//02 Handheld Trimmer - Ergonomics

//02

Hand-held Trimmer Human Factors Project.

This project focuses on the physical and semantic interaction that users have with products. Designed for the ‘Garden Proud’ user group this product was focused on the skilled enthusiast.

//The Market Professional Quality Area of Opportunity

A - Bosch ISIO - £64.99

The best selling product of it’s kind on Amazon, reviews are very positive and praise it’s long battery life, easily changed blades and build quality.

A

Price -

Price +

Garden Proud // Oliver & Mary // 58 & 60

B

Partners of 35 years Oliver and Mary live near Bath in their family home, since their children have left home Oliver and Mary have decided to invest their new-found free time into their garden.

The couple’s love of gardening extends beyond the work they do in the garden, regularly they read gardening publications and visit public gardens, last year visiting the RHS Chelsea Flower Show

Their garden is a great source of pride and whilst gardening is a great way for them to spend time together they both feel that the main sense of reward comes from showing off their hard work when they host garden parties in the summer months.

Oliver and Mary take great time and care choosing and maintaining their equipment, and as such are willing to invest large amounts of money into high quality products.

B - BLACK+DECKER GSL700 £54.99

Despite being only £10 less than the Bosch this product has many more negative reviews with key criticisms being a weak motor, poor build quality and an uncomfortable design.

Entry Level Quality

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//Existing Product Research // Product Disassembly

Dismantling an existing product provided me with many useful insights into the construction of other products on the market, regarding injection moulding techniques and also the packaging of components.

Gaining a greater understanding of the components themselves and their dimensions was also invaluable, as was understanding the relationship between parts.

//Key Ergonomic Factors // Grip Type

The nature of the tool and the task will require a power grip.

Maximum grip strength is found at 40mm diameter in men, and since the female hand is 20% smaller, circa 32mm in females.

It’s important to remember the user will likely be wearing gloves.

// Deviations

Deviations of the wrist can lead to trauma in the carpel ligament and cause carpel tunnel syndrome.

A radial deviation is a deviation towards the thumb side of the hand and an Ulnar Deviation is toward the little finger side of the hand. Ulnar Deviations are more damaging than radial.

Radial Deviation

// Flexions

Neutral

Ulnar Deviation

Dorsiflexions

As with Deviations, Flexions over extended periods can cause discomfort and damage.

Dorsiflexions are the most damaging flexion, especially when paired with Ulnar Deviations.

Neutral

Palmar Flexion

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//Ideation

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//Final Model

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// Feature

A key part of the ergonomics of the tool are visual; the 3 raised lines on the blade release button offer a grippy surface and visually suggest that they should be interacted with.

// Feature

The large front button features a latch which holds the front of the blade unit in place, when this is pressed the blade is released allowing the user to swap it for a different tool.

// Feature

The 4 indents which pass from tool to blade cassette help the user to visually align the two parts ensuring they’ve securely attached the cassette.

During my disassembly I found the blades on the Bosch tricky to change and felt that this system would make changing the blades easier and safer.

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// Handle Length

The handle spans 150mm allowing for a comfortable grip for even the largest hands, it also helps to offset some weight from the heavier front to the back, allowing for a better balance.

// Grip Diameter

The diameter of the handle is 35mm, a happy medium between the ideal 32mm for women and 40mm for men -this also allows for a comfortable grip in gardening gloves.

// Comfort

TPE grips increase users grip of the tool reducing the need for an over firm hand grasp. This helps to make the tool comfortable to use over extended periods of time.

// Colour Theory

Using red for function buttons makes the product more intuitive through colour semantics, suggesting that the red shoudl be interacted with but also acts as a gentle reminder that this is a safety switch and the tool should not be misused.

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// Handle Grip

// Motor and Gears

Colour: Deep powder blue with white speckles.

3.6v motor driving a gearbox made from poly-amide nylon, which is resistant to chemical degradation and hard wearing, ideal for gears which need to be greased.

Material: Over-moulded TPE. Finish: Matte rubber effect.

// Body Colour: Brilliant White Material: HDPE with glass bead filler for added toughness and tensile strength.

Finish: Matte.

// Battery and PCB

1500mAh Lithium Ion battery allowing for circa. 60 minute run time.

PCB with switch for activation and charging port at the rear.

Located as far back as possible to offset the weight of the motor and balance the product better.

// Trigger Colour: RGB Red Material: Polypropylene with added glass bead create matte texture and improve properties.

Finish: Matte.

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// Screws

6 Screws hold the left and right shell together. Spreading the load evenly avoiding areas of high stress.

// Bungs

To avoid unsightly holes in the product TPE Bungs are manufactured to match the shell and cover the screws once they’re in place, this helps to reduce the risk of water and dirt ingress and also reduces the risk of users tampering with the product.

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