user,

both when in motion and when at rest The dolly must lift the trailer receiver to a minimum height of 20” The dolly must inhibit trailer movements at speeds beyond 2 mph The dolly must allow forward and reverse movement, as well as steering to the tightest possible

turning radius. The dolly must be able to stop itself in emergency situations once properly activated by the user

The objective design constraints of this project are as follows:

Minimal cost must be achieved while meeting all requirements. The trailer must remain functional throughout any use of the dolly The design must maximize safety of anyone near the trailer during operation. Operation of the dolly must require minimal training. Since this is a prototype, manufacturing must be as simple as possible

3.0 Embodiment3.1 Morphological ChartThe only differences between the black box system and our morphology chart were the inclusion of the material and support stand components.

Power Source:

Material:

Movement System:

Stand Support:

Steering System:

Braking System:

The three types of power we decided upon were electric, gas, and a hybrid of both. For electric the dolly would contain an internal battery and electric powered motor. For the gas it would contain a gas tank and a gas power motored. Lastly the hybrid option would contain both the battery and tank along with a hybrid electric/gas motor.

The three types of material of we decided upon were carbon steel, titanium, and carbon fiber. The metal components of the dolly will be composed solely of one material.

The four options for the movement system we decided upon were twin-tired, tricycle tired, four tires, and continuous tracked. For twin-tired the tires are placed side by side. For tricycle tired the tires are arranged one in the front and two in the back. For the four tires and continuous tracked option they are arranged standardly. Plus all tires are assumed treaded.

The four types of stand supports we decided upon were an adjustable stand, a two-stand support, a wheel support, and none. These supports are used for the dolly to stand when it is not in use. For the adjustable stand it is a single stand in which you can change its length and position it rests. For the two-stand support it is similar to a wheel burrow stands. The wheel stand is an extra wheel that supports the dolly to stand. For none the dolly rests on its main body or wheels depending on the movement system.

The three types of steering systems we decided upon were a T-bar handle, a steering wheel, and a pump truck handle.

The four types of braking systems we decided upon were handle brakes, sensory brakes, a combination of handle and sensory brakes, and bumper brakes.

Table 1. Morphological chart showing design options

Option 1 Option 2 Option 3 Option 4

Power Source

Electric Gas Hybridized

Material Carbon steel TitaniumCarbon fiber

Movement system

Twin-tiredTricycle tired Four tires Continuous

tracked

Stand support

Adjustable stand Two stand supports Wheel StandNone

Steering System

T bar handle Steering wheel Pump truck handle

Brake system

Handle brakes Sensory brakes Combination of handle and sensory

Bumper brake

brakes

3.2 Evaluation of the Initial ConceptTo further evaluate each viable options Pugh screening method was applied.

Power Source Option 1 Option 2 Option 3 Option 4 Benchmark

Safe 0 - - 0

Usability 0 0 0 0

Easy to maintain 0 - 0 0

Easy to manufacture 0 - - 0

Durable 0 0 0 0

Score 0 -3 -2 0

Rank 1 3 2

Continue YES NO NO

The criteria for the power source were chosen when taking into consideration the ease of maintenance and manufacturing. It is simpler to manufacture electric motors due to them having less moving parts and batteries take up less space and last longer then fuel tanks for gas powered motors.

Material Option 1 Option 2 Option 3 Option 4 Benchmark

Safe 0 0 0 0

Usability 0 0 0 0

Easy to maintain 0 0 0 0

Easy to manufacture 0 - - 0

Durable 0 0 0 0

Score 0 -1 -1 0

Rank 1 2 2

Continue YES NO NO

The criteria for the material were chosen with consideration to safety, durability, and material cost. Out of the three options listed above all of them pass the safety and durability aspect of the criteria but in terms of material cost carbon steel was the most viable choice.

Movement system Option 1 Option 2 Option 3 Option 4 Benchmark

Safe 0 0 0 0 0

Usability 0 0 0 0 0

Easy to maintain 0 0 0 - 0

Easy to manufacture 0 - - - 0

Durable 0 0 0 0 0

Score 0 -1 -1 -2 0

Rank 1 2 2 3

Continue YES NO NO NO

The criteria for the movement system were chosen when taking into consideration the ease of maintenance and manufacturing. When compared to our benchmark, which is also twin-tired, the other options fell a bit short due to the fact that they added more parts to manufacture and maintain.

Stand Support Option 1 Option 2 Option 3 Option 4 Benchmark

Safe 0 0 0 0 0

Usability 0 0 0 0 0

Easy to maintain - - - 0 0

Easy to manufacture 0 0 - 0 0

Durable 0 0 0 0 0

Score -1 -1 -2 0 0

Rank 2 2 3 1

Continue NO NO NO Yes

The criteria for the stand support were based on the idea of necessity and cost of manufacturing. Since our benchmark did not include a stand and was still able to stably lean and rest on its exterior, it was proven that a stand was not a necessity to the design.

Steering System Option 1 Option 2 Option 3 Option 4 Benchmark

Safe 0 0 0 0

Usability 0 0 0 0

Easy to maintain 0 0 0 0

Easy to manufacture 0 0 0 0

Durable 0 - 0 0

Score 0 -1 0 0

Rank 1 2 1

Continue NO NO Yes

The criteria for the steering system were based on the functionality and durability. Since the pump truck handle had scored just as well as the T-bar handle, its extra functional uses such as operating the hitch ball lift and braking outclassed the T-bar which was just for steering.

Braking System Option 1 Option 2 Option 3 Option 4 Benchmark

Safe 0 0 + 0 0

Usability 0 0 0 0 0

Easy to maintain 0 0 0 0 0

Easy to manufacture 0 0 0 - 0

Durable 0 0 0 0 0

Score 0 0 1 -1 0

Rank 2 2 1 3

Continue NO NO Yes NO

The criteria for the braking system were chosen when taking into consideration the safety of the system. The combination of both the handle and electronic brake ensure a better overall safety in the case one fails to work the other would act as its safety/backup.

3.3 Revising of the conceptThe final design uses a standard trailer hitch ball, powered by 1 HP motor attached to a 12V battery. In the rare case of a power outage or emergency, the dolly can also be operated by hand. The dolly is

made out of 1050 carbon steel, weighing in at 300 lbs. This allows for a moderately lightweight dolly to be easily maneuvered by a single person. The design uses only a single power switch and forward backward dial, allowing an ease of use for anyone to use without any extensive training.

3.4 Product Assembly The simplistic look of the dolly is not only cost effective but also marketable and easy to manufacture. This basic box design makes it so that the minimum material is used to save on manufacturing the dolly. The dolly uses a simple electromagnetic motor attached to 12V battery which is easy to use and manufacture.

This dolly has a maximum speed of 3.5mph and has a maximum capacity to lift 7 US tons. The dolly can lift the trailer to a maximum height of 27”. Handles allow for a turning radius of up to 105 degrees, allowing it to rotate a trailer completely 90 degrees about its central axis, as well as move both forwards and backwards, to fit the trailer into the tightest space.

The low profile dolly with minor wheel gap is a major safety factor which prevents anyone’s feet to get stuck under. If the dolly had a greater height, it would run a risk of one’s feet to get stuck under. There is also a large red emergency stop button on the side of the dolly. This clearly labelled button immediately shuts off the motor in an emergency situation.

The dolly comes with top quality Yokohama all-purpose tires installed. These tires are intended to provide grip and ease of maneuverability on both asphalt, gravel and hard-packed dirt. The lightweight aluminum alloy performance WORK VSKF custom rims maximize the rotational power transferred to the wheel from the motor.

3.5 Ergonomic FactorA lot of ergonomic factors were taken into consideration in the design of the dolly. The ergonomic handle the user to push and pull the dolly without any long-term or short-term wrist pains. The handle is designed so that the user’s wrists stay straight, not putting any pressure on the wrist joints. This height fits the standard North American height average which allows both short and tall people to use the dolly without having to bend over to push or pull the dolly.

4.0 References [1 ]http://www.grizzly.com/products/Motor-1-HP-Single-Phase-1725-RPM-Open-110V-220V/G2905

5.0 AppendixFigure 15.1 Material Selection

Carbon steel 1050 NormalizedE=30×103 kpsi(Table A−5)

Sut=108 kpsi , S y=62 kpsi¿ (Table A−21)

Member Stiffness

Members aremadeof the samematerial thefore equation8−22wasused

Km=0.577 πEd

2 ln 0.577 l+0.5d0.5774 l+2.5d

=19.04×104 kips /¿

Joint Stiffness

C=Kb

Kb+Km=0.1733

5.2 Fastener Analysis Bolt Characteristics:

34 Inch -10 UNC X 3

12 in grade 8.2 (Machined)

At=0.334 ¿2 Ar=0.302 ¿2 ¿ (Table8−2 ) ,

Sp=120 kpsi , Sut=150kpsi , S y=130 kpsi ¿(Table8−9)

E=30×103kpsi(Table A−5)

Fastener Stiffness

l=3 inch

H= 4164inch (Table A−31 ,Hexagonalnut )

L>3+ 4164

=¿ L=3.75inch (round up )

LT=2d+ 14=1.75 inch (L≤6 inch )

Ad=π d2

4=0.442 ¿2

ld=L−LT=2inch

lt=l−ld=1inch

Kb=Ad A t EAd lt+A t ld

=3.99×103kips /¿

Preload on Bolt

F i=0.75 Fp=0.75 A tS p=30.06 kips

Endurance Limit:

Se=S'eK aKb ( Assumeother factorsare1.0 )

K a=2.7Sut−0.265=0.716 (using table6−2 )

K b=0.879d−0.107=0.906 (using 6−20 )

S' e=0.5Sut=75 kips (using 6−8 )

Se=(75 ) (0.716 ) (0.906 )=48.68kpsi

Figure #. Assuming worst case scenario

2 Pbending (4 )=Fxhitch (6 )

Pbending=0.68 kips

Paxial=F yhitch

4bolts=0.23 kips

Ptotal=Pbending+Paxial=0.91 kips

Factor of safety gaurdingagainst static stress exceeding proof strength of bolts

np=S p A t

C P total+F i=1.32

Factor of safety gaurdingagainst joint seperation

no=F i

P total (1−C )=40

Goodman fatigue Factor of safety failure criteria

n f=2Se (Sut At−F i )C Ptotal (Sut+Se )

=62.2

σ a=C Ptotal

2 A t=0.236 kpsi

σ m=σ a+FiA t

=90.236 kpsi

Fatigue factor of safety against proof strength:

np=Sp

σa+σ m=1.32

Load factor guarding against overloading:

nL=Sp At−F iC P total

=63.5

Factor of safety guarding against shearing:

F s=F xhitch

2=0.0775 kips

nshear=π d2S y (0.577 )

4 F s=427.6

5.3 Shaft Analysis

Figure #. Free body diagram of shaft looking from front plane

Figure #. Free body diagram of shaft looking from top plane

D pulley=3 inch

dshaft=2.61 inch

W dolly=300lbs

Fwheel=W dolly

2=150 lbs

asystem=¿ 0.5 ft/sec2

M dolly=30032.2

=9.32 slugs

2 Ftraction=(M trailer+M dolly )asystem=0.16 kips

F traction=0.08kips

∑Torqueshaft=0=Fpulley (3/2 )−2 F traction (8/2 )

F pulley=0.427kips

F t1=Fpulley0.85

=0.502kips

F t2=0.15 F t1=0.075 kips

Figure #. Moment Diagram along the shaft a) front view b) side view c) shaft cross-section

Mmax=2.6kip−¿

T max=0.85F t1D pulley

2=0.64 kip−¿

M a=2.6 kip−¿

Mm=0

T a=0

T m=0.64 kip−¿

Se=S'eK aKb ( Assumeother factorsare1.0 )

S' e=0.5Sut=75 kips (using 6−8 )

K a=2.7Sut−0.265=0.787 (using table6−2 )

Kb=0.91d−0.157=0.783 (using 6−20 )

Se=(75 ) (0.787 ) (0.783 )=46.22 kpsi

r=0.0522 (notchradius )

rd=0.02 (shoulder fillet sharp )

K t=2.25 ( fig . A−15−9 )

K ts=1.5 (Fig . A−15−8 )

qshear=0.8 ( table6−21 )

q=0.8 (table6−20)

K f=1+q (K t−1 )=2.36

K fs=1+qshear (K ts−1 )=1.4

Fatigue factor of safety of the shaft:

n=π d3

16 { 2SeK f M a+

√3SutK fsT m}

−1

=12.31

5.4 Motor Requirement Type: Open

Size: 1 HP

RPM: 1725

AMPS at 110V/220V: 11.6A/5.8A

Reversible rotation

Figure #. Grizzly motor [1]

V trailer=3 ft /sec ¿180 ft /min

wheel perimeter=dwheelπ=(8 )π=25.1∈¿ rev=2.09 ft /rev

motorrpm=V trailer

wheel perimeter=86.12

Torquemotor=F pulley

D pulley

2=53.375 lb−ft

Horsepowermotor=Torquemotor×motorrpm

5252=0.875hp

5.5 Hitch ball Force Analysis

Figure #. Diagram of hitch ball with bolted members

Must inhibit trailer velocity of 2mph, which is equal to 3ft/sec

accelerationtrailer=final velocity−initial velocityfinal time−starting time

=3 ft /sec−0 ft /sec6−0

=0.5 ft /sec2

Masstrailer=10000 lbs /32.2 ft / sec2=310.56 slugs

F xhitch=Masstrailer×accelerationtrailer=310.56 slugs× 0.5 ftsec2 =0.155 kips

∑ Fwheel=0=10000 (120−102 )−F yhitch (198 )

F yhitch=0.91 kips

5.11 Fatigue Simulation

Figure #. Fatigue simulation performed in Solid works

Figure #. Fatigue simulation performed in Solid works showing stress on handle hinge

Figure #. Fatigue simulation performed in Solid works top view

5.6 CAD Drawings