The VR diagram book referred to these wagons as being for loco boiler transport, in service they were simply a heavy duty flat wagon capable of carrying unusual loads. In the 70's I saw them carrying very large rolls of cable in drums, these drums were too high to be carried on regular flat wagons but the depressed centre of the QB meant that the load stayed within the loading gauge.
There were 13 wagons in the class, numbered 1 -13. They were built between 1902 and 1925. In the 1979 re-coding they became VWAA.
Steam Era Models make an superb HO brass kit of this wagon class
ABOVE: QB 1, in as built condition, circa 1905. (PROV collection)
ABOVE & BELOW: QB 1, unloading a Harman crane circa 1937. (PROV photos)
ABOVE: QB 1 at Nth Geelong, mid 1970s, (photo courtesy David Hewitt)
ABOVE: QB 2 hauling stationary boilers at Yallourn. Oct 1921 (photo courtesy State Library Victoria)
ABOVE: QB 2 at Nth Geelong with roller bearing bogies and container brackets. June 27 1978. (photo courtesy Geoff Winkler)
ABOVE: QB 4 loaded with poles for the electrification project, possibly the Hurstbridge line at Arden St. circa 1925
ABOVE: QB 6 circa 1939. (PROV collection)
ABOVE: QB 8 loaded with a damaged BC 12, Oct. 10 1933. BC 12 had been the rear vehicle on a down Serviceton goods which was rear ended whilst waiting at the Sunshine arrival home signal by the 8.10pm down Seymour goods.
ABOVE: QB 10 still in service for a private operator and now classed ZWAY at Bunyip March 2004 Photo courtesy Geoff Baxter
ABOVE & BELOW: QB 12, was a different design to the rest of the class. ABOVE: Nth Dynon Sep 1975, BELOW: at Nth Geelong Dec 5 1975 (photos coutesy David Hewitt)
ABOVE: 2 QB's carrying a part for a gantry crane in the electric crane area of Melb yard. July 10 1972 Official VR photo PR6421
ABOVE: QB 2 loaded with the remains of one of the S class diesels involved in the Southern Aurora smash, Feb. 1969. Note the diamond frame bogies Official VR photograph