[pianotech] tightening the pressure bar

[ed440 at mindspring.com]

Slide a thin rule along the short string length that goes from the V-bar and under the pressure bar.
Ed Sutton

-----Original Message-----
>From: Gene Nelson <nelsong at intune88.com>
>Sent: Jul 30, 2011 1:41 PM
>To: pianotech at ptg.org
>Subject: Re: [pianotech] tightening the pressure bar
>
>Ron,
>I appreciate the detailed information - also, Isaac Sadigursky took the time
>to call me at home to tell me that the ideal angle was 7.5 degrees - thank
>you Isaac.
>Has anyone accurately measured this angle or must it be calculated? I could
>probably set in on a compass, compare and guess close enough.
>If I do this work it likely will be on my own time and I would be pleased to
>report back anything that I learn.
>Gene
>-----Original Message-----
>From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
>Of Ron Nossaman
>Sent: Friday, July 29, 2011 6:05 PM
>To: pianotech at ptg.org
>Subject: Re: [pianotech] tightening the pressure bar
>
>On 7/29/2011 6:56 PM, Gene Nelson wrote:
>> I am curious to hear your thoughts about tightening up the hold down
>> screws on an upright pressure bar – pulling the bar down to put more
>> pressure on the strings.
>>
>> That is; when do you decide to tighten and why – that is before you
>> experiment – before you tighten and just see what happens?
>>
>> Working on a 40’s vintage Wurlitzer 42” console I found it sharp from
>> the lo-tenor to the top and after 3 passes it still wanted to pull sharp
>> (likely a separate issue).
>
>Might well be related if the pressure bar friction is low enough.
>
>
>> It has semi loose tuning pins – the type where you could feel every tick
>> with the slightest movement of the tuning hammer and every tick produced
>> a noticeable pitch change – it was not easy to set the pins.
>>
>> Thinking that tightening the pressure bar could add some drag/friction
>> and help with this situation?
>
>It might help at that, but there are potential complications. The 
>danger, of course, is breaking screws. Restringing old uprights, I found 
>that when I put the pressure bar back on, I could have a fair amount of 
>tension on the strings and still turn the screws. Small increments, from 
>one end of the bar to the other, and I could chase the bar down to where 
>it originally was. The original position was obvious as the screws quit 
>turning when the threads met virgin maple. I presume the screws in your 
>Wurlitzer are already there, so driving them in farther becomes more 
>difficult and chancy.
>
>Also, some pianos have pressure bars bottomed out on plate mounds so the 
>factory elves can't clamp the strings between the pressure bar and the 
>plate. You might check that second.
>
>The first thing to check is the approximate counter bearing angle. If 
>it's already in the 15°+ range or so, lowering the bar probably won't 
>help much. If it's in the 5°-10° range, it might.
>
>If you decide on lowering the bar, and the screws resist turning in to 
>the point you worry about breakage ( you may have to lower tension 
>some), you can remove screws one at a time, check hole depth, and run a 
>longer heated screw down deeper into the hole than the original to 
>extend the threads. Put the original screw back in with a bit of soap or 
>wax on the end, and do the next one. Then CA the tuning pins. The 
>question is if the whole thing is worth the time and expense to learn if 
>it will help. If you can get it paid for, it's a good educational 
>experience, and you can enhance our education with a report afterward.  <G>
>
>Ron N
>