February_1971 — Page 45

contractors

plant

WELDER

Independent voltage and current control are provided on the Listomac Mk.2 diesel welding machine which embodies a generator with a rating of 300 amp. at a 60 per cent duty cycle.

Mounted on a four-wheel chassis, the machine derives its power from a Lister HR2 diesel that develops 271⁄2 h.p. and is self-priming to eliminate the need for bleeding should the machine run out of fuel. Starting is manual, and the two-speed engine con- trol permits fuel to be saved when weld- ing is not being carried out.

Independent voltage and current control allow the operator to choose a hard or soft arc for any selected cur- rent by varying the voltage regulator. Current diverters and heavy series

Michigan 280 with compactor wheels

against shocks and vibration.

Complete wheel assemblies include an outer steel drum mounted on a pneumatic tyre and rim with wheel disc machined to fit the hub and bolt circle of the tractor axle. Installation of the wheel assembly is carried out in the same manner and with the same equipment as is used to fit standard tyres. Specially designed pads on the compactor wheels are spaced and shaped to provide maximum traction and maximum compaction force.

SMOKE DETECTOR

An easy-to-install instrument for indicating smoke density has been de- veloped by Hird-Brown Ltd., Lever Street, Bolton, UK, as an aid to com- plying with clean-air regulations.

The equipment consists of a light projector and a photocell receiver,

Listomac Mk2 welder

resistances have been eliminated from sited on opposite sides of the chimney the machines.

The makers are Rockweld Ltd., Frimley Road, Camberley, Surrey.

COMPACTOR WHEELS

Compactor wheels for the Michigan line of tractor dozers are now available from Clark International Marketing S.A. and its Michigan distributors.

The compactor wheels are designed to fit as a complete unit for either the front axle of the rigid frame Model 180 or for both axles of the Models 280 and 380 articulated tractor dozers. They are fitted over special pneumatic tyres which effectively cushion the tractor and operator

Far East BUILDER, February 1971

or flue, their mountings comprising

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Hird-Brown smoke detector

two 2 in. (51 mm) standard pipe flanges. Both projector and receiver are linked, by twin 3/.029 cables, to a wall-mounted control unit (illustrated)

which measures 12 in. by 9 in. by 5 in. (304 by 228 by 127 mm) and houses a low-voltage transformer for projector, indicating and alarm contacts.

The projector throws a beam of light across the chimney, this being picked up by the receiver, which in- corporates a cadmium-sulphide photo- conductive cell. Being extremely sensi- tive to changes in light, the cell passes a varying current proportional to the variations in smoke density; should the latter rise above a pre-determined level, a relay will operate, activating a light, bell or other alarm.

The equipment operates on a vol. tage of 110-, 240- or 440-v., single- phase, 50 or 60-Hz. a.c., and power consumption is approximately 30 va. The relay is rated at 5 amp. 240 v. A smoke-density meter, voltage stabiliser chart recorder and alarm bell are among the accessories offered.

ROCK DRILL

Atlas Copco AB, Stockholm, Seden, have introduced a down-the- hole drill, COP 4, for drilling in me- dium and hard rocks. It covers the hole dimensions 4 in. to 5 in, and is specially developed for drilling at high pressure, up to 18 kg/cm2 (250 psi).

The COP 4 has low air consump- tion, 3.4m3/min (117 cfm) at a pres- sure of 6 kg/cm2 (85 psi) and 6.5 m3/min (230 cfm) at a pressure of 10.5 kg/cm2 (150 psi). The feed and the rotation unit require 3 m3/min (106 cfm).

Construction of the drill is simple and robust with few moving parts. The driver chuck in the front end of the down-the-hole drill has a hard weld coating (Stellite) which is extraor dinarily resistant to wear. The coating protects the chuck against the flow of cuttings from the bit and considerably lengthens the service life of the drill. Sandvik Coromant down-the-hole bits have been developed and tested to- gether with the down-the-hole drills. They are available in sizes 105, 110 and 115 mm (4-1/8 4% and 41⁄2 in.) and in two versions the normal bit with a core crusher and heavy duty version. They are manufactured of Cr-Ni-Mo alloyed steel with tungsten carbide cutting inserts, which are avail- able in a choice of grades of varying toughness.

Central flushing cools the bit and keeps the drill hole clean even in fis- sure and water-bearing rock. It is sim- ple to fit the drill to most kinds of

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