The Wheelbarrow – Components, Structure and Materials
The ubiquitous Wheelbarrow consists essentially of three component parts using commonly available materials of steel or hardwood. These components are characterised by,
• The frame (with handles)
• The carrying receptacle
• The wheel(s)
Each of these parts plays their own essential role in the efficacy or fit for purpose, ease of operation and durability of the tool.
The materials used for the frame consist of either of two principle materials, one being a hardwood and flat steel bar (bolted together) or secondly, combinations of both steel tubing and flat steel bar, (bolted or welded together) the use of each of the two principle materials dependent on availability and ease of processing at the region of manufacture.
The Carrying Receptacle
The carrying receptacle will be of a metallic or polymeric (plastic) (rigid or flexible) material usually dependent on usage and manufacturing technique. Metallic receptacles may be galvanised, powder coated or painted. An open box shape (with or without sloping sides) will almost always be utilised to facilitate conveyance of particulate materials, however a flat platform may also be used for the conveyance of self supporting stack-able materials, for example, baked-bricks.
The wheel(s), single or double, will consist of a variety of manufactured configurations, these could be, various diameters of a moulded, solid, round section, polymeric material permanently affixed onto (usually) suitably pressed steel rims with an axle system, or pneumatic tyres contained in the classical configuration which would allow for removal of the tyre, for repair, in the event of a puncture.
The design and engineering of each of the above components contributes, as stated above, substantially to the efficiency, effectiveness and durability of the wheelbarrow
The two differing construction materials of hardwood and steel and their individual assembly each contribute in their own unique way to the efficacy and durability of the tool.
The traditional wood construction consisting of a strong, straight, load bearing beam allows for greater loads and greater leverage with comparably less mass than an equivalent steel counterpart but requires a greater number of constituent parts than a steel tube construction. Whereas the use of tubular steel, which can be die pressed in one operation enables the lower cost manufacture of a one piece construction wheelbarrow frame albeit with lower carrying capacity because of the restriction on the length of the one piece tube.
The die pressed tubular steel frame has induced in itself an inherent weakness in that due to the structure of the die and the press the resultant frame shape can result in excessive stress at the resultant bends, whereby the outer circumference wall is unacceptably thinned and the inner circumference is compressed resulting in a ripple skin. This results in poor flex resistance and is often the cause of frame failure during robust use, this is particularly so when thin walled tubing is used. Internal rust also attacks these stressed areas, contributing to premature failure. The pressed steel frame size of itself restricts the size of the carrying receptacle to a 65l (3.2 cu ft) bin whereas the wood section allows options ranging up to 300l (11 cu ft)
The Carrying Receptacle
The carrying receptacle construction material (commercially) consists of either pressed steel or a moulded, ridged polymer or a woven flexible tear resistant fabric. (The latter is an aberration used for wheelbarrows whose frame can be folded down to facilitate convenient storage)
Pressed steel has been the traditional norm but commercial cost pressures have resulted in ever thinner metal gauges and hence reduced wear and tear resistance. The advent of polymeric substitutes to steel has resulted in cost competitive alternatives. An additional benefit has been a product that withstands environmental attack, such as rust and acid/alkali. With a density considerably lower than that of steel a lighter pan results.
A significant contributor to the efficacy of a wheelbarrow is the type of wheel structure and the materials used.
If the tyre width is too narrow then any traverse over sandy soil will be extremely difficult due to the wheel sinking into the sand and rendering maneuvering equally difficult. The outside diameter of the wheel will likewise prove problematical. Too small and the rolling resistance will increase by orders of magnitude.
The wheel bearings used will determine the life of the wheel.
Synthetic bushes kept clean and not oiled will usually outlast the ‘barrow, and provide a great service.
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