Back Country Chainsaw System

Kristiaan Brauer

Problem Statement:Design a battery-powered chainsaw system for use

by trail builders in the backcountry

Who are trail builders?

Trail builders create and maintain the millions of miles of trails that hundreds of millions of people use every year

Trails represent the primary means for people to access and enjoy the outdoors. Hiking, biking and horse riding especially rely on well maintained trails. Trail builders try to both create and maintain trails that minimize the impact of human activity on the landscape.

Why this topic?

Trail builders, at the core of it, represent my favorite group of users to design for:

They represent a skilled, passionate and talented group of amateurs and professionals, who very literally work to create the world they want to see.

They serve as evangelists for the woods, building infrastructure to help others get out and experience the joy and serenity that can be found in the wilderness.

They steward the wilderness and manage the natural resources so that they can be enjoyed for generations to come.

It’s not easy breaking trail...

Trail building uses a great number of tools to plan, layout and build trails - a number of specialized tools originally used in wilderness firefighting, log cabin construction, landscaping, as well as more general tools like saber saws, drills and, of course, chainsaws.Of all these tools, the chainsaw is the tool that

is least suited to the difficulties of trail building in the backcountry.

What’s wrong with today’s chainsaws?

Chainsaws work really well, and that’s why people accept their drawbacks

Chainsaws have an amazing power to weight ratio and make quick work of wood cutting tasks. However, because of their light weight, they do not absorb vibration or noise well. Additionally, because they are powered by two-stroke engines, they consume gasoline and oil, and produce sparks that can light brush on fire.

Are Trail Builders a good market?

Trail builders represent the most demanding user group for a chainsaw

Trail builders need to use chainsaws far away from outside support and without knowledge of what they will need to cut.

If trail builders are satisfied, then less demanding user groups, such as hunting guides and grounds keepers, will have their needs more than covered.

From there, the saw, or the technology used in it, can serve other user groups such as arborists, hotshot crews and even Christmas tree farms.

Don’t battery-powered chainsaws exist?

Battery powered chainsaws do exist already, but trail builders have not yet adopted them

Battery powered chainsaws have just begun to be introduced, but they have not yet been widely adopted by trail builders. There are various reasons for this, but the most common is a reluctance to rely entirely on batteries when there is no way to charge them in the back country.

Part One:

Research

Research Plan

InterviewsTalk to those involved in trail building and associated professions. Get a thorough understanding of users’ processes and needs

Tech InvestigationsInvestigate current and near-future technologies to get an understanding of their potentials and pitfalls

Hands-On ExplorationGain hands-on experience with chainsaw use and trail building

Marketplace AnalysisGain a thorough understanding of the current market landscape

Background ReadingScour internet forums and trail building manuals for insights

I’m not an expert trail builder, but I got a few of them to talk to me

I contacted a number of trailbuilders across the US and Canada. Their experience covered the full gamut, from managing trailbuilders along the whole Appalachian Trail to small, local mountain bike trails. Their expertise and experience was invaluable in helping me understand the problems and challenges that trail builders face.

Interviews with Trailbuilders

Building techniques and conditions change across the country...

...and I wanted to understand the picture across the whole country. I interviewed people who represented all different levels of experience and worked in every imaginable environment: front country and back country, sagebrush to swamp and everything in between.

“Two-cycle motors are very finicky, sometimes they won’t start for no reason”

“Battery-powered saws can be good, but they need to be able to operate rain or shine”

“We have to stop working with gasoline at 1 pm because of the fire danger in California”

“Electric has never let me down”

“We don’t need a chainsaw everyday, but when we do it’s absolutely necessary”

Technology Investigations

ErgonomicsHand Placement and More

Battery TechnologyDifferent Chemistries

Motor TechnologyBrush-less vs Brushed

A chainsaw is only as good as its components...

A chainsaw is only as good as its drive train. The drive train must be powerful, but also as light as possible. Gas powered chainsaws do away with batteries, water-cooling and transmissions to eliminate all possible weight. Electric powered chainsaws can drop even more weight, but must use the right batteries and motors to squeeze as much power into the chainsaw as possible.

Rechargeable Battery Chemistries

Lead-AcidAlkalineNickel-CadmiumNickel-HydrogenNickel-Metal HydrideNickel-Zinc

Lithium-Air (Li-Air)Lithum-Titanate

Lithium-IonLithum-Sulfur

Silver Oxide

2.11.51.21.51.21.65-1.7

2.7-2.912.3

3.2-3.71.7-2.5

1.86

60-11025050-15060140-300170-280

2,000?

250-730350+

240-500

180 ~80050 ~1,000150 ~2,000220 ~20,000250-1,000 ~2,000900-3,000 ~1,000

400 ~1004,000+ ~9,000

250-3,000 ~1,200~1,500

30-428540-607530-12060-100

11,14090

100-265400-500

130

3-4% Toxic, certain constructions can spill0.3% Rechargeable version of standard batteries10% Now largely obsolete

Complex construction, used in satellites30% Used for electric vehicles due to low cost

Good replacement for Alkaline

Unknown Still in laboratory developmentMain advantage is speed of charge

5-10% Most common current battery typeJust leaving laboratory

5%/yr Very expensive due to silver content

Chemistry Voltage(V) (Wh/L)

Power(W/kg)

Cycles(Max)

Discharge(%/Month)

Notes(Wh/kg)

Energy Density

While there is an astounding variety of battery chemistries, even more than listed here, only a few stand out as stellar, general purpose, rechargeable batteries. Nickel-Cadmium was the first reliable battery chemistry to replace rechargeable Alkaline batteries. In the 1990’s Nickel-Metal Hydride and then later Lithium-Ion batteries began to replace Nickel-Cadmium batteries.Since then, battery chemistry has been refined and perfected - several new battery chemistries are just coming to market, the most promising of which is Lithium-Sulfur.

Brushless vs Brushed Motors

BrushlessBrushedBrushed electric motors use two carbon brushes to transmit electricity to a central column which then transmits the electricity to electromagnets in the center. Magnets around the outside of the motor attract the electromagnet at the center. As the axle rotates the polarity of the electromagnets switches and pulls the axle a fraction of a turn, at which point the polarity switches again.

Brushless electric motors reverse the normal arrangement. Magnets are attached to the axle and the electromagnets on the outside are pulsed by an controller in sequence to rotate the axle. Brushless motors are more expensive and require a controller (known as an ESC) but generate 50% more work for the same sized battery and last approximately twice as long as brushed motors.

Without a good grip on the chainsaw, all the other safety features are effectively useless

A comfortable, secure grip on the chainsaw is its most important safety feature. Uncomfortable and awkward grips can cause premature fatigue, muscle twitches and decreased blood-flow, all conditions which can contribute to chainsaw accidents as well as long term health conditions.

Ergonomics Research

Charging in the backcountry is getting easier, but for large amounts of current, the technology still isn’t there.

With a standard chainsaw battery holding 162 watt-hours of current and weighing 3.8 lbs., the weight and

extra complexity of charging system does not begin to offset the weight of extra batteries until more than a day’s worth of batteries are carried.

0.778 Wh/lbs2.678 Wh/lbs

2.661 Wh/lbs 0.066 Wh/lbs

Backcountry Charging Research

Hands On Research

I bought a chainsaw and cut down a treeI bought an electric chainsaw and practiced using it. I also cut down a small tree with an ax to understand a chainsaw’s advantage.

I maintained trails so hard, I broke my bootsI went trail building at the East Fork Park in Bethel, Ohio with the Cincinnati Off-Road Alliance.

Current Stihl Electric System

Arborist Chainsaw

Consumer Chainsaw

Light Duty Professional Chainsaw Universal Battery

Battery Backpack

Battery Charger

Battery Waistbelt and Harness

Summary:

The Stihl battery powered line is aimed mostly at consumers and landscaping professionals, for whom the noise and smell of gasoline is unacceptable. However, the cost of investing in a full system (Chainsaw, Batteries, Charger) could give consumers sticker shock.

Weed Trimmer Pole Hedge Trimmer

Leaf Blower

Hedge Trimmer

Lawn Mower

Husqvarna Electric System

Arborist Chainsaw

Consumer Chainsaw

Light Duty Professional Chainsaw Universal Battery

Battery Backpack

Battery Charger

Summary:

The Husqvarna line is aimed at a more professional market than the Stihl line. There are fewer tools, and less overlap between their functions. The double handed weed trimmer and ride-on mower especially are aimed at a more demanding and professional user base.

Weed Trimmers

Ride On Mower

Hedge Trimmer

To round out my research, I sat down to do some reading.

To get a more complete picture of trailbuilding and chainsaw use, I read magazines, books and mountain biking forums online.Through forums I gained insight from trailbuilders

of all levels of skill and commitment. Books and magazines covered the fundamentals of chainsaw operation and trail building.

Background Reading

Documentary Watching

Backcountry Charging

Charging Is HeavyIn general, chargers are heavier than the battery weight they eliminate. The equation only starts to change during expeditions of over a week in duration.

Charging Is SlowChargers can provide enough current to charge mobile phones and cameras, but more power-hungry batteries will take days to charge.

Chargers Are InconvenientChargers need near optimal conditions to do anything other than trickle charge. Outside of these conditions chargers offer little benefit.

Chainsaw Shareholders

BuildingOrg

Building Lead

Trail Builder

Land OwnerStihl

Dealer

Repair Shop

Stuck In The Middle...

Builders and the organizations they represent want a reliable, light and capable chainsaw.

Land owners want to avoid lawsuits arising from injuries on their land.

Chainsaw makers want to sell a great product that builds repeat customers who trust the battery system.

Mountain Biker Lifestyle Board

Hiking/Backpacking Lifestyle Board

Part Two:

Research Findings

Key Research Insights

Trail building has its own culture, people do it because

they love it

Chainsaws are not used everyday, but when they are,

they are irreplaceable

A battery’s biggest advantage is that it can be positioned

remotely

Who: Three Basic Personas

Trail Building LeadBuilds almost semi-professionallyWell trained (B Sawer, WFA, etc..)IMBA MemberOwns their own chainsaws and toolsGuides others in building

Occasional BuilderBuilds once a month or lessSpends most weekends hikingBuilds as a way to give backUses provided tools

Parks DirectorManages trails for a park or cityMust manage parks as well as helping with trail buildingDeals with insurance, purchasing and permitting

What: Medium Bar, Small Powerhead Electric Chainsaw

10” Hand Saw 16” Bar1.7 hp Engine8.6 lb Powerhead

25” Bar4.6 hp Engine13 lb Powerhead

Where: Front and Backcountry Trail Systems

North AmericaThe majority of trail builders in North America are volunteers who build and maintain the trails that they use. Because they are volunteers, they want to enjoy the trailbuilding experience.

EuropeEuropean trail builders are professionals employed by the state to build trails. Strict environmental regulations have pushed the adoption of electric landscaping tools.

When: Lithium Sulfur Batteries Mature (2020)

Lithium Sulfur - Future ChemistryLithium Ion - Current ChemistryLithium Ion batteries are based on a handful of similar battery chemistries that use a lithium-based cathode and a graphite- or carbon-based anode immersed in dissolved lithium salts. This chemistry replaced Nickel Metal Hydride, the previous dominant rechargeable battery chemistry in the mid-2000’s.

Lithium Sulfur batteries use a similar electrolyte to lithium ion batteries, but use a sulfur-based cathode and either a silicone- or lithium-based anode. This chemistry uses common materials and offers a number of advantages, including higher energy density and greater number of charge cycles. My research suggests that these batteries will start to be used by consumers by 2020.

Why: Chainsaws are only tolerated

Saws are HeavyPowerheads range in weight from 8 to 15 pounds. Including bar, chain and consumables the weight can reach upwards of 20 pounds.

Saws require Gas and Bar OilSaws can use up to a gallon of gas and a half gallon of bar oil during a single day of work.

Saws are DangerousWhile not every danger can be eliminated, electric motors are quieter and do not produce sparks, eliminating the need to carry a fire extinguisher.

From these findings, I constructed a list ofdesign requirements and determined which system

components were needed

Design Requirements

Can easily handle a 15” diameter tree, even 30”

at a stretch

Lighter than an equivalent gas chainsaw

and consumables

As powerful as a gas powered chainsaw of

the same size

Able to operate safely in rain, fog and drought

conditions

Powerful Light Reach Weatherproof

Chainsaw System Components

Chainsaw

An electric chainsaw. To stay light, the chainsaw will be powered by externally

carried batteries.

Battery and Carrier

Batteries are carried externally, allowing the chainsaw to be more agile

and less fatiguing to use.

Part Three:

Ideation

Initial System Sketches

Initial Form Ideation

Color Breaks and Forms

Detail Sketches

Battery Ideation

Part Four:

Refinement and Testing

Chainsaws aren’t perfect, but the basic design works.

For my design to work, the batteries had to not only provide more energy, but be easy to carry and use.

So I designed four carrying solutions and went back to my interviewees to find out what worked best.

Concept 1

Stand AlonePower Brick

The tray accepts up to eight batteries, allowing the user to balance run time and weight. The power brick can be put in a user’s existing backpack.

Battery Pack in Bag

Concept 2

Battery Belt

The battery belt rides below the user’s backpack, allowing users to use their own small backpack or use the belt on its own. The belt places the weight on the hip bones, minimizing fatigue.

Battery Belt on Waist

Concept 3

Battery Backpack

A backpack carries the batteries, chainsaw and other tools. This option provides a self contained system incorporating the chainsaw and all related equipment.

Batteries in Backpack

Concept 4

Battery Vest

The battery vest carries the batteries close to the body’s center of gravity. Multiple carry options allow for a variety of packs to be worn.

Multiple carry positions

Validation Results

While I tried to force conclusions from the feedback I got, there wasn’t a real consensus.

Physiology played a big part, short people liked one thing, tall people liked another. No one could agree

on what solution was best...

...but I noticed you could also clip a whistle onto everyone’s favorite carrying solution.

Batteries can be treated the same way.

Using a clip to hold the battery, the user can adapt the system to their work habits, instead of the reverse.

There’s a way to end achy trailbuilding days

Using foamcore models, I replicated the postures and cutting angles used on the trail. Of particular interest was the thinner gloves that trail builders use and the lower height at which they cut downed trees.Through these tests, I was able to determine the

proper handle shape as well as the handle and blade angle.

Ergonomic Testing

Every good chainsaw starts with a good handle...

It all starts with the handle. Making sure I got the handle right was essential. Without the right controls, the right shape and the right angle, a user’s comfort and control of the chainsaw can be severely compromised.

Part Five:

Final Design

The New Stihl Trail Boss Chainsaw

There’s A New Boss On The Trail

The Stihl Trail Boss is the first chainsaw designed from the ground up for use maintaining trails in the backcountry. Everything, from the ergonomics and the drive train, down to details like the oil fill cap have been designed to function safely and exceptionally in the backcountry.

Body Only: 14.58”

With 12” Bar: 26.00”With 16” Bar: 29.92”

With 10” Bar: 24.01”

8.33”

9.33”

6.07”

7.23”9.76”

Chain Saw Dimensions

The Trail Boss is a compact, adaptable saw. The powerhead is noticeably shorter than an equally powerful gas chainsaw. This means a more compact, easily transportable chain saw. For felling trees and sectioning logs, the chainsaw can use a 16 inch bar, while for detail work, the saw can also use a 12 or 10 inch bar.

Power Cord Detach

If the saw kicks back or falls out of the user’s hands, the force will disconnect the power cord.

Tool-Free Chain Tension

The tool-free tensioning system enables the user to leave the chainsaw wrench at home.

Battery Charge Indicator

The charge indicator allows the user to check the remaining power and be warned of overheats.

Chainsaw Exterior

Gloves-On Oil Fill Cap

The flip-up lever on the oil fill cap enables it to be easily opened while wearing gloves.

Oil-Tank Window

The oil window allows the user to easily see how much bar oil is left in the reservoir.

Removable Bumper Spikes

Bumper spikes enable the saw to work on larger trees, but can be removed when not needed.

Chainsaw Interior

Oil PumpThe oil pump automatically lubricates the chain in response to chain speed and motor load.

Ruggedized Circuit BoardsCircuit boards control motor speed and the oil pump, and monitor variables like motor temperature, torque, oil level and more.

Brushless Inrunner MotorThe brushless motor takes up most of the interior of the chainsaw. Its large diameter provides the necessary torque.

Plate ClutchElectric motors are sensitive to drive-train stoppages so the plate clutch disengages when the chain stops.

The Motor

The motor is a brushless, inrunner style, electric motor. While outrunner motors produce more torque, they are slower and more prone to jamming in enclosed dirty environments. Iron cored stators stop the motor from spinning when power is removed.The motor’s open construction and impeller fan

ensure significant airflow to both cool the engine and dislodge any wood chips that work their way into the motor.

Cooling Impeller

Rare Earth Magnets

Iron-Cored Stators

Hand Brake DisengagedWith the brake wedge down, the pump belt can run free

Hand Brake EngagedWith the wedge up, the clutch stops rotating and disengages

Hand Brake

Kickback is a major concern when using a chainsaw. The Trail Boss uses two systems to prevent kickback injury. The first is the magnetic connection between the power cord and body, which detaches when the saw kicks back, cutting power and stopping the motor.Secondly, the forward hand brake, which the user’s hand pushes forward as the saw kicks back, pulls

up on an internal wedge, which jams the clutch and disengages the motor from the drive train.

The oil filler is obstructed by the hand brake. When pushed forward to open the oil filler cap, the hand brake is engaged.

The saw uses the same trigger safety as gas powered saws, instead of the side button safety common with electric saws.

With the hand brake pushed forward, the oil filler cap is accessible and the chain cannot accidentally start moving.

Only once the users palm or thumb has depressed the safety on top of the handle is the trigger able to be depressed.

Flipping the black lever up on the filler cap unlocks the oil reservoir allowing it to be filled safely with oil.

This type of safety is better suited to chainsaws which have to be used either vertically or horizontally.

Filling Bar Oil

Trigger Safety

Rain-Proof Venting

Trailbuilders need their tools to work year round, rain or shine. Up until now, electric chainsaws were unable to operate in the rain because water would fall through vents and cause short circuits in the motor.The Trail Boss uses a baffle inside the vent to

prevent water from making its way into the saw’s interior while allowing air to cool the motor.

Plate Clutch

Gas chainsaws use a centrifugal clutch to prevent an idling motor from driving the chain.Electric motors, on the other hand, need a clutch

that disengages when the chain gets stuck in a cut, to prevent damage to the motor. The Trail Boss uses an adjustable, single plate clutch to disengage the chain before the motor might be damaged.

Shallower Bar AngleThe bar has a slightly shallower angle that gives better control and precision while working close to the ground.

Shallower Handle AngleThe Trail Boss handle is angled to reduce strain on the user’s wrist while working close to the ground.

Smaller Handle OpeningTrailbuilders use thinner gloves than lumberjacks, so a smaller opening gives the user more control.

3.5°

Ergonomics

6.5°

Gasoline Powered

Battery Powered

The Battery

Voltage Regulator + Microcontroller

Vent

Lithium Sulfur Cells

Leave The Gas-Can At Home

The power for the chainsaw comes from these batteries, smaller and with more endurance than all current 36/40 Volt batteries. The lithium-sulfur chemistry allows the batteries to have an energy density only slightly lower than gasoline and requires no conflict minerals or heavy metals for their construction.

There’s Still Room For Beer

Just two batteries provide four hours of continuous chainsaw run-time. Since the batteries are only slightly bigger than a beer can, you only have to take half a six pack out of your pack to have enough power for a full day of work.

Put Power In Your Pocket (Or Backpack)

A lighter chainsaw is more agile and less tiring to use. By carrying the battery (the second heaviest component after the motor) externally, the chainsaw is less tiring to use.

Charging/PowerPort

Hangs On Like A Koala

The battery’s holster can clip on to any piece of webbing, like backpack straps or belts as well as pockets or chaps.

Stihl MS 180 C-BE: 10 lbs 13.1 oz Stihl Trail Boss: 7 lbs 14.3 oz

3 Batteries: 3 lbs 1.3 oz1 Gallon of Gasoline: 7 lbs 15.9 oz

1/2 Gallon of Bar Oil: 3 lbs 11.2 oz1/2 Gallon of Bar Oil: 3 lbs 11.2 oz

Total Weight: 22 lbs 8.2 oz Total Weight: 14 lbs 10.8 oz

Weight Comparison

8 lbs lighter

Butch FarrelCincinnati Off-Road Alliance

Shannon FreixMontana Wilderness Association

Doug GeersBryan Equipment

Jim GodbyCincinnati Parks

Bill HawleyPacific Crest Trail Association

Josh KloehnAppalachian Trail Conservancy

Matt PattersonDirt Corps

Ray PetroOcala Mountain Bike Association

David RoePacific Crest Trail Association

Dr. Peter VinkTU Delft, the Netherlands

Mike WestraEvergreen Mountain Bike Alliance

Ben WhiteSan Gabriel Mountain Trailbuilders

This project would not have been possible without the help of the following people:

Thank you for your time

Kristiaan Brauerkrisbrauer@gmail.com206-755-3679