Discussion in 'Everything Else Heritage' started by Eightpot, Jan 1, 2022.
Two speed differential as well?
No, worm and worm wheel differentials.
I was just wondering what the driver kept flicking under the steering wheel, in between gear changes. I've been on classic buses with two speed diff and wondered.
12 speed gearbox though, crikey.
The 12-speed box is in two parts and is a combination of a range change and a splitter. The main section has 4-speeds and a reverse. Behind that is a 3-speed epicyclic section comprising a low range of 3.29 : 1, a direct through range of 1 : 1, and an overdrive range of .77 : 1. Main section changes are done with the gearstick being operated by his left hand. In this case the low range isn't being used, but with a heavy load on a hill start the sequence could be 1, 2, 3, 4 in low range, pre-select direct (the little lever being operated by his right hand) and a quick change into 2nd. From there it would be 2 o/d, pre-select direct and into 3rd, and so on up to 4th overdrive. It is a 'crash' box - no synchromesh in the main section. To get low range the r/h operated little lever is positioned back closer to the driver, seen here he is just using the direct and overdrive parts of the epicyclic section.
When I woz a lad I 'was allocated' a Foden eight wheeler with a 12 speed box, I only used it for a fortnight and am somewhat ashamed to admit I don't think I got a 'clean' change in the whole 2 weeks. I mastered Fuller Range change, Eaton Twin Splitter, 18 speed Volvo, and the easy peasy DB crash box, but I had to admit defeat with the 12 speed Foden. 2 speed diffs ?? no problem, change Hi/Lo ratio without using the clutch.
Best gearbox I ever used ?? Fuller Range Change.
Everything is automatic these days (not to my liking), Automatics for cars .....ok, but manual gearboxes for lorries, a driver needs to 'feel' what a lorry is doing (just my opinion)
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