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Author Topic: Portcullis Chain Barrier Test  (Read 1941 times)

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Offline kyn

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Portcullis Chain Barrier Test
« Reply #1 on: December 18, 2009, 16:12:22 »
The Times

28 April 1858

Yesterday the troops belonging to the Royal and East India Company's Engineers at Chatham were engaged in some siege operation of a somewhat novel character, for the purpose of testing the merits of a portcullis chain barrier, the invention of captain Spencer Westmacott, R.E., and its capabilities of resisting the effects of several charges of gunpowder and roundshot.  One of the chain barriers was erected beneath the archway of the sallyport, leading to the spur battery, and Fort Amherst Redoubt, where the experiments took place.  The invention is exceedingly simple, and consists of nothing more that a chain three-eighths of an inch in thickness, which is formed into squares or about a foot in length, and composed of five links.  The merit claimed for the invention by Captain Westmacott is that it will effectually resist the passage of troops into a fort or garrison, and that, owing to its non-resistance, it cannot be destroyed in the ordinary way by charges of gunpowder.  The experiments, which were tried yesterday in the presence of about 200 officers, were undertaken with the view of ascertaining whether the portcullis could be destroyed.  A charge of 60lb. Of gunpowder was first fixed against the barrier, and the thick wooden doors closed.  The powder was then fired, the result of the explosion being that, although the doors were shivered to atoms, the brickwork of the sallyport loosened, and all the shutters and doors of the rooms near blown off, yet the chain remained perfect.  Captain Westmacott then had another charge of 60lb. Of gunpowder hung on the chains of the barrier, and on this being fired not the least impression appeared to be made on the chain portcullis.  Colonel Sandham, director of the Royal Engineers' establishment, by whom the experiments were conducted, then directed two charges, each of 60lb., to be tried against the barrier, the charges of gunpowder being secured to oaken planks, and placed against the barrier.  Notwithstanding the tremendous explosive force of this charge, which actually tore away a portion of the brickwork in the thick arch of the sallyport, the only impression made on the chain barrier was the tearing away of that part of the portcullis which was attached to the  balk of oak timber by stanchions, only one link of the chain itself being forced asunder.  The chief strain, it was considered by the inventor, would fall on the sides of the barrier, and these were secured by rings to iron pillars, but in any future experiment additional strength will be given to that part of the chain attached to the upper part of the arch.  After the whole of the charges had been ignited Colonel Sandham directed a 6-pounder field-gun to be wheeled up for the purpose of trying the effects of shot on the barrier.  Here, however, as may be readily supposed, the portcullis offered no resistance to the cannon shot.  The first ball, fired from a distance of about 40 yards, broke an aperture in the chain sufficiently large to enable and troops to pass through.  Several other shots from the 6-pounder were likewise fired, and in each case portions of the chain were carried away.  On the whole the experiments, which were witnessed by a large number of scientific gentlemen, were considered very satisfactory, and should the newly-invented chain portcullis fail in acting as an impassable barrier, it will, it is supposes, prove wherever used a very formidable obstacle to the passage of troops.

The walls and roof of the arch leading to the unrestored area of the fort show signs that this was probably the site of the portcullis.

 

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