My Memories of those single tyre Silly wheel pusher Axles, Is..
In the early 70's when Triaxle trailers were allowed People started fitting them to existing Trailers to get the Extra Weight. .By the Late 70's The Govt mandated they had use Load sharing Suspension(As well as Brakes), Because as Xspannerman said a lot of them had Airbags & blokes could Manipulate the old split weigh Weighbridges with them..
But Don't mind being Corrected..
Seed I dont think the tippers shown were ever bogies as the mud guard is full length and it looks to me like these were built this way
Either way it is all very interesting to me and amazing how much of this stuff we have forgotten already
Jeffo, I cn honestly say I have never seen a single axle dolly with out brakes, mind you I wouldn't of worried about looking unless I had a reason to
Paul