Hi Greg I was curious as to what is happening with your troubled action. I got asked to defend my skepticism to moving the whippen flange out in the case your original hammer flanges had their center pin holes 1 mm closer in to the flange mounting screw. I havent had time until now to put out some rough numbers but here goes.. and perhaps you will see why I opt for trying to just keep the old flanges in this situation. To begin with, if you have hammer flange centers 1 mm distal from originals and paper your whippen flange 1 mm out to match then all you have done is basically to move the stack distal 1 mm and the hammers inwards 1 mm to keep the same strike line. Thats where a large portion of whatever change in ratio will occur. I'll give a simplified example. Start with a say 5.25 ratio comprised of a 7.0 shank ratio, 1.5 whippen ratio and 0.5 key ratio. Assume also the following parameters. Hammer center moulding to center pin 136 mm Bore length 48 mm Knuckle core to center pin 16 mm Whippen center to cushion/capstan contact 62 mm Whippen center straight up to the contact point of the jacktop /knuckle 93 mm This is all basically following Overs way of measuring the ratio. Yeilds an hammer shank long moment arm of about 144.34 and a short moment arm of 20.62 Now if you just move out the whippen and shank flanges distal 1 mm and the hammers in 1 mm to keep the strike line...then the shank ratio drops to about 6.954 from 7.0 In addition the whippens ratio changes slightly. The long arm is typically about around 30 degrees out from the horizontal line from the whippen center and the lower arm about 18-20 degrees. This means a horizontal move of the whippen flange center will lengthen the upper arm slightly more then the move will add to the lower arm. Using 18 and 30 degrees the moment ratio drops to 1.4933 The new total action ratio is then 5.19. (6.954*1.4933*.5) Using the same calcs if you've installed 17 mm knuckle length and move the whippen flange out 1 mm more to keep the jack on the parallel with the knuckle core the whippen ratio drops to around 1.487 and the hammer shank ratio changes to 6.72 which gives 6.72*1.487*0.5 = 5.0 for the new total ratio. Thats beginning to be a significant drop. In itself not necessarily a bad thing... but there is another situation going on here I am less comfortable with. A distal horizontal move of the whippen flange center also changes the effective travel of the jack tip fairly significantly. In the above example you are roughly 58 mm straight out from the whippen flange center to the point on the lower arm directly above the whippen cushion / capstan point. If the key moves that say 5 mm upwards, then a jack tip that is 120 mm away from the flange center will move about 10.3 mm. (of course the jack tender will get in the way but I'll get to that.) With a 2 mm distal move of the whippen flange center jack tip rise is reduced to 10 mm. The jack itself is a roughly 2:1 ratio lever so the jack top will move twice as much as the tip. Since it comes into play about 80 mm into key dip you are looking roughly at a 0.5 mm reduction in jack top travel. None of this even gets into the fact that with a move of the flange center by itself (as in the case of compensating for the 16 to 17 mm knuckle distance difference) requires you to lower the capstan so as to get the same blow distance... which again changes the jack angle slightly outwards. In reality, going from 16 to 17 mm knuckle difference requires a bit more of a 1 mm distal move of the whippen flange center to maintain both the same blow distance and the jack being on line with the knuckle core. At the same time it reduces jack travel slightly... enough to have an impact on letoff and drop timing. To maintain simultaneous contact you will have to lower the let off button. But the jack wont come out from under the knuckle quite as far (key dip staying the same). There is more one could get into here if one wanted to...such as jack stop cushions (both for and aft)...etc, but I think this all sort of explains why I prefer to stick with the original hammer shank flanges instead of papering the whippens out. On the other hand... if the whippens were too close in to begin with... well thats another matter. Hope this clarifies somewhat... sorry about the length but even general numbers force a bit of explanation Cheers RicB
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