Author Topic: Smiths Selectroshift  (Read 5626 times)

Bob Purton

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Smiths Selectroshift
« on: February 17, 2015, 01:19:51 pm »
Does anyone know anything about the semi automatic Smiths system used on some Isetta's?
Reading the material here it sounds quite ingenious but was it reliable?

richard

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Re: Smiths Selectroshift
« Reply #1 on: February 17, 2015, 01:40:00 pm »
Am I right in saying that is used in mikes Gogginobil Coupe and possibly the Victoria Spatz , certainly the electro shift in the former works well
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Bob Purton

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Re: Smiths Selectroshift
« Reply #2 on: February 17, 2015, 01:47:16 pm »
Not sure but I think that pre selects gears by means of solenoids where as this is just an automatic clutch?

Big Al

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Re: Smiths Selectroshift
« Reply #3 on: February 17, 2015, 02:31:17 pm »
Pre selector on Goggo and Spatz was a fully functioning gear selection system. You selected a gear, engaged and then selected the next gear required on a switch. Thus loaded, the system would do the gear change in relation to the clutch pedal. An early productionised system of the now much vaunted paddle gear box from Hans Glas - who pioneered the rubber cam belt. The man was an engineering hero.
So the one thing they did not have was automatic clutch. I do not know about the Spatz, which had five speeds, but the Goggo had one of the best manual gear changes of a car I have ever driven. Certainly most rear engine cars would dream of such a change. So why they bothered with the complication, I do not know. Its is alleged that it was to help disabled servicemen to drive them, but you need all limbs still, so I find that hard to believe. I prefer the manual, which is that good you can make clutch-less gear-changes once you have learned the box and engine speeds. For a 400cc it thus will out accelerate a lot of big hitters up to about 40 mph. Heb used to have burn ups with his twin Amal tuned Dart where he would out drag a V8 Holden or whatever, handbrake turn and wave at them going the other way. Try that in a Tiger!

The Smiths system is an automatic clutch. It used activated iron particles through which an electric current was applied to gradually create a solid magnet. The problem was continual slipping of the clutch, or mal-adjustment of the unit, meant the iron particles wore into rounded shapes and then had less grip on each other.

Both systems relied on contact sets and switches. Any of which could get fouled, burned or fail. It was another thing to go wrong.

Yet Goggo managed to supply perhaps half its 400cc models with the pre-selector, offering it as an optional extra in many cases. I have evidence of only one total failure, A destroyed gear set from the Great Bradley hoard. The switch gear tends to be the weakness though the ball bearings used to lock the gears have been known to wear with the activating rods. The entire gear set and diff were different and not directly interchangable with the manual set. It had a manual stuck in second pull lever on the gearcase to get you home if there was a failure. The first limp mod, by Hans Glass, as well? Is it any wonder BMW wanted to buy Glas....

The Smiths clutch was not a sales success. I believe it was something like only 12 examples sold. I had one of the working ones, a 4W RHD top of the range car. It really offered very little extra to driving the car, save you might cut one leg off. I think the IC potential was of interest to BMW Brighton. That went to a chap called Chamberlayne who got heavily into the club for a spell. Another in less good condition came through too. I forget who had that one but I am pretty sure it went to Canada eventually. At the time of ownership the cigarette industry where still using the technology and from there activated iron could be got. Wills of Bristol, old school contact, don't y'know old boy. I might even still have a bag, kept just because.

The Smiths appeared in other cars, I think particularly Hillman Minx, was it? Also think it was made nearby at Minster Lovell - Witney to you lot. Root's Grandfather might even have been involved!
« Last Edit: February 17, 2015, 02:42:44 pm by Big Al »
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Bob Purton

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Re: Smiths Selectroshift
« Reply #4 on: February 17, 2015, 03:49:21 pm »
It does beg the question, why bother when you can have the simplicity of a centrifugal clutch.

Big Al

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Re: Smiths Selectroshift
« Reply #5 on: February 17, 2015, 04:00:14 pm »
The traffic clutch rather died out at the time of Microcars. The freewheel clutch remained while two stroke cars were produced. Though the idea was fundamentally different for operational effect. Not sure there are any other centrifugal clutches on cars, though they certainly appear as part of the governing system. AS soon as you include belts and cone drive you create drag, that saps power and performance. Automatics look easy, but to actually create an efficient one is extraordinarily difficult. They are still trying! It is, of course, one area where IC/electric scores. Strangely we never hear about it in all the other less convincing green blather.
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Bob Purton

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Re: Smiths Selectroshift
« Reply #6 on: February 17, 2015, 06:07:27 pm »
Belts and cone do create drag but they also can be set up for tapping into the power band so they are changing up at optimum revs, that cancels any drag disadvantage out. MOdern scooters are a good example of this, getting the most out of a small engine.

Big Al

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Re: Smiths Selectroshift
« Reply #7 on: February 17, 2015, 06:53:28 pm »
Which is why I would like to make a Wankel engined DAF. A Wankel is at its best in a narrow power/rev band. So as a pump, or drone engine, they are excellent, running on low grade fuel. Yet have we a small portable Wankel powered automatic bike you can take on a train etc, that acts as a chair out of use, no! Add that to a pc/phone system joined at the hip and you have the two items needed in the city for modern living, neither exist despite the technology being there for a decade. The land of pillocksville and why its better in th carrot crunching veldt where such things do not matter much.
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AndyL

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Re: Smiths Selectroshift
« Reply #8 on: February 17, 2015, 08:10:36 pm »
Perhaps it was just a simple matter of cost, the selectroshift must have added significant manufacturing cost to the bog standard dry plate clutch set-up.

I've never been a fan of automatics or semi-automatics, I never felt in full command of the machine, and I get bored without a cog box to stir.
« Last Edit: February 18, 2015, 08:34:33 am by AndyL »
1959 LHD 3-wheel Isetta.

Grant Kearney

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Re: Smiths Selectroshift
« Reply #9 on: February 17, 2015, 09:16:00 pm »
There is a nice example up my part of the world that has the mega rare Smiths Selectroshift.  Attended last years NMCR at Wetherby.  I have no real knowledge but recall being told that the cost of the replacement  'iron filings' required during restoration were comparable to gold..............

richard

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Re: Smiths Selectroshift
« Reply #10 on: February 17, 2015, 09:48:57 pm »
Did you only ask because of the one presently on eBay - unlikely coincidence  ;)
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Big Al

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Re: Smiths Selectroshift
« Reply #11 on: February 18, 2015, 09:04:09 am »
The activated iron was not that cheap. I think it was £56 a lb when I got some. The unit worked very much the better for it though. Quite how long a well serviced instillation would work I do not know, but its probably like a plane where equipment is measured in hour usage, not distance covered.

So there is one on EBay. Ideal for someone else. I see the Walkers have been busy while the chanel crossings are cheap. More French Fridges than you can shake a stick at. Narry an Avolette though!
Messerschmitt set, Goggo Darts, Heinkel 175, Fiat Jolly, Autobianchi, Fairthorpe Electron Minor, Borgward, Isuzu Trooper
Citroen BX 17TZD & GTI 16v
Held - MG Magnette ZB & 4/44
For sale - Vellam Isetta, Bamby, AC Type 70, Velorex, Church Pod, Reliant Mk5, KR200,  Saab 96, Bellemy Trials, Citroen BXs