OVERHEAD CONSTRUCTION
IRON POLES AND OVERHOUSE POLES

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P.O. ENGINEERING DEPT
ENGINEERING INSTRUCTIONS
LINES
OVERHEAD
C3276
Issue 1, 7.9.37

IRON POLES, OVERHOUSE POLES AND STANDARDS

1. Ground Poles
Iron or steel poles were used in the past in suburban neighbourhoods where Local Authorities expressly asked for them on the ground of appearance. They proved to be a source of danger, however, as they rusted internally and in the sockets, where the damage could not be inspected. For this reason and on account of their high cost they should not be erected in future.

2. On existing lines, when the renewal of iron or steel poles becomes necessary, wood poles should be erected in their place, or, alternatively, the circuits should be diverted underground, if justifiable.

3. Overhouse Poles
Where, in the past, it has been impossible to obtain' a route for lines on ground poles in congested town areas, subscribers' and trunk circuits have been carried on steel structures on the roofs of buildings. Such lines are expensive to construct and to maintain, and work of this kind should be limited to renewals required from time to time on existing structures. When renewal becomes due, alternative arrangements should be considered, and underground plant should be adopted if possible.

4. Ordinarily, overhouse lines are carried on "Poles, House," of which three sizes are stocked, viz.:-

"No. 3" - Length, 18 ft. - One section, 4 inches diameter
"No. 4" - Length, 23 ft. - Two sections, 41; and 4 inches diameter, respectively
"No. 5" - Length, 28 ft. - Two sections, 41 and 4 inches diameter, respectively.

5. The poles are supported in "Chairs, Roof," of which one size only, "No. 7," is now stocked. This chair is suitable for use either on a flat roof or on a ridge. A typical pole is illustrated in Fig. 1.

6. The poles are used either singly or as double poles, fixed to each other at a convenient distance by "Arms, Iron, Channel."

7. Roof Standards
When a comparatively heavy line is to be terminated, a more substantial structure known as a "standard" is used. The fittings which make up a standard are stocked under the general classification "Structures, Overhead " and a typical case is illustrated in Fig. 2. This shows a two-tube standard, but the principle may be extended to a greater number of tubes, -u to a box-like structure, if necessary. Rolled-steel joists, anchored to the building by anchor rods and wall plates, are provided for a foundation. A cast-iron chair, bolted to the joist, supports the pole. The space between the tube and the socket in the chair should be filled with " Lead Strip" and caulked.

8. To reduce the effect of vibration, three or four thicknesses of roofing felt are placed under the chair, and, when a standard is erected on a ridge, a piece of 5-lb. sheet lead is placed under the felt. Poles should not be passed through a roof because of the difficulty in maintaining the roof watertight.

9. Fittings - Pole Steps
A special type of step, known as "Clips, Climbing," is provided for use with iron poles.

10. Fittings - "Arms, Iron"
These are tubular arms and should be fitted on iron ground-poles (see C 3507). With these are required subsidiary fittings as follows:-

"Strips, Insulating," made of hardwood, and held in position on the upper side of the arm by the insulator spindles (if any). If insulators are not fitted at the outset, the strips should be held in place by a "Bolt No. 1."
"Washers, Galvanized No. 1" are fitted on the underside of iron arms, on each insulator spindle or "Bolt No. 1."

11. Fittings - "Arms, Iron, Channel " are also available for poles upon which this type of arm has already been
fitted, or on which 8-way arms are required (see C 3507).

12. Fittings - "Arms, Steel, Channel"
These should be used for heavy roof standards (see C 3507).

13. Protection against corrosion
All screw threads should be liberally treated with "Tallow, Tar and Pitch Composition." Poles and standards and all ungalvanized iron fittings should be painted as described in C 3376.

14. Arm Spacing
The same spacing on the pole should be adopted for iron arms as is detailed for wood arms in C 3551.

15. Staying of House Poles and Roof Standards
Adequate stays should be provided for these structures. At least four for each standard are necessary, to ensure that the pole will remain in stable equilibrium in case of breakage of the line wires. The tubes are provided with steel collars, to prevent slipping of the stays.

16. "Wire, G.I. Strand, 7 /14" (or 4/8) should be used, made-off in the usual way above the collars, the lower end of the stays being made-off on "Spikes, Eye" driven into the walls. Positions for spikes should be chosen carefully and any weak brickwork, such as parapet walls, should be avoided. It may be found desirable to cut a hole through a parapet wall so that a stay may have a direct pull on the lower portion of the main wall.

17. To provide the necessary tightening facilities on 7/14 and 4/8 strand wire used for staying overhouse lines, "Swivels, Stay, 1/2 inch," and 5/8 inch, respectively, should be used.

18. Earth-wiring House-poles and Standards
House poles and standards should be connected to earth by means of "Wire, Copper, Soft, stranded 7/16 run by a route which is as straight and direct as possible. A water pipe having direct connexion with a main will usually be available in such circumstances and should be used as an earth electrode ; if a water pipe is not available, the case should be referred to the E.-in-C. (Cn 2) with proposals for an alternative earth.

19. Precautions against accidents
When working on overhouse poles or roof standards, the precautions of J1001, J1201 and Pamphlet RG41 must be observed strictly.

P.O. ENGINEERING DEPT
ENGINEERING INSTRUCTIONS
LINES
OVERHEAD
C3507
Issue 1, 7.9.37

ARMING
Iron and Steel Arms

1. General
This Instruction details the Iron and Steel Arms at present used for new work and indicates briefly their field of use.

2. "Arms, Iron"
These are of tubular form and carry 4 wires, with 12in. spacing for the insulator spindles. Two sizes are available - "No. 6" and "No. 7" - which differ only in that the former grips poles of 3½in. to 6 in. in diameter whilst the latter can be used on poles of 6in. to 8in. in diameter. Fig. 1 illustrates the general appearance of this tubular arm. "Arms, Iron, No. 7" is similar to No. 6 but has a larger saddle.

3. Both types may be used on iron ground-poles, whilst the "Arms, Iron, No. 6" should be fitted on iron house-poles when 4-way arms are required (see C3276).

FIG. 1 - TUBULAR IRON ARM "ARM IRON No. 6"

4. "Arms, Iron, Channel"
These are Iron arms in a channel form and are in two halves which are bolted together to grip the pole or poles. Longer bolts, namely "Bolts, No. 21," are used in the holes at which the Combiners are to be fitted as shown on the diagrams of typical channel-iron arms in Fig. 2 and 3.

5. Channel-iron arms are for use on:-

iron house-poles
for poles on which this type of arm has already been fitted, or
where 8-way arms are required.

FIG. 2. - TYPICAL "ARM, IRON, CHANNEL" FOR 4 WIRES

FIG. 3 - TYPICAL "ARMS, IRON, CHANNEL" FOR 8 WIRES

6. "Arms, Steel, Channel"
These are of 2in. by 2in. Section, and of similar design to "Arms, Iron, Channel," but are made so as to fit two tubes at 6ft. centres on a heavy roof standard (see C 3276). A typical channel-steel arm is illustrated in Fig. 4. fitted at the outset. They are normally held in position on the upper side of the arm by the insulator spindles. If insulators are not fitted initially, the strips must be held in place by means of a "Bolt, No.1".

FIG. 4. - TYPICAL "ARMS, STEEL, CHANNEL"

10. The insulating strips act as packing pieces, thus allowing the use of standard spindles; they also provide the shoulder of the spindle with a flat and secure seating on the curved arm.

11. "Washers, Galvanized, No. 1"
These should be fitted on the underside of iron arms on each insulator spindle or "Bolt, No. 1". The upper face of the washer is shaped so as to provide a bearing surface between the arm, and the nut on the spindle or bolt.

12. Spacing
The spacing between iron arms should be the same as specified for wood arms in C3551.

Additional Pictures

National Telephone Company
The Derrick (cable standard) on the Roof at Coleman Street, London (Picture dated 1880)

National Telephone Company's Cable Gantry on Roof of its Contract Office (Picture dated 1895)
Obviously just been constructed and has no overhead plant connected.
Check out the RSJ's that are supporting the structure and amount of straining ropes.