Richard and list, Your quoted text contains a combination of my reply and another person's, the email of which I didn't receive. >(Ron Os earlier reply) As mentioned in my earlier post, we > > have found that soft duplexes will not stand up to commercial > > service. D. We first restrung this piano in 1993, when >the > > capo and duplex bars were reshaped (but not hardened). This >> piano is one of the high use pianos I referred >to in my post > > of earlier today. >> > > > (unknown replier - it may be you Richard, but it has come through >to me as quoted text) Am I correct in assuming this is the piano you >mentioned that > > gets like 3-4 tunings a week or something like that ? Yes. >Also looks to me from the picture that you are using significantly > > more then 0.5mm surface area for the capo. Do you have any > > measurements for that.. It's hard for me to be absolutely sure about that now (since the evidence has been removed). But I do remember comparing the capo radius with my 0.1 mm step drills to establish the radius of the bar (I was taking the photo for the writing of my '1998 lecture' on our website at the time). Furthermore, I remember thinking that the actual photo of the capo didn't look as small in radius as the bar was in reality. We restrung the piano again in 1997, when the bar was reshaped again and subsequently hardened (when we first restrung the piano in 1993, the bars were reshaped but they weren't hardened). It was this piano which made me realise just how hopeless the standard cast iron is as a bearing material - it was 'cut to shreds' as I mentioned yesterday. >Also, since I have never actually >> checked (measured) the hardness of the capos and V bars I have >> reshaped, I wonder if you (or somebody) could describe whats > > involved in doing so. Hardness is normally established with a hardness tester. This is a special machine which presses a small spherical ball into the surface of the material being tested. The machine applies an increasing pressure until the test ball imbeds into the test material to a prescribed depth. The test ball will deform the test material until an equilibrium is established between the test ball and the deformed test material. The hardness is relative to the depth of the ball impression in the test material. > (unknown reply) Since apparantly my experience with > > relation to the hardness of the bar differs from some off you >> others, it might be usefull for me to find out what the actuall > > hardness numbers are for the future. We use the 'deform the piano wire on the bar' test after hardening (using our high-tech ball pane hammer as described in my post of yesterday) to test the hardness. While this does not give a bar hardness reading, it does tell us how the bar is going to withstand the piano wire (the relative deformation of the two tells us everything we need to know - note that this test is not done in the middle of a string section, but between the two capo sections where it will not damage a string termination point). In practise, if the bar deforms noticeably less than the piano wire, we will be satisfied with the result. Try the same test with brass, bronze, mild steel or annealed silver steel sometime. The results will surprise you. The V process plates seem not to harden to quite to the same degree as the traditionally cast plates, but we still achieve adequate hardness with V process plates. The actual as cast hardness of plates will vary considerably according to the freeze time of the actual plate and its analysis. Typically V process plates are much softer, and it is these which are the worst offenders with regard to string noise. Ron O -- _________________________ Website: http://www.overspianos.com.au Email: mailto:ron@overspianos.com.au _________________________
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