Hints and Tips - Preselector Gearboxes

From: Kevin Sullivan
To: Berry Kercheval
Date: 08 December 1999

Hey, how does a pre-selector gearbox work, and how is it operated?


From: Berry Kercheval
To: Kevin Sullivan
Date: 08 December 1999
Subject: Re: pre-selector gearbox

The basic idea is FIRST you move the gear lever to the next desired gear, and THEN when you wish to change you operate the pedal. The box then declutches, changes gears and reclutches.

I am not sure if the pedal operates the clutch AND the box, or the pedal works the box and the box works the clutch.

--berry


From: John Hardy
Sent: 09 December 1999
To: Berry Kercheval
Subject: Re: pre-selector gearbox

Kevin et al,

This is as much as I know which is precious little.

The driver operates the gearchange by the selection of the gear required on a quadrant similar to an auto box selector but marked...... R (reverse) N (neutral) 1 2 3 4

To start off from stationary first is selected and the change gear pedal (NOT the clutch) depressed. The engine speed increased until (at about 850rpm) the centrifugal clutch bites by means of bob weights which fly out and cause pressure plates to close on twin clutch plates.. A fluid flywheel acheives this by the transfer of fluid to the outside or periphery of the flywheel. As soon as the change gear pedal has been released the next gear can be selected. The change itself if occurs when the pedal is again depressed. And so on. On my Lynx, with a rebuilt box, I find the change very quick and smooth.

The actual way the box operates is a mystery to me but I have copies of brochures which run to 4 sides of foolscap, explaining the process. I just haven't had the mental space for it lately. Its all to do with planetary gears, springs, brake bands and lots of other gubbins. I can tell you this, however. A preselector box weighs a bloody ton !

Perhaps someone could provide us with a potted version. How about it Mr Sixshrubs.

JH


From: TA Terry
Sent: 08 December 1999
To: John Hardy; Berry Kercheval
Subject: Re: pre-selector gearbox

In a message dated 99-12-08 16:55:03 EST, John Hardy writes:

<< A preselector box weighs a bloody ton ! >>

and takes a bloody lot of power to operate....If you have the MG Blowers manual, there is an explaination in it....also there is an article on rebuilding said pre-selectors in the MG prewar 6 cylinder book. Most cars using these boxes have superchargers to take care of the extra power required.....those that have them love them except when they need rebuilding!! Riley's are a source for preselector boxes....of course Rileys were alway donating to MGs....

:-)
Terry


From: Bill Tantau
Sent: 09 December 1999
To: John Hardy; owner-british-cars-pre-war; Berry Kercheval
Subject: Re: pre-selector gearbox

In a message dated 12/8/99, John Hardy wrote:

<<The actual way the box operates is a mystery ..........>>

No doubt... and if you've ever read the manuals???Hoooeee!

But, who cares unless you want or need to "get into it". The important thing is how sweet the preselect is! Hardwire is right, you start out from stop much like a clutched machine, but from then on the sweetness comes out. Right after you are away you (pre)select the 2nd gear and when you are ready for it you just jab the pedal down and up as quick as you can and "presto" you are there... no hesitation/grinding etc... and so on up thru the gears amd/or back down again.

It do weigh lots, but sweet it is!

Bill Tantau


From: David Whittle
Sent: 09 December 1999
To: british-cars-pre-war
Subject: Re: pre-selector gearbox

Raymond Mays used them to good effect with the ERA Racing Cars. I believe all but one of them had pre-selectors, I read somewhere that during his record breaking runs at pre-war Shelsley Walsh Hill Climb he often knackered the bands on one run i.e about 40 seconds, but that in a 5 hour circuit race they often showed little wear, very strange!

I have also read that one ERA was modified with a Riley crash box in order to try to save weight, the gear lever ended up in a most uncomfortable and dangerous place. The weight saving was not able to overcome the slowness of the crash box and its castrating threat, and times were if anything poorer.

Whilst on the subject of ERAs I feel I should just mention the late River Fletcher who died in September, I only talked to him once but his writings on ERAs and MGs and all things Motoring were most enjoyable, and made people fondly remember him as a true enthusiast. The site of him wrestling that heavy Alvis up Prescott with failing eyesite, at the age of well over 80 will stay with us as a lasting memory.

Regards
David Whittle
Wantage
UK


From: Maggie Shapland
Sent: 09 December 1999
To: british-cars-pre-war
Subject: Re: pre-selector gearbox

I have a leaflet about the wilson preselector box if anyone wants me to copy it for them.

----------------------
Maggie Shapland, Computing Service, University of Bristol
Web page: http://www.cse.bris.ac.uk/~ccmjs/
1925 Lanchester 21, 1925 Talbot 10/23, 1929 Peugeot 190S, 1986 Moss Monaco


From: Clive Sherriff
Sent: 09 December 1999
To: David Whittle
Subject: Re: pre-selector gearbox

Re: Re: pre-selector gearbox

Message text written by "David Whittle"
>Raymond Mays used them to good effect with the ERA Racing Cars.<

True - as did other racers up to the mid 50's - the connaughts, and the Laystal Cromard for example.

A point here is that they were not the standard Armstrong pre selector boxes, but race versions - often with close ratio gearing, electron casings, and importantly an additional auxilliary oil pump driven by the OUTPUT shaft. This is why you see the ERAs Connaughts etc with their wheels jacked up and spinning in the paddock when warming up engine and gearbox oils prior to racing.

Now the point here is that in the early post war days all the boy racers in their Jap/Matchless 500 racers, Cooper 500's et al, Fraser Nashes if lucky etc, saw this and thought that's the way to go fast - so jacked their rear wheels up and spun their wheels too! Did'nt do a bit of good, and probably wore out a set of drive chains! - but they felt they had done what was needed...........

Clive Sherriff


From: Berry Kercheval
Sent: 09 December 1999
To: owner-british-cars-pre-war
Subject: Re: pre-selector gearbox

At 07:18 PM 12/8/99 -0500, Bill Tantau wrote:
>It do weigh lots, but sweet it is!

I bet if someone were to design and build a modern preselect box it would weigh much much less -- *ALL* gearboxes of that period were heavy!

Sounds sort of like an automatic without the funky hydraulic analog computer (yeah, that's what it really is!) deciding when to shift for you.

--berry


From: Lawrie Alexander
Sent: 09 December 1999
To: Bill Tantau
Subject: Re: pre-selector gearbox

Bill........

Hesitation? Grinding? This is what happens in your PA?

I guess that's what we Brits get for permitting the export of our fine machines to a country where kids grew up learning to drive on automatic 'boxes............ {G}

Lawrie


From: John Hardy
Sent: 10 December 1999
To: Clive Sherriff
Subject: Re: pre-selector gearbox


>
>True - as did other racers up to the mid 50's - the connaughts, and the
>Laystal Cromard for example.
>
>A point here is that they were not the standard Armstrong pre selector
>boxes, but race versions - often with close ratio gearing, electron
>casings, and importantly an additional auxilliary oil pump driven by the
>OUTPUT shaft. This is why you see the ERAs Connaughts etc with their
>wheels jacked up and spinning in the paddock when warming up engine and
>gearbox oils prior to racing.
>

These competition gearboxes were made by Armstrong Siddeley on the night shift. a couple of years ago I met an old chap at Prescott who was a apprentice with them then. He told me a few snippets about them.

As far as this wheel spinning on jacks in the paddock is concerned, I thought it was due to the competition clutch arrangement used on these cars (not a heavy mass of bobweights and centrifugal doodads) and most others with preselectors in competition. The drive is there all the time and it is not possible to have a fast tickover and remain stationary. Could be wrong. I quite often am.

JH


From: ronald
Sent: 10 December 1999
To: Berry Kercheval; owner-british-cars-pre-war; british-cars-pre-war
Subject: Re: pre-selector gearbox

Not all gearboxes - have you tried lifting the gearbox of an Austin 7? You can do it with one finger!!

A school master at Brighton College had a Riley with the pre-selector gearbox. Nice car with two doors, rear hinging (suicide doors). He had bought it new and the salesman told him that if he wanted to stop in a hurry, you could pre-select reverse. However, you could only do it once per gearbox! I don't suggest anyone ever try it.

Ian


From: Bill Tantau
Sent: 10 December 1999
To: Lawrie Alexander
Subject: Re: pre-selector gearbox

In a message dated 12/9/99 10:31:07, Lawrie Alexander wrote:

<<Hesitation? Grinding? This is what happens in your PA?>>

With plenty of the former... there is little of the latter. The ENV eliminates both.

bt


From: Bill Tantau
Sent: 10 December 1999
To: John Hardy
Subject: Re: Re: pre-selector gearbox

In a message dated 12/9/99 14:39:24, John Hardy wrote:

<<The drive is there all the time and it is not possible to have a fast tickover and remain stationary. Could be wrong. I quite often am.>>

I do believe you are right, JH.

bt


From: Bill Tantau
Sent: 10 December 1999
To: Berry Kercheval;
Subject: Re: Re: pre-selector gearbox

In a message dated 12/9/99 5:40:16, Berry Kercheval wrote:

<<I bet if someone were to design and build a modern preselect box it would weigh much much less -- *ALL* gearboxes of that period were heavy!>>

My only experience was with the ENV 75 pre-select as mounted in an MG Ptype with hotted up engine. I now have that same g'box on the shelf awaiting installation in a future project. It weighs about 90 lbs and is at leat twice the weight of the std P box.

bt


From: Clive Sherriff
Sent: 10 December 1999
To: ronald
cc: Berry Kercheval
Subject: Re: pre-selector gearbox

Message text written by ronald
>A school master at Brighton College had a Riley with the pre-selector gearbox. Nice car with two doors, rear hinging (suicide doors). He had bought it new and the salesman told him that if he wanted to stop in a hurry, you could pre-select reverse. However, you could only do it once per gearbox! I don't suggest anyone ever try it.<

I believe this happened once to one of the A Type GP Connaughts in a race, by accidental selection of reverse rather than third from top going into a corner, - the reverse gear selected perfectly - and the car flipped over in a backward sumersault! I nearly did something similar once in the '51 Laystal Cromard F1, which had an early ERAWilson Preselector box, I car but caught it just in time! But from that experience I can believe that the car could flip over!

I've never followed this story up - anyone know where - when and to whom?

Clive Sherriff


From: Peter Thompson
Sent: 11 December 1999
To: ronald; Berry Kercheval; owner-british-cars-pre-war; british-cars-pre-war
Subject: Re: pre-selector gearbox

I remember a colleague at college who drove a Riley saloon with a pre-selector box. The brakes were pretty awful so he used to use reverse for emergency stops, and for passing the MOT test (they used to do a road test then, with a Tapley meter on the floor, and would let you drive yourself if you wished). The snag would be that the friction lining on the reverse gear band would wear out, but I don't recall that happening to him.

Peter Thompson


From: John Hardy
Sent: 13 December 1999
To: Peter Thompson
Subject: Re: pre-selector gearbox


>I remember a colleague at college who drove a Riley saloon with a
>pre-selector box. The brakes were pretty awful so he used to use reverse for
>emergency stops,

I would deduce from this that his studies did not include the adjustment of brakes nor engineering in any sense. And they wonder why the gearboxes on these cars are knackered on unrestored examples.

JH


From: C. Knight
Sent: 12 December 1999
To: British cars pre-war mail list
Subject: Re: pre-selector gearbox

Clive Sherriff wrote:
> Message text written by ronald
> >A school master at Brighton College had a Riley with the pre-selector
> gearbox..... the salesman told him that if he wanted to stop in a hurry, you
> could
> pre-select reverse. However, you could only do it once per gearbox! I don't
> suggest anyone ever try it.<

Early Daimler Conquest manuals of the 1950s stated that reverse could be engaged at up to 40 mph as an emergency brake.

As a slight digression from the thread my late father-in-law who only had one leg nearly succeeded in running himself over by starting his Daimler on the starting handle with bottom gear preselected and the choke out. The engine fired, the revs increased to about 1200 and the car sedately drove off into his orchard leaving poor father-in-law hopping after it on his one leg. Damage, apart from pride, was confined to a spotlamp.

Cliff


From: Clive Sherriff
Sent: 13 December 1999
To: C. Knight
cc: British cars pre-war mail list
Subject: Re: pre-selector gearboxs


>The engine fired, the revs increased to about 1200 and the car sedately drove off into his orchard leaving poor father-in-law hopping after it on his one leg. Damage, apart from pride, was confined to a spotlamp.<

Quite a sight! But a serious note - over the years many people have been killed or seriously injured by reving the engine from tickover when drive was selected and mowing themselves down. I remember some years back talking to the owner of a Daimler Jaguar old parts business who had regularly attended inquests as the Expert Witness to explain how this happened.

Beware of the "Drive" selector position when working on these cars!

Clive Sherriff


From: David Cochrane
Sent: 13 December 1999
To: british-cars-pre-war
Subject: Re: pre-selector gearbox

Georges Roesch put a nice development of the pre-selector gearbox into his later Talbots which he called his accelerative gearbox. This automatically pre-selected the next gear up until it got to top, when it would pre-select 3rd, then top again, etc. I have never driven one of these, but would be interested to know how it works out in practice.

ERAs used them as well, and I remember Dudley Gahagan saying how good they were, as you could pre-select the next gear you wanted on the straight and hang onto the steering wheel with both hands going round a corner, instead of having to fiddle with the gear- lever as with conventional gearboxes.

Regards,

David C.
Rugby, England


From: Clive Sherriff
Sent: 13 December 1999
To: David Cochrane
Subject: Re: pre-selector gearbox

Message text written by INTERNET:David Cochrane
>Georges Roesch put a nice development of the pre-selector gearbox into his later Talbots which he called his accelerative gearbox. This automatically pre-selected the next gear up until it got to top, when it would pre-select 3rd, then top again, etc. I have never driven one of these, but would be interested to know how it works out in practice.

ERAs used them as well,................ <

David,

I might be wrong, but I think all the ERAs used a "normal" preselector - you always had to select the next gear by hand.

CS.


From: Maggie Shapland
Sent: 13 December 1999
To: David Cochrane
Subject: Re: pre-selector gearbox

buses had them too. I once drove a bus at one of these events where you try out lots of different vehicles and I remember that when I drove it, I had no problem changing gear due to my double- declutching experience I guess- whereas other novices managed to get standing passengers all to the front of the bus or to the rear of the bus with every lurch of the gear change!

How about early Lanchesters (ie edwardian) with epicyclic gearboxes? (mine has a crashbox)

----------------------
Maggie Shapland, Computing Service, University of Bristol
Web page: http://www.cse.bris.ac.uk/~ccmjs/
1925 Lanchester 21, 1925 Talbot 10/23, 1929 Peugeot 190S, 1986 Moss Monaco


From: David Cochrane
Sent: 13 December 1999
To: Clive Sherriff
Subject: Re: pre-selector gearbox

> > ERAs used them as well,................ <
>
> David,
>
> I might be wrong, but I think all the ERAs used a "normal" preselector -
> you always had to select the next gear by hand.

Yes, of course you are right, by "them" I meant pre-selector 'boxes, not the Roesch Talbot type. Sorry for the confusion.

David


From: Bill Tantau
Sent: 13 December 1999
To: David Cochrane;
Subject: Re: pre-selector gearbox

In a message dated 12/13/99 2:39:51, David Cochrane wrote:

<<.......you could pre-select the next gear you wanted on the straight and hang onto the steering wheel with both hands going round a corner, instead of having to fiddle with the gear- lever as with conventional gearboxes.>> That, indeed, is one of the best virtues of the pre-select.

bt


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