Hi Ron, I think you could be right, I can't make out if there's springs on the front of the saddle on the photo,will see if I can find a better picture of this type of seat in use on a wartime motorcycle.
I don't know... I've seen two of these contraptions before (the 4 spring short Acumen), and I've always thought that they were DIY conversions.
But now we have a third and a fourth (!) one, and they all look “exactly” the same.
Let's resume what we know about the Acumen pillion seats. The long Acumen came out in 1942, there was an Ariel and a BSA version (the rear springs were positioned differently). And for the reason that Ron already explained it was superseded by the short version for the very last WM20 contracts (1945 only). I can't imagine that the 4-springer (which was based on the short Acumen) was also introduced during the war, as I've never seen such a device in a war time photograph. (The pillion seat in your (post war) picture is a normal short Acumen Steve, I can clearly see the front bracket and the triangular reinforcement).
So I'm pretty sure these 4-springers are post-war, but while initially I was suspecting a DIY construction, it is hard to believe that several individuals came up with exactly the same result. These 4-springers must have come from the same supplier. The work is neatly executed, so they may perhaps have been made by Acumen with the remains of their WD stock?
Hi Jan, thanks for that information, although not very clear the photos of the bottom saddle have got traces of khaki paint under the black, will try and find some better pictures if I can.
I would imagine its a bit "wibbly wobbly" if your passenger is heavyish? but I suppose these rear saddles were only supposed to be used on a rare occasions.
I can assure you that the four spring versions are not DIY conversions as Globe Motorcycles in Smethwick used to sell them along with other wd types of pillion seat in the 1970s for 21/- shillings which is £1.05 today. I bought 6 pillion seats from Globe which I still have including the the 4 spring version.