<HTML><HEAD> <META charset=UTF-8 http-equiv=Content-Type content="text/html; charse= t=utf-8"> <META content="MSHTML 6.00.2730.1700" name=GENERATOR></HEAD> <BODY style="FONT-SIZE: 10pt; FONT-FAMILY: Arial; BACKGROUND-COLOR: #fffff= f"> <DIV> <DIV>         &n= bsp;  John</DIV> <DIV>         &n= bsp;  Thanks for the non math clarification. My comments by the way sho= uld not be taken as a complaint. Your desription of MOI is useful & I se= e more clearly where this discusion is trying to go. Intuitively many of us = realized long ago that measuring static weights could not predict what an ac= tion does in a dynamic sense we just didn't have a tool for analyzing it. Me= thods popularized & developed by D. Stanwood has helped enomous. This to= me is the next step. Yes it will take time.</DIV> <DIV>    Dale</DIV> <BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue = 2px solid">Dale wrote: >&nbsp= ; Ron >   I just wanted to say publicly--Thanks . This is a = great clarifying > summary. Clarification is always enlightening. You= r post also points out > that "the confusion that remains is still ho= w all this stuff > mechanically relates" which is true. At the end of= the day we have to > put all this into a useful sytematic practice i= n rebuilding the actions > we all work on.These discussion  incr= ease our confidence secure better > results for us & perfromance = benifits for our clients. Dale, Several people have compla= ined that this material has just brought more   confusion to our un= derstanding of the grand action. That's understandable since the study o= f the dynamic action is at least ten time more involved that studying th= e static action. It took many years for the simple static principles Sta= nwood has developed to be accepted and understood. I would expect these = dynamic principles to take a lot longer. The task is especially daunting= since getting a mental grasp of how it works requires familiarity with = math and physics. I expect that most piano technician's would need to bo= ne up on high school level algebra and physics to gain access to this kn= owledge. Even though this is going to be a lot of work, as you said, = it can be accomplished one step at a time. The first step is getting the= notion of moment of inertia clear in ones mind. Envision a cylinder att= ached to an axle with a rope wrapped around it. We pull on the rope and = the cylinder rotates around its axle. If the cylinder is made from a lig= ht material like wood, it is easy to pull the rope. If it is made from a= heavy material like steal, it will be hard to pull the rope. The moment= of inertia describes how hard it is to pull the rope and get the cylind= er to move. Knowing the MOI of the cylinder and the radius we can predic= t how hard it is to move. We can also know how much tension there is in = the rope. With a high MOI the tension is high and with a low MOI the <BR= >tension is low. "What the heck does this have to do with pianos John= ?". Well, if the MOI of the action is high it will feel harder to play. = I am not sure if the player could feel this with playing cords slowly at= various dynamic levels but it will certainly feel hard to play scales a= nd fast passages. Let's imagine a room full of our cylinders each with a= rope attached. Your job is to pull each of these ropes in fast order. I= t will be a lot easier if they are made of wood rather than steel. <B= R>But what about balance weight? Use the cylinder again, but this time w= rap another rope around the back side and attach a weight. have a shelf = for the weight to rest on. Now when you pull the rope you have a weight = to lift along with the inertia of the cylinder. The cylinder doesn't mov= e until the weight is lifted. Go back to the room of cylinders. Would yo= u like to have the wood cylinders with a heavy weight attached or the st= eel ones with lighter weights? One of the things learned from studyin= g MOI is just what Balance weight does. It determines (along with fricti= on and let off resistants) the minimum force to move the action. The tot= al force after that is determined by the force required to accelerated t= he action minus the force of the BW. At very soft levels of playing the = BW will be a significant part of the total force while at forceful level= s the balance weight is insignificant. Through the dynamic range of play= ing the force needed to accelerate the action increases while force to o= vercome the BW stays the same. Hope this attempt at a non math ex= planation helps. John Hartman RPT</BLOCKQUOTE></DIV> <DIV></DIV></BODY></HT= ML>