Melbourne Cable Tramways – Macmeikan & Pollock Reports

Grips

The initial cable grips were imported from America with the rolling stock for the Richmond line. These grips were of the design shown in Figure 36 and were later manufactured at the Tramway Workshops at Fitzroy. This type of grip was not entirely satisfactory for local conditions, the following two problems being encountered.

Figure 36. General arrangement drawing of first type of grip used by Melbourne cable trams.

From the Macmeikan report.

When the rope was thrown out of the grip by the lifter bat (A) raising the conical pulley (B) up the vertical spindle (C) it resulted at times in the conical pulley (B) becoming jammed by grit and dirt on the vertical spindle (C) and would not drop back to its original position. This resulted in the rope being taken in between the dies (D) with the conical pulley (B) above the rope (E) and not in a position to force the rope (E) out of the dies (D) when such operation was required.

The second issue was that the method of adjustment of the dies (D) was unsatisfactory for various conditions of work ropes and dies. The adjustment was made by the adjustment screw (F) before the grip was placed in service in the morning. To provide for die and rope wear, a long rack (G) was cut in the quadrant (H) so that sufficient travel was available for the lever (J), this movement of the lever was most undesirable because the brake levers situated one on each side of the grip lever were adjusted to operate at approximately a vertical position. It will be understood therefore that the most desirable position for the grip lever operation was somewhere about the vertical.

To minimise the first problem, men were employed at termini to hose the grips and wash out the dirt on days when conditions were unfavourable with rain washing the road grit down the slot.

It was also necessary for gripmen to feel that the cone pulley (B) was down the spindle (C) by operating the lever (J). Resistance would be felt when the conical pulley (B) came in contact with the cable (E). If the cable (E) was accidentally thrown out of the grip it had to be replaced between the dies by means of a hook which was put down the slot in front of the dummy and the cable lifted by the conductor to elevate it into the grip while the gripman moved the lever to close the dies on the cable.

Photographic study of Melbourne grip fitted with screw for die adjustment, 1898. Taken by noted Scottish photographer Charles Wilson.

Photograph courtesy University of Aberdeen.

The second problem was overcome by having frequent adjustments made to the grip by the car depot staff.

A new design of grip [14] was put in hand to make the mechanism more positive and also enable a ready adjustment of dies to be carried out. The new grip when completed gave a splendid performance and with very minor alterations was in use until the last cable line was closed in 1940.

Experimental work was carried out with different types of grip dies made of various metals and different lengths.

Grips – Construction

The following section covers the construction of the final form of the grip mechanism used in Melbourne, as displayed in Figure 37.

Figure 37. Detailed drawing of final type of cable grip used by Melbourne cable trams authorised by the MMTB Chief Engineer T.P. Strickland – January 1933.

From the Macmeikan report.

The grip lever (1) of mild steel, forged in one piece, fits into the cast steel socket (12) which is pivoted to the cast steel slide (18) by the mild steel pin (47). The palm handle (2), having a base or cheeks (58), is also a one piece mild steel forging and is attached to the lever (1) by the mild steel lever bolt (73) and to the pawl rod (59) by another mild steel bolt (73) at the pawl rod end (60).

The mild steel pawl rod (59) passes through a bronze bracket (3), a bronze pawl spring box (50) and a bronze pawl box (7). The spiral steel pawl spring (4), held by the pawl spring pin (49), forces the mild steel pawl (5) downwards into the rack of the cast steel quadrant (16). The bronze pawl box (7), which has a mild steel guard plate (55) to keep the pawl (5) in position, is bolted to the lever (1) and is a guide for the pawl rod (59) at its lower end. There are two mild steel latches (6) for operating the pawl (5) by foot instead of the palm handle (2). The latches (6) are carried by a cast steel pawl latch bracket (8), which is attached to the lever (1).

The adjusting rod (9) of mild steel has a bronze adjusting wheel (11) secured by a nut at the top end. The adjusting rod (9) passes through the bracket (3) and down to the mild steel adjusting screw (10) to which it is held by a cotter pin. The adjusting rod (9) is pinned to the adjusting screw (10) which engages with right hand and left hand nuts (14) in the cast steel shoe (13) and the cast steel socket (12).

The mild steel adjusting screw (10) is machined with a right hand and left hand thread, which, when turned by the adjusting rod (9), moves the shoe (13) and socket (12) together or apart, resulting in an altered relative distance between the shoe trunnion (38) and the slide pin (47), giving an adjustment for the varying sizes of cables.

The shoe (13) slides on the lever (1), which has screws (69) to adjust for wear while the lever (1) and the socket (12) remain fixed to the slide (18).

The mild steel links (15), one on each side of the grip, are attached to the shoe (13) by the shoe trunnion (38) at the top end and to the crossbar (17) by a mild steel pin (48) at the bottom end, in both places washers and cotter pins are used to secure the links (15).

As described above, the lever (1) and socket (12) are fixed to the cast steel slide (18) at the mild steel slide end (45) by the slide pin (47), also the cast steel quadrant (16) is riveted to the slide (18) which maintains the same relative position to the quadrant (16) and lever (1). This enables the lever (1) to operate round the quadrant (16) for the engagement of the pawl (5) in the rack cut in the quadrant (16).

The cast steel slide (18) is guided between two cheeks (19) made of shear steel; these cheeks are protected from wear due to rubbing against the slot beam by the protection pieces (20) which are cast steel and reversible to obtain double life out of them. A top guide plate (46) in cast steel and a bottom guide plate (51) in mild steel serve as guides for the slide (18).

The protection pieces (20) are held in mild steel top and bottom slips (21 and 22) which are bolted to the cheeks (19). The slide (18) carries the top die holder (24) which is bolted to the back guard (25) by the top die holder bolts (52).

The cheeks (19) are bolted to the crossbar (17) by the mild steel bolts (65 and 66) at the top end and held firmly in position by the mild steel wedges (37), and at the bottom end the cheeks (19) are held by the bolts (68) and set screws (71) to the cast steel sole plate (29). The cast steel bottom die holder (28), bolted to the sole plate (29) by the bottom die holder bolts (56 and 57), is fitted with the rolled steel bottom die (27) which meets the rolled steel top die (26) fitted to the top die holder (24).

The cast steel sole plate (29) has fitted into it cast steel swinger frames (35) which are secured at the top and bottom by mild steel bolts (63 & 64). The swinger frames (35) have cast steel swingers (34) held in them by the mild steel swinger pins (40) on which they pivot. The swingers (34) carry cast iron cones (32) attached to them by mild steel cone pins (39) held by mild steel washers and cotter pins. At the top of the cast steel swinger (34) cast steel kickers (33) are pivoted on mild steel kicker pins (53) held by cotters. This mechanism is for “throwing the rope”.

The top die holder (24) has bolted to it a small cast steel lifter bar (23) which rises with the top die holder (24) and engages with the cast steel kicker (33) which rotates on the kicker pin (53) causing the swinger (34) carrying the cones (32) to swing outwards and force the cable out of the dies (26 & 27).

Cast steel sheaves (31) and cast steel sheave centres (62) are bolted by a mild steel sheave stud (43) and washer (70) to the sole plate (29). These sheaves (31) carry the cable when it is released by the dies, and cast steel sheave protectors (61) are provided to guard against the sheaves being damaged due to worn dies.

The lever (1) is limited in its travel by a mild steel lever stop (42) at its lowest position, i.e. with the dies fully opened and a mild steel bolt (41) through the quadrant (16) at a position where the dies are fully closed at the end of their travel. The cast steel back guard (25) is used on curves.

Grips – Operation

The grip as shown in Figure 38 is operated by the grip lever (1), which is moved in the direction shown by the arrow in order to grip the cable. When the grip lever (1) is adjusted by the adjusting screw (10) for normal running conditions, the pawl (5) is in the 7th notch of the quadrant (16). From this running position the operation of the grip is as follows:

The grip lever (1) is moved in the opposite direction to the arrow to the lazy notch on the quadrant (16) to release the cable and allow the tram to stop. To start the tram the gripman forces the lever (1) in the direction shown by the arrow, maintaining pressure on the palm handle (2). To hold the pawl (5) from engaging in the quadrant rack until the tram has attained full speed, then the palm handle (2) is released and the pawl (5) drops into 7th notch on the quadrant if adjustment is correct for the size of cable gripped.

Figure 38. General arrangement drawing of cable grip showing key functional components.

From the Macmeikan report.

The action of this operation is to force the slide (18) carrying the top die (26) downwards, owing to the links (15) being fixed to the crossbar (17) by the pin (48) at one end, and to the shoe (13) on the lever (1) at the other end. It will be observed that this gives a toggle action and that if the lever (1) were to be moved in the direction of the arrow so that the links (15) took up a vertical position the slide (18) would not move downwards because pin (47) attaching the lever (1) to the slide (18) would be in line with the links (15); on the other hand the further the lever (1) is moved down towards the stop (42) on the quadrant the greater the movement of the links (15) from the vertical position and, consequently, the greater the movement of the slide (18) carrying the top die (26); this gives a rapid opening of the dies.

This toggle action and the movement of the lever (1) to the stop (42) as shown in Figure 39 in the procedure adopted when the cable is to be “thrown” or forced out of the grip dies (26 & 27). This operation is as follows:

The tram is running at speed and when it reaches a point where the cable is to be thrown, the gripman moves the lever (1) down to the stop (42) on the quadrant (16); this rapidly opens the dies (26 & 27), the top die (26) being fixed to the slide (18) at the same time as the dies open the kicker gear comes into operation and the cones (32) force the cable out of the dies (26 & 27).

Figure 39. General arrangement drawing of cable grip detailing cones and gripping dies.

From the Macmeikan report.

After the dies have opened nearly to their full extent, the cones (32) are freed and drop down, taking up their original position. The grip is then ready to receive the cable with the dies (26 & 27) fully open. The tram arrives at the point where the cable is to be picked up; the gripman then moves the lever (1) from the stop (42) up to the lazy notch on the quadrant (16) which takes the cable between the dies ready to be gripped and the tram to proceed on its journey.

The following is a description of how the grip operates in service. A dummy with its grip is run out of the car depot and stopped in position over the grip hatch, through which the grip is to be lowered into the tunnel. The grip hatch is opened from the inside of the dummy with a hook, which is carried on all dummies for this purpose and also for picking up the cable should the gripman accidentally release it from the grip in service.

After lowering the grip into the tunnel by means of a rope tackle block attached to the grip lift bar in the dummy as previously described, the hatch is then closed with the hook. The grip is now in position to receive the cable, which is lifted into the grip dies by a hand pick-up. The grip lever is then operated to close the dies on the cable and the grip is then ready for service. As the grip moves along the tunnel it lifts the cable clear of the pulleys, but after passing, the cable lowers on to the pulleys again.

When the grip arrives at an intersection, curve or other position where the cable had to be thrown out of the dies, special precautions were taken to prevent damage to the cable should the gripman fail to operate the grip correctly. The action taken in this direction was to install a check bar at a certain distance beyond the throw rope position. This bar and its functions are described under the heading of cables. Before the installation of check bars very serious damage was caused to the cables, due to the grip cutting or badly kinking them, when the gripman failed to operate his grip correctly.

When the grip arrived at the “throw rope” position the cable was running at its normal height and direction through the grip dies, but after this point had been passed the cable direction was changed by special pulleys, such as a depression pulley at an intersection. The effect of this was that if the gripman failed to throw the cable out of the grip at the correct place or thereabouts, the cable gradually became pressed down into the bottom die of the grip. This pressure rapidly increased and prevented the gripman from releasing the cable, with the inevitable result of serious damage to it.

After the installation of check bars damage could still be caused to the cable by a careless gripman throwing it beyond the throw rope mark and before the check bar. This resulted in damage to the cable while it was being forced out of the dies by the sharp edge of the worn die cutting or burring it. This damage to the cable was detected during its examination at the engine house after service at night. The Workshops Superintendent was notified the next day of this damage, and the rope involved. He then directed the shed staff at the depot or depots concerned to examine all dies. This usually resulted in the marked dies being found, and the dummy number obtained, from which the Line Manager was able to find the gripman responsible for the damage.

On the curves where the cable is carried round in the grip dies, special curve drums and rubbing bars are employed. These drums are spaced at 4' centres on a 50' radius curve and are mounted on vertical spindles. The drums, which revolve horizontally, have a 10 inch vertical face with a flange at their lower edges. The face gives freedom of movement for the cable, when the grip lifts it away from and returns it to the drum. This also takes care of any variation in height of the grip. The flange is to prevent the cable running off the bottom edge of the drum. The faces of the drums are a few inches inside the centre line of the slot round the curve. The rubbing bar is supported by brackets attached to the yokes and at a height of approximately 6 to 8 inches above the cable. The rubbing bar is shaped to give a lead‑on for the grip before it actually enters the curve as per Figure 40.

Figure 40. Drawing of cable rubbing bar for transitioning cable from straight section around curve. TP = transition point from straight to curve.

From the Macmeikan report.

This enables the grip with the cable between the dies to enter the curve with the top die holder or back guard bearing against the face of the rubbing bar. The side of the grip which bears against the rubbing bar depends on which direction the curve takes.

The rubbing bar is made of 3" × 3" × ½" commercial mild steel angle and is situated in front of the curve drums at their upper edges. This allows the grip to hold the cable away from the drums as it proceeds round the curve, the cable returning to the drums as the grip passes. Another important function performed by the grip in service is its operation during shunting at termini.

The method of shunting is known as the “flying shunt” and is employed where practically level tracks exist. The following is a description of this mode of shunting, pictorially represented at Figure 41:

Figure 41. Stages of performing a ‘flying shunt’ at a level terminus.

From the Macmeikan report.

1. The coupling pin is withdrawn, freeing the dummy from the trailer car.
2. The car is slowed down by the light application of its brakes.
3. The cable is thrown out of the grip.
4. The grip strikes a “kicker bar” which sets the points for the dummy to pass over the dummy shunt.
5. The grip strikes another “kicker bar” which resets the points for the car to proceed on the straight track and at the same time returns the first “kicker bar” to its original position.
6. The dummy is slowed by light application of brakes, allowing the car to overtake it.
7. The car runs over the turnout on to the track ready for coupling to the dummy.
8. The dummy moves down to the car and coupling operations are completed.
9. A hand pick-up is used to replace the rope in the grip and the tram is ready to proceed.

Grips – Maintenance

The general service maintenance of grips was carried out at the car depots. This work comprised mainly the replacement of parts worn or broken in service, which generally were:

• Dies;
• Protection pieces;
• Sheaves;
• Pins;
• Adjusting screws;
• Swinger cones;
• Pawls;
• Latches; and
• Bolts.

The dies were replaced when the wear gave a depth between the edge of the die and the bottom of the groove of 3/8".

The protection pieces were used to prevent the slot beam from wearing the grip cheeks. The new castings were ground to a thickness of 21/32" and condemned when worn down to 17/32". This gauging was carried out be the shed staff who were supplied with standard gauges for the depth of die wear and protection pieces. Adjusting screws were replaced when wear became noticeable in making grip die adjustments. This was a matter for the judgement of the leading-hand shed man, who possessed a general knowledge of grip operation.

The sheaves and pins were also replaced when obviously worn. The shed staff were able to keep the grips in very satisfactory order, but when the wear became general after a lengthy period in service the grips were forwarded to the workshops for overhaul.

The overhaul of grips was based on wear, which was shown as lost motion in the grip parts when the dies were closed on a mild steel bar representing the cable. The most obvious wear was in the links, side end and pin, and shoe pin or trunnion.

The overhaul procedure was to disassemble the grip entirely and rebuild it. The parts which could be reconditioned, such as the lever, links, slide end, latches, pawls, quadrant, slide and cheeks, were reused, and other parts required were drawn from the stores and replaced. The practice as with all dummy and car parts was to stock every grip part and so draw out any material required and proceed with the assembly of the grip.

A grip took 3-4 days to assemble and when complete was tested for die movement, adjustment and correct motion of all moving parts, and passed by the leading hand in charge of the grip section, who had a thorough knowledge of the work and the grips.

The grips were assembled on stocks, which were wood posts set in the floor with steel brackets and pins attached to them, being about 4' 6" above floor level. On these pins the crossbar of the grip was mounted and from this part the grip was assembled, firstly the cheeks, then the soleplate and so on, each part being gauged for fit and movement.

Grip Kicker Gear Operation

The grip kicker gear was engaged to force the rope out of the jaws (or dies) of the cable (“throwing the rope”). The following description of its operation is illustrated at Figure 42, each letter point corresponding to the position of the lifter bar in the diagram.

Figure 42. Cross-sectional drawing of grip kicker gear used to lift cable out of the jaws of the grip.

From the Macmeikan report.

1. The lifter bar fitted to the top die holder remains approximately in position A while the grip is operated in normal gripping and releasing of the cable.
2. The grip lever is moved towards the position for throwing the rope, and by raising the top die holder & lifter bar, causes the lifter bar to make contact with the kicker.
3. The lifter bar forces the kicker backwards, operating the swinger, which in turn forces the cable out of the dies by contact with the cones.
4. The lifter bar disengages with the kicker, and the swinger falls back into its original position in the swinger frame. The rope has now been thrown from the dies of the grip.
5. The kicker, which is pivoted on the swinger, moves to allow the lifter bar to pass and the top die holder to regain its position where the die is closed on the cable.
6. The kicker falls back to its original position on the swinger, and the gear is in its position for a repetition of the cycle of movements.

Grip Dies

MTOC conducted experiments with the original grip design, in an effort to reduce costs and maximise mileage obtained from grip dies. Different cast metals were employed in the early tests, the dies and die holders being cast in one piece, and the length of the die portion of the casting was 14 inches.

Later the die was increased in length to 18 inches and cast separately from the holder in special cast iron, being very similar in appearance and performance to the finally accepted material, rolled steel, which came into standard use from 1892.

Finally, in 1903 the design of the grip underwent its final evolution with the die length being set to 19".

Wearing qualities and cost were not the only criteria used for assessing materials for use in the die. Special attention was paid to the quality of the bite of the dies on the rope; if the bite was too severe on the rope, the rope was more likely to be damaged, and smooth acceleration of the tram to the speed of the rope was not achieved.

It should be noted that as speed of the rope was increased there was a corresponding reduction in die life, due to the greater friction involved, together with the increasing loads placed on trams through growth in passenger numbers. Furthermore, the condemning wear depth of the dies was reduced from 7/16" to 3/8", resulting in reduction in die lifespan, but this resulted in longer rope life – which had been reduced by the increase in rope speeds. It should also be noted that it was later the practice to replace all dies on a line when a new rope was installed.

The table below illustrates the results obtained with different materials and rope speeds.

Metal	Grip Die Length (inches)	Average Distance per Die (miles)	Wear Depth (inches)	Cable Speed (mph)	Remarks
Phosphor Bronze	14"	413.17	7/16"	8	Mileage too low.
Cast Steel (hard)	14"	3760.21	7/16"	8	Condemned due to breakages & blow holes.
Cast Iron (soft)	14"	329.17	7/16"	8	Mileage too low & bite on cable too severe.
Malleable Cast Iron	14"	4312.28	7/16"	8	Too hard for good gripping and castings expensive.
Wrought Iron	18"	1261.70	7/16"	8	Similar results to rolled steel dies.
Cast Iron (special)	18"	1438.93	7/16"	8	Similar results to rolled steel dies.
Lowmoor Iron (forged)	18"	–	7/16"	8	Bite on cable too dangerous, condemned immediately. Used for trial run only.
Rolled Steel	18"	2296.50	7/16"	8	Used 1892 - 1900.
Rolled Steel	18"	1226.00	3/8"	10	Used 1900 - 1902.
Rolled Steel	19"	1061.00	3/8"	10	For 1903 - 1904.
Rolled Steel	19"	800.00	3/8"	12-13	For 1934.

Grip Die Movement

The following table shows the grip die movements corresponding to the lever movements from the lazy notch up to the stop at which point the straight line position of crossbar pin, slide pin and trunnion pin occurs.

Start Notch	End Notch	Die Movement between notches (inches)	Cumulative Die Movement from Lazy notch (inches)
Lazy	1	0.201	0.201
1	2	0.031	0.232
2	3	0.029	0.261
3	4	0.027	0.288
4	5	0.024	0.312
5	6	0.022	0.334
6	7	0.020	0.354
7	8	0.018	0.372
8	9	0.015	0.387
9	10	0.013	0.400
10	11	0.011	0.411
11	12	0.009	0.420
12	13	0.006	0.426
13	Stop	0.006	0.432

From this table it can be seen that the grip was a piece of precision engineering, with die movements measured to an accuracy of better than one thousandth of an inch (approximately 0.025 mm), belying its somewhat crude appearance to modern eyes.

Footnote

[14] The new design of grip gave provision for the driver to adjust the dies while in traffic, which was previously impossible, as this had to be carried out by maintenance staff at the car depot. The advantage of this is that it meant that on multi-rope routes the driver could adjust the grip dies to take account of the different amount of wear on each rope. This translated into better grip action and extended cable life.

The other major feature of the new grip design was the introduction of grip kicker gear operating the conical pulleys that reset to vertical position immediately on throwing the cable, rather than closing when the grip was re-engaged. This minimised the potential for the conical pulleys becoming jammed in the throw position through accumulation of dirt, thus preventing the cable from becoming jammed under the conical pulleys when the grip was re-engaged.

If the cable jammed in the grip, the tram could not be stopped until the grip was broken, either by striking a stop bar or by striking some other more expensive piece of equipment, or by damaging the cable to such an extent that it could no longer be drawn by the engines.