That's right! 100 blocks per hour ... provided you have
the help and the space and racks to cure the blocks
properly. In Figure 1 (in the Image Gallery) you see the outfit complete, ready for
work. It's a self-contained unit mounted on its own
two-wheeled, pneumatictired trailer with a supporting
caster wheel under the drawbar. There's nothing to take
apart and put together again when you move the machine.
Merely disconnect the water hose and the power line, hitch
it to a truck, and away you go.
Figures 4 through 7 (in the Image Gallery) show how it works. Figure 2 details
the metal mold and Figure 3 the ejector plates and assembly.
In Figure 4 the mold, supported by a crane, is being lowered
into place on the molding "board," in this case a steel
plate somewhat larger than the mold. In Figure 5 the mix is
being scraped and troweled into the mold. When full, the
mold is vibrated by means of a footoperated take-off drive,
and then the excess material is struck off the top with the
fence or striker board. Next, the crane is hooked to the
mold and the ejector is swung into place. In Figure 6 the
operator bears down on the ejector and simultaneously
presses a foot pedal to raise the mold off the formed
blocks. In Figure 7 the finished blocks are being moved to
the curing racks.
Figure 8 shows the main frame, entirely a welded job using 3-
and 4-inch pipe, steel plate, and steel channel. Only
general dimensions are given as some of these parts must be
sized to fit during the assembly of other parts of the
machine. With the exception of the motor, which is only a
representation, the crosshatched views in Fig. 9 are
intended to give a general guide to proportionate sizes of
the machine parts and their relative positions. To make the
manner of assembly more clear, certain parts have been
omitted from these details. No detailed dimensions have
been given in Fig. 9 because these will vary somewhat
according to the materials and parts which you have or
which are available.
Figures 10 to 15 inclusive show the assembly. From these
details you will see first that the main drive from the
motor to the mixing chamber is made from a Ford Model-A
rear axle and drive shaft, (Figure 11). One axle housing is
removed and the open end of the differential housing is
covered with a sheet-metal disk bolted on with a gasket
between to prevent leakage of lubricant. A roller-chain
drive sprocket is welded or keyed to the axle and a
two-step V-pulley is attached to the drive shaft. The drive
thus formed from this unit is welded to the trailer frame
at three points: at the end of the Model-A axle housing
where it passes through a hole in the mixing-drum bracket,
and at the differential and the forward end of the
drive-shaft housing, where it also is supported on
The hopper, Figure 10, and the mixing drum are made of heavy
sheet metal welded at all joints and reinforced with steel
angles welded on as stiffeners wherever large areas of the
metal are subjected to severe strain. The steel mixing
blades of the agitator, Figure 9, the top view, have a
clearance of about 3 inches inside the drum.
Figures 13 and 14 and the two upper views in Figures 11 detail
the crane and ejector arm. The crane is an allwelded
assembly of standard rod and pipe sizes and is operated by
a pedal which extends underneath the machine. However, the
ejector mechanism is a somewhat more intricate affair. The
ejector plates must raise and lower in the same plane,
making two pairs of adjustable parallel arms necessary. A
"helper" spring eases the lift of the assembly and another
coil spring swings it to one side. Bearings at both ends of
the four arms should fit accurately. Figure 11 shows the
frame which supports the crane and ejector.
The hopper is raised for dumping by a hydraulic cylinder,
Figure 11. Arrangement of the hydraulic system is shown in
Figure 12 and the drive to both the hydraulic pump and the
mixer is detailed in Figure 15. Raising and lowering of the
hopper is controlled by a three-way valve, Figures 11 and 12.
By-passing the hydraulic fluid allows the pump to be
operated continuously, thereby simplifying the drive. The
vibrator shaft, Figure 15, is pedal-operated and runs only
when the pedal is depressed. One belt from the two-step
cone pulley passes around an idler. The pulley driving the
vibrator is located between the driving pulley and the
idler as shown in Figure 15. When the pedal is depressed the
center pulley engages the belt, and "throw" of the
off-center weights, Figure 11, vibrates the mold. The mold
must be held rigidly in place for this operation and Figure
11-A details the quick-acting clamping device especially
made for this purpose.
The mold and the ejector, Figures 2 and 3, are made for three
blocks. There are two cores in each compartment of the mold
and note especially that each core is vented (Fig. 2) and
tapered slightly so that it will draw easily without
breaking the edges of the block. Cores can be cast from a
rich cement-sand mixture or they can be made of heavy sheet
metal, welded. Where facilities and materials are
available, they also could be cast from aluminum.
Figure 16, details A to E inclusive, shows a one-core mold (A
and B) which is suitable for certain special types of
blocks. Detail C supplements Figrue 6 and shows more clearly
the procedure and placement of the hands in ejecting the
block from the mold, while details D and E suggest types of
elevated tracks or rails for moving blocks away from the
machine and to the curing yard, as in Figure 7. Curing racks
of any convenient size may be assembled from hardwood
boards, steel angles, and flanged rollers as in Figure 16-D.
Detail E suggests one way of providing for easy handling of
the blocks from the machine to the curing racks.
General assembly views of a hand-operated machine for
making a few blocks at a time are given in Figure 17. Here
most of the work is done by hand, only the vibrator being
motor driven. It's easy to build for either a one-, two-,
or threeblock mold. Proportions of the mix which have been
found most satisfactory are 7 parts pea gravel, 12 parts
sharp sand, 2 parts silt, and 2 1/2 parts portland cement.
The amount of water is determined by experiment as it
depends on the dampness of the aggregate.
This article reprinted by permission from Popular
Mechanics. Copyright © 1946, The Hearst