I've delved through the "Wagons Roll" column in RAIL magazine for this period, and the only info is a brief report of possible "problems with acceptance." 19 of the FLA wagons are reported as being in service on 25/07/91, and another six on 18/09/91 (dates for the rest not reported).
Paul Shannon's book
Freightliner (Ian Allan 2013) has this to say about the FLAs:
In order to achieve the deck height of 720mm, Powell Duffryn Standard had developed a reduced-size version of the low track force bogie that it had previously installed on its 102-tonne aggregates wagons for ARC. The wheels of the 'lowliner' were just 520mm in diameter. The penalty with such small wheels was the reduced stability of the wagon and the increased likelihood of a derailment occurring on points and crossings where they had to negotiate a short gap in the rail. There was also a possible issue with overheating, because the wheels had a lower mass and were therefore less able to absorb the heat generated during a brake application. (page 28)
A research paper on the topic of smaller wheels on freight wagons makes a similar point:
...to reduce the wheel diameter ...is not a drawback-free solution since an excessive reduction of wheel diameter involves many troubles concerning the stability of the vehicle, maximum axle load, wear of bearings and rolling surfaces of rails and axles. Also designing the braking system is very complicated because the reduced number of encumbrances available makes the placement of internal disks on the axles difficult.
https://www.researchgate.net/public...cial_freight_wagons_with_small_wheel_diameter
The new bogie type is reported as LTF13 on the Greenbrier website (I assume they have the rights to the wagon or bogie design and perhaps supply parts):
https://www.greenbrier-europe.com/2022/10/08/ffa-g-2-x-40-8-axle-uk-container-wagon/
Given the challenges involved with designing low-deck wagons, it wouldn't be surprising if the introduction of these new bogies with small wheels resulted in some delays to acceptance of the production batch if any issues arose that needed resolving. For example, if anything needed redesigning, that could result in wagons sitting around pending modifications. I think they were built by Powell Duffryn at Cardiff, so it was probably a relatively small-scale production line which would have taken a while to produce the full batch in any case.
I'm not sure how different the production batch was to the prototype set (PDUF 95090 / 95091/ 95092) where you would hope most of the design issues would be resolved, but it was later reported in RAIL that the prototype was undergoing conversion and I think they ended up renumbered as part of the main FLA fleet as 605028 (FLA-J with design code FL005A) and 606019 / 606020 (FLA-P with design code FL004A) with a build date of 1989 in TOPS. Possibly they received modifications that had been incorporated into the production batch?
Photo of the prototype set on display at the 1989 Cricklewood exhibition:
https://www.ltsv.com/rd/photo_view.php?id=7276
The much later IDA wagons, also using small wheels for a low deck height, had similar issues to those mentioned:
After initial optimism, the IDA ‘twin’ intermodal flats have yet to achieve their full capability for Direct Rail Services due to ride issues over poor track. Gareth Bayer describes the rise and fall of the innovative WH Davis ‘Super Low 45’ and their slow return to service.
https://www.railexpress.co.uk/1201/going-low-with-the-ida-flats/
See also:
https://www.orr.gov.uk/sites/default/files/2024-01/raib-gloucester-derailment-2024-01-04.pdf
*
The FLAs were initially used on a twice daily service from Grain to Stratford FLT where the containers were transhipped to conventional freightliner wagons.
12:52 SX Grain - Stratford is seen here using the FLAs in 1992:
https://www.flickr.com/photos/36034969@N08/53461955991/ (Photo: Adrian Nicholls)
https://www.flickr.com/photos/locohunter/18174551444/ (Photo: Ian Cuthbertson)
A temporary terminal at Grain opened in 1991 for this traffic. Initially the low-deck FLAs were required to move even the standard 8 foot 6 inch containers, before the route to Grain was upgraded to W8 gauge in 1993 (the same year the proper Freightliner terminal was opened there). After that date, 8 foot 6 containers could travel on standard Freightliner flats to Grain and the FLAs were only needed for high cubes - which was also the case for Southampton at the time.
I can't find a news story giving the exact date in 1991 when the temporary Grain Freightliner terminal opened, but I suppose it's possible the FLAs were sat around waiting for the start of this service. On the other hand, given the suggestion of delays to acceptance reported in RAIL, I wonder if the commencement of the service was delayed by the slow introduction of the FLA wagons?
