Bechstein plate cracks

[Arnold Duin]

Hello Doug

I am not a mechanical engineer or a welder so please don¹t expect any specific technical details. Over the years I have done a lot of Bechstein grands with cracks, sometimes I left them alone and the cracks didn¹t go any further, but most of the times I tried to repair them. Customers don¹t like the idea of having a crack in the plate, even if nothing happens to it in time. Probably they are afraid that the plate will collapse. 
Most Cracks in Bechstein plates especially of the old B and C models are evidently caused by shortcomings of the plate design on these well known spots. The plate (in that area) can¹t withstand the tension of the strings and the pinblock isn¹t capable of resisting those forces either. As a result the pinblock tilts and the plate will crack. One solution for this problem is of course to reinforce those troublesome spots, e.g by welding metal plates on both sides of the studs or underneath the stud. If you want to replace the pinblock anyway you can consider to weld the cracks when the plate is still under tension in the piano. After removing the plate you can strengthen it with metal plates. The tuning pins are close to the studs so you have to alter the layout of the tuning pins holes a bit to accommodate for the thicker studs. 

Since Œ93 I am using the Metalock method with great results. Probably you or your brother already know about this method but I will explain it anyway. In Holland we have one firm which has a licence to use this method and there several companies all over the world who are licensed to use the method so look in the Yellow pages. The patented method (originated in America) is the process of making cold repairs in cracked, broken or weakened machine parts or pressure vessels of cast or forged metals. 

Metalock is a custom formed lock or key made of special alloys.The size and number of metalocks vary with conditions and the amount of strength to be restored to the fractured metal. Slots are cut transverse to the fracture and metalocks are inlaid by cold working into the parent metal. Thus, the locks hold cracked or broken pieces together and restore strength to fractured sections.

Another proven method pointed out to me by Mr. Schulze of the Bechstein factory mostly used at a starting crack, is to drill a conical hole at the end of the crack of ± 6 mm glue a conical metal of the same size in it. In normal conditions it will prevent the crack to go any further.

Hope this information will help you a little

greetings Arnold