Humboldt H-3860A Los Angeles Abrasion Machine - Manual (Page 3)

Control Contacts: Any of the following control contacts can be incorporated:
•
Wiping contact at zero (duration of contact is for 1 count only and is, therefore,
dependant on the counting speed, e.g. 100 ms for gearing ratio of (50 revs = 1
count at 10,000 rpm)
• Permanent contact at the changeover from 0000 to 9999, in which case one
number less than required has to be preset for correctness. This contact remains on
until the counter is reset. Max presetting range is 8999.
• An additional fixed pre-contact (speed dependent wiping contact) can be
incorporated at any given number upon request.
Safe load of contacts: Max. switching output 30W 100 VA
Max. switching voltage 230V
Max. switching current 2A
Maintenance: The counters do not require any particular attention. However, for reliable
functioning of these precision instruments careful handling is absolutely necessary.
Operation
Machine
The Los Angeles Abrasion Testing Machine consists of a hollow steel cylinder, closed
at both ends, having an inside diameter of 28" and inside length of 20". The cylinder
is mounted on stub shafts attached the ends of the cylinder but not entering it and
mounted in such a manner that it may be rotated about its axis in a horizontal position.
An opening in the cylinder is provided for the introduction of the test sample. The
opening can be closed dust-tight with the removable cover bolted in place.
The cover is so designed as to maintain the cylindrical contour of the interior surface.
The shelf is so located that the charge will not fall in the cover or come in contact with it
during the test.
A removable steel shelf projecting a radial 3- ½" into the cylinder and extending its full
length is mounted along one element of the interior surface of the cylinder. The shelf
is of such thickness and so mounted by bolts or other approved means to be firm &
rigid. The position of the shelf is such that the distance from the shelf to the opening
measured along the circumference of the cylinder in the direction of rotation is not less
than 50".
If the cover stops at the bottom in a difficult to reach location, jog the barrel by pushing
the outer weight-plate forward then reverse and pull to jog the barrel to the desired
position.
Abrasive charges
The abrasive charges consist of cast-iron spheres or steel spheres approximately
1-7/8" in diameter and each weighing between 390g and 445g. The abrasive charge
depending upon the grading of the test sample as described on page 4 shall be as
follows:
Grading Number of Spheres Weight of Charges, g.
A 12 5000 ± 25
B 11 4584 ± 25
C 8 3330 ± 20
D 6 2500 ± 15