The firm was originally started by Henry Stothert in 1837 as Henry Stothert and Company. An early order was for two broad gauge 2-2-2 Firefly class express passenger engines Arrow and Dart with 7 ft driving wheels delivered for the opening of the Great Western Railway from Bristol to Bath on August 31 1840. This was soon followed by an order for eight smaller 2-2-2 Sun class engines with 6 ft drivers.
When Edward Slaughter joined in 1841, it became Stothert , Slaughter and Company. By 1844 the works were named "Avonside Ironworks" and in 1846 built Avalanche the first of five six-coupled saddle tank banking engines for the GWR. Another large order came for ten broad gauge passenger 4-2-2s with 7 ft 6 in drivers and eight goods engines from the Bristol and Exeter Railway for the independent operation of that line from May 1 1849.
In 1851 the company acquired a ship building yard, which Henry Stothert took charge of as a separate undertaking. In 1856 Mr. Grüning became a partner of Edward Slaughter at the locomotive works, which then became Slaughter, Grüning and Company.
In 1864, with Edward Slaughter still in control, the company took advantage of the Companies Acts and became the Avonside Engine Company Ltd. As if to mark the occasion, the works received a large order (the first from the GWR for some years following the development of Swindon Works) for twenty 2-4-0 Hawthorn class engines with 6 ft drivers.
During the 1860s and 1870s the Avonside company built broad gauge and standard gauge engines for many British companies, large and small but they also built up a considerable export business. Unfortunately detailed company records from this period have not survived.
This lack of records is particularly unfortunate in that the company was the largest British builder of the Fairlie articulated locomotive. Amongst the first to be built at Bristol was James Spooner built in 1872 for the Ffestiniog Railway. Although built to the same basic design as the remarkably successful Little Wonder built by George England in 1869, it incorporated many detailed improvements and became the prototype for subsequent Ffestiniog Railway engines built in that company's works at Boston Lodge.
In 1872 on the recommendation of Sir Charles Fox and Sons, Avonside built two large 42ton 0-6-6-0 Fairlies for shipment to Canada, one each to the Toronto Grey and Bruce Railway and the Toronto and Nipissing Railway. The Avonside Works Manager at the time these locomotives were built was Alfred Sacré, the brother of Charles Sacré Locomotive Engineer of the Manchester Sheffield & Lincolnshire Railway. Alfred Sacré trained under Archibald Sturrock at the Doncaster Plant of the Great Northern Railway and in 1872 moved from Avonside to the Yorkshire Engine Company, Sheffield where he built more Fairlie types.
Earlier in 1875 the company had built four powerful tank engines designed by a Swedish Engineer H.W. Widmark to operate on the Fell mountain railway system on the Rimutaka Incline in the North Island of New Zealand. These and two later engines of very similar design built by Neilson and Company handled the entire traffic for eighty years until the opening of the five mile long base tunnel in 1955. Widmark was an inventive engineer and patented a design of steam operated cylinder cocks which were of great use to Avonside on articulated locomotives since they dispensed with mechanical linkages.
Avonside was a very early British builder of the 4-6-0 type of tender locomotive. Ten narrow gauge freight-hauling 4-6-0 locomotives, of weight varying from 20 to 25 tons, were supplied to the Toronto Grey and Bruce Railway and the Toronto and Nipissing Railway. These very successful and reliable wood-burning locomotives pre-dated the first significant British domestic railway 4-6-0, the Jones 'Goods', by over 20 years.
The Avonside company was unusual in that most of its production for over 40 years comprised main line locomotives largely for British railway companies but also for export. By 1881 main line locomotives were getting much bigger and exceeding the capacity of the manufacturing equipment. They made a positive decision to concentrate on the smaller locomotive types within the capacity of the existing plant. This change was to a degree forced on the company as a result of financial difficulties following Edward Slaughter's death. Edwin Walker of the Bristol Engineering firm Fox, Walker & Co. joined Avonside and endeavoured to turn the company round, but without success.
Walker was forced to liquidate the old company and form a new company with the same name to carry on the same business at the same address. At about this time the old firm of Fox, Walker & Co. was taken over by Thomas Peckett and became Peckett and Sons. In 1905 the Avonside firm left its historic home at St. Philips for a new plant at Fishponds but still with a small engine policy.
The company closed in 1934 and the goodwill and designs of the company were bought by the Hunslet Engine Company.
Avonside Engine Company locomotives preserved in the United Kingdom include:
Avonside Engine Company locomotives preserved in New Zealand include: