Jim Kinnear rote, 3/18: <<I seems that even though the castors were working alright, one of the assemblies always veered as you described. I decided that the castor was not installed with the socket EXACTLY perpendicular to the floor, removed it and shimmed itwith thin washers on the side to which it wandered, reinstalled it and the problem was solved.>> Yup, that's the basic principle of casters, that if a stem is not exactly plumb, when the wheels therebelow are asked to move, they'll insist on moving in the direction in which the stem's lean is pointing (with the stem leading and wheels following). How this works to produce the situation over here on my piano, I still don't understand. If three stems out of four are plumb, they'll "outvote" the leaning stem and force it to move in the direction they're going (which because they're good little casters is the direction you're pushing in). The bad stem here will have its casters fishtail as a protest to not moving in the direction it's pointing. As the number of unplumb stems in a set increases from one on up, the choas grows, and mainly because the chances are strong that the lean of these unplumb stems will point in different directions. What I saw on my piano was a set of four casters which rolled smoothly without fishtailing, and could change direction easily. What *was* happening was that while the piano's back stayed parallel with the direction you wanted to push in, the piano itself moved off that vector by 5 degrees. The only explanation satisfying the above *known* principles of casterology is that all four casters are leaning in the same direction. How 'bout them odds? (Or maybe this piano was abducted one weekend by space aliens, studied for possible reproductive purposes and returned "caster-ated".) My next step is to tilt the piano up, and with a dial indicator study the levelness of the sockects, as you did. What kind of surface I'll indicate from, I won't know until I see the condition of the underside of the piano. At the worst, I'll bring along a wooden right-angle "corner" which can sit on the margin of the bottom edge of the piano back and with the hieight of the bottom board, with a 6"x12" piece of masonite which can rest both on this wooden rught angle and the bottom board (thus making a level surface out oof a chwed up bottom board). The masonite will have a 3" dia hole through which the indicator will do its probing. Wish me luck, especially the space aliens return. Bill Ballard RPT NH Chapter PTG "When writing a mental note, first procure a mental piece of paper" ............mental graffitti
This PTG archive page provided courtesy of Moy Piano Service, LLC