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PS ‘Maid of the Loch’ / Windlass: Some Notes on the Electric Capstan

by James Mitchell


Figure 1 The Electric Capstan / Windlass, PS ‘Maid of the Loch’ in its heyday

When the ‘Maid’ (The Maid of the Loch) went into service in 1953, she couldn’t follow the tradition
of her predecessors on the loch, where all rope handling, fore and aft was managed by hand. The
‘Maid’ was much larger than her predecessors and with her higher upperworks, presented more
‘windage’ when coming alongside piers. Paddle steamers are notoriously difficult to steer at
low speeds and ‘coming alongside’ needs slick seamanship – and a bit of nerve, so mechanical
help in closing with the pier was vital. Direct current (DC) had been chosen for the windlass instead
of steam so this logic was followed for the steering improvements. The additional load meant that
her rather small 10kW generator had to be doubled up. The ship’s power needs had been small;
mostly lighting and the windlass. All of the power was provided as DC, still common on ships
at that time. Direct-current motors allow for changes of speed by adjusting the current. An
adjustable speed drive would consist of an electric motor and controller to adjust the motor's
operating speed. Power electronics-based variable frequency drives are rapidly making older
technology redundant.
Figure 1 shows the windlass in its heyday. From extreme right to left we can see (1) the DC
speed controller; (2) is the motor drive into the gearbox; (3) is the brake cover and brake
winder; (4) is the capstan head; (5) is the anchor chain windlass; (6) is the chain guide; (7)
is the spurling pipe, allowing chain to feed in and out of the chain locker and (8) is the hause pipe,
carrying the chain through the ship’s side to the anchor. The windlass was removed when the
promenade deck was re-laid in steel in the late 90’s; one of the first major jobs on the ship. It lay
in storage on the quayside for over 20 years, losing the motor and having a shaft severed by cutting
for reasons unknown.

In 2019 a visitor to the ship, Eddie Van der Stighelen offered to take parts away to his works
(Vantech Engineering Services) for refurbishment. The windlass seemed an ideal candidate and
weighing around one tonne, was a bit much for our volunteers to manhandle. Around the same time,
we secured the placement of a Fellowship from Historic Environment Scotland to train in traditional 
engineering skills for a year and this seemed a great little project for Steve to pick up on, helping
Eddie at his works in East Kilbride.


Figure 2: WIndlass

The Windlass can be seen in Figure 2 in transit storage, shortly before it was sent to Vantech. It
had been many colours over the years, from silver to black, white red and green! This image
shows the brake cover removed, showing the brake caliper. The knob on top of the capstan head
is we believe, to ‘shed’ a slipped rope back down onto the drum as it turns.
The ‘windlass’ name refers to its anchor handling capacity. However, it does include a capstan
for rope handling. Anchor chain and rope handling are two different operations and would probably
never have been carried out together. The arrangement here is unusual and may have been
designed specifically for the ‘Maid’ by the engineers at Inglis’ shipyard. Coincidentally Eddie’s
 dad was an engineer at Inglis at the time.


Figure 3: a simplified sketch of how the windlass works

When the windlass arrived at Vantech it was stripped of many layers of paint externally, the
 capstan was removed then the vertical 3rd motion shaft with the worm wheel. However, lets
look at how the whole thing works first…The first two gears halve the 7.5kW motor speed then
the worm and wheel gearing reduces it again by 32 times. So, the motor runs at 1,000 RPM.
The first two gears reduce this to 500. The worm-and-wheel gear reduces this again 32 times
to 15.625 RPM. This is the turning speed at the capstan. The motor speed has been reduced
by a factor of 64. This means an increase in power by the same factor (excluding
mechanical losses) 7.5kW x 64 = 480kW (643.6HP).


Figure 4: The capstan-head, cover and 3rd motion shaft being removed


Figure 5: internal examination revealed the 1st and second motion shaft

Looking closely at the 1st and second motion gears, it can be seen that the teeth
have been heavily worn; almost to a point. This can be seen better on Figure 6.



Figure 6: motion gears, teeth worn

It can also be seen that the gears have been poorly lubricated, using grease.Originally oil
was used so that the gears ran in an oil ‘bath.’ For some reason… probably oil leaks, the oil
was replaced with grease. This accounts for the failure of the gears… remember the smaller
one was turning at 1,000 RPM! Fortunately, the (expensive-to-replace) crown wheel and pinion
were in good condition and careful cleaning and dressing with a file by Steve, see Figure 7.


Figure 7: Cleaned and file dressed

The new gears as they should be, can be seem in figure 8.


Figure 8: Beauty in the beast

Making two new straight gears was the single most expensive part of the restoration.... Again, Gary
of West of Scotland Engineering, (WOSE) one of our great suppliers, came to the rescue with a
pair of fine gears, one in steel and one in bronze, at a really good price. Eddie has pre-empted future
oil leaks by designing and fitting an oil seal carrier thus ensuring we can go safely back to oil
lubrication.
“Under the bench” restoration is a mark of true improvisation and skill! It means what it says,
in that it’s based on the idea of finding something ‘under the bench’ that can be modified, remade
or provide material for machining. Eddie managed to make a new seal housing, new input shaft,
motor base adapter.... in fact a recycled motor and switchgear, all from “under the bench.” This
allowed actual purchases to be kept to a minimum.
New non-asbestos brake lining material was provided for free from Jim Jack Services of
Cumbernauld and this was assembled onto the brake bands by Eddie. Steve wasn’t idle when
he was at Vantech. His baseline task was removing nearly 70 years-worth of paint and caked-on
grease and dirt. All of the parts had to be cleaned and examined to allow a decision on whether
they were fit for reuse. Steve learned how to carefully file-dress the bronze crown wheel back to
(almost) pristine condition and make new feathers and keys for the various shafts. These hand
tasks were backed up by experience on Eddie’s Lathe and other machine tools Finally the windlass
was painted and assembled. Eddie also managed to ‘find‘ switch-gear to run the windlass in both
directions. The motor is AC and without fitting an inverter drive (beyond the current budget!) it will 
only run at one speed. However, this will be managed by the rope handling technique. A new
mounting frame has been made by WOSE and this will be welded to the steel deck before the
windlass is delivered (in ‘delivery white’) when things get back to normal.
See https://vantechengineeringmy.sharepoint.com/:v:/g/personal/info_vantechengineeringservices_
com/EUcVIa5MY2BArwQU5quTa78BmLNoydaoJbIpumzrtW_FXQ

A final point to make: Once again all of this work was carried out within 40 miles of the ship.
Our great thanks to:
Vantech Engineering Services, East Kilbride
Jim Jack Services, Cumbernauld
West of Scotland Engineering
Eddie & Colin Van der Stighelen
Steve Moffat (Fellow, Historic Environment Scotland)



Jim Mitchell ACR, Conservation Engineer
 

To all our STICK friends

Keep Safe! 


 


 
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