Underlever height would be 1.5" from the key bed if it were a S&S whose key end felt usually is 1 3/8" at rest. That is, if the back rail or key end felt has not been altered unknowingly. Damper lift is ~1/4", making it ~1 3/4" from the key bed for a S&S (not counting excessive key dip as a result of poor action geometry).
Now to further complicate the issue. Have you noticed a through dug into the key end felt on some pianos? This is caused by the underlever (u/l) scrubbing on the felt, a consequence of the angle of the u/l being too great. I contend that the key should lift the u/l to parallel to the key bed, thus producing the least amount of friction caused by the forward, sliding motion of the end of the u/l. Lifting beyond parallel reintroduces the sliding motion at the end of the key stroke which will wear the rear corner of the felt. **
To correct this, measure the height of the key end felt with the front of the key full depressed. Lift the u/l to that height and notice the angle between the u/l and key bed. If the u/l is still sloping towards the front, you have sliding friction. Lift the u/l to parallel and measure. The difference between the two measurements is the amount the tray pivot has to move for the u/l to be parallel. I find generally it's 1/4". The pianist will notice the loss of friction. Photos on request but may already be in the archives.
If the dampers are lifting early which might be the reason for adjusting, then you might get a two-fer by lowering the tray pivot. You don't need to remove the dampers, just the pivot blocks. If the amount to relocate the pivot hole brings it too close to the original hole; I cut a 1/4" plug from the lower portion of the block. Before you drill everything out, map out the new location for the hole to be drilled once the plug is installed and trimmed. Simply reinstall the blocks. Now, if you're lucky, the damper timing will be delayed to the proper height because the fronts of the u/l's are a bit higher now that you lowered the pivot point; the u/l being suspended by the damper wire at the top flange causes the front to rise as the rear is lowered.
On one asian make recently, I rose the aluminum rail tray support system 6~8 mm for lifting to parallel, the spoons required minor tweaking. Same theory, reduce sliding motion.
** Add to the problem: rough bottom surface of the u/l and the 'sharp' front corner. I sand smooth if the system is removed, eased if not.
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Regards,
Jon Page
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Original Message:
Sent: 02-24-2018 19:01
From: Thomas Black
Subject: Under lever height
Thank all of you again for responding. When my best ole buddy RPT told me WNG required 1 1/2" from keybed to underlever, I thought there may be readily available measurements on other pianos I wasn't aware of. I thought ya'll may have known something I didn't know about that particular measurement. I'm still trying to learn and must thank particularly Jon for sharing some new info with me on that subject. Thank all of you.
Sent from my iPhone
Original Message------
Another method is to measure the height of the key end felt at rest and add 3 mm. Replace action to verify.
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Regards,
Jon Page
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