The A.T. instrument..Speedometer, Tachometer and Smiths A.T. instruments....

Sometime in 2009 I did a post on the Smiths racing tachometer, the ATRC tachometer, badged Smiths and coded ATRCxxxx...
It has generated interest over the intervening years and I've manufactured a few more as a result of the post.
so lets have another look at this instrument that carries this A.T coding...
They are characterised by the pointer rotating through a slot in the instrument dial with the pointer blade sweeping the surface of the dial rather than from completely above it as in other speedometers made by smiths and other manufacturers.
The A.T  Speedometer Company Ltd of 140 Long Acre, London WC was advertising in "Flight" magazine in July 1915 so they are one of the originals in automotive,motorcycle and aviation instrumentation....

Sometime around 1927-1930 Smiths Motor Accessories acquired the firm and they were manufactured in Chronos Works, North Circular Road, London N.W.2...

Their speedometers had been in Rolls Royce cars since the 1920's and in Bentley cars from around this time also....
Simon Roope, with who I have a correspondence has responded with some interesting, additional information in the comments section below but I've incorporated it here....thanks Simon...
 


The AT showroom was at 140 Long Acre before the Great War; an original 25 page AT Speedometer catalogue from 1912  I own has this address printed on each page.
From the early 1920s AT instruments were fitted to many prestige vintage cars, including Rolls Royce, Bentley and Frazer Nash. By then, manufacture of AT instruments had moved to West London and from October 1924 to 20 Avonmore Rd, London W14 (pg. 36, Motorsport, October 1924)
AT had German parentage (instrument manufacturers Deuta-Werke GmbH, Berlin) and under the newly formed Trading with the Enemy Act of 1914 company assets were confiscated at the outbreak of war. Ownership passed to Smiths, then to S.D Mckellen in 1920, and to Jaeger in December 1928 who in October the previous year had been bought by Smiths. In 1930 manufacture of AT instruments moved to the newly built Chronos Works. (pg. 82, James Nye's new book 'A Long Time in Making; History of Smiths' and pg. 42-44, 'Roadcraft' magazine published by Smiths for the 1937 London Olympia Motor Show).
In 1931 Bentley Motors went into liquidation and was acquired by Rolls Royce. 
Two years later the first Rolls Royce made Bentley car (3 1/2 Litre saloon) went on sale. So in 1933 it is the model of car that is new not the fitting of AT instruments to Bentley cars; this had happened ten years earlier.



Lets have a peruse of a 1934 A.T. catalogue to view the items they made then.

In the early 1950's Smiths responded to the demand for a racing tachometer without the inherent lag of the chronometric principled tachometer and introduced the ATRC version....see my 2009 post on this.

Following are examples of car and lorry dashboards from around 1955 which utilise the A.T. versions Smiths made.

 

Smiths AT speedometer from a Leyland bus....

During 1964,1965 Smiths made industrial versions of the A.T. Tachometer available also....

As mentioned I did a posting in 2009 and this discusses the principle of operation of the A.T instrument and is useful to assist....

Finally, Smiths made hand held industrial tachometers to measure rotating shaft speeds etc and these of the A.T principle.....

They often had multiple scales altered by a knob on the case....

Removal of a Smiths chronometric speedo or tacho bezel rim.......

This could be the last post from me for the year and it is an item long overdue from me to add to the several posts I've done on the Smiths chronometric speedometer and tachometer.
The bezel of the 80mm diameter (3") chronometric has a rim with an 80mm x 0.9mm thread. The thread is relatively fine for the diameter and removal of the bezel from the case by unscrewing is not always easy.
You need a good strap wrench...the best I came across was a type and you'll see it illustrated, that was made in the USA and has s mall rubber type suction pads.
I dont think they make them like this now as years back I tried to get more and they had gone over to plastic which as you read down the blog, you'll see is not suitable.
Putting too much pressure onto the rim will distort it and that in turn causes the bezel to grip harder.
So what is one of the major reasons a bezel is stuck?
The 'O' ring seal used by Smiths was made of natural rubber and these perish over time and appear to 'melt' effectively glueing the rim to the glass and oozing onto the glass carrier or slipring/mask.
The rim wont move under normal pressure if it is like this.
The trick is to use careful heat, played around the rim edge until the remains of the 'O' ring really do melt and then quickly fit the strap wrench and in 99.9% of cases the rim quickly and easily unscrews and when cleaned up of the resulting rubber mess can be re-used.
As well there is no damage to the dial and internal components.
I suggest you make up, from some convenient angle piece a bracket to mount the instrument to and hold this in a vice.
Left click on the images to enlarge them for better viewing....

The smoke from the rubber melting indicates the bezel is close to ready for unscrewing...

More Motometer instrumentation...information on the BMW R65, R65LS and R45 motorcycles....

Well I'm on a role here...I've scanned in all my Motometer stuff and will feature information on BMW motorcycles that used Motometer instruments from 1973 to, well into the 1990's, perhaps later. I was out of it by then....
This blog features the boxer engined R65, R45 and R65LS models. As well some of the R80's appear to have used these as well.
Left click on the images to enlarge.....
I made pencil notes on the gearing over the years and have scanned this in as well...a bit scratchy, but the effort needed to type it up is more than I'm prepared to do.....

The BMW R65 LS model....the engine and instrumentation were the same for the other variants....gearing excepted etc...

The R65 used a 200kph or 120mph speedometer scale with a cable driven instrument and the tachometer was electronic. 
The R45 used a 180kph speedometer.
Information on how to connect a tester to the tacho follows in some of my pencil notes...

Exploded parts view of the tachometer...

Details to the bottom right of the electronic tachometer connection and odometer gearing details for the 120mph speedometer to the mid RHS.

Exploded parts view of the speedometer...

DQs scratchy notes on odometer gearing...covering the R45 and R65 on the RHS.

Trip odometer details....
Details for the additional Motometer quartz clock and voltmeter offered as an extra on these models are in the previous blog......

Detail of the speedcup shaft bottom pivot length. This wears on the end stone in the bush at the top of the mainshaft and the inside of the aluminium speedcup "poles" on the magnet, eventually destroying it.
You can lightly stone the worn end of the shaft and then tap it though the brass piece in the speedcup to the correct setting...0.140" protruding.