The Bristol RE of the 1960s & 1970s was a real busman’s bus. Reliable, economical, powerful and, with up to 53 seats on a single deck chassis, the RE was only some seven seats short of the Bristol LD and FS double decks early RELLs replaced. And, crucially, it allowed one person operation with a relatively high seating capacity.
And from a passenger viewpoint, the bus was good. All but the earliest models were bright and airy inside and, for the first time, there was an uncluttered entrance by the driver. The engine and gearbox noises were somewhat intrusive, if only from a passengers’ perspective.
Before being prematurely killed off by the Leyland National, little wonder that Hants & Dorset ordered 68, 50 of which were service buses (others being coaches). 470 or just over 10 per cent of the total produce were delivered to United.
The semi-automatic gear change was as smooth or rough as a driver wanted to make it. But does anyone recall being able to change from little-used first into second, without that telltale “clunk” and slight lurch? Clunk free? I’d say it was an impossibility.
Tuesday, 26 September 2006
Clunk
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2 comments:
You're right! 1st to 2nd always caused a jolt. 1st was always best avoided. I remember spending a day behind the wheel trying every way I could to avoid said jolt, without success.
My experience with semi-automatic boxes is that there is sometimes a phenomenon of delayed release of certain gears, i.e. you deselect the gear so as to pause, but the gear could in fact remain engaged for a moment or two.
If first gear did not release as expected, the drag resulting from lifting the accelerator pedal while the gear remained engaged [though deselected] would cause the bus to slow in quite an exaggerated way. The engine would still be revving quite fast by the time a pause of normal duration had passed, resulting in a clunk when second was engaged. If the pause was extended to allow the engine revs to die away, then the bus would be going so slowly by the time you got the next gear that you'd get a clunk anyway.
Because first tended to be used rarely I think that it aggravated the dragging phenomenon which I understand to be caused by poor circulation in the pneumatic control pipes.
The smart driver would identify issues of this kind during a "warm-up" period after taking a vehicle over, and then allow for the drag by keeping the accelerator depressed for however long the gear remained engaged after being deselected. You had to be careful not to leave your foot down too long, since you'd find yourself revving up when the gear disengaged, which is obviously not good.
From one bus to another the time factor, and indeed the gears concerned, would vary. Add to this the opposite effect, i.e. "slipping" where a gear might take a few seconds to bed in, and things could get quite complicated requiring a fair bit of hand/foot/noggin co-ordination with one body part acting a couple of seconds ahead of the other. However, to those of us who respected our buses it was a challenge and added an extra level of skill to the job.
In the hands of the lazy "slammer" drivers, gearboxes with slipping and dragging gears would suffer since the driver would be trying to engage one gear before the previous had disengaged, or else the engine would rev wildly until the next gear engaged properly.
IMHO, some semi automatics were more difficult to handle than crash boxes because of this phenomenon. Of course, failing to get a gear in a crash box is more drastic than a clunk in a semi, but the mechanical linkages were more predictable: your average driver would clunk semis many more times than he'd clip crash gears.
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