Not an engine...
Was asked by a piano shop if it is possible to repair stress cracks on the harp of a 100 year old piano. Removing it from the piano is the easy part.
The cracks are on the "struts" that run from the tuning area up to the curvy part of the harp. A repair has obviously been done once before (probably not a good thing) and this too has cracked. At this point I don't know if that was a braze or a weld. This is a known weak point on all of these harps from this period. The stress crack is about 1"-2" long and essentially cuts the strut along its width, 10" or so from where the tuners are located.
The question I have is can this sort of crack be TIG'd or MIG'd with or without a pre-heat and if so, what alloy would likely work. Let's assume for the discussion that there were no prior repairs... then factor in the variables.
On my mind are thermal expansion coefficients as well as hardening of the casting in the weld area (making it easier to crack?).
We have access to a local foundry that would make us a section of this strut *if* it made sense to cut a section out and splice in a newer better designed (better profile, less likely to stress crack) section. We can precisely cut it along a long path, for example.... (assuming some sort of weld/braze would *work*)
Heating the entire harp is not likely to be practical. ( possible but unlikely to find a large enough or hot enough oven?? This is a Baby Grand size)
The cracks, btw are near where a large screw fastens the harp to the soundboard - and look like the force of the screw holding the harp down (wood expansion, etc...) has pulled the harp *closer* to the soundboard and caused the crack to propagate from the bottom up... forces *up* at the ends, and down at the screw... crrraaaaccckkk...
Anyone with experience and expertise ("the answer") please also email me at "bear at bearlabs dot com" - TIA.