Weed whacker redesign

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Contents

Executive Summary

User Testing

Research and Observations

Shopping

After asking many potential customers who were looking at weed whackers we found that the main concerns of users were:

  • Cost
  • Maintenance
  • Safety
  • Ease of use

Other concerns included:

  • Weight
  • Noise
  • Vibration
  • Power

We noticed that many of them assumed characteristics of the design.

Gas powered:

  • High power
  • Noisy
  • Vibrates
  • Hot

Electric powered:

  • Not enough power
  • Low battery life

Usage

After observing a few weed whacker users, we asked them what their main complaints and difficulties of using their particular weed whacker.

Gas Powered:

Awkward holding position: The design of the weed whacker forces the user to hold it in a position that has been reported to be very awkward to the user. The right hand holds the handle where the trigger is located and the right arm is what holds most of the weed whacker's weight. The left hand is located about ten inches down shaft of the trigger hand, and The right arm is mostly kept bent and the left arm mostly kept straight throughout the usage in order to keep the weed whacker angled downwards toward the grass. After a short time of use, the user's right arm would get tired and straighten, thus making the weed whacker hard to maintain over grass.

Weight Distribution: Users complained about the weed whacker being heavy. Also they didn't like how most of the weight was located in the back where the engine is. Users found it unnatural to maneuver, and some muscles, such as biceps and back muscles, were being over used.

Vibrations: The constant vibration of the 2 stroke engine proved to be quite an issue for users. The engine is constantly erratically vibrating while idle and while throttled, which added to the inconvenience of holding the weed whacker for a prolonged amount of time in the holding position. Also, when the trigger is pulled to throttle the engine, the sudden clockwise rotation of the axle creates an opposite reaction of the weed whacker being suddenly thrust in a counter clockwise moment. This twisting of the weed whacker seemed to be small issue with some users.


Electric:

Awkward holding position: Similar to the gas powered weed whacker, the hand positions are awkward making the left arm completely extend forward and the right arm bent to the user's side. We observed this position made it difficult to sweep the device from side to side.

Weight Distribution: The electric weed whacker design had most of the weight too far forward as the motor was located at the head of the weed whacker. Although it is lighter, users experience that more effort is needed to hold the weight. Over time we observed the user resting the end of the weed whacker on the ground to rest their arms.

Power supply: The particular design used a power cord to supply power. This allowed the motor to spin at optimal speeds so we did not observe a lack of power. Vibration and noise did not seem to be a problem either. However the user constantly pulled and relocated the power cord while usage. This problem was not reported as a problem when asked. We observed that the cord could cause major injury if cut or caught on the user.

Conclusions from User Study

From our user shopping research, we found that appearance made a larger impact than the specifications listed on the box. In order to keep potential customers from overlooking our product, we must explicitly show that it is a weed whacker, and will provide the services needed. We also found that users had a preconceived notion regarding the type of engine which made them overlook the power provided.

Because of this, we decided to keep the string as the blade. The type of power source would determine the main focus of design. However, because battery power and life are extremely difficult to improve, we decided to keep an engine.

From the user study, we were able to define the major areas of improvement. Because we are continuing to use a engine as the power source, our main concerns are:

  • Awkward holding position
  • Weight
    • Weight distribution
  • Vibrations
  • Cost
  • Safety
  • Intuitive use

Existing Designs

Currently there are an exorbitant amounts of weed whacker/string trimmer designs. Most of which regard attachments, blades, wires, or the wire feeding mechanism.

Regarding the entire apparatus, we found a few existing designs that focus on usability rather than novelty or alternatives.


Weed Whacker/Blower/Vacuum

Image:Weedwhackerdesign1.jpg
Out of the many novelty patents we found this particular design vaguely relates to one of our concepts. We considered creating a vacuum or blower combination with the weed whacker, but we decided that its usefulness is very limited. Instead we shifted focus on redesigning the weed whacker to be easier to use.
Pros

  • Has multiple uses

Cons

  • Higher weight/inertia
  • Same handling problems as basic weed whacker


Backpack Weed Whacker

Image:Weedwhackerdesign2.jpg
Using a torsional cable, this design can put the majority of the weight on the users back. This is where some of our ideas were formed. However, the direct drive shaft and bevel gear casing are still required adding a substantial weight. We thought that this concept was a great idea, but changed the method of power transfer to pneumatics for reduced weight, and focused on the way the user handles the cutting end.
Pros

  • Relieves majority of the weight
  • Lowers inertia

Cons

  • Same awkward handling problems as basic weed whacker
  • Weight is shifted too far forward requiring 2 hands or a large force on user's wrist

Height Adjustable Wheeled Design

Image:Weedwhackerdesign3.jpg
Using wheels can alleviate the weight issues, as well as keeping a uniform cut length. However the wheels will add friction and inertia making the apparatus more difficult to manuever. The wing nuts require too much adjusting to get the angle and height to desired specifications. Mimics a lawn mower by removing many functions of a weed whacker. We looked at this design, and thought that using wheels may be another way to decrease weight and allow the user to handle the weed whacker more efficiently.
Pros

  • Less weight on user
  • Uniform length

Cons

  • Same awkward handling problems as basic weed whacker
  • Heavier
  • Too many parts
  • Requires too much adjusting
  • Can't reach hard to reach places
  • Can't edge trim

Other Design Options

Blades
Pros

  • Better cutting ability

Cons

  • Image
  • Safety
  • Cost/maintenance
  • Loss of edge trimming

Electric Motor
Pros

  • Better for the environment

Cons

  • Power
  • Battery costs
  • Battery life

Corded
Pros

  • No battery
  • Much higher power output than on battery

Cons

  • Requires outlet
  • Cord gets in way

Motor attached to cutting head
Pros

  • Better power transfer

Cons

  • Much higher inertia

Concept Designs

Concept 1

Concept 2

Concept 3

Concept 4

Concept Evaluation

Pugh Chart

Description Standard Weed Whacker Concept 1 Concept 2 Concept 3 Concept 4
Sketch
Criteria Weight Datum Design 1 Design 2 Design 3 Design 4
Handling 3 0 0 0 0 0
Vibration 1 0 0 0 0 0
Weight 2 0 0 0 0 0
Affordability 1 0 0 0 0 0
Safety 2 0 0 0 0 0
Ease Of Use 3 0 0 0 0 0
+ 0 0 0 0 0
0 0 0 0 0 0
- 0 0 0 0 0
Net Score 0 0 0 0 0

Design Schedule

Appendix A: Brainstorming Ideas

Weed whacker head

  • Blades instead of wire
  • Plastic Blades
  • Heavier wire
  • Metal wire
  • Non-circular wire (star cross-section wire)
  • Weed “vacuum”
  • Opposing rotation whacker heads
  • Full shield (360 degrees)
  • Adjustable shield
  • Clear shield
  • Automatic line feed
  • Heavier shield
  • Disk shield located higher on shaft
  • Laser cutting
  • Scissor
  • Heat generating blades
  • Adjustable string length
  • Adjustable angle of attack
  • Height reference attached to whacker head to ensure consistent height of grass

Shaft/axle/power transfer

  • Length adjustable
  • Telescoping shaft
  • Hula hoop weed whacker
  • Rotatable shaft
  • Clear plastic shaft
  • Angled shaft
  • Bendable "snake"
  • U shaped weed whacker
  • Locking positions
  • Torsion cable
  • Hydraulic
  • Pneumatic
  • Electric cables
  • Simple Electric Power Switch(better usability)
  • More gears to provide more speed

Handle

  • Clamping handle
  • Smaller handle
  • Ergonomic trigger
  • Button or slide instead of trigger
  • Grip trigger
  • Shoulder strap
  • Strap to arm
  • Shoulder mounted weed whacker
  • Arm attachment weed whacker
  • Split weed whacker (dual wielding)
  • Back-Pack like straps
  • Luggage like straps and wheels
  • Push handle forward or backward will angle whacker head forward or backward
  • Button on handle to feed wire

Power Source

  • 4 stroke engine
  • Self-starting engine (no pull cord)
  • Electric motor
  • Power source closer to head of weed whacker
  • Back pack style power source
  • Solar powered
  • Hydrogen powered
  • User powered
  • Corded
  • Hybrid powered

Safety

  • Built in safety goggles
  • Safety goggle compartment
  • Safety gloves
  • Safety glove compartment
  • Safety boots

Miscellaneous

  • Night light
  • Vacuum attached to whacker
  • Blower attached to whacker
  • Wheel on bottom
  • Plastic whacker
  • Tripod whacker
  • Robotic
  • Remote controlled
  • Auto kill-switch
  • Attachments for other lawn care
    • Leaf Blower
    • Mulcher
    • Spray gun
    • Hedge trimmer
  • Hovering weed whacker
  • Magnetic weed whacker
  • Collapsible for easy storage
  • HUD for weed whacker properties
    • Display of amount of the gasoline left
    • Display of amount of the co2 emission
    • Display of amount of the oil
    • Display of the how many hours the fuel will last
  • Pager
  • Intercom
  • Mp3 player
  • Radio
  • Beverage holder
  • A GOAT
  • Advanced mechanics to reduce the sound of the engine
  • Holes in the materials
  • Collapsible for different shape and usage
  • Add key for security
  • Aesthetically pleasing design
  • Two weed whackers at the shoes
  • Use of electric shock to cut the weeds
  • Engine-less device that is pushed and rolled to cut the weeds
  • Contain the co2 by putting co2 absorbing chemicals or bags

Current Trend in Weed Whacker

Fifteen years ago, first metal weed whackers were sold. It was highly dangerous and bystanders were told to stay 30 feet away. The major danger comes when blade get caught up in the thick brush, and cause a "Kick Back", throwing all the energy stored in the blade back to pole. That can cut the head and leg muscle. In early 1998, when high school football star had started the gasoline engine of his weed whacker, plastic hub broke. And flying metals struck his legs. Other blade designs that has been released for weed whacker has not been safe or reliable. And therefore, current trends of the weed whacker is using the plastic strings. Consumer Product Safety Act often realize that the blade based weed whacker contains a defect which could create a substantial hazard or unreasonable risk of injury.

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