>I'm curious what any of you have found/prefer/come to any conclusions about >when it comes to choosing between the two different Renner wippens on older >Steinways. Since I amd often changing the capstan, most of the time >relocating it anyway, the existing angle of the capstan isn't an issue. >I'm more wondering about general performance characteristics associated >with the difference between the regulated height of the capstan on each >(the straight heel usually ends up with a lower capstan profile) and >whether the straight heel offers any advantage due to it's relationship to >the arc scribed by the capstan in comparison with the angled heel. While I >have stretched strings to look at magic lines and such, the results of >these methods are inconclusive to me in terms of differences. > > >David Love David, I haven't done anything scientific, but I have done some playing around with this. My conclusion (if that's not too strong a term) is that what seems to matter is the magic line and the actual location of the capstan-wippen heel contact point on the key lever, and that straight or angled doesn't really matter. This conclusion is based on measuring DW and friction for various configurations. Part of the problem is that it's difficult to compare apples to apples. For a given action setup, if you put on a new Renner angled heel wippen and take some measurements, and then take that wippen off and put on a new straight heel wippen and take measurements, there will likely be differences in the numbers. But as you point out, the capstan will have to be a different height to accomodate the different wippens, which is changing the contact point relative to the magic line. Also, the capstan-wippen heel contact point distance from the key balance point is probably not the same for the two wippens because the angled heel ends up laying on a slightly different spot on the capstan than the straight heel does, so that leverage is going to be slightly different. I have to say that I find it difficult to look at installed parts and accurately determine the capstan-wippen heel contact point and to tell with any confidence whether it's on the magic line at half stroke. I have tried putting on a new wippen, checking the magic line, having it look like it's right on at half stroke, and then taking some measurements. Then cut the heel off that wippen, put on an identical heel that's been sanded down so that it's markedly shorter than the original, put it in the same spot on the wippen, adjust capstan for blow distance, and take measurements. Then gradually build up the height of the wippen heel with 1 mm shims, taking measurements at every increase in wippen heel ht. The point where I get the min friction I'm assuming is the point that's truly on the magic line. That height doesn't necessarily end up being the same height as the original wippen heel, which appeared to me to be on the magic line when checked with a string. I've also tried putting on both a straight heel and an angled heel and moving them back and forth along the wippen and taking measurements. In theory, the leverage should be determined by the location of the capstan. However, since the wippen cushion is not flat on the bottom, as you move it along the wippen the position of the 'hump' relative to the capstan changes, altering the contact point slightly, which is changing the leverage slightly, which will affect at least the starting DW. For a given capstan location and angle (I've tried straight up, angled a bit, and angled a lot - but no so much that the corner of the capstan is digging into the cushion) I've found that by playing with heel height and location I can get the numbers to come out the same for an angled heel or a straight heel (call the configurations where the numbers are the same the 'optimized' configuration). However, that's not to say that the straight heel optimized configuration I end up with in terms of heel location and height, or the angled heel optimized configuration I end up with in terms of heel location and height, look like their respective standard wippen right out of the box. I think either standard wippen (straight heel or angled) will rarely match this optimized wippen. Which one will come closer I think will just depend on how those wippens interact with the particular capstan location and height you end up with, in terms of contact point and magic line, and I don't really think you can predict that beforehand. It's also not always the case that an angled wippen heel will work better with an angled capstan, and a straight heel with a vertical capstan, although that usually seems to be the case in my experience. I think you just have to try a sample of each one and see. Phil Phillip Ford Piano Service and Restoration San Francisco, CA
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