The Inglis Bridge
This post has been updated and moved to HERE
Keeping with the current theme of the WWI commemoration I want to expand on an earlier post on WWI bridging, specifically looking at the Inglis Bridge.
That should actually read, Inglis Bridges, because there were several.
Most people tend to think of the Bailey Bridge as the first sectional military bridge but before the WWII Bailey Bridge, Charles Inglis designed the first dry gap prefabricated military bridge in service with any Army. A number of Stock Spans were introduced earlier but these were used in construction bridging rather than as a self-contained portable bridge.
One might not immediately envisage the trench warfare of WWI having a great deal of need for bridging, the majority of engineer tasks were fortification, infrastructure, tunnelling and the myriad of other duties that the Royal Engineers had, let’s not forget the Royal Engineers were the birthplace of the modern RAF, REME and Corps of Signals. When planning for the advance, several designs for lightweight transportable bridges were considered before those of Charles Inglis were selected.
Charles Edward Inglis (pronounced Ingles) was born in July 1875, after winning a scholarship to Kings College Cambridge and spending time as a bridge design engineer he took up a lecturers post at Kings College in 1908. He would go on to a distinguished career spanning many decades, responsible for a wide variety of engineering innovation.
But what of bridges and WWI?
In the early pre war period Charles Inglis was involved with the Royal Engineer section of University Officer Training Corps and started the preliminary design work on a portable infantry bridge but with the outbreak of war that had taken a back seat as he volunteered for service, appointed to an instructor post at the School of Military Engineering in Chatham.
By 1916 he was in charge of the Corps bridge design and procurement section.
From this point, Charles Inglis would design a number of important military bridges that would be in service until soon after WWII.
The Inglis Pyramid Bridge
The first Inglis bridge stemmed from his work carried out in 1913.
Officially called the Inglis Portable Military Bridge – Light Type it was generally known as the Inglis Pyramid Bridge.
As can be seen from the diagram below, the Warren trusses were angled in and secured with a single tubular top chord placed in compression. The bottom tubes were in tension and a number of trusses supported the single gangway.
Although the transoms were heavy at 198 pounds (90 kilograms) the tension tubes were very light and this, coupled with the simple construction technique, enabled a 108 foot long bridge to be completed in less than 15 minutes. Originally intended only for infantry and able to carry single file infantry over a 96 foot span it was actually possible to carry 3 ton vehicles by keeping the centres less than 16 feet apart and combining two bridge sets.
10 sets were ordered for use in France
Soon after the BEF requested a modified design that could carry first line transport vehicles.
Inglis responded by designing the Inglis Heavy Type Bridge
Instead of 8 foot tubes the Heavy type used 12 foot tubes and could carry loads up to 7 tons over a span of 96 feet. The tubes were fabricated at the Round Oak steelworks in Brierley Hill, West Midlands, which is now the site of the Merry Hill Shopping Centre.
17 Heavy Type Inglis Bridges were ordered and received into France in 1916 although they did not see widespread use because the triangular construction meant tall vehicles could not traffic the bridge.
A further modification was proposed that truncated the pyramid structure although this was not produced
There is only one Inglis pyramid bridge left anywhere in the world.
An Inglis Portable Military Bridge (Light Type) with the pyramidal construction is situated in Aldershot, just off Laffans Road near Browning Barracks. Laffan of course is familiar to any Sapper in the Hurrah for the CRE song, a former CRE. In WWII, Malta Barracks was on the edge of Laffans Road on the edge of Watts Common and was used for Royal Engineer training as well as the nearby Hawley Lake.
The bridge itself is between the Claycart and Farnborough Road bridges (AG and AH on the map above or see the Google map below)
It is used as a pipe support although not sure what the pipe carries
This marvellous and historic piece of the nations military engineering heritage sits there alone and largely undocumented although the Basingstoke Canal Society do have some information on it.
The Inglis Bridge Mark I and Mark II
With the emergence of the tank it was clear that the existing stock spans and portable bridges would be unable to carry the vehicles. Now responsible for all military bridging in the British Expeditionary Force Charles Inglis was tasked by the Engineer in Chief to design an improved tubular bridge to carry heavier loads as typified by early tanks.
The resultant design took the tubular construction from the earlier Inglis pyramid bridges but used a more practical design with a lightweight pierced top web. The junction boxes were still cast iron and it used the same tubes as earlier designs.
The Inglis Mark I was able to traffic Class A loads (17 ton axle load) over gaps up to 96 feet wide using a 12 foot bay.
After arriving in late 1917 it was widely used in the final advance in 1918.
From Canada in the Great War
A number of standard-span portable bridges, varying in span from sixteen to eighty-five feet, were stored at the base depots. These bridges consisted of loose members and were bolted with machine-turned bolts. They were, however, very cumbersome, and this rendered their erection slow. The weight was another disadvantage, e.g. the eighty-five-foot span was a single-way bridge and weighed sixty-three tons.
Fortunately a new bridge, called the “Inglis Portable Military Bridge, Rectangular Type,” had been invented by Captain Inglis, R.E., and was adopted by the British Army. This bridge was the Warren girder type and was composed of a number of identical bays, each twelve feet long, twelve feet high, and twelve feet wide. It was designed to carry a dead load of eighty-four tons distributed over a clear span of eighty-four feet. Each part could be easily manhandled and the span could vary in multiples of twelve feet, e.g. sixty feet, seventy-two feet, eighty four feet, ninety- six feet, and one hundred and eight feet, to suit the gap. The bridge was built on blocks in skeleton form with a counterbalance arm and jacked up on to a two-wheeled trolley. It was then pushed over the gap, the counterbalance removed, then jacked down on the abutment, and the decking laid. On the 28th of September, 1918, a bridge of this type was erected complete over the Canal du Nord at Marquion in twelve and a half hours actual working time under severe shell-fire. A party of approximately two hundred sappers was employed on the construction of the bridge with the necessary approaches and abutments. The span was one hundred and eight feet clear and the safe distributed load fifty-one tons.
And here is a picture of them doing just that at the Canal du Nord in 1918
An Inglis Mark I was also used to span the Jordan River in Palestine, this being called the Allenby Bridge
Although a big step up in load carrying from earlier designs the unequal tube lengths could cause confusion during night builds and the new heavy tanks were still too heavy.
By the end of the War the Inglis Bridge Mark II was under trial, essentially a strengthened Mark I with 15 foot bays. A key improvement was a return to identical length tubes.
The Inglis Bridge was without a doubt the best military bridge of the time with short construction times and high carrying capacity but because it’s tubular steel construction, expensive.
After the Great War the Inglis Mk II continued to be used and developed into assault and floating bridges.
The Inglis Assault Bridge was a 135 foot long span with a pair of idler tracks. The concept called for the Royal Engineers Tank to use its jib to push the assembled bridge over the gap. In less than a minute a 70 foot gap could be bridged without exposing any personnel to fire, the first true assault bridge to use a bridge of substantial length, over the standard 30 foot assault bridges of the time.
With the demise of the RE Tank (a modified Mark V** shown below) the Inglis Mk II Assault Bridge was not brought into service but the experience would inform later assault bridge designs.
The use of the Inglis Mark I and Mark II in floating bridge arrangements were also trialled in the immediate post war years.
The image above shows a Mark V** Female tank and Inglis Mk II pontoon bridge Experimental Bridging Establishment, Christchurch 1918.
The Imperial War Museum has an online video of Inglis pontoon and assault bridging at Christchurch in 1918[browser-shot width=”600″ url=”http://www.iwm.org.uk/collections/item/object/1060000186″]
After leaving the Army and returning to Cambridge after the war Charles Inglis continued his close association with military bridging, designing the Inglis Heavy Floating Bridge for example.
By the early thirties the Inglis Mark I and Mark II were out of service although they continued to be used for training and development and occasional use outside the UK such as the Barra Bridge in the Peshawer District India, in 1930
From the National Army Museum
The ‘Inglis’ pattern bridge, named after its inventor, Lieutenant later Professor Sir, Charles Inglis, (1875-1952) was constructed across the Bara River by No. 4 Field Company, King George’s Own Bengal Sappers and Miners. The specifications required that it be capable of carrying infantry in fours or 10 ton steam rollers, one at a time. Work began on 29 October 1930 and the bridge was open for traffic on 23 November. Photograph from an album compiled by C G S Clarke, 1st King George’s Own Bengal Sappers and Miners, 1930-1931.
As with the Inglis Pyramid Bridge(s) there is only one Inglis Mark II bridge in existence, in Monmouth, over the River Monnow, built in 1931 to replace an old wooden bridge.
Recently closed to vehicle traffic it was maintained by the MoD because it marked the entrance to the headquarters of the Royal Monmouthsire Royal Engineers (Militia) at Vauxhall Field.
The Inglis Mark III Bridge
At the outbreak of WWII the Royal Engineers found themselves, like much of the British Army, without sufficient equipment for modern mobile armoured warfare and a widespread design effort was initiated.
Charles Inglis suggested a redesigned Mark II Inglis Bridge.
The Mark III Inglis Bridge was very similar to the Mark II but allowed the tubular trusses to be double or tripled up using a redesigned junction box. Top chords were not used.
The bay length was the same as the Mk I at 12 feet but as a result of this geometry, overhead bracing was not possible. After some controversy regarding the testing method used an order for one hundred 120 foot sets was placed but was soon eclipsed by the Bailey Bridge.
The Mark II did have one last hurrah as the Ingls Mobile Bridge although after extensive testing, it was not bought fully into service.
During this Period Charles Inglis also designed an improved crane system for building his bridges and a trestle for pontoon or floating bridges.
Professor Sir Charles Edward Inglis OBE died in April 1952, less than three weeks after his wife
The Journal of the Cambridge University Engineering Society 1952 has a very good obituary
Donald Bailey is rightly famous, but without the concepts developed by Charles Inglis we might not have seen the Bailey Bridge and for that, we owe him a great deal.