Connection between Thule’s customers and IrregularST

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Connection between Thule’s customers and IrregularST

Thule’s strollers are tested according to Thule’s internal test requirement and EN-1888 test standards. These tests are suggested procedures for testing durability, safety, strength and more, where IrregularST is a part of them. An earlier study has been conducted at Thule to investigate the connection between a typical Thule user and Thule’s internal test standards as well as EN-1888 standards. The test that was compared in the study was the European standard test IrregularST and Thule’s own two different outdoor test tracks. The purpose of the study was to see if the current EN-1888 test standard, IrregularST and Thule’s two test tracks reflect the use of Thule’s customers. [4] The study consists of a customer survey where a typical Thule user exposes the stroller for a walk as they would use it for. These different terrain types were mapped and compared to Thule’s own two test tracks to see if those were comparable. The stroller was then tested and compared with IrregularST. The researcher used accelerometers to collect data from different tests. To use accelerometers, loads that occur during strolling over obstacles can be measured. These loads can be described as acceleration, or movement, in different directions.


Benchmarking is a method where already existing- or competitor products are described that fulfills the same need as the project’s product is going to do. The method can be applied in a different stage of the product development phases, and the goal is to understand a design problem. The purpose of doing benchmarking is to create a learning of what already exists, and also it reveals opportunities to improve on what already exists. In benchmarking for new development, advantageously each competing product needs to be compared with customer’s requirements. If any competing product achieves all the requirement, it could be a good inspiration for the development project. Thus, various patent must be kept in mind. If the development is a redesigning of an already existing product, the current product could be a benchmark, reference point. If some features helped to meet an important requirement, the features shouldn’t be changed. Benchmarking is done in order to avoid needless work in the future. [11, pp. 158-160]

Experimental analysis

Before it was possible to improve the comfort of the front wheel, decisions were made on what possible increased comfort could be throughout an experimental analysis. Because Thule Chariot CAB doesn’t have front fork suspension, an experiment was performed to test the stroller with front suspension. By doing that, possible differences of the stroller’s behavior may occur and be inspected. To ensure that the stroller’s two different setups were tested properly and comparable, the stroller was driven on the IrregularST. Thereby, there was no difference at the test tracks obstacles, speed and how the stroller should have been driven by its user. The experiment can be divided into two different test configurations (see Table 1). – Configuration 1: Thule Chariot CAB with its original front wheel and original rigid front fork. – Configuration 2: Thule Chariot CAB with its original front wheel but with front fork including suspension. The purpose of the experiment was to see how the two different configurations differ in performance and behave differently when it rolls over obstacles. By doing this experiment, estimation of what possible improved comfort is, could be determined.

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Thule Chariot CAB’s literal competitors are other multisport- and bike trailers. Because the focus of this project was to increase the comfort of the front wheel, other stroller wheels of nearly the same size were selected for benchmarking. The competitors’ front wheels found in Thule’s development site in Hillerstorp was used, because of the opportunity to test them. Information about market cost was found under the brand’s own online store. All of the wheels that were compared in this benchmarking are constructed in two different ways. In the section views (see Figure 10), the different constructions of front wheels can be seen. The main difference between these constructions is that there is one extra material of rubber that encloses and protects the inner core of soft material (EVA). The extra material of rubber (EPDM) also increases the strength and durability of the wheel. For material information, see chapter 2.6 Materials. Other comparisons can be seen in (Appendix 2. Benchmarking).

Benchmarking setup

Before the benchmarking was performed, a test equipment was developed to make the benchmarking process both faster and easier. From the experimental analysis, the assessment was made that if the wheels bounce fewer times, and the movements in the z-direction decreases (see Figure 9), it will improve the comfort characteristics. Decisions to stabilize x- and ydirection to make the measurements in z-direction more clearly was made. The equipment was also made so that the measurement can be done near to the wheel and only regard the wheel. By doing that, no movement is disappearing throughout the body of the stroller itself, and the measurement on the wheel becomes more accurate. To collect data and measure how the different wheels behaved when pass obstacles, the wheels were measured with an accelerometer. By measure accelerations, the difference bounce height can be analyzed by the derived equation from chapter Use of accelerations. Accelerations were measured by attaching a smartphone on top of the test equipment. By an app named google science journal ( Measurement tools, Accelerometer – Science Journal by Google), the accelerations were recorded and saved so it could be analyzed afterward. Since the accelerations can be interpreted in different ways, all wheels were video recorded so conclusions could be drawn afterward.

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Table of content :

  • 1 Introduction
    • 1.1 Background
    • 1.2 Problem description
    • 1.3 Purpose and aim
    • 1.4 Delimitations
    • 1.5 Outline
  • 2 Theoretical framework
    • 2.1 Connection between aim and theory
    • 2.2 EN-1888 Irregular surface test (IrregularST)
    • 2.3 Connection between Thule’s customers and IrregularST
    • 2.4 Mathematical formulas
    • 2.5 Product development
    • 2.6 Materials
    • 2.7 Feasibility Evaluations (Gut Feel)
  • 3 Method
    • 3.1 Connection between aim and method
    • 3.2 Methods for pilot study
      • 3.2.1 Experimental analysis
      • 3.2.2 Benchmarking
        • Measurement tools, Accelerometer – Science Journal by Google
      • Use of accelerations
      • 3.2.3 Quality Function Deployment – QFD
    • 3.3 Methods for concept generation and elimination
      • 3.3.1 Brainstorming
      • 3.3.2 Idea sketching
      • 3.3.3 Rapid prototyping
      • 3.3.4 Pugh’s matrix
    • 3.4 Validity and reliability
  • 4 Implementation and result
    • 4.1 Pilot study
      • 4.1.1 Experimental analysis
      • 4.1.2 Benchmarking
      • Benchmarking setup
      • Benchmarking result
      • 4.1.3 Quality function deployment (QFD)
    • 4.2 Concept generation and rapid prototyping
      • 4.2.1 Brainstorming
      • 4.2.2 Idea sketching
      • 4.2.3 Concepts
      • Concept
      • Concept
      • Concept
      • Concept
      • 4.2.4 Rapid prototyping
    • 4.3 Concept elimination
      • 4.3.1 Testing the wheels
        • Testing result
      • 4.3.2 Pugh’s matrix
  • 5 Analysis
    • 5.1 Thesis question
    • 5.2 Thesis question
  • 6 Discussion and conclusions
    • 6.1 Implications
    • 6.2 Conclusions and recommendations
    • 6.3 Future work
    • 6.4 Reliability and Validity
    • 6.5 Project reflections

Concept Development of Stroller Wheel

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