Type 73 Sectional Mast Systems
You do not experiment when you choose type 73. Thousands, world-wide,
guarantee the success of each further application. With every product,
in every activity, there emerges a supplier and model which meets many
different customer requirements and which becomes classic.
The Clark Masts Type 73 mast is one such example. From its conception in 1970 until today, it has played many roles as a vertically erected, manually operated sectional mast which is fully controlled by guys during erection. Easy change in height or headload has been a key factor in its success.
Type 73 versatility
It's the sound versatility of Type 73 which makes it so attractive to users.
There are other more sophisticated options, for example a 10 metre mast with antenna stabilisation by means of special guys.
These give a torsional deflection, under load of less than 0.15°.
Type 73 Standard Components
| Item | Cat. No. | Description | Qty |
| Kit | 18130 | 10 Metre mast kit complete | 1 |
| This Kit contains the following components: | |||
| 1 | 18205 | Mast guide box | 1 |
| 2 | 10772 | Step assembly | 4 |
| 3 | 18020 | Leg assembly | 3 |
| 4 | 18114 | Foot assembly | 3 |
| 5 | 7600 | Hoist | 1 |
| 6 | 13973 | Hoist support bar | 1 |
| 7 | 5246 | Lifting block | 1 |
| 8 | 5426 | Bubble level | 1 |
| 9 | 5373 | Foot adjustment brace | 1 |
| 10 | 18021 | Guy winch kit (leg mounted) | 1 |
| 11 | 18037 | Picket | 3 |
| 12 | 18039 | Picket clamp | 3 |
| 13 | 18034 | Picket driving cap | 1 |
| 14 | 18033 | Picket extractor | 1 |
| 15 | 6409 | Spike | 3 |
| 16 | 18022 | Guy collar set | 1 |
| 17 | 5231 | Mast section | 7 |
| 18 | 14522 | Mast section carrier (3 sections) | 1 |
| 19 | 14524 | Mast section carrier (4 sections) | 1 |
| 20 | 18150 | Radius line | 1 |
| 21 | 18025 | Winch bag | 1 |
| 22 | 18026 | Hoist bag | 1 |
| 23 | 18027 | Equipment bag | 1 |
| 24 | 18031 | Accessory bag | 1 |
| 25 | 18035 | Leg bag | 1 |
| 26 | 18028 | Picket bag | 1 |
| 27 | B12173 | Hammer | 1 |
Some Typical Type 73 Mast Components
Guide Box
The
first item of the system is the guide box and 3 legs which form the base
of the erection gear. The guide box has a long, turnable sleeve
with a brake and is PTFE lined. A bubble level is fitted during erection.
Mast Section
The
second item is the mast section. It is made from a special billet of
high strength aluminium alloy for reliability. The method of section
joining, by means of a simple long spigot and key, ensures that the
connection functions correctly in dirty or muddy conditions. It is
anodised and dyed green or desert sand being the usual colour.
Hoist
The
mast section is positioned in the mast guide box, in which it is lifted up
by a manual hoist and lifting block. The geared hoist is a special item
which is wound up, secured by driving rachets and can be reversed only
when a push-button brake is operated. In addition there is a centrifugal brake
which limits the free running winch to a speed of approximately 150mm
per
second, regardless of load.
After raising the first section which is secured with a crosspin, the lifting block is lowered and the second section inserted, the crosspin removed and the section raised. A guy collar is fixed to the first tube section using the crosspin hole for security.
Guy Winch
Guys
are part of the mast structure. During the vertical erection of a sectional
mast, it is essential that guy tensions are continuously controlled.
The Type 73 Guy Winch Unit, innovated by Clark Masts in 1970, is the manual
device that does
this.
As the mast is extended the guy wires are paid out together from the winch unit, or adjusted individually in the case of sloping ground. Safety at all times is maintained. For mast retraction the guys are similarly wound in. Each winch unit is fixed to an erection gear leg or to the ground.
Picket
Pickets pose a problem. Length generally should be according to the ground;
short pickets for hard ground, long for soft. However, type of ground is
not known until erection is required on a particular site. Type 73 uses a
1 metre long tubular picket with a toughened tip.
An exceptional feature is the picket clamp which sets the guy attachment point at ground level however deep the picket is hammered into the ground. Use of a Picket Driving Cap, protects the picket from damage by the hammer. When it becomes necessary to withdraw the picket, an extractor does the work efficiently and quietly. A Type 73 picket becomes a long-life component.
Carrying Bags
All
bags are made from decontaminable, coated, textile base material with simple
buckles on nylon straps. Normal colour is military dark
green although white and desert sand can be available. Bags are reinforced
with removable plastic panels.
Guy Collars
The guy wires are attached to guy collars which are fitted to any mast
section as required. A nylon lined bearing makes mast rotation easy and
which once set in
the right direction is held with the screw operated brake on the Mast Guide
Box.
Antenna Attachment
The method of attaching the antenna depends on the type of antenna. The
Type 73 has two basic methods. A Top Flange Fitting provides the top
of the mast with a flange to which antennas or rotators can be attached.
Alternatively a side Mounting Adaptor allows a 40 mm male antenna adaptor
to be placed at any height on the mast.
Interface
Antenna mounting
Clark Masts always concerns itself with the interface between mast and
antenna, mounting of which can give a physical problem due to antenna
bulk.
A hinged antenna adaptor enables the antenna to be mounted at ground level and then swung into the operating position. Alternatively, a crane kit is available for even heavier headloads, to lift them from ground level to the retracted mast head.
Quality
Sometimes military equipment will go straight from delivery into User stores where it can stay for a period. With this possibility, effective final, functional works inspection becomes vital. After manufacture, every Type 73 mast set of components are fitted to each other and functionally tested to ensure that no snags arise when it is required for service.
