Engr. Segun R. Bello

Department of Agricultural Engineering Technology Federal College of Agriculture, Ishiagu

E-mail: segemi2002@yahoo.com

Prof. Onilude M.A Department of Agricultural and Environmental Engineering

University of Ibadan, Nigeria E-mail: ma.onilude@mail.ui.edu.ng

BUILDING A MOBILE WOOD CHIPPER

2 | P a g e

Introduction

Wood chips have various uses such as being spread as a ground cover, being pressed into particleboard or fiberboards, or being fed into a digester during papermaking. The use of wood waste in animal bedding is known to be widespread (CALU, 2005). Dry woodchip has been used as an alternative to straw under sheep and cattle housed in sheds (Frost et al, 2005). Initially woodchips are spread across the shed floor to a depth of 10cm (CALU, 2005).

The farmers using the system have been pleased with the results compared with straw. The woodchip utilization in animal bedding is less labour intensive and stock remains clean with low incidences of foot problems and reduced need to belly clip lambs before dispatch to the slaughterhouse. Chip compost has been re-used as bedding and as a growing medium for tree seedlings. There have also been research interests on the suitability of composted woodchip bedding as a substrate for growing exotic mushrooms (CALU, 2005).

Wood waste converted to mulch covers the soil and absorbs the erosive impact of rainfall and reduces the flow velocity of runoff, significantly reducing soil loss from a site. Wood chip mulch may be applied after the site has been rough graded to control erosion. It provides a temporary cover that reduces soil loss and allows vehicular and foot traffic over the area. Mulch also provides benefits to the site beyond erosion control. The wood chips form a blanket over the soil, and moderate its temperature, conserving moisture and providing an environment conducive to seed germination. Wood chip mulching is a versatile practice that is applicable on sites where sheet flow is maintained and slopes do not exceed 3:1(DNR Publication, 2004).

The local herb producers equally improves the market value of their products by locally chipping roots and herbs to increase the surface area for increased water absorption consequent release of the chemical constituents required for curative uses.

Chipping is a fast, simple and environmentally friendly way of disposing agricultural wastes to high quality fiber value which has various uses such as being spread as a ground cover, being pressed into particleboard or fiberboards, or being fed into a digester during papermaking as well as bottom cover and covering for paths with a low traffic pressure. The use of wood waste in animal bedding is known to be widespread (CALU, 2005).

Due to the economic value of wood waste, a significant portion of them does not adequately meet the needs of the consumer industries. The complexity of different attributes of wood waste and other considerations provides criteria for the selection of materials and the design of suitable size reduction technology and equipment. The equipments vary with respect to the forms of wood wastes that can be effectively handled, and the quality of the product produced.

3 | P a g e

General Machine Description

The chipper consists of a chipper disc assembly, frame, a disc housing, an infeed chute and an exhaust or discharge chute. The disc chipper employs a rotary cutting steel disc secured to a shaft and simply supported on friction bearings to cut wood into chips. The cutting disc is formed from mild steel 25.4mm (1’) thick. There are 3 cutting knives; 200mm in length fixed to the cutting sides of the disc bolted directly to the rotating disc.

In operation, the disc is spin by a suitable electric motor to drive the shaft and the disc. The wood to be chipped enters the machine through the infeed chute, and resting on the anvil attached to the chute bracket. The wood is drawn against the anvil as the knife cut a chip which is ejected through the aperture and out of the chipper through the discharge spout.

Machine Fabrication Procedure

The design of my chipper revolves around the rotary action of the chipper disc and three knives enveloped in a round housing and two side plates made from the same material. The entire system was powered by a 15hp electric motor to drive the disc.

Other components and shapes are produced from secondary machining operations including cutting, grinding, and trimming, drilling, sawing, and turning. The conditions of tools used for machining has greater influence on component performance, hence adequate care was taken to establish and maintain the optimum tool conditions. Detailed description and fabrication process is discussed as follows:

The Infeed Chute: The components of the infeed chute were designed to give protection

against both upper and lower limbs of operator from being pulled into the machine. 1/8" thick steel metal plate was used for the construction of the chute sides. The angle of

inclination of the chute to the side plate is 35o

. Outer edge opening of the infeed chute is a

minimum of 41” wide x 39” high. Opening at feed spout is designed to be a minimum of 14” wide x 12” high. It was constructed from 14 gauge steel on top, sides, and bottom up to the chute bracket. The external length from feed spout to ground level is 800mm. The chute edges have a ¾ square pipe welded right round to prevent the sharp edges from causing accident.

Side Plate and Chute Bracket: The anvil and the chute bracket were constructed and

set at 35o

angles and welded to the chute opening on the side plate. Other sides of the

chute were also welded to the anvil support and in place.

4 | P a g e

Plate 1: Infeed chute side plate

Anvil and the Infeed Roller: The anvil and the infeed roller were constructed and

installed to control the knife clearance and the material feed into the knife respectively.

Plate 2: Anvil and Infeed roler

The vertical height of the roller is limited to the maximum feed capacity of the machine (76.0mm). The roller also prevents log lifting when it comes in contact with the knife especially when the length is small.

5 | P a g e

Plate 3: Anvil and infeed roller (close up view)

Chipper Side Plates: The side plates were cut from a flat metal plate, marked and cut

into sides as shown and the housing was cut from and rolled into desired size on a hydraulic sheet metal rolling machine. The housing was then welded to the discharge housing permanently.

Plate 4: Chipper housing welded to the discharge side plate

Chipper Disc Assembly: This is concealed within the chipper housing and comprises of

the disc, knife, and chip thrower. The function of the disc assembly is to develop enough inertia to chip wood fed into it and to eject the chips through the chip discharge chute.

The Chipper Disc: Blank material sourced from the Agodi Gate steel market was smooth

and appeared to have been cut with an automated torch to 24” diameter. The roundness actually saved a lot of work in squaring and cutting. Because of the initial cutting forces

6 | P a g e

required by the machine to chip wood, the disc must be dynamically balanced and heavy to carry the cutting inertia.

Plate 5: Marked piece of steel recovered from local metal market

The disc was laid out according to design specifications, marked and after a lot of cutting, trimming and grinding to required size and shape, the slots were grinded using a hand grinder.

Knives: There are three knives and chip throwers arranged radially at an angle of 120o to

each other on a massive steel disc which develop a lot of kinetic energy and inertia to slice through wood fed into it. Each knife has a dimension of 190 x 76 x10mm and was fastened to the disc by three 14mm countersunk bolts and nuts. The knives material was recovered from an out of service swipe blade, cut into sizes and sharpened into double sided 9.0mm thick, 190.0mm (7”) long and 76.0mm (3”) wide. Once the knives get dull you can turn them around.

Plate 6: Disc showing mounted blades (Front side)

7 | P a g e

The Disc Assembly: The chipper disc was balanced on a balancer built prior to welding

the shaft to the disc. The balancer comprises of two bearings on each side of the stand with a V- grooved metal plate welded to each stand. The disc is fully assembled with knives and the chip thrower is a piece of 50 x 50x 5mm angle iron 190mm in length and was attached to the disc with three grade 8 1/2" bolts and LocTite nuts to prevent them from vibrating out. The shaft and disc assembly is positioned on the bearings for balancing.

Plate 7: Disc showing mounted chip throwers (Back side)

The Drive Shaft: The shaft was turned from a solid piece of 76.0mm (3") stock on a 9” x

20” metal lathe. The 21" disc has a 2 1/2" center hole and fits over the widest portion of the shaft.

Plate 8: The drive Shaft

Before welding the shaft to the disc it was ensured that all the knives and chip thrower holes were correct and also ensures that the shaft fits all the bearings properly. The disc was then centered and welded to the shaft by a 200 amp AC welder (ESAB) and 6011 electrodes

8 | P a g e

for the first two welding passes then used 6013 electrodes for two more passes. A total of four beads each were made.

The Discharge Chute: The chip delivery channel was made of gauge 14 mild steel plate

formed into an s-shaped chute ending in a rectangular flat plate bracket for fasteners to the main housing.

Plate 9: Discharge chute

Chip discharge from the chute is accomplished by a combination of centrifugal force and air created by a separate impeller/thrower mounted on the discharge end of the disc. The discharge chute is equally equipped with a hand adjustable deflector at the end of discharge. This is attached to chute with one hinge and can be folded back for easy access to rear of chipper.

Plate 10: Chipper outlet

9 | P a g e

The Frame: The frame is built from two 2" x 2” angle irons faced together and welded to

form square tubing. Angle iron forms the platforms on which the chipper and the electric motor were mounted. The frame was equipped with two wheels at the rear to ensure transportability and optimal weight distribution.

Plate 11: The chipper frame mounted on two wheels

The Chipper: The outcome of machine design and fabrication is as shown in Plate 12. The

overall dimensions of the machine are; Length: 1676.4mm, Width: 609.6mm and Height: 800.0mm. The height is adequate for ergonomic reasons considering the bending and feeding of the machine.

Plate 12: The wood chipper

10 | P a g e

The machine consists of five functional component parts; infeed chute and bracket, chipper disc assembly, an exhaust or discharge chute, frame and power drive.

Machine Specifications

The machine specifications are as shown in the table below.

Table 3: Machine components and specification

COMPONENTS SPECIFICATIONS

Engine:

Atlas 3-phase double winding 15hp synchronous electric motor

Speed: 1440rpm, voltage 1.2v, frequency; 50Hz

Infeed Chute: Chute opening at chipper disc; w180mm x h150mm /w450mm x h360mm at feed point

Discharge Chute Discharge chute: provided with directional flip cover. 900mm from wheel

Chipper Disc: Disc Size: 1100mm x 60mm, Disc Weight: 86kg, Disc Speed: 540 rpm

Knives: Three knives made of hardened spring steel. 190mm x 76mm x 10mm double edged, reversible and re-sharpen able.

Drive Belts: Industrial "V" B51/5L540 (two)

Anvil: Made from hard wearing metal with easy external adjustment

Infeed Roller: 38.2mm diameter steel roller, in-between the anvil and the knives

Chipper Housing 12mm plate front and back, 6mm plate disc cover.

Chip thrower Minimum feed rate approximately 80 feet per minute.

Frame Support: The frame is a network of angle iron and squared pipes welded together.

Land wheels: Wheels 15 x 6.00

Machine Capacity 76mm (3 inch) – rated to 3 inches whole log

11 | P a g e

PARTS LISTING

COMPONENT MATERIAL DIMENSION (L X B) MM

QTY

Infeed chute 3mm (1/8”)

thick ms plate 540 x 800 600 x 800

2 2

Discharge chute 3mm(1/8”)

thick ms plate 1200x1200 1

Infeed bracket 12.7mm (1/2”) thick ms plate

170 x 250 208 x 250

2 2

Anvil 12.7mm (1/2”) thick ms plate

170 x 250

1

Side plates 12.7mm (1/2”) thick ms plate

609.6 x 609.6

2

Disc housing 3mm (1/8”)

thick ms plate Diameter =549.4

Width = 93 1

Chipper disc 25.4mm (1”)

thick ms plate Diameter = 533.4 2

Frame 2” x 2” square tube 50x50x1200 2

Knife 10mm (3/8”) thick spring

190 x 76 x 9

3

Drive shaft 60mm (3”) dia. ms steel

rod 50 x 228.3 1

Motor seating 2” x 2” Ms angle iron 2

Bolt and nuts

Side plate Bearing seating Knife (c/sunk)

Thrower Anvil

Discharge Motor seat

Infeed chute seating

M19x1.5x50 M14x1.5x50 M14x1.5x50 M13x1.5x25

M17x1.5x25.4 M13x1.5x25 M19x1.5x25 M19x1.5x50 M19x1.5x25

6 4 9 8 3 6 4 2 8

Side plate bracket 2”x2” Ms angle iron 80 x50 x 50 4

Bearing seat 2”x2” Ms angle iron 24PMF.02.017 2

Washer Split washer GB93-87 14

Bearing KG Bearing 38UCP208 2

15HP motor 3-phase low speed 1

Drive Wheel 3.5kg weight 1 pair

Wheel shaft Ms Rod 1” diameter 1

Wheel bearing KG Pillow Bearing 25UCP206 2

12 | P a g e

Small pulley

125mm dia Double grooves

24PMF.02.104 1

Big pulley 192mm dia Double

grooves 24PMF.02.103 1

Belt Fiber reinforced rubber V-

belt B-62 17 x 1625 2

Bibliography

Bedair Steve, 2005. 5" Horizontal Wood Chipper. Gladewater, Texas 10-2005. Firefox

document. Modified on 3 August 2008

Bjurulf, Anders, 2006. Chip Geometry Methods to impact the geometry of market chips.

Unpublished Doctoral thesis, Swedish University of Agricultural Sciences, Uppsala

2006

BS EN 294:1992. Safety of machinery – Safety distances to prevent danger zones being

reached by upper limbs British Standards Institution 1992

CWC, 1997. Wood Waste Size Reduction Technology Study NIST MEP Environmental

program (# CDL-97-3) www.cwc.org.

Frost D., McLean B. and Wildig J., 2005. The Multi-Use of Woodchip - From Animal Bedding

to Mushroom Production. Farm Woodland Forum Meeting, 29 June – 1 July 2005.

Grieve J. David, 2004. Manufacturing Processes - MFRG 315. 17th December 2004.

Retrieved from...\.\Downloads\machgeom1_files\machgeom0.gif.

Segun R. Bello and Musiliu A. Onilude (2011). Force Relations and Dynamics of Cutting Knife

in a Vertical Disc Mobile Wood Chipper Leonardo Electronic Journal of Practices and

Technologies Issue 18 17-36. Romania Academic Direct Pub. House, Academic

Direct Organization URL:http://lejpt.academicdirect.org/A18/017_034.htm

Spinelli Raffaele, Bruce R. Hartsough, and, Natascia Magagnotti, 2005.Testing Mobile

Chippers for Chip Size Distribution. International Journal of Forest Engineering.

http://www.lib.unb.ca/Texts/JFE/July05/spinelli.pdf

Wen-Hsiang Lai, 2000. Modeling of Cutting Forces in End Milling Operations. Tamkang

Journal of Science and Engineering, Vol. 3, No. 1: 15-22