Classic cars forum & vehicle restoration.
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peter scott
Joined: 18 Dec 2007
Posts: 7118
Location: Edinburgh
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 Posted: Fri Nov 18, 2022 8:33 pm Post subject: |
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Crash boxes make for rather slower upward changes so the preselector box might give better 0 to 60 mph times.
Peter.
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1939 SS Jaguar 2 1/2 litre saloon |
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bjacko
Joined: 28 Oct 2013
Posts: 362
Location: Melbourne Australia
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| Posted: Sat Nov 19, 2022 7:08 am Post subject: Pre-selector gearboxes |
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My uncle had a pre-war Daimler with a pre-selector gear box which worked well but the acceleration was rather poor, but then Daimlers were meant to be sedate cars!
Modern auto gearboxes are mush quicker. i have an auto in a 6 cylinder Turbo and according to the test drives in the news it is quicker from 0-60mph than a V8 GT because it can change gears quicker than the manual GT! |
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Rich5ltr
Joined: 28 Mar 2008
Posts: 678
Location: Hampshire, UK
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| Posted: Sat Nov 19, 2022 10:56 am Post subject: |
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Taking Ray's point that I could reduce the weight of the exiting flywheel, in reality I should probably reduce the weight of the existing driver.  It would have more effect! |
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alastairq
Joined: 14 Oct 2016
Posts: 1954
Location: East Yorkshire
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| Posted: Sat Nov 19, 2022 1:51 pm Post subject: |
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| Penman wrote: | alastairq
Reading various comments about pre-selectors on the sct61 site there would seem to be a number of different ttypes in bus use, some have commented on the gear change pedal "snapping back" at the driver, which I take to mean coming back up so sharply it jars the driver's left leg.
Incidentally, when DVLA separated auto from manual for licencing purposes; the pre-selector was designated as an Auto for driving test purposes regardless of the fact that it had 3pedals |
My experience was solely with the LT AEC RTs
Indeed, snapping back of the pedal was noticed, but it wasn[t a regular feature. Might have depended on the state of the gearbox, for example?
Since a vicious gearchange pedal wasn't conducive to passenger comfort [resulting in jolting gearchanges], attention had to be paid more to the sound of the engine revs for a smoother ride.
London Transport had a division of Inspectors from Chiswick works, who spent all day riding around behind varios drivers, assessing smoothness, and driver skills.
Sometimes they would 'target' specific drivers....mainly if there had been passenger complaints.
Also, new drivers were monitored frequently during the first year.
Don't really get such levels of attention these days?
The DSA didn't get involved with sub categories of PSV licences until the middle of the 1980's.
Prior to that time, all PSV licences and tests were conducted under the auspices of the local Area Traffic Commissioners. Not the DSA, unlike HGV [later, LGV] licences.
However, in practice the Examiners on those tests would work for both authorities, often.
The Area Traffic Commissioners had a different system, but still applied ''auto'' and ''manual'' to each category.
I believe it was London Transport who initiated the separation of gearbox types. LT were also the Traffic Commissioners for the greater London area[as well as the City]...and would test the Met Police, LFB, Ambulance, etc as well
London Transport, by the late 1960's [I took my test in 1972]....had already identified a serious problem of retention of drivers in the London Area. Perhaps long before the rest of the country.
Hence, drivers were acquiring their licences with LT, then leaving to go work elsewhere [mainly due to living accomodation problems in London].
Since the ROutemaster was an auto box [with a manual over-ride]...., that left only the RT's to worry about, so they used the fact the RTs [and their offshoots] didn't have a physical 'clutch' in the system. So from the late 1960's, all LT -trained PSV licences were 'auto' only.
This stopped the brain drain, as not many bus operators elsewhere, didn't have manual gearboxes somewhere in their fleet.
Other attempts to stem the retention issue concerned the building of super comfortable canteens [I was at New Cross depot, which got one of the first super canteens...like a luxury hotel it was]....plus accommodation bureaux, and 'land ladies' on their lists, etc.
All intended to entice drivers to stay put.
I left after two years and moved up to Scarborough, and, eventaly, East Yorkshire, for a nicer way of life than London. Despite the stone age wages.
I already had the ''all types, auto'' PSV, but one other issue for bus drivers[and conductors] was that, if one moved area, to work, one had to take a 'new' test with the new Local Traffic Commissioners[Traffic Area]...
One simply couldn't just 'go somewhere and work'.
In the space of a few weeks after moving up here, I took two more PSV tests, acquiring and 'single deck manual', then an 'all types manual' licence.
The Traffic Commissioner system differentiated between single deck [I think, two or three sub categories] depending on the number of seats on the single deck test vehicle.....and double deckers.
I took the single deck [full size, an AEC Reliance] PSV because I had got a temporary job driving for a local bus & coach company, while I awaited ''the call'', from the main bus company, United Auto.
Many folk confuse ''pre-selector'' boxes on buses, with semi-auto boxes.
Plus, semi auto boxes weren't full 'autos' either.
Simply described, a semi auto box is an auto box without the ''auto'' bit. {Bristol VR, for example?}
However, many auto box types could have gears changed 'manually' by the driver...but they retained the auto option. [Best example being, the old Routemaster, where by if top gear was selected, this also put the gearbox into automatic mode, so could be left alone if things had gotten busy?]
Of course, there were differing methods whereby semi auto gears were 'changed' by the driver...the Bristol VR having an electric gear change, and many Leyland Leopards had an air operated gearchange [ a ruddy nightmare at times].
Then came the push buttons [for cheapness]....They were also a nightmare, as the buttons broke easily.
There were some odd Leyland Olympian gearboxes as well...auto, in one gear position, and 'hold' in the other...so, when using[holding] the gears to accelerate [a euphemism with these buses, sorry]...at the right moment one flicked the [right hand side] gear lever into auto, which changed the gear, then one had to smartly flip the lever back into the hold position, to manually control the next gear....and so on.
Any auto box can be controlled manually, and be as effective at stroking ones ego as a manual gearbox.
As with a manual gearbox, all the driver is doing is controlling at what engine revs the gearbox changes gear at.
With a bus, one was hamstrung by the engine's governor.
Thus there was a limit beyond which it was pointless hanging onto a gear..one wasn't going to increase speed one jot.
Indeed, with many auto boxes, one was prevented from making the two mistakes a driver makes with a manual box, namely,
trying for too low a gear for too high a road speed, or too high a gear for too low a road speed.
The engine governor really hamstrung a bus driver on an inter-urban route....making the overtaking of a cyclist a real nightmare. Especially when the road wasn't wide enough to pass safely, without occupying a significant proportion of the opposite direction carriageway.
The difficulty was...most buses of the day were ''all in'', rev wise, at around 30-32 mph, before top gear was needed.
Thus one did one's overtaking, in top gear only, since no other gear was available or useable at that speed. This could involve being on the opposite side of the road for a mile or two, until one had 'built' up enough significant speed above that of the cyclist.
30 mph meant top gear, no choice, so all one's speed building was done in top gear......
An experienced bus driver on one of these routes [50 mph speed limit, hah!] got to learn the whereabouts of every little dip in the road, and how far they needed to see, in order to take advantage of gravity, and build up more speed more quickly.
One didn't have the time [table] to do what they do these days, and follow a cyclist for 5 or 6 miles....
Tractors of the old school were also a nightmare.
Life as a driver changed when the Olympian deckers were moved on, to be replaced by large Volvos, etc....These could really accelerate...even if only up to 55 mph.
Up to 30 or 40 mph they could out accelerate even a Ford Escort of the day...which used to annoy many a car driver who really really wanted to be, 'in front''....[in towns, of course] I liked to annoy certain car drivers.....in my view, they needed annoying.
On the open road, the Volvos could outpace even ambulances on blooos n twooos....no need to find a huge layby to 'pull into'...one simply was too fast for them, bless! Humberside Ambulance had some real bangers on their fleet.
I don't really know about the modern stuff used....a bit after my time as a driver....
I bet they are more''driver -considerate''. comfort-wise, than the old Bristol BU single deckers I got to drive for a living?
Where, often, the clutch pedal was adjusted so darned high that the distance between the clutch pedal, and the underside of the steering wheel, was less than my shin length. Making double declutching an embarrassing nightmare....especially if around Robin Hoods Bay area!
Modern day drivers simply don't know how lucky they really are, all those mod cons and adjustable this, that and tuther....
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Dellow Mk2, 1951 built, reg 1952.
Fiat 126 BIS
Cannon special [1996 registered. Built in 1950's]
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Ford Pop chassis, Ashley 1172 bodyshell, in pieces. |
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Penman
Joined: 23 Nov 2007
Posts: 4757
Location: Swindon, Wilts.
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| Posted: Sat Nov 19, 2022 2:40 pm Post subject: |
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Alastair: unless you are already on there under another name could I suggest you have a look for some of your old buses on http://www.sct61.org.uk/ and join the conversations with your tales.
There are certainly old LT crew/employees contributing and also quite a few from the E Yorkshire coastal area.
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Bristols should always come in pairs.
Any 2 from:-
Straight 6
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