<!doctype html public "-//w3c//dtd html 4.0 transitional//en"> <html>   Folks I keep being bothered by the differing conventions for measuring the ratio of the hammer shank. From the Law of Levers we know that the ratio is the same whether its weight, speed, or distance we are looking at. Below are a couple pictures showing a method of checking the hammer shank ratio by measuring the weights involved. First is the SW and second is a difficult (but doable)  quantity to measure, the actual weight of the hammer assembly at the knuckle. The flange is replaced by an adapter to the Stanwood kit so as to achieve as solid and friction free a measurement as possible. And the wood dowel used to contact the knuckle is glued in place to tray so as to remove any influence from it moving around. About 50 samples were taken, and compared to a 60 second sampling under vibration.... the variation of the samples was at highest 80,4 grams and at lowest 73.1 grams. About 80 % of the samples were right around 76 grams, and the average weight under vibration was at about 75 grams, though as soon as the vibration was shut of the scale settled at 76.5... which ended up being the picture I took. All in all it seems pretty reasonable that in this case the established ratio is  76.5 / 10.1 which gives a ratio of  7.57 for this hammer shank assembly.           <img SRC="cid:part1.3E494D3F.37D73195@grieg.uib.no" height=333 width=320><img SRC="cid:part2.3E494D3F.37D73195@grieg.uib.no" height=312 width=320>      Now the interesting part of all this comes when you compare the different conventions for finding the ratio by measuring lever arm distances. Remember that whatever method is chosen simply must conform reasonably to the ratio established above. So first .... some distances. --From center of hammer shank diameter to knuckle contact point 13 mm A) From middle of center pin to middle of hammer molding straight down the shank -- 136 mm B) From middle of center pin to center of gravity point on the hammer 142 mm C) From middle of center pin to tip of hammer 148 mm D) From middle of center pin to middle of knuckle molding -- 17.3 mm E) From middle of center pin to knuckle contact point 21,64 calculated as root (17,3^2 + 13^2) Now lets take a look at which convention most closely conforms to the already established ratio. A/D = 7.86  (given by Vincent RPT) B/D = 8.21  (discussed informally on the PTD list) B/E = 6.56  (I ran into this one in Stockholm last year in informal discussions) C/E = 6.84  (given by Overs) A/D = 6.28 (suggested by a technical editor informally in private correspondence) Its quite obvious which one of these comes out best. But what is most interesting is the degree of deviation from those that conform poorly. >From this the initial conclusion is inescapable, that the method Vincent gives for measuring lever arms is the most dependable. I intend to further refine the weight measurement method, and supplement it with a contrivance for moving the assembly at the knuckle a given distance and comparing that to the distance the hammer moves. Fun eh ??? Cheers RicB</html>