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Before starting the woodchipper, locate a flat surface devoid of pits and holes, and then clear it of any debris that can trip, or cause an accidental fall. Always avoid slopped surfaces.

Relatedly, a woodchipper is a machine with rotating parts which makes safety a top priority, and the standard ABC (Always Be Careful) of safety applies to the use of any kind of woodchipper.

Next, ensure that the discharge spout expels the woodchips away from the user.

This is because the chips are expelled at a high velocity and their momentum can cause considerable injury if they hit a person, especially considering that they are discharged as a deluge of chips.

Likewise, the chipper must be positioned so that the wind does not blow the chips towards the user.

Thereafter, sort the wood that is to be fed to the chipper and remove unwanted materials such as nails, plastics, screws, and metals. This ensures that the chipping blades and flails are not quickly blunted or damaged by unwanted materials.

If the chipper uses an internal combustion engine, check to ensure that there is enough fuel in the fuel tank, and enough oil in the crankcase.

woodchipper image

For an electric motor, check for loose wire connections that can cause sparks (which can ignite dry combustible chips or wood debris), and ensure that the motor is well lubricated.

Also, check to ensure that there is no debris or stuck wood in the chipping chamber. Most importantly, check to ensure that feeding tools are not in the chipping chamber.

Debris and wood stuck on flails can impede rotation of the chipper which disrupts power transmission from the engine, besides causing transference of inertia to the engine which can result in engine knocks.

The other key safety features of the woodchipper are the safety grid and safety switch, both of which need to be engaged before the chipper can start working.

For models that use electric motors, an anti-jamming feature prevents damage to the motor. Likewise, some drum chippers allow the user to reverse the direction of rotation so as to allow him/her to remove his/her piece of cloth that has been caught by wood being fed into the chipper.

As expected, avoid any woodchipper model that does not have safety features.

When using the chipper…

Use the feeding tool to push the wood into the chipping chamber. This ensures that hands are far away from the chipping chamber, and a safe distance from the inlet chute or hopper.

Wear protective gear, including steel-toed boots, helmets, thick work gloves; and use eye and ear protection.

Avoid wearing jewelry, or shirts with hanging cuffs or sleeves. It is preferable to wear snug-fitting clothes. Always tuck in the shirts and sweaters (or jacket), and secure belts tightly around the waist.
When chipping woods, always place small amounts of wood on the inlet feed.

Placing too many woods increases the risk of the chipper unit throwing some of the wood back to the user, which can result in blunt force trauma (which is the most common injury associated with using woodchippers).

After shutting off the chipper, clean area around chipper of debris that can cause slippage or tripping.
Now that one understands the basics of woodchipper safety and how to use it, there is a need to explain how the chipper works.

How the Woodchipper Works

The blades of the chipping unit are attached to an impeller, which is then fitted onto a blade-shaft. This blade-shaft is positioned in the central axis of the impeller or screw blade, which ensures that the impeller is perfectly balanced when rotating and that no wobbling occurs.

It is this blade-shaft that causes the flywheel, drum, and screw blade to spin, and it is driven by the engine either directly, or through a drive belt or a PTO transmission system.

If a drive belt is used, the small pulley of the engine drives the larger pulley connected to the blade-shaft, and this difference in pulley size reduces speed in the larger pulley (in relation to engine speed) while increasing its overall torque.

For PTO systems that have a gearbox, the gears serve to regulate torque in the blade-shaft, which in turn regulates the amount of kinetic energy that blades attain when chipping wood.

In the chipping chamber, there can be more than one blade-shaft positioned parallel to each other, so that the blades they drive can intermesh during rotation.

This allows the blades to quickly crush and chop up wood into small pieces, besides being able to pull the wood which creates a self-feeding mechanism.

This is common in drum chippers which have two horizontal drums placed parallel to each other (that is, one drum is at top and the other at the bottom). Intermeshing also cuts the chips to a relatively uniform size, as compared to using a single blade-shaft.

wood chippings

Once the IC engine is started, it needs to accelerate till it reaches a specific speed (as measured in revolutions-per-minute, rpm) that creates enough flywheel momentum that forces it to be engaged to the clutch.

The clutch is connected to the motion transmission system that transfers engine motion to the blade-shaft. The rotating blade-shaft spins the impeller which sets its blades in motion.

The rapidly spinning impeller imparts kinetic energy to a blade, which makes the pressure on its cutting edge to be so high that on impact with wood, it slices or shears through it; while the blade with semi-blunted cutting edge simply pulverizes the wood.

If the blades are intermeshed, then the wood pieces are further broken down into small bits that can fit through the spaces between intermeshed blades, and this results in the production of uniformly sized chips.

In high-quality models, if the drum jams, then the clutch can be automatically disengaged to prevent engine knocks due to jamming of the crankshaft.

The chips are then propelled towards the outlet by the rotating blades, with rapid airflow created by the rotating impeller adding to the momentum of the chips which causes them to be blown out, or blasted out, through the discharge spout.

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