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Pole Arms

Engineering Instructions
Issue 2, 30.7.36


1. General
The pre-cutting of poles (which includes the scarfing, boring of bolt holes and the trimming of the top of the pole) at Pole Depots, is described in C 1102. This instruction details the method of fitting the arms on such poles.

2. "Braces, Arm" used for fitting wood arms on pre-cut poles are made from galvanized mild-steel strip and are available in various sizes. Particulars of use and particular dimensions are as shown in the table associated with Fig. 1.

Fig. 1
Arm Braces

Fig. 2
Arm braces with 4 way arms on light poles

3. Fitting of Arm Braces
The method of fitting arm braces is illustrated in Figs. 2, 3 and 4. It will be seen that the braces for arms, other than the lowest, are bolted to the front of the arms. Braces for the lowest arm are bolted to the pole and to the back of the arm ; this also applies where only a single arm is fitted.

4. The lower ends of the braces are secured by means of the arm-bolt immediately below, an additional (shorter) arm-bolt being used for bottom braces. To avoid inconvenience in climbing, this bolt should be fitted with the head at the front of the pole. One "Washer, Galvd., No. 4" should be recovered from each arm-bolt securing the braces, the nut-washer being retained on the bottom bolt and the neck-washer on other bolts.

5. The upper ends of the braces are secured by means of 3/8in. diameter bolts, "Bolts, No. 22" being used for arms 3in. wide and "Bolts, No. 26" for 2in. arms. These bolts are now issued with a washer, and they should be fitted with the nut and washer at the back of the arm (see Figs. 2 and 3). Where "Arms, Wood, No. 28" are used, however, the washer of the lowest bolt may advantageously be fitted under the bolt-head (see Fig. 4).

6. Arm-bolts
It is important to note that 1/2diameter arm-bolts are not to be used under this scheme, 5/8in. diameter arm-bolts being the standard for arms of all types and sizes.

7. Preparation of Arms - Holes for arm bolts
It will be necessary to enlarge the holes, normally bored in arms for 1/2in. diameter bolts, to 5/8in. diameter clearance. The ordinary screw auger or bit is not suitable for enlarging existing holes. Arrangements are being made for the issue of "Bits, Enlarging" of the correct size and these may be requisitioned from 1st August onwards. Requisitions should circulate via the E.-in-C. (Cn 1).

8. It is important that arms should not be weakened at the bolt-hole. No auger or bit of a size greater than 21/32in. may be used for enlarging the 1/2in.holes.

9. Holes for brace bolts
When the pre-cutting scheme is in full operation, the standard borings for all arms for use on single poles will include holes for the brace bolts. Meantime, these holes should be bored locally; it will be realized that accurate boring and close fits are essential for a good job. Using a 3/8in. screw auger or bit, holes for Bolts, No. 22 or 26 should be bored at the appropriate spacing from the arm-bolt (see Fig. 1), and on the exact centre-line of the arms. In those cases where the arm-bolt hole is noticeably out of centre, the positions of the 3/8in. holes should be arranged accordingly, so that alignment with the arm-bolt hole is obtained.

10. Use of arm braces - 4-way arms (except Arms, Wood, No. 28)
Two braces should be fitted to each arm, as shown in Fig. 2. Braces, Arm, No. 4 should be used for all arms except the lowest and single arms, where Braces, Arm, No. 4A (designed so that the twists will clear the pole) will be used. When an additional arm is fitted, the No. 4A braces should be shifted one position down, No. 4 braces being substituted in their place.

11. Use of arm braces - 6-way and 8-way arms
Two Braces, Arm, No. 2 should be fitted to the uppermost, and two to the lowest, arm, as illustrated by Fig. 3. Combiners, fitted as detailed in C 3511, will impart the necessary rigidity to intermediate arms. When additional arms are fitted, the bottom braces should be shifted down as required.

12. Arms, Wood, No. 28
Only one Brace, Arm, No. 3 per arm should be fitted. Braces on successive arms should be fitted to right and left hand sides of the pole alternately, as shown in Fig. 4.

13. Side-armed poles
Where side-arming is unavoidable, one Brace, Arm, No. 2 should be fitted to each arm, and the strut below the bottom arm - specified in T.I.XIII para. 93 - dispensed with. Combiners should be fitted, as detailed in C 3511.

14. Cross-armed Poles
Where cross-arming is necessary, the pole should be scarfed and bored locally as described in C 1102, to accommodate the lower set of arms.

15. Arming and poling - sequence of operations
With this method of arming, it is almost as easy to arm poles after erection as on the ground. Whilst the usual practice of arming poles before erection should generally be followed, poles should be armed after erection where such is definitely advantageous e.g. on new work where the additional weight of arms and fittings would render erection difficult, and on existing lines where difficulty would be experienced in erecting the armed pole through the bed of wires.

Fig. 3
Arm braces with 8 way arms on medium or stout poles

Fig. 4
Arm braces with Arms, Wood No. 28 on light poles



Pole Spindles

Issue 1, 4.1.37

Insulator Spindles

1. General
This Instruction describes the standard types of insulator spindle and their conditions of use.

2. Material and design
The Department's spindles are made of mild steel, with 3/4in. or 5/8in. "Cordeaux" insulator threads. The different patterns are illustrated in Fig. 1. The 3/4in. spindles are designed to withstand a test load of 10cwt.; the permanent deflection under this load not to exceed 1/8in. The 5/8in. straight and "U" type spindles are made to withstand 7cwt., and the 5/8in. "J" type spindles 2cwt., test loads.

3. Conditions of use of the different types, together with Rate Book Nos. of the insulators suitable for the various requirements, are given in Table 1.

4. Spindles on arms
Normally, straight spindles should be used at "through" wire positions, "U" cup holders at transposition points, and "J" spindles at terminal and distribution poles. Where, however, certain of the wires on the line are to terminate at an intermediate point and the adjacent wires are carried on straight spindles, "U" cup-holders or straight spindles should be used for the terminated wires, for the following reasons:-

  1. The equidistance of wires, desirable for reducing interference, is maintained between terminated and through wires.

  2. The reduced spacing between wires on J-spindles and wires on straight spindles immediately below, increases fault liability.

  3. It is difficult to fit straight spindles in positions immediately below J-spindles.

Generally, this arrangement has the further advantage that no change of spindle is required in the event of the terminated wires being extended later along the line.

5. Where wires of 200lb. per mile and under are to terminate from opposite sides of an arm on J-spindles, Spindles No. 10 should be used, provided that the wires on each side are approximately in line. If, however, the wires are not in line, a Spindle No. 10 would have a tendency to slew and become loose, thus upsetting the regulation. Under these conditions, therefore, the wires should be terminated on Spindles No. 8, fitted in accordance with para. 14.

The spindle at the back of the pole should be attached to a terminal iron, secured to the arm by the spindle on the opposite side.

6. "Spindles, No. 7A"
These may only be used in spindle positions on arms where the fitting of an additional arm (or arms) to carry Spindles Nos. 8 or 10 is impracticable.

7. Spindles on saddles
Spindles Nos. 2, 4 or 5 are used for single wires on saddle positions, and Nos. 13 or 14 secured by means of a "Bolt No. 6" - for two-wire circuits. For the insertion of transposition crosses or where pairs from both sides of a pole terminate - e.g., at a distribution pole - in a saddle position, "Spindle, No. 15" is used for wires up to and including 200lb. per mile. This spindle consists of a pair of Spindles No. 13, a "Coupling" and two "Bolts No. 25" assembled as shown in Fig. 1 and attached by means of a Bolt No. 6. For wires of 300lb. per mile and over, two "Spindles, No. 14" should be used with the coupling and bolts; in such cases it is necessary to requisition the items separately.

8. Terminal irons (illustrated in Fig. 1)
These are used to secure J-spindles to arms, either in the ordinary spindle positions at angles in the line (see para. 5 and C 3551) or at the extreme ends of the arms for the purpose of leading-off circuits. The irons are available in two sizes, "Irons, Terminal, No. 3 and No. 4," the former for use with 5/8in. spindles on arms 2in. in depth, and the latter with 3/4in. spindles on 3in. (terminal) arms.

9. Fitting - Oiling threads
Before fitting spindles, the "Whitworth" screw threads should be well oiled, as a protection from corrosion and to facilitate removal. New spindles are issued with the threads already oiled, but the threads of re-used spindles, either shifted or re-issued, should be oiled locally with "Oil, Bearing, No. 14" before being fitted. See also para. 19.

10. Nut washers
"Washers, Galvanised, No. 12" (square, 3/4in.) and "Washers, Galvanised, No. 13" (circular, 5/8in.) are fitted to all spindles with Whitworth threads, and to "Bolts, No. 6 and No. 25," when issued. The washers are obtainable separately on requisition, and washers missing from spindles or bolts to be re-used should be replaced.

FIG. 1




11. "Washers, Galvanised, No. 11"
At angles in the line, and at terminations on straight spindles, where the spindle is required to withstand a considerable bending moment, a special washer should be fitted between the arm and the spindle seating, to provide a greater bearing surface on the arm. These washers, known as "Washers, Galvanised, No. 11," should be used with spindles with 5/8in. shanks and Bolts, No. 6; they are not required with Spindles Nos. 6 and 12, which have suitable flanges. The washers should be used generally on "Arms, Wood, No. 28," owing to the comparatively soft nature of the wood of which these arms are made.

12. "Sleeves, Galvanised"
should be used when it is necessary to use spindles with fin. shanks or Bolts, No. 6 on terminal arms (bored for 3/4in. spindles), to make up the spindle or bolt to the larger diameter.

13. Spindle nuts should be screwed up tightly by means of a spanner - not merely by hand pressure on the insulator and nut nor by the use of pliers - to avoid loosening through shrinkage of the arm or vibration.

14. Single-J and vertical double-J spindles
These should always be fitted so that the plane of the spindle coincides with the resultant pull of the wire or wires attached thereto. Thus, in the event of the spindle becoming loose through vibration or shrinkage of the arm, there will be no tendency for the spindle to slew and thereby upset the regulation of the wires.

15. Spindles No. 10
For the for the same reason, these should be fitted at such an angle as approximately to balance under the pull of the wires attached to either side.

16. Terminal irons
These should be fitted in accurate alignment with both the J-spindle and the line wire. These irons are normally attached to the arm by means of a spindle. If a spindle is not likely to be required in the arm, the iron should be secured by means of a Bolt No. 6. It will be seen from Fig. 1 that a slot is provided at the open end of the irons: this permits of attachment to an existing spindle without the necessity of completely withdrawing the spindle from the arm. A 2in. tubular washer - "Washer, Galvanised, No. 16" - should always be used at the closed end of the iron, as shown in Fig. 1, in order that the spindle may be tightened effectively.

17. "Bolts, No. 6"
4in. by 5/8in. - are provided for securing Spindles Nos. 13 and 14 to arms, and Spindles Nos. 13, 14 and 16 to saddles. In the latter position, the bolt-head and washer should be fitted above the spindle, and the nut in the cavity under the saddle. This arrangement, in addition to affording protection for the screw thread, renders the above spindles interchangeable with straight spindles without removal of the saddle.

18. On tubular-iron arms
"Strips, Insulating" if not already in position, should be fitted to the upper side of iron arms, and curved washers - "Washers, Galvanised, No. 1" - to the underside, to enable the spindle shoulders and nuts to bed properly on the curved surface. At vacant spindle positions, the strips should be secured by means of "Bolts, No. 1" and curved washers.

19. Shifting and recovery of spindles
"Rust Solvent" should be freely used on the threads of spindles which have become rusted-up through prolonged exposure. The solvent should be applied in advance of the work of dismantling, if possible. In addition, "Oil, Bearing, No. 14" should be used when unscrewing the nuts. A convenient means of application is by the use of a "Brush, Sash, No. 4" and "Tin, No. 3". To avoid overfilling the brush, only a small quantity of solvent or oil should be maintained in the tin.

20. Nuts, otherwise immovable, can often be started by the use of two hammers. One hammer is held against one side of the nut, and the opposite side struck smartly with the other. To prevent the spindle from turning during the process of unscrewing, a special spanner - "Spanner, Spindle, Insulator" - which grips the arm and the flats of the spindle simultaneously, will be found of great assistance. The spanner is illustrated in Fig. 2.



POLE Wiring

Issue 2, 14.12.38

Connexions between open wires and covered conductors

1. General
This Instruction details the method to be employed in connecting open wires to the single-pair cables required for:-

  1. cross-connexions on poles

  2. leading-in to:-
    i) buildings, e.g. subscribers' premises.
    ii) pole test-boxes.
    iii) cable pairs in aerial cable, and underground cables generally.

2. For instructions relating to leading-in cabling at subscribers' premises see G 3020, and for details regarding the method of connecting terminal blocks to cables see Underground, K 3102.

3. Insulators
Three types of terminal and leading-in insulators are available:-

"Insulator No. 16" threaded for a 5/8in. spindle.
"Insulator No. 17" threaded for a 3/4in. spindle, suitable for line-wires of 300lb. per mile and over.
"Insulator No. 21" similar to "Insulator No. 16" but having a side-knob.

4. Pole-leads
"Cable, I.R.V. core" should normally be used for leads from terminal insulators and is available with:-

a. 121lb. conductor in a twin cable of flat type.

b. 40lb. conductor in a single or twin cable of circular section.

5. In general:-

a. "Cable, I.R.V. core, T. 1pr./12" is used with 40lb. and 70lb. open wires.

b. "Cable, I.R.V. Core, Single (or Twin) 40lb." is used with 100lb. (or heavier) open wires.

6. Where drop-wire is used (see E 3101), the drop-wires ("Cable, I.R.V., Braided and compounded") are taken direct into the terminal block (but see para. 20).

7. Terminal blocks
These are normally used to facilitate the connexion, by means of individual cable leads, of the open wires to the underground, aerial, or leading-in cables. Details of the sizes available and appropriate for different types of cable are given in Underground, K 3102.

FIG. 1

FIG. 2

8. Terminal blocks are not required for terminating leads:-

a. in leading into a building where only a few circuits are ever likely to be required, or

b. in connecting overhead wires to a pole test-box.

In such cases the I.R.V. leads should be taken direct to the protective apparatus, or to the test-box connexion tags, as the case may be.

9. Numbering of cable pairs and lay-out of pole-leads
The standard numbering scheme for the cable pairs in the terminal blocks is illustrated in Fig. 1, which also indicates how the sequence of numbers is continued when a second block is fitted. The corresponding ideal position for the open wires served by each pair is indicated in Fig. 2 (see also para. 23).

10. Arrangement of pairs on terminal blocks fitted to isolated lengths of underground cable
At power crossings and other places where a length of cable is used to connect two sections of an overhead line, the standard wiring lay-out described in para. 23 should be followed. Assuming that the line-wires for each circuit occupy similar positions on the poles at each end of the cable, it will be clear that if the cable pairs at one terminal pole (preferably at the UP end) are terminated in the sequence illustrated in Fig. 1, they should be so arranged in the terminal block at the other end that the numbering commences at the top of the right-hand strip and is continued down the block on left and right, alternately. For the latter block a specially engraved label should be requisitioned; see Underground, K 3102.

FIG. 3

11. Running and fixing the pole-leads
From the terminal block the pole-leads should be run symmetrically alongside the main cable, thence round the pole at arm level, and along the underside of the arms, as shown in Fig. 3.

12. On the pole, the leads should be fixed, depending on the number, by means of either:-

  1. " Lugs, Lead, 1in.," or

  2. " Lead Strip, 1in., 5lb." ; "Washers, Galvanized, No. 19" ; and "Nails, Bonding" or, where leads are likely to be added from time to time, "Screws for Wood, Brass, No. 12, Round Head, 1in." may be used.

13. On the arms the leads should be fixed by means of "Clips, Pole-lead, No. 1".

14. The clips are made of spring steel, sherardized. The general pattern and the method of attachment to the arms are shown in Fig. 4. The down-turned nibs - A, Fig. 4 - assure that, even if the spindle works loose on the arm, there will be little chance of the clip slipping out of position.

FIG. 4

15. To insert a pole-lead in position in a clip, it is not necessary to slacken, or otherwise interfere with, the spindle nut. Threading the lead is unnecessary; the clip is sufficiently flexible to allow of the lead being slipped into place from the side of the arm by depressing the tips of the fingers - B, Fig. 4.

FIG. 5

16. Fixing to spindles and combiners
The pole-leads should be fitted close against the spindles, to which they should be attached by means of "Lead Strip, 1/4in." as shown in Fig. 5. The leads should be secured clear of the sumacs against which the hook of the regulating tool will bear, during regulation of the open wires. The cross-connecting leads between the wires of pairs erected on the twist system in the outer positions of 8-way arms should be run via, and secured to, the combiners, as shown in Fig. 5.

17. Within the terminal block, the sheathing should extend to approximately 1 inch from the terminals. Each individual lead should be sealed with "Compound No. 5" and the terminals well smeared with "Compound No. 7" which consists of a mixture of four parts of beeswax to three parts of petroleum jelly.

18. Connexion of pole-leads to open wires
The method of making the joint between the pole-lead
and line-wire will depend on the size of wire. Figs. 6 to 9 illustrate the more usual leading-in schemes. It will be seen that a sleeve is available - "Sleeve, Jointing, No. 10" - for jointing 121lb. conductors direct to 40-lb. line-wires. To connect 121lb. conductors to other sizes of line-wire, it is necessary to extend the 12lb. conductor by means of a short length of "Wire, Copper, Binding, 40lb." and make the joint to the line-wire outside the insulator.

19. By means of the appropriate nib jointing-sleeves and copper packing-tubes, see E 3070, 40lb. conductors (either the short intermediate length as above, or the 40lb. pole-lead conductor itself) may be connected to line-wire of any Weight up to 150lb. per mile. Heavier line-wire necessitates soldered joints, as shown in Fig. 9; resin-cored solder "Solder No. 6" may be, used for this purpose. Full details of jointing are given in E 3070.

FIG. 6


FIG. 7


FIG. 8

FIG. 9

20. When it is necessary to terminate open, wire by means of covered drop-wire, the drop-wire conductor should be connected in the same way as the 40lb. conductor of 1-pr. I.R.V. cables.

21. Insulator cavities should be filled with "Compound, No. 5," to prevent ingress of moisture. The holes should first be plugged with compound, and a layer of compound placed over the bottom of the cavity. For effective sealing, the lead covering of the cables should project slightly into the compound. The joints should then be pressed into the layer and more compound added until the cavity has been filled.

22. Precautions
When terminating an I.R.V. lead, the following precautions should be observed. The tape which surrounds the insulation should be stripped back at least in. from the exposed conductor. Particular care should be taken to guard against trapping moisture within the compound. In wet weather, it may be advisable to postpone the sealing of the cavities until a more favourable opportunity.

23. Systematic wiring of Terminal and Distribution Poles
Every effort should be made to wire distribution poles neatly and systematically. As far as possible, wires to the left of the pole should be connected to the cable pairs on the left of the connexion strip in -the terminal block, wires and pairs to the right being similarly connected to the terminals on the right of the connexion strip. This will minimise the crossing of leads from one side of the pole to the other, and crossing the cable should be avoided. A suitable lay-out with 8-way arms is illustrated by Fig. 2  the modification necessary for arms of different capacities may be seen from the wiring diagram Fig. 10. The diagram shows the arrangement of the leads under both the transposition and twist systems. Leads to serve the inner pair on successive 6-way arms should be run from the left and right hand sides of the terminal block, alternately. When the saddle position is used, this should be given the first number and the numbering of the remaining circuits on the pole should be arranged so that odd numbers on the first block are still on the left, and even numbers on the right.

24. Pole-leads, once run, should be interfered with as little as possible. Only in exceptional circumstances should circuit changes be made at the terminal block.

FIG. 10


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Last revised: March 30, 2023