The I wagons was probably the largest single class of vehicle in Australia with 15,000 in service by late 1929. The wagon construction covers 1859 through to 1929. The vehicles were issued firstly with wooden bodies, no brakes and an 8 ton capacity. Through the 1880's and 1900's, capacity increased to 11 tons with stronger axles and better wheels; Westinghouse Brake conversions started from 1891 with most vehicles done by 1905.
In 1902 steel I wagons began to be constructed of 12 ton and then 15 ton capacity. From 1907 the current standard 'I' wagon design evolved with construction through to 1920's.
A drop door version was introduced to service about 1903. These were rated at 12 ton capacity. Between March 1904 and July 1904 these wagons were altered to _IG_ classification. More drop door wagons of 15 ton capacity were built from 1908. These wagons were placed into the I number group but were issued with 'IG' class letters.
Prior to World War I, a group of 16 ton I wagons were built with wooden sides and ends with steel doors. At the time there was a shortage of boilermakers and alternate materials were used in construction. The wagons were called 'shandies' by rail staff. The wagons were rebuilt to steel in the 1930's.
In 1929 the I wagons were split into basic capacity groups. With the massive withdrawal of 8 to 11 ton capacity wagons starting to affect traffic, there were problems with selecting 10,11 and 15 ton I wagons for placement.
The sub classes were: 'I' became 15t capacity; _IB_ was for vehicles with 8/10/11t capacity and _IA_ had a dual capacity of 11/16 ton. The _IG_ wagons of 15 ton capacity were relettered to 'I'.
The dual capacity was a government concession for farmers with 'less than car loads'. Loading to 11 ton was charged at 11 ton rate and loading over 11ton was charged at 16ton rate. The railways preserved the 1929 ratio of 11ton to 16ton truck by marking an I wagon to IA every time an IB wagon was scrapped. I to IA recoding occurred regularly through to the 1960's by which time all IB's were removed from service. At times it was found there were more IA's than the quota. In these cases, _IA_ wagons were marked back to I. By the mid 1960's onwards I wagons were also coded 11/16ton.
In 1935 the railways turned to bulk grain transport. Up to this date grain was bagged first then loaded onto available wagons. The 12 ton version of the IG wagons were recoded to _IX_ as 'G' was used to denote 'bulk grain'.
I wagons were scrapped progressively through the 1960's, then rapidly from the 1970's as bogie vehicles were introduced and traffic requirements eased off.
Inspection of photographs taken in the 1970's has revealed something of interest. The handbrake position can be at the narrow door end or the wide door end. Diagrams and plans only show the handbarke at the wide door end. In general, the handbrake is on the narrow end. Apparently from 1904 the underframe and brake rigging arrangement was changed. To 1904, the handbrake was on the No.2 side ( No.1 side was brake cylinder side ). These wagons had hand brakes secured directly to the underframe. From 1904, the handbrake was placed on the No.1 side. The handbrakes are noted by the handbrake shaft running across the wagon and displaced from the underframe to clear the rigging. From 1929, the handbrake shaft only ran to the centre of the wagon.
There have been many body types over the years and diagrams tend to confuse any compilation. To assist in this research construction lists have been compliled from the data that was used to create the vehicle history lists. The construction list has two groups:
The graph below shows an approximate introduction to service of all open wagons including the I wagon class and the resultant code changes of sub groups:
Vehicle history lists: