• 1.  B72 as capstans coating ?

    Posted 05-20-2023 22:36


    I'm presently polishing the capstans of a grand and I though it could be a doable thing to coat them after the job with a thin layer (low ratio) of the paraloid B72 stuff (used by many of us as hammer hardener). I don't know the final result about the friction but if it's low, it could be great to prevent oxydation/verdigris and wear of the capstans. What's your opinion ? 

    Thank you :)

    Bruce SATO

  • 2.  RE: B72 as capstans coating ?

    Posted 05-20-2023 23:13

    buy capstans from WN&G  the capstans do not wear out plus not sure what b72 will do to the whippen felt which will probably wear off any finish

    James Kelly
    Owner- Fur Elise Piano Service
    Pawleys Island SC
    (843) 325-4357

  • 3.  RE: B72 as capstans coating ?

    Registered Piano Technician
    Posted 05-21-2023 00:36
    The fact that you are polishing these capstans should be telling you something. If there was any appreciable sliding motion the capstans would already be polished. That they are not tells you that the interface between the capstan and the wippen's capstan block is near perfect and they are very nicely aligned along the so-called "magic circles"and there is virtually no sliding motion. (I worked this out once -- it's a very small fraction of a millimeter.) Hence it doesn't much matter what you do to the tops of the capstans. Polish them if it makes you feel better (and they certainly do look pretty), but it isn't going to change how the action performs. 


  • 4.  RE: B72 as capstans coating ?

    Posted 05-21-2023 10:29
    B-72 is too soft. You would want something hard like a metal lacquer or sandarac( which is what was used for metal finishes a hundred years ago).

  • 5.  RE: B72 as capstans coating ?

    Registered Piano Technician
    Posted 05-21-2023 12:06

    You might try CeraKote or switch to hard anodized capstans

    Parker Leigh
    Winchester VA
    (540) 722-3865

  • 6.  RE: B72 as capstans coating ?

    Posted 05-21-2023 12:13

    Thanks to all for your answers and comments!

    capstans polished

    Here are some pics showing the work in progress... Even if the difference in friction before and then is minimal I can clearly feel it's better, rubbing the finger tip or a q-tip on the capstan surface. The capstans are not sticky anymore. I think they were treated with an inapropriate lubricating stuff in the past (the piano is a 2009 kawai) causing some verdigris like deposit on the capst. and the weepen heel cloth (not shown in the pic and partially removed recently with protek clp).  Anyway the Flitz gaves back to them their stock beauty and smoothness :)

    Bruce SATO

  • 7.  RE: B72 as capstans coating ?

    Registered Piano Technician
    Posted 05-22-2023 09:59
    I remeber Bill Spurlock doing a test at a convention. He put sandpaper on the rep cushion felt , it made no difference in the numbers! I’m sure it was a well aligened action.

    Andrew J. Lyford, RPT
    Lyford Piano Works

  • 8.  RE: B72 as capstans coating ?

    Posted 05-23-2023 11:32

    I also remember Bill's class demo and have had the same results. 

    Regarding the lighter weight of the WNG capstans, I have not been convinced the time & money to install them outweighs their
    benefit, lovely as they are, black and stealthy and invisible as I look for the hole, and acknowledging they due indeed have some benefit. Perhaps if I didn't have to throw away the old ones.
    Of course, if you are moving the capstans your labor is a wash.
    I believe 4 grams is about the weight difference. If the total weight of the capstan is to include the weight of the whip and hammer assembly that it supports, 4 grams is about 4 percent plus or minus depending on where you are in the scale. 

    The weight  of the action  components can easily put over 100 grams on the capstan.
    4 grams could also be gained, or lost,  by only an approximate .4 gram reduction in hammer weight, most hammer/whip assemblies clock in at about an 1 to 11 ratio. Additionally, with your standard .5 key ratio, that 4 grams will only be 2 in FW.
    If your looking for just one thing to do to lighten touch, I wouldn't look here, as part of an action rebuild/redesign I usually clean up the old capstans, simply for aesthetics, then reinstall in their old or new location as required. As to inertia concerns, that additional 4 grams, just half way out the back of the key, moving up and down  5 mm or so, will not bother me in a well set up action. If your having inertia problems, it's not the capstan. A friend always told me, it's not the what it's the how, I'm more concerned with the location of the capstan, both fore and aft and height, than what it's made out of.
    My 2c

    Fenton Murray, RPT

  • 9.  RE: B72 as capstans coating ?

    Registered Piano Technician
    Posted 05-23-2023 12:44
      |   view attached

    Hi Fenton,  Glad to hear your comments.  Some back ground on the Aluminum Capstans.  I published the idea of hard anodized capstans in the October 1990 PTJournal. Thank you WNG for taking up the concept of producing capstans, key pins as well as other action components out of this durable low friction material and making them available for all.   I was looking for ways of lightening grand action components on the backside of the action and consulted with a machinist in Old Lyme Ct named Matthew Goldman about making capstans out of aluminum.  He suggested the process of hard anodizing and produced many sets of hard anodized aluminum capstans for me which I used on all my rebuilding work since those early years.  They take a high polish with white rouge which lasts forever.  So I've got a very long track record with this type of capstan.  I took this photo of two Hamburg Steinway heel felts after 20 years of use.  One sat on a hard anodized capstan and the other sat on a conventional brass capstan.  The contrast is pretty stunning.   So at the very least the hard anodized aluminum capstan is valuable for eliminating brass tarnishing and the resulting adulteration of the felt which reduces resiliency and produces more noise over time.  As you say they also reduce the front weight by about 2 grams which means less weight need to balance the keys.  It's not the same as just reducing 2 grams of FW because there is a reduction of weight on both sides of the key.  When changing out only the capstans pianists definitely notice the difference in weight.  As you say it's not a solution for a basic mismatch of ratio and hammer weight.  My original AL caps were light green in color and easier to see.  

    David Stanwood RPT
    Stanwood Piano Innovations Inc.
    West Tisbury MA
    (508) 693-1583

  • 10.  RE: B72 as capstans coating ?

    Posted 05-23-2023 16:00

    Mr. Stanwood, A pleasure indeed. Your articles beginning in about 1990 took 10 years for me to partially understand, afterwards I have not had a single action rebuild failure!!
    Also, a big thank you to WNG, for their investment in piano component design, and their sharing with the rebuilding community.
    Their capstan, of your design, is one of the many ingredients of a top rebuild recipe, I hear it touted as an elixir, often it seems with out real investigation into geometry, AR, Weight and Balance, etc. Hence my scoffing, also, I can be cheap.
    Again, thank you for your reply and clarification.

    Fenton Murray, RPT