The Harvester Is A Type Of Heavy Machinery That Isemployed In Cut To Length Logging Operations Forfelling, Buckling, And Cutting Up Trees. Normally,a Harvester Is Employed Alongside A Forward Thatwill Haul The Logs And Trees To A Roadside Landing.Harvesters Were Developed In Sweden And Finland,and Today They Do Nearly All Of The Commercialfelling In These Countries. They Work Best For Less Difficult Terrain For The Clear Cutting Areaof Forest. For Steep Hills Or Removing Individualtrees, Chain Saws Are Normally Preferred. Inthe Nordic Countries, Small And Agile Harvestersare Used For Thinning Operations And Manual Cuttingis Only Used During Extreme Conditions Or By Selfemployed Owners Of The Forest Or Wooded Area.The Leading Manufacturers Of Harvesters IncludeTimberjack (which Is Owned By John Deere) And Valmet, Which Is Owned By Komatsu.Normally, Harvesters Are Built On A Robust Allterrain Vehicle, Which Can Either Be Wheeled Ortracked. Sometimes, The Vehicle Can Be Articulatedto Provide Tight Turning Around Obstacles. A Diesel Engine Will Provide Power For Both The Vehicle And The Harvesting Mechanism Through Ahydraulic Drive. An Articulated, Extensible Boom That Is Similiarto That Of An Excavator, Will Reach Out From Thevehicle To Carry The Head Of The Harvester. Thereare Even Some Commercial Harvesters That Are Adaptations Of Excavators With A New Harvester Head, While The Others Are Purpose Built Vehicles.The Normal Harvester Head May Consist Of:1. A Chain Saw To Cut The Tree At Thebase And Also To Cut It To Length. The Saw Ishydraulically Powered Rather Than Using A 2 Strokeengine Of A Portable Version. It Offers A Morerobust Chain And A Higher Output Power Than Anysaw Carried By Man.2. Two Curved De-limbing Knives That Canreach Around The Trunk To Remove Branches.3. Two Feed Rollers To Reach Out And Graspthe Tree. The Wheels Will Pivot Apart To Allowthe Tree To Be Embraced By The Head Of The Harvester,and Pivot Together To Hug The Tree Tight. 4. Two More Curved Knives For De-limbing.All Of This Is Controlled By An Operator Who Sitsin The Cab Of The Vehicle. A Control Computer Isused To Simplify Mechanical Movements And Keep Thelength And Diameter Of Trees That Have Been Cut.The Length Is Computed By Counting The Rotationsof The Gripping Wheels. The Diameter Is Computedfrom The Pivot Angle Of The Gripping Wheels Thathug The Tree. Harvesters Are Normally Available For Cutting Treesup To 900 Mm In Diameter, Built On Vehicles Thatweight Up To 20 T, With A Boom That Reaches Up Toa 10m Radius. The Larger, More Heavier Vehiclesdo More Damage To The Forest, Although A Longer Reach Will Help By Allowing More Trees To Beharvested With Less Movements Required By Thevehicle.PPPPP(word Count 481)
