This is another model built with my 1930 red and green Meccano set number 7 that I keep in Canada. The plans were first published in 1928 as SML No.7 “Meccano Platform Scales” and could be built with the parts in the then current No.6 Outfit. An earlier version of this model had been published in the 1919 book of instructions. Platform scales of this type were a common  item in railway offices and on station platforms. See picture of the Avery Scales taken from the instruction leaflet below right. Although the model is fairly straightforward the mechanism was fairly complicated and difficult to assemble within the framework of the model. This is part due to the none to clear written instructions however my patience prevailed and I finished the model. One major problem was the strip coupling 63b the slot of which is thinner than the width of a 25 hole strip making it impossible to fit and slide along its length. I had to widened the strip coupling. When completed and set up it does work very well and will weigh from light objects up to a few kilos. This is one of very few Meccano models that put the centre fork p/n 65 to good use, those I used on the scales are much thinner and sharper than the later version.  The centre fork is used as a knife-edge bearing resting on two 19 tooth pinions and is very effective I doubt the model would work as well with the post war blunt version of the centre fork. Front page of original instructions. Instructions of 1919 version of model  I made few changes to the model using an early ratchet/pawl as the sliding pointer instead of one cut out of card as suggested I also dispensed with the card arrow and indicator to show when the steel yard is level as I thought this spoilt the look of the scales and was not needed.
Page published November  23 2017 revised February 22  2018
Click on images to enlarge.
The model made a fresh appearance in the October 1947 Meccano Magazine being described as our “new model of the month.” This was a revised version using flexible plates to fill in the frame work but much of the model remained much the same. The instructions though lack the detail or print clarity of the SML.