Thank you all for responding and Neil for your welcome, the lorry has been out of the country (Canada) since 1958, and has only recently been repatriated to the UK. The front driven axle is sprung almost conventionally with the spring fixed at the front but a cast slider locating the rear of the spring rather than a swing shackle allowing the rear of the spring to slide in the cast bracket permitting the spring to deflect on compression. From the slider the chassis was cut and nothing exists rearward of the original chassis. The six wheeler was a rare beast and with a single drive axle rather than a double drive rarer still?? (maybe only this example).
There is a well known photograph of an eight wheeler which when blown up seems to show no spring behind the second rear axle, I have put forward the suggestion it may have been fitted with a quarter elliptical spring (as Austin Healy Sprite rear spring) rather than a half elliptical spring. This would explain no evidence of the other half of the spring. As the chassis to the rear of the drive axle is missing there is no clue as to the design of the spring and how it is fitted to the chassis or axle.
I understand at the time this lorry was built Sentinel were short of cash so components may have been sourced from the parts bin
Phil thank you, can you kindly pass my contact details to Diane and ask if she would mind contacting me. However others involved in the project are familiar with existing Sentinels and her S6 may be known to them, but any information will be useful.
Robert Butler