from Mr WIKI
Atkinson nomenclature
This was very simple in style, and a system that in its basics, lasted from 1933 to 1975 consisting of a number for weight (initially estimated payload, but after 1964[7] maximum gross vehicle or gross-train weight) then a second number for wheels and then the number of cylinders, assuming initially vertically mounted Gardner LW series engines.
Thus an Atkinson 646 would have been a 6-ton payload 4x2 wagon with four wheels and a Gardner 6LW engine.
A 1066A would have had a ten-ton payload, to 6x4 layout and an AEC (seven-seven) powerplant.
During the 1950s as well as the already-existing suffix for engine-type, prefixes H, M and L (for heavy, medium and light duty frames) were adopted, the Alpha had a second prefix P (for passenger) Thus an early Alpha could carry the code:
PL745H (H used for horizontal Gardner engines)
By the mid-1950s Alphas had pre-prefixes depending on whether they had overdrive constant-mesh (C, for coach) or direct-drive synchromesh gearboxes (B, for bus) hence BPL745H for the first 18 Venture examples, the last six being CPL745H.
The double-decker had the unique frame-code D. Whether that stood for double-deck or dropped frame is not clear, but the PD746 designation given to the two built showed a seven-ton payload, four wheels and a Gardner 6LW. Assuming somebody would have wanted a pantechnicon with a dropped-frame at that time from Walton-le-Dale, it may have been a D746.
Relaxation of legally allowed length and widths resulted in further suffix letters: The first two Sunderland buses were L644LWs (lightweight frame, six tons, four wheels, 4LW engines, long wheelbases, wide-track). The New Zealand survivor is given as an L644XLW (extra-long, around 33 ft long).
The final three Alphas were coded PM746HL, viz: passenger, medium-weight frame, six-tonne payload, four wheels, Gardner 6HLW engine, long wheelbase.
Later Atkinson codes included T3246RR for a 32-ton GCW Borderer with a Rolls-Royce Eagle engine. A Rolls-Royce-engined Borderer was T3446RR220 or T3446RR280[8]
The work with the Alpha was also taken into Atki's mainstream wagon business, there were Atkinson customers, particularly breweries, who ordered underfloor engined Atki wagons, enabling a three-seat cab. The platform body had a trap in it so the (Gardner 4HLW) engine could be seen to. Sentinel, Albion, Guy and Dennis had also done the same but not as reliably because they did not use a Gardner.
External image
image icon "Atkinson Defender KVT 604 P: The very last Atkinson built, Gardner-engined 'Defender' chassis number FC29941, reaches the end of the Walton-le-dale production line in April 1975..."
Atkinson merged with Seddons of Oldham late in 1970. The last "true" Atkinson, a Defender 8-wheel rigid bearing chassis number FC29941, was built at Atkinson's Walton-le-Dale works in 1975. It went to G & B McCready of Newcastle-under-Lyme and carried the registration KVT 604 P. Today it remains with them.[citation needed]
Alongside Seddon's facility at Oldham, the Atkinson works assembled the Seddon Atkinson 400 Series and also the first batch of the new 401 model, before closing at the end of 1981. Oldham remained operational until late 2004, when production was moved to Spain.[2]
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