So… it was a graph that was bothering me… i couldn’t let it go. I was looking at data from a recent piano where the hammer weight was sloped (as it should be – there are larger hammer in the lower notes of a piano and small ones in the top) and what i found to be interesting was that the frictional component was also sloped. Why would that be? But there was no more time for today…I locked the door, closed the shop for the weekend. But it was on my mind. According to the stats, i needed to reduce about 3-5 grams of friction in the lower hammers. Then i got to thinkin’… what would happen if you had a wagon that was empty versus one that was full. The coefficient of friction would remain the same – meaning that the percent or ratio of friction would be the same – but the load would actually change the ‘weight’ of friction. Thinking again about the wagon… if it was empty it would be quite easy to move right? Load it full of bricks and all of a sudden, the force required to move the wagon increased proportional to the load. So in essence, the ratio doesn’t change but the weight of friction will change with the load. Back to the piano – the hammers i measured were slightly heavy… too heavy in fact for this piano. I referenced my graph again… i was examining the weight of friction and not the coefficient of friction. After i did many checks and balances again on certain joints, i finally did the reduction of weight which you can see the article on entitled Hammer Shaping. What gave me a tickle though was the fact that with the load reduced, so also the friction reduced by the exact amount i needed – a few grams.

PS… don’t know whether the coefficient of friction changes when the friction becomes the kids fighting… <sigh> i remember those days all too well :)