Spacer Cart MECHANICAL/STRUCTURAL ISSUE

ANALYSIS AND REDESIGN Product Design Specifications Report - Winter 2016

Sponsor company: Bonneville Power Administration

Contact Engineer: Kevin Machtelinckx

Academic Advisor: Huafen Hu, Ph.D.

Group member: Bao PhanCarlos JiménezRobert LawrenceAustin FerranteMackenzie Larson-WeberSam Levin Stephen Randall Joshua Ponder

2/16Table of Contents:

● Introduction ………………………..………………………………………….Page 3● Purpose of document ……………….………………………………………….Page 4● Mission Statement ……………….………………………………………….Page 4● Project Plan ………………………..………………………………………….Page 4● Customers Identification

○ External Customers ……….………………………………………….Page 7○ Internal Customers ……….………………………………………….Page 7

● Customers Feedback and Interview ………………………………………….Page 8● Project Design Specification ……….………………………………………….Page 9● Conclusion ………………………..………………………………………….Page 12● Appendix …………………………………………………………………...Page 13

List of Exhibits:1. Spacer Carts Mechanical/Structural Issues Analysis and Redesign, Machtelinckx, Kevin,

October 2015, BPA Internal Report.

3/16Introduction:

Since the United States established a

power grid, power transmission lines have

required maintenance. On modern high

voltage power transmission lines,

maintenance is often performed via a ‘Spacer

Cart’ which is hung on the transmission lines

themselves and can drive itself along the

lines using an onboard motor. There are

several companies which design and sell

these carts, but all have their own

advantages and drawbacks, none of them

are completely ideal. BPA (Bonneville Power

Administration), using their own fabrication

shop and in-house expertise, created their

own

‘Spacer Cart’ for use in transmission line repair.

However,

though the

‘Spacer Cart’ they

have created is

capable of

performing its

intended job,

several details in

regards to

usability and

safety were not

addressed during

its initial design, therefore they have requested the help of

Picture 2: Example of a spacer cart

Picture 1: Power Transmission Line

4/16a Portland State Capstone team in evaluating and

addressing different aspects of the ‘Spacer Cart’ design.

Purpose of Document:

The purpose of this PDS (Product Design Specification), as its name implies, is to define

the scope of the project and the requirement(s) due at final product delivery by the Portland

State University (PSU) Capstone Team, as defined by the customer, Bonneville Power

Administration (BPA). The document will outline a set of specifications that will be addressed by

the Capstone team, each specification being ranked in regard to its level of importance to the

customer.

Mission Statement:

The purpose of the project is the re-design of the spacer cart currently in use by BPA.

Overall project scope is limited to addressing safety/functionality limitations with the current

design. The goal of the new design is to reduce stresses in the frame caused by impacts

sustained during normal operation, and to address access and ease of use issues experienced

with both the supporting crossarms which connect and bring the suspension arms in-line, and

the pinch wheel assemblies which increase driving wheel traction with the conductors. These

new designs must all pass design envelopes specified by BPA for line clearance. BPA would

like a prototype available to them for testing by June 1, 2016.

Project Plan: Owing to the fact that there are several separate design goals and a large team, the

team has separated into 3 subgroups, each tasked with a single design goal: the frame

5/16redesign, the pinch wheel redesign, and the crossarm redesign. Table 1 below illustrates the

tentative dates and milestones for the project.

Table 1: Project Milestones

Plan Dates

Project Tasks Start Date End Date

External Search 1/25/16 2/1/16

PDS Report and Presentation 2/2/16 2/2/16

Internal Search 2/1/16 2/8/16

Concept Evaluation and Selection 2/8/16 2/12/16

Detailed Design 2/12/16 2/26/16

Design Review with BPA 2/29/16 2/29/16

Design Modifications 2/29/16 3/4/16

Final Design Review with BPA 3/7/16 3/7/16

Progress Report and Presentation 3/8/16 3/8/16

Fabrication 3/14/16 4/11/16

Laboratory Testing 4/18/16 4/22/16

Redesign (if needed) 4/22/16 4/29/16

Final Design Fabrication 5/2/16 5/30/16

Field Testing 6/1/16 6/1/16

6/16

Documentation 6/1/16 6/6/16

Final Presentation and Project End 6/8/16 6/8/16

7/16

8/16Graph 1: Spacer Cart project timeline

Customer(s) Identification:

External Customers:

● Linemen at BPA (end users)

○ Interest: A ‘Spacer Cart’ with features that are easier to use while performing

maintenance on the lines, such as the crossarm assembly and the pinch wheel

assembly.

● Fabrication Shop at BPA

○ Interest: Completed drawings and assembly instructions for fabricating

components of the ‘Spacer Cart’ per BPA drawing specification.

● Maintenance Department at BPA

○ Interest: Re-designed features on the ‘Spacer Cart’ that are durable and easy to

maintain.

● Kevin Machtelinckx, Project Engineer at BPA

○ Interest: A completed ‘Spacer Cart’ that meets all of BPA’s specifications.

Internal Customers:

● Portland State Capstone Program

○ Interest: Completion of the Capstone project by meeting all sponsor expectations

and specifications.

● Dr. Faryar Etesami, Mechanical Engineering Professor overlooking Capstone Projects

○ Interest: Completion of design process, planning and execution following the

guidelines and parameters established in the Capstone program. Completion of

the Capstone project by meeting all sponsor expectations and specifications.

9/16

Customers Feedback and Interviews:

Initial interview with Kevin Machtelinckx, our primary BPA contact, was held on

November 20, 2015 at the BPA site in Vancouver. The project team met with Kevin, as well as

several other employees of BPA to discuss the mechanical and structural issues of the ‘Spacer

Carts’. Our team also also performed a physical inspection of the current ‘Spacer Cart’ design,

discussed the scope of work to be accomplished, and received a document detailing the current

mechanical and structural issues from Kevin M. A follow up meeting was held at the BPA facility

on January 13, 2016, in order to discuss, in more detail, the issues with the ‘Spacer Carts’ to

allow the Capstone team time to review the discussed project scope and provided

documentation. The Capstone team also detailed design envelope requirements with regard to

the Product Design Specifications during this meeting.

Product Design Specification:

Table 2: PDS - Performance

Performance

Requirements Primary Customer

Metrics & Targets

Metric Target Target Basics

Verification

Angle of Incline BPA

Cart must climb/descend

a line at an angle.

degrees 35 Customer Defined Site Testing

Weight Rating BPA Working Load Limit lbs 550 Customer

Defined Site Testing

Pincher Wheels BPA

Must traverse on wire and pass armor

rod lip

inches ½ Customer Defined Site Testing

10/16

Table 3: PDS - Safety

Safety

Requirements Primary Customer

Metrics & Targets

Metric Target Target Basics

Verification

Structural Frame BPA

Frame to withstand

vibrations and impact load

under working weight limit

(Impact Loads to be provided

by BPA)

Physical Testing 550

Withstand / support all

loads (Static / Dynamic) associated with normal

cart operation and WLL

Lab Testing

Safety Factor BPA

Establish safety factor

based on industry

standards(applicability to be defined

by BPA)

Specified applicable

design criteria

N/ACustomer/

Project Team Decision

Customer Interview

11/16

Table 4: PDS - Environment and Ergonomics

Environment and Ergonomics

Requirements Primary Customer

Metrics & Targets

Metric Target Target Basics

Verification

Crossbar Redesign BPA

Crossbars should be

redesigned to be easier for

technicians to remove

Operation Efficiency

BPA Foreman Approval

Ease of Use Site Testing

Wind, Rain and Cold

EnvironmentBPA

Cart must withstand use in wind, rain

and cold environments

Duration-Years 5 Corrosion

Resistance Field Use

Operational Design

EnvelopeBPA

All physical modifications

must fall within

operational envelope

restrictions

Design envelope standardAppendix

A

All modifications fall within design

envelope restriction

Specified Design

Envelope

Physical Inspection

Table 5: PDS - Maintenance and Parts

Maintenance and Parts

Requirements Primary Customer

Metrics & Targets

Metric Target Target Basics

Verification

12/16

Frame Reinforcement BPA

Years in service

without frame repair

Years 5 years Customer Defined

Site Testing, FEA

analysis

Table 6: PDS - Installation

Installation

Requirements Primary Customer

Metrics & Targets

Metric Target Target Basics

Verification

Pinch Wheel Assembly BPA

Pinch Wheel mechanism to

be installed easily

Operation Efficiency

BPA Foreman Approval

Ease of Operation Site Testing

Cross-Arm Bar Assembly BPA

Cross-arm bar assembly to be easy to

use while on the line

Operation Efficiency

BPA Foreman Approval

Ease of Operation Site Testing

Table 7: PDS - Cost

Cost

Requirements Primary Customer

Metrics & Targets

Metric Target Target Basics

Verification

Cost must not exceed

original spacer cart production cost by a significant

amount

BPA N/A N/AA

relative value

BPA will decide what cost(s) are acceptable.

Record keeping of

budget expendi-tures and production

costs

13/16

Conclusions:

This document has outlined the specifications for the redesign of BPA’s spacer cart. The

main goal of the redesign is to address stress issues in the frame and increase ease of use on

some of the features. Secondary goals of the project are both to make the cart lighter and

cheaper if possible. We have met with Bonneville employees and engineers to discuss the

specific goals and outline a rubric of guidelines to follow during our design process. Also defined

in this report is a progress goal timeline which has been shared with BPA to update them on our

project milestones. For this project we will need to create 3D and 2D CAD models of our design

ideas for fabrication, perform FEA analysis utilizing the dynamic/static loading scenarios the cart

will undergo during operation, and verify all of our design criteria through physical failure testing

with a fabricated prototype. Fabrication will be done by BPA which will save the project team

labor hours and allow deeper focus on design goals. One of the project’s largest challenges is

prototype fabrication will take several weeks, therefore the project team must be certain that the

design is sound before delivery to BPA for fabrication. Given the aggressive timeline specified

there might exist only one shot to make a working prototype and meet final delivery deadlines.

By splitting into “sub-teams” focused on specific design areas/criteria, the large task of

redesigning the cart has been pared down to more manageable sub-tasks. This has allowed the

large project team to collaborate on design ideas while assigning individuals a specific task/goal

to accomplish.

14/16

Appendix:Section A. Design Envelope Restrictions

15/16

Figure 3: Design change limit envelope - Axial view

16/16

Figure 4: Design change limit envelope - Transverse view