How it Works. You will see from the picture that each cylinder has three big ends on the crankshaft. The centre one drives the lower cylinder piston. The two outer big ends drive the piston in the upper cylinder, through the reciprocation of the connecting rods. When the lower piston crank is at the top of it's stroke, the outer two piston cranks have pulled the upper cylinder piston down into the cylinder, so that too is at the top of it's (inverted) stroke. Most slow speed marine engines are two stroke. This means that the compression stroke includes the intake of air through the inlet ports which are assisted by a scavenge feed pump. The exhuast stroke occurs when the gases (which are expanded because of the heat generated by the explosion in the cylinder) are released into the exhaust manifold, as the piston's clear the exhaust ports. A really efficient design and concept. The drawback? Can you imagine having to change the piston rings? 

I meant to put this topic with the City of Worcester notes. However, it applies to most ships.

One of the other watchkeeping duties is to monitor the stern gland. The stern gland is the seal around the propshaft, where it enters the stern tube. Seawater seaps into the stern tube from the propellor end of the shaft. You cannot have conventional bearings, because of this seapage. To overcome this problem the sterntube is lined with Lignum Vitae. The stern gland has a collar on it that compresses the Lignum Vitae bearing, and creates a tight fit around the prop shaft in the stern tube. However a little sewater needs to be allowed to pass through the stern tube to act as a lubricator. The stern gland is also lubricated by a non emusifying lubricant that is pressurized and lubricates the inside ege of the gland. Usually, when the gland is adjusted properly (this is done by either tightening or loosening the nuts around the collar) there will be a slight trickle of seawater running into the tunnel bilges, these are usually pumped out on every watch.

Drawing of a Stern Gland.

City of Delhi.

This is the City of Ottowa (Sister ship to the City of Winnipeg/Delhi) The ships are identical.

A Brief History of Trinity House.

Henry VIII and Pilotage
It is often stated that the origins of Trinity House date back to a charitable guild of sea Samaritans established by Archbishop Stephen Langton in the 12th Century. The first official record is the grant of a Royal Charter by Henry VIII in 1514 to a fraternity of mariners called the Guild of the Holy Trinity, .. "so that they might regulate the pilotage of ships in the King's streams". At the time of inception, this charitable Guild owned a great hall and almshouses, close to the Naval Dockyard at Deptford on the River Thames. In 1604 James I conferred on Trinity House rights concerning compulsory pilotage of shipping and the exclusive right to license pilots in the River Thames. Until our responsibility for District Pilotage was transferred to Port and Harbour Authorities under the 1987 Pilotage Act, we were Pilotage Authority for London and over 40 other Districts, including the major ports of Southampton and Harwich.

Today the Corporation is comprised of a fraternity of approximately 300 Brethren drawn from the Royal and Merchant Navies and leading figures in the shipping industry. Its Master since 1969 has been the Duke of Edinburgh.

Seamarks and Ballastage
Trinity Houses connection with seamarks dates to the Seamarks Act of 1566 which gave us powers to set up "So many beacons, marks and signs for the sea…whereby the dangers may be avoided and escaped and ships the better come into their ports without peril.". Unfortunately, Trinity Houses funds were extremely limited until in 1594 the Lord High Admiral of England, surrendered his rights to the sale of dredged ballast to sailing vessels discharging their cargoes in the port of London. The rights to Ballastage passed to Trinity House who took over responsibility for dredging shingle from the bed of the River Thames and selling it to masters requiring ballastage. With the rapid growth of the shipping to the port of London, ballastage was a very profitable business, however business declined and at the end of the nineteenth century, when steel ships capable of holding seawater ballast were introduced.

Lighthouses
The first lighthouse built by Trinity House was at Lowestoft in 1609, which was part of a series of lights to help guide vessels through a maze of sandbanks between Happisburgh and Lowestoft. The lighthouses were paid for by a levy charged on vessels leaving the ports of Newcastle, Hull, Boston and King's Lyn, a method of payment which is similar to the current light dues system that remains in use today.

The next two hundred years saw a proliferation of lighthouses, many privately owned, with an annual fee paid either to the Crown or Trinity House. The owners of the private lights were allowed to levy light dues from passing ships when they reached port. The reliability of many of the private lights left much to be desired and so in 1836 legislation was passed for all private lights in England, Wales and the Channel Islands to be compulsory purchased and placed under the management of Trinity House. The previous owners were compensated on the basis of their receipts from light dues, a payment of nearly half a million in respect of Skerries Lighthouse, off Anglesey.

The following is the link to the cadetship site.

http://www.trinityhousetraining.org/

Steering Gears

The direction of the ship is controlled by the steering gear. As the ship moves through the water, the angle of the rudder at the stern determines the direction it will move. Modern ships are so big that moving the rudder necessitates the use of hydraulics or electrical power.

The steering starts at the Bridge. The required rudder angle is transmitted hydraulically or electrically from the steering wheel at the Bridge to the telemotor at the steering gear, just above the rudder.

There are a few common arrangements for using hydraulic power. There are the 4-rams, 2-rams, and rotary vane types. The heart of these hydraulic systems is the marine steering gear, rudder, stern, hydraulic, electrical, power, telemotor, fluid, ram, direction, feedback, Marine Engineer Shipping variable delivery pump. This type of pump can be controlled by just moving a spindle. The pump is driven by an electrical motor at constant speed. By moving the control spindle away from the central point, the pump stroke increases, and the hydraulic fluid is pumped in one direction. Moving the spindle more from the central point will cause more fluid to be pumped and consequently more pressure is generated to drive the rams. Moving the control spindle back to the original position and then away in the opposite direction causes the hydraulic fluid to be pumped in the reversed direction. The rams will also move in the reversed direction.

By using a floating lever feedback mechanism, when the rudder stock has reached the desired angle, the pump control lever moves back to the original position, and the pumping action stops. The rudder is stopped at the required angle. Moving the steering wheel to the opposite direction will cause the rudder to come back to the original zero position.