Not quite that straightforward. I always straighten the capstans on action rebuilds. I also use Renner parts and choose the square heel wippen to match. Angled capstans have more sliding on the wippen heel and have more friction and less efficiency.
You'll have to determine the capstan location in conjunction with the shank choice and hammer weight selection.
If you are keeping the same key leverage then the capstan should enter the key at a point directly below the original wippen contact point and perpendicular to the key (for a straight capstan). So it will not enter the key in the same spot as the angled capstan. If you do that you will change the leverage. That means that the hole for the straight calstan will enter the key slightly behind (distally) the original. Generally that means you can just fill the original hole with a west system epoxy and a light density filler and an injector. Overfill slightly (make the filller thick enough that it doesn't run all over the place but can still be injected), sand it flush with an orbital sander. The drill bit will enter the rear portion of the origianl hole but because of the angled original you will be drilling into wood. Use a cross vise mounted on your drill press for consistency and making small adjustments.
If you are altering the key ratio then you'll need a system to calculate that or make a small capstan boat to move around and test.
Whether you use wng anodized aluminum or brass is of no consequence in terms of weight. The staic weight difference is only about 1.5 grams at the key and the change in inertia between the two is barely measurable and of no consequence at all. I've had a few experiences where aluminum started to squeak so for now I'm sticking with brass. Plus with the black color I cant see the hole for regulating easily with a capstan wrench.
Your concern that “if not done right it will screw up the action” is probably overblown but you will want to get the action ratio right and so should make that determination with the new shank knuckle position and the new hammer weights in mind.
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David Love RPT
www.davidlovepianos.comdavidlovepianos@comcast.net415 407 8320
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Original Message:
Sent: 05-31-2018 22:13
From: Willem Blees
Subject: replacing capstans
I'm rebuilding a 1915 Steinway O. What I didn't notice when giving the estimate is that the capstans are the big octagonal ones, at an angle.
I want to change them out, but I've never done that before. To me it looks pretty straight forward. Remove the old ones, plug up the holes, and drill new holes for the new capstans.
Am I missing something very important that if it's not done right will totally screw up the action.
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Willem "Wim" Blees, RPT
Mililani, HI 96789
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