For Transmission-Class Reconductoring
Single-Conductor Capacity


  • Extra-wide throat to accommodate joints, swivels & connectors.
  • 10 in, 12 in., 14 in. & 16” Sheaves.
  • Available with polished-groove sheaves or lined with urethane.
  • High-strength Aluminum-alloy frames and sheaves.
  • High-efficiency bearings, with provision for pressure-lubrication.
  • Forever Warranty™



About Transmission Construction
Transmission-class line construction is very specialized. 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. Some lines are strung using conventional, ground-based equipment and tools, while others require stringing using helicopters.

The configuration and quality of the blocks in which sheaves are mounted are as important as the sheaves.

About 73 Series Transmission Blocks
The 73 Series single-conductor stringing blocks are an ideal choice for reconductoring mid-size-diameter conductor, especially when old conductor is used to pull in new conductor. In addition to being available with 10″, 12″, 14″, and 16″ (OD) sheaves, they have an extra-large throat, and do not have a conductor guard. This design permits easy passage of connections between conductors and pulling lines, compression joints, swivels, and/or splices in the pulling line.

73 Series blocks are light-weight, yet exceptionally rugged, reliable, and durable. Their low-friction bearings render high block efficiency, which helps to maximize stringing distances while minimizing pulling tensions and reducing loads on stringing equipment. Combined with the associated family of hardware and accessories, the 73 Series affords utilities and their contractors exceptional versatility in how and where it may be deployed and in the range of installation problems it can help solve.

The 73 Series blocks’ light weight and durability derive from the materials and methods used to make them. The material used for the frame is “virgin” A356-T6 Aluminum, which is an aluminum alloy with very tightly controlled proportions of other materials to assure optimum performance during manufacture and in the field. Virgin material is material that has not been mixed with scrap material, not even with scrap of what may have once been the same alloy. That Sherman + Reilly uses “virgin” material assures that the material is exactly and only the pure and correct alloy, and that it has not been contaminated by impurities (notably iron) that often accompany non-virgin material.

73 Series frames are cast (molded) as molten metal. The properties and purity of the A356-T6 Aluminum used by Sherman + Reilly assure that the molten metal flows smoothly and evenly throughout the mold, assuring proper and uniform density throughout the finished frame. Proper density and uniformity combined with the purity and metallic properties of the alloy assure that the frame is strong but light-weight, and assure that there are no internal voids or brittleness that could cause sudden complete failure of the block in the field.

The sheaves of the 73 Series are also made of the same virgin A356-T6 Aluminum as the frame. They are also similarly cast, but they have the additional manufacturing step of having the grooves and bearing surfaces machined for smoothness and precision fit. Combined with low-friction, lubricated-for-life bearings, the sheave materials and how they are made assure high-efficiency and smooth-stringing performance.

Configuring 73 Series Transmission Blocks
Configuring 73 Series transmission blocks is relatively easy to do, and it can be done using the information and tools on this website. Configuration requires that you determine:

1. Sheave size.
2. Sheave lining, if any.
3. Fitting (for hanging the block)
4. Attachments.

Sheave size is largely a function of the size of the conductor being strung and of span length and terrain over which the conductor will be installed. Sheave lining is largely a function of the type of conductor being used and/or requirements from the conductor manufacturer. Determining the fitting is simply choosing the hardware that slips into the socket connector at the top of the block. Attachments are a function of how the conductor will be installed and grounded.

Ordering 73 Series Transmission Blocks
Prepared with the above configuration information (or if you need any help configuring and/or ordering your blocks), you may order your blocks by consulting your Sherman & Reilly Representative or you may consult Sherman & Reilly directly. For help with configuring and pricing your from Sherman + Reilly directly, you may call 1-800-251-7780 ask for “Quotes.”

Maximum Working Load: Please refer to Dimensions & Specifications
Efficiency: 98%
Maximum Conductor OD: Please refer to Dimensions & Specifications
Sheave OD: Please refer to Dimensions & Specifications
Sheave Groove Radius: Please refer to Dimensions & Specifications
Sheave Throat Width: Please refer to Dimensions & Specifications
Sheave Throat Height: Please refer to Dimensions & Specifications
Sheave Rim Width: Please refer to Dimensions & Specifications
Width, overall, nom.: Please refer to Dimensions & Specifications
Height, overall, nom.: Please refer to Dimensions & Specifications
Frame Material: A356-A6 Aluminum (virgin)
Sheave Material: A356-A6 Aluminum (virgin), excl. lining, if any
Sheave Lining Options: Urethane or Neoprene
Materials, other: Please refer to Dimensions & Specifications
Dimensions, other: Please refer to Dimensions & Specifications
Weight, nom.: Please refer to Dimensions & Specifications
Hanging Hardware: Socket connector

Please refer to the Product Sheet found on this page under Downloads.