Transmission Blocks – 70 Series

About Transmission Construction
Transmission-class line construction is very specialized. Compared to distribution construction, structures are taller, spans are longer, conductors are larger/heavier/stiffer, and pulls are longer and can extend over steep and very uneven terrain. In addition, aluminum conductors vary in construction requirements, calling for special handling techniques, tools, and equipment.

Transmission construction also involves different line and structure designs, as well as different
conductor configurations (including simultaneous stringing of multiple conductors (‘bundles”)
using a single pulling line). These configurations can range from single to bundles of two, three,
four, and six conductors per phase. Some lines are strung using conventional, ground-based
equipment and tools, while others require stringing using helicopters.

For all these reasons, the configuration and quality of the blocks in which sheaves are mounted
are as important as the sheaves.

About 70 Series Transmission Blocks
The 70 Series single-conductor stringing blocks are an ideal choice for simultaneous stringing
of multiple large-diameter transmission-class conductors. These blocks are the result of extensive
field research, laboratory testing, and real-world experience over a period of 75+ years. With some
exceptions, 70 Series blocks are available in two, three, four, and six-conductor configurations
per phase, with or without separate pulling-line sheave. Combined with the associated family of
hardware and accessories, the 70 Series affords utilities and their contractors exceptional versatility
in how and where they may be deployed and in the range of installation problems they can help solve.

With some exceptions, 70 Series blocks are available with 20″, 22″, 28″, 35”, and 42″ (OD) sheaves,
which are light-weight, yet exceptionally rugged, reliable, and durable. The sheaves are cast from
virginA356-T6 Aluminum, which is a high-strength aluminum alloy. The properties and purity of
the A356-T6Aluminum used by Sherman + Reilly assure that the molten metal flows smoothly and
evenly throughoutthe casting mold, assuring proper and uniform density throughout the finished
sheave. Proper density and uniformity combined with the purity and metallic properties of the alloy
assure that sheaves are strong but light-weight, and assure that there are no internal voids or
brittleness that could cause sudden complete failure of the sheave in the field. Combined with low-
friction, lubricated-for-life bearings, the sheave materials and how they are made assure high-
efficiency and smooth-stringing performance. The sheaves’ low-friction bearings render high
block efficiency, which helps to maximize stringing distances while minimizing pulling
tensions and reducing loads on stringing equipment.

The 70 Series blocks are of a rigid-frame design made of hot-dipped galvanized steel. Steel is used,
as opposed to aluminum, in order to have the strength needed to handle the loads that multi-sheave
blocks endure when high conductor counts are being pulled through them simultaneously.
70 Series blocks are available in any of the three designs that Sherman + Reilly offers:
symmetrical, slim-line or offset.

Specifications:

• Available for 2, 3, 4, and 6 conductors, plus pulling-line sheave.
• 20 in. – 42 in. sheaves
• Sheaves available as polished-groove or lined with neoprene or urethane.
• Available with choice of Y-clevis or head-bar hanger hardware.
• Forever Warranty™