hammermaker's corner 13

[ari isaac]

Hammer maker's corner 13

Ari Isaac

I don't know whether I'm equal to telling the story of my hammer wiring machine. Here it is.
I was convinced, inspite of my wise friend S's suggestion, that the hammer needs a secondary fastener and, what is more relevant here, I was convinced it had to be a twisted wire. The secondary fastener is actually important because, it provides tension around the outside of the hammer. This is true only if the secondary fastener is designed and installed properly.  I decided on a twisted wire because it seemed to me the most efficient.  Now  I started looking for a machine to do the job.  You can't buy that machine, it hasn't even been designed yet.
My first stop was the file filled appartment of a machine designer who had been recommended to me. After listening to my description of what I needed the machine to do,he said the design would cost $25000. I abandoned that avenue looked for a less expensive way.  I found it in the guise of another English machinist. I'm certin there must be many outstanding British tmachinists, I  just didn't have the good fortune to meet them. This one actually had a pretty impressive machine shop and he promised to build my automatic hammer wiring machine for $12000 and to have it ready in three months.  I was happy with the prospect.
Let me try and describe the automating of hammer wiring. The process needs to be broken down into component operations: drilling two small holes through the hammer - felt and wood. cutting a piece of wire to length and forming it into the shape of a letter u. inserting the two legs of the formed wire through the hammer so they stick out about .5" on the opposite side.  Twisting the two wire legs as tight as possible without breaking them off. Cutting the twisted wire down to the desired length.  purshing the twisted  length of wire up against the felt.  Add to this the loading and unloading of each hammer, holding the hammer so that the various operations may take place and moving the hammer from one operation to the next.  Each one of these operations presents real difficulties.   Take the first operation; drilling two small holes through the hammer.  The hammer width is, on average, .400", allowing for upright and grand hammers. The wire we had to use was .030" in diameter.  We quickly discovered the felt was so springy that it filled the just drilled holes immediately the drill was pulled out.  We had to enlarge the hole diameter to almost double the wire diameter.  Now, .400" minus .110", the combined diameter of the two holes leaves .290" or about 9/32". The space between the two small holes needs to be as large as possible to enable the wire to grip as wide an area of felt as possible, after all, binding the felt with maximum tension around the hammer is what wiring is all about.  How close to the outside of the hammer can you drill a hole without piercing the side? If we say 1/16 then we have only 5/32" between the inside edge of the two small holes.  All of this needs to be converted into a real live machine, or part of ,nnma machine and it's only the first station.i had purchased an automatic air drill which was capable of auto feed and returning.
The second designer i went to, before committing to the british machinist, charged me $500 for a drawing which, after looking at it, went straight to the trash can. in the end i settled on a turntable. not a vinyll record playing turntable but an industrial one which divided each rotation into 7 precise segments. its precision was within .0001". this means that each time it was activated it moved through one seventh of one rotation and stopped there till the next command to activate. once the turntable came to a stop all of the seven stations began their individual operations.
the drill came down, drilled one hole, came back up, moved, or was moved, over to the next hole about 5/32" away from the first hole, came down again, drilled hole number 2 into the same hammer and came back up and over to its original position.
at the same time station #2 pulled the appropriate length of stainless steel wire, bent it into the shape of a letter 'u' and pushed the two legs of the wire staple into the just drilled two holes.
station #3, at the same time, had two jaws which came up to grab the two legs of wire sticking out from the bottom of the hammer, twisted them three rotations and released.
station #4, at the same time, cut the twisted wire so that what stuck out from the hammer was about 7/32" long.
station #5, at the same time, pushed the twisted wire section sticking out from the hammer up deep into the felt.
station #6 didn't do anything because there was nothing else to do.  The table with the closest specifications to what i needed had seven stations.  one remained just  a stop.
the next station was the loading and unloading station.
what i've described so far was the way the machine was meant to work. during the two or three years of its reign at isaac pianos it almost never worked in this way. by the time we through up our hands and decided to change to a different secondary fastener we had spent close to $20000 on debugging it and countless hours of three people's time.
i remember one evening when paul, the wonderful and talented machinist who babied this machine with incredible patience, just lost it. he grabbed a sledge hammer and began to strike the steel table on which the machine was mounted. he didn't harm anything but it was really something looking at him letting the table have it. the problem was that the machine, whose design was sound, had been built with not nearly enough money. according to my friend c, it  should have cost not $30000 but $100000 - then it could have been expected to work well. i decided, when it became evident the automatic wiring machine was never going to work without a lot of babying, to switch to special staples.  more about that next time.