The life of Isambard Kingdom Brunel, Civil Engineer Part 31

NOTE (p. 255).

_Dimensions of the 'Great Britain' Steam-Ship._

feet inches

Total length 322 0

The length of keel 289 0

Beam 51 0

Depth 32 6

Feet of water 16 0

Tonnage measurement 3,443 tons.

Displacement 2,984 "

_Dimensions of original Engines, &c._

Number of cylinders 4

Diameter of cylinders 88 inches

Length of stroke 6 feet

Weight of engines 340 tons

Weight of boilers 200 "

Water in boilers 200 "

Weight of screw-shaft 38 "

Diameter of screw 15 ft. 6 in.

Pitch of screw 25 ft.

Weight of screw 4 tons

Diameter of main drum 18 feet

Diameter of screw-shaft drum 6 "

Weight of coal 1,200 tons

CHAPTER X.

_STEAM NAVIGATION._ _INTRODUCTION OF THE SCREW PROPELLER INTO THE ROYAL NAVY._

A.D. 1841--1844. aeTATIS 36--39.

APPOINTMENT OF MR. BRUNEL TO CONDUCT EXPERIMENTS FOR THE ADMIRALTY WITH VARIOUS FORMS OF THE SCREW PROPELLER, APRIL 1841--TRIALS WITH THE 'POLYPHEMUS'--OPPOSITION TO MR. BRUNEL'S EXPERIMENTS--TRIALS WITH THE 'RATTLER,' OCTOBER 1843-OCTOBER 1844.

Soon after Mr. Brunel had taken the bold step of recommending the adoption of the screw propeller in the 'Great Britain,' he was asked to send a copy of his report to the Admiralty. He did so; and in the course of a few months was invited to attend the Board on the subject of some experiments their Lordships proposed to make.

An interview took place on April 27, 1841; of which Mr. Brunel gives the following account:--

I attended the Board: Lord Minto stated that he wished a complete experiment to be made on the applicability of the screw to Government boats, and he proposed to place the conduct of the experiments in my hands as a professional man. I stated that I should have great pleasure in doing it, and should take great interest in it, provided they intended to make a good experiment and would place it entirely in my hands, without the intervention of any Government officers, but that I should communicate direct with the Lords, and of course with Sir E. Parry.[135] He said he proposed to build a vessel and engines on purpose, and that he particularly wished it to be left entirely in my hands, and took me apart to the window to impress this last condition on me.

Within a fortnight of his appointment, Mr. Brunel invited Messrs.

Maudslay and Field and Messrs. Seaward to send him designs for the engines: they were to have been of 200-horse power, with a stroke of 4 feet. The engines were to make a smaller number of revolutions than the screw, the motion being communicated from the engine shaft to the screw shaft by drums and straps. This arrangement was adopted in preference to tooth-gearing, in order to facilitate the variation of the number of revolutions, in the experiments with different screws.

The designs ultimately sent to Mr. Brunel for his approval were those of Messrs. Maudslay and Messrs. Forrester. He reported to the Admiralty in favour of Messrs. Maudslay's engines.

Before drawing up the detailed specifications, Mr. Brunel was desirous of procuring data for estimating the surface of the screw required to obtain the same resistance as that offered by the paddles of a ship similar to the new vessel. With this object he applied to the Admiralty for permission to make an accurate trial of the performances of the paddle steamer 'Polyphemus' at various speeds. This permission was granted; the trial, however, was fixed for such an early day that Mr.

Brunel had barely time to make the preliminary arrangements, with the a.s.sistance of his friend Captain Claxton.

When Captain Claxton arrived at Southampton, the day before the trial, he found that there was no measured mile set out. He immediately hired men, got chains, staffs, and flags, and set out both a nautical mile and a statute mile. They made half a dozen runs each way with the 'Polyphemus,' noting carefully all particulars of speed, revolutions, &c.; and the results obtained were considered very satisfactory.

On October 1, Mr. Brunel received information from the Admiralty (now under the administration of the Earl of Haddington) that Messrs.

Maudslay and Field's tender was accepted. The engines were immediately put in hand, under Mr. Brunel's supervision.

When they were approaching completion, he became anxious to learn something about the progress of the ship which was to have been built for them. Nowhere could she be found. The minutes were searched at the Admiralty, and it was ascertained that the ship was ordered, but that no ship had been laid down. This discovery, as might be supposed, excited considerable surprise. Mr. Brunel was sent for to the Admiralty to see Sir George c.o.c.kburn, the First Naval Lord. Almost the first words to him were: 'Do you mean to suppose that we shall cut up Her Majesty's ships after this fashion, sir?'--Sir George at the same time pointing to a model of the stern of an old-fashioned three-decker, in which large slices were taken off to give room for the screw, and the whole of the lower deck exposed to view, thus making the application of the screw look very ridiculous. On the model was written, 'Mr. Brunel's mode of applying the screw to Her Majesty's ships.' Mr. Brunel smiled, and denied its being his idea at all; he had never seen it before, and knew nothing about it. 'Why, sir, you sent it to the Admiralty.' This also Mr. Brunel denied having done. While an enquiry was being made as to where the model came from, Mr. Brunel employed himself in effacing the inscription with his knife. When the messenger returned, he reported that the model had come from the office of the Surveyor of the Navy. He was sent for, but did not appear. Mr. Brunel, to terminate this awkward interview, pleaded business, and bowed himself out.

Mr. Brunel often told this anecdote, and spoke of the adverse influence which had been exerted in some department of the Admiralty to prevent the successful issue of these experiments.

Soon afterwards Mr. Brunel was informed that the 'Acheron' would be prepared for the screw. He thereupon represented to their Lordships that the 'Acheron' could not, from her full after-body and other defects, be converted into such a ship as the Board had originally determined to construct for trying the screw; and, indeed, her unfitness was admitted by the authorities themselves.

To a letter on this subject, in which he stated that the attempt to apply the screw propeller to the 'Acheron' would not answer any of the objects which their Lordships had in view, Mr. Brunel received no reply, and for the next four months was kept quite in the dark as to what was going on. At length he made enquiries as to the cause of a treatment which, he said, he had never before experienced from any public body.

These enquiries proving fruitless, he at last wrote to the Admiralty, declining further interference, as it had appeared on investigation that the condition on which he had accepted his position from Lord Minto--namely, that he should have the entire superintendence of the experiments--had not been observed.

On the receipt of his resignation, Mr. Brunel was summoned to the Admiralty. He thus described his interview in a letter to a friend:--

Not a word was said about my complaint of the past, but they said they wished me to continue the experiments, and that my screw was to be tried first. I said that was not at all what would suit me; that I would, if they wished it, conduct an experiment as originally proposed; that I had no screw, that I was no compet.i.tor, but an arbitrator in whom the Admiralty had perfect confidence; that I was this or nothing. Then commenced a tedious fencing....

However, it ended in all parties being written to, and told that they were to follow my directions, and that I was to proceed to give such instructions as should enable a full experiment to be made of all screws generally. I then requested that this time I might have my instructions in writing.

In a few days Mr. Brunel received an official intimation that the 'Rattler' was to be adapted for the screw, under his directions.

The 'Rattler' was a vessel of 888 tons burden, 176 feet 6 inches between the perpendiculars, and 32 feet 8 inches beam.[136] She had been commenced for a paddle-wheel steamer shortly before, and was of nearly the same tonnage and midship section as the 'Polyphemus,' but she had not the fine lines aft which were so important for the use of the screw.

She was not launched until April 13, 1843, just two years after Mr.