Proposal

PREPARED FOR PROF NEIL WALKER

Authored by: Art Gostick Student Number:

9500734

Bike Trailer Proposal MECH1912 Contents 1.0 Introduction

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2.0 Design Requirements 3 3.0 Proposed Design Concepts

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3.1 Wheels 5 3.2 Trailer Frame

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3.2.1Horizontal Support Members

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3.2.2 Vertical Side Wall Columns 6 3.2.3 Trailer Attachment Device 6 3.3 Analysis Plan

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4.0 Alternative Design Concepts 7 4.1 Alternate Design 1

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4.2 Alternate Design 2

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5.0 Project Plan

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6.0 REFERENCES

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Appendix A A1

List of tables

Table 1- Compliance Matrix..........................................................................................................3

List of Figures

Figure 1 Project Plan Gantt Chart................................................................................................8 Figure 2 Kids Bike Trailer [4]......................................................................................................A1 Figure 3 Proposed Design Concept...........................................................................................A2 Figure 4 Proposed Design Tongue Weight Analysis..................................................................A2 Figure 5 Proposed Design Tongue Weight Calculations...........................................................A3

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Bike Trailer Proposal MECH1912

Figure 6 Universal Mounting Bracket.........................................................................................A3 Figure 7 Rod End Ball Joint [5]..................................................................................................A4 Figure 8 Alternate Design 1 Seat Post Clamp...........................................................................A4 Figure 9 Alternate Design 1 Trailer U-Joint................................................................................A5 Figure 10 Alternate Design 2 Trailer Frame...............................................................................A6 Figure 11 Alternate Design 2 Tongue Weight Analysis..............................................................A7 Figure 12 Alternate Design 2 Tongue Weight Calculation.........................................................A7

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Bike Trailer Proposal MECH1912 1.0 Introduction This project is to design a prototype cargo trailer to be towed behind a bicycle. It is to be designed for bicycle intensive urban markets. This trailer will provide transport of goods with a foot print of 3 feet by 4 feet and up to 200 lbs. This project is for course MECH1912 Mechanical Systems Design and is a simulation of a work project. 2.0 Design Requirements The design requirements for the bike trailer are specified in Table 1. Table 1- Compliance Matrix Requirement Number

Requirement

Statement of Compliance

1.

The trailer must be able to attach safely to a typical adult bicycle. Attachment can be to the seat post, frame, rear axle, or any other feasible location.

The trailer will be attached at the rear bike axle. The attachment arm will use a ball-joint type of connection that will allow proper freedom of travel when towing the trailer.

2.

The trailer should be large enough The cargo area of the trailer will leave to transport a box with a footprint 1 in. clearance for a cargo box of 3 measuring 3 ft by 4 ft. ft. by 4 ft.

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Requirement Number

Requirement


3.

The trailer should be strong enough to transport 200 lb. cargo. Dynamic loads due to road conditions and maneuvering are set at 0.5 g in the sideways direction (hard cornering), 0.5 g in the forward and reverse direction (sudden braking/low-impact collisions), and 1.5 g in the vertical direction (bumpy roads.)

The trailer will be constructed of aluminum hollow square tubing.

4.

A design factor (i.e., minimum allowable safety factor against yielding or proof load) of 1.5 is required

The trailer will be designed to safely transport 300 lbs. of cargo in addition to its own weight.

5.

The trailer should be as light as possible, consistent with structural adequacy and general robustness and suitability. Maximum allowable trailer weight is tentatively set at about 100 lbs. (45 kg).

The trailer will be constructed of aluminum hollow square tubing to keep the weight as low as possible. The smallest size that will meet all the design requirements will be used. Final size to be determined after 3D model stress analysis.

6.

The trailer should be constructed from commercially available structural members such as ANSI rectangular or square tube, angle iron, channel, etc. Steel or aluminum plate may be used where necessary.

The trailer will be constructed of aluminum hollow square tubing of standard size. The smallest size that will meet all the design requirements will be used. Final size to be determined after 3D model stress analysis.

7.

Standard, commercially-available parts should be used wherever possible. (E.g., wheels, bearings, fasteners, etc.)

Any parts that can be sourced from an economical outside source that will meet the design requirements will be used. All others will be fabricated.

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The welds will be of significant strength and be able to meet strength / safety requirements. Each wheel will be capable of supporting 300 lbs. in the event of an uneven road surface to avoid failure. The trailer will be subject to a full stress/strain analysis after the 3D modeling is complete.


Requirement Number

Requirement


8.

The trailer should be reasonably aerodynamic and low-profile.

The trailer frame will be designed with 6” of clearance from the ground to clear any curbs and will be designed as aerodynamically as possible.

9.

The trailer must be attractive, low The entire trailer frame will be maintenance and corrosionpowder coated to ensure maximum resistant. corrosion resistance while having an appealing appearance. Bearings will be of the sealed type so no further lubrication will be required.

3.0 Proposed Design Concepts The design concept is similar to the trailers used to transport children (Figure 2). This follows some of those same principles but it increases the trailers cargo area and load capabilities. This trailers main function will be to transport cargo with a maximum foot print of 3 ft. by 4 ft. weighing 200 lbs. The weight of the trailer is not to exceed 100lbs with a safety factor of 1.5. See Figure 3 for proposed design concept. 3.1 Wheels The wheels will be standard tube filled bicycle tires able to absorb light impact and capable of withstanding a minimum of 300 lbs. This will be enough to support the weight of the trailer and 200lbs of cargo. The wheels will be attached to a straight axle that will attach under the trailer.

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3.2 Trailer Frame The proposed design (Figure 3) is well balanced (Figure 4) with approximately 8% (Figure 5) of the trailer weight being tongue weight. Ideal tongue weight is 10% [1]. 3.2.1Horizontal Support Members The horizontal support members will be fabricated out of aluminum 6061-T6 hollow square tubing to maximize strength and reduce weight. This material was chosen due to its excellent joining characteristics and good acceptance of applied coatings. It combines relatively high strength with good workability, and high resistance to corrosion [2]. It is also widely available. The size of these members will be determined after the stress/strain analysis is performed at a later date. The smallest possible size will be used as determined by this analysis. 3.2.2 Vertical Side Wall Columns The vertical side wall columns will be fabricated from 6061-T6 aluminum hollow square tubing to maximize strength and minimize weight. The vertical support column will be welded to the horizontal support members. The size of these columns will be determined at a later date. 3.2.3 Trailer Attachment Device The trailer attachment apparatus will be a custom designed mounting bracket (Figure 6). The bottom clamp attaches to the lower rail and using the pivoting upper mounting bracket and the elongated slot attaches to the upper rail that goes to the seat post. This design should allow utilization with almost every brand of bicycle. The bracket will have a rod-end ball joint (Figure 7) where the trailer arm will attach. The trailer arm will be held in place with a hitch pin for quickly connecting and disconnecting. 3.3 Analysis Plan The main structural beams of the frame will be analyzed for maximum bending loads [3]. All welds and bolted joints will be tested for bending and shear stress failure in Inventor using the 3D model. 4.0 Alternative Design Concepts 4.1 Alternate Design 1 The first concept was to attach the trailer to the seat post (Figure 8) and using a u-joint at the trailer (Figure 9) to allow for range of motion when turning. This initial design allowed for no movement at the seat post creating a long moment arm which would put significant stress on the attachment clamp when cornering. 4.2 Alternate Design 2 The second concept (Figure 10) was designed to attach and pivot at the rear axle of the bicycle and have a u-joint that would allow the trailer to pivot side to side when cornering. This design had the trailer wheels at the rear of the trailer. This design does not balance 6

Bike Trailer Proposal MECH1912 the load (Figure 11). This design would cause the u-joint to have to support 30% (Figure 12) of the cargo weight. Optimum weight at the u-joint would be 10% [1].

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Bike Trailer Proposal MECH1912 5.0 Project Plan

Figure 1 Project Plan Gantt Chart

6.0 REFERENCES

[1 W. Nichols, "AutoZone Reference Library," Chilton, 1998. [Online]. Available: 8

Bike Trailer Proposal MECH1912 ] www.procare.com. [Accessed 29 January 2012]. [2 "MatWeb Material Property Data," [Online]. Available: http://www.matweb.com. ] [Accessed 1 February 2012]. [3 R. Budynas and J. K. Nisbett, Shigley's Mechanical Engineering Design, New York: ] McGraw Hill, 2011. [4 "Bicycle Trailers," [Online]. Available: www.bicycletrailers.com. [Accessed 30 January ] 2012]. [5 "Accent Bearings," 12 October 2007. [Online]. Available: www.accentbearing.com. ] [Accessed 1 February 2012].

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Bike Trailer Proposal MECH1912 Appendix A

Figure 2 Kids Bike Trailer [4]

A1


Figure 3 Proposed Design Concept

Figure 4 Proposed Design Tongue Weight Analysis

A2


Figure 5 Proposed Design Tongue Weight Calculations Cargo

U-joint

Wheel

Figure 6 Universal Mounting Bracket

A3


Figure 7 Rod End Ball Joint [5]

Figure 8 Alternate Design 1 Seat Post Clamp

A4


Figure 9 Alternate Design 1 Trailer U-Joint

A5


Figure 10 Alternate Design 2 Trailer Frame

A6


Figure 11 Alternate Design 2 Tongue Weight Analysis

Figure 12 Alternate Design 2 Tongue Weight Calculation

A7

Proposal

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