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Isaac:

Don't mistake Jim for someone else we both know who is a bit of a dragon. I know Jim, and he's a creampuff. He is a nice guy.
Smart too. Not a bad combination.

Will

Thanks Jim for both the pictures of your layout, and your explanation.

It cannot be round if bored with an angle. In any case. But the second punching is prepping the centering and the orientation, then certainly a small gig may ensure more consistency.

I just learned that the pins have to be lightly tapped after stringing, and also the bridge is designed with the small imprints of the strings taken in account, that will determine the location of the pin.
When I see how strong the strings where or are massaged at the factory, I would not be surprised than part of the final indentation of the cap is yet installed immediately at stringing time.

About tone clarity, without voicing much is expected, with voicing the piano is way more forgiving.

The energy raise obtained with voicing tend to drive the tone more, and light defects are hidden.
False beats are not a common problem, in my case. I don't dismiss their existence and more with bad constructions but I can get rid of them, most often.

I just provided him all my personal translation of the German design books, Klauss Fenner, Ulrich Laible , Bluethner, without a thank you nor any comment, constructive or not.
A good guy that want to discover all by himself.
That is, some are of course agressive and not listening at all, but that lack of curiosity for the German masters is astonishing (yes I know they loose the war..).

You cannot on one side praise the European piano building as a good example and on the other dismiss what was written.
At last a critical reading would allow to add something.
But no, soundboard are good without inner stress to lighten them, and others the tone exigence quality seem to be so different, may be in the end those books where of no interest in the end!

Regards

Out of curiosity: do rebuilders have any strong opinions on how the side-bearing of the strings should be set/calculated? Like down bearing, I find modern day side-bearing to be generally excessive. Do you care about bridge pin size, and/or the height of the pin above the bridge?

interested in the minimum side bearing that allows complete termination, but not sure what that minimum is

experimenting with Ed Mcmorrow's protocol here, # 6 pins quite tightly spaced front to back high treble,10mm graduating to 12mm around #69. #6 well down the long bridge, transitioning to #7 for wrapped tri chords or bi-chords bottom of long bridge. #8 hi bass, #9 monochords. I think Ed may be doing this a bit differently, but that's what I've done so far...pending results


don't care

Jim Ialeggio

I'm going to assume that the tight spacing front to back is to give more side bearing in the top section, and that is where we most often see the least amount of side bearing angle (and sometimes too little).

Is the use of the smaller bridge pin sizes to give a sharper bend of the wire at the bridge pin, and perhaps a more defined termination?

Will

Actually on this, I'm relying on Ed's empirical evidence for now, and seeing what happens. I have not been happy with the impedance model for the top capo section and this has inspired me to purchase a 1 piano license from Ed to do a test of his Fully Tempered Duplex Scale according to portions of his patent application.

My sense is that the high treble is mostly about the terminations, and I think he has a good line on what's going on up there. The explanations regarding the L modes are an unproved hypothesis at this point, but whether his explanation is correct or not, his empirical evidence says to me he's on to something up there, and I'm going with it to see where it goes.

Add to that, as I travel around to service calls, I have noticed, even here in New England piano heck, that though the mid trebles and their boards are dead in tired New England grands,and the bass is always without any musical sustain, though the high treble is beat, bridges hurting, etc, given some time with the hammers I routinely can find possibilities up there by dealing with other than soundboard related issues. I would really like to just do some seious bridge work, hammer work, and strike point work up there on a beat grand and see just how much can still be had out of a dead belly's high treble. The reiterate, I'm referring to the top capo section in particular, not the rest of the belly.

So anyway, the tight spacing is on Ed's advice...as far as side bearing, no, for me, its not, about increasing side bearing. My layout jigs are producing consistent 13 deg angles through the entire compass.

Smaller bridge pins are about reducing bridge weight.

Its all an experiment which, from what I can hear right now in this belly is going to work nicely...I will not know for sure until the fat lady sings, and I get the action done sometime late in august.

Jim Ialeggio

Have you ever experimented with what a 12 deg angle feel like when tuning, or 11, 10, 9, etc.? When the combined down-bearing and side-bearing angles are too extreme, I immediately know it when I am tuning: the string movement is not as smooth and it requires more rendering (aka banging) to equalise the madness. Does anyone know what the sound/feel problem is when there is not enough? What observations tell us there is not enough? I'm not sure I know this problem through experience...

The first set of these layout jigs which I used on a different piano, were targeting 10 deg, but ended up, with drill bit entry drift at 7 deg. Bass, tenor, 1st capo were fine, actually singing quite nicely, great sustain, no noise. However the top capo section, which for me is where I'm really working these questions, was a chorus of false beats which I could not cure. They quieted down with a good tuning, but they were still there and pissed me off.

I'm not quite sure its fair to finger the 7 deg angle as the culprit, but I'm gun shy right now. At least until cause and effect of recalcitrant falseness becomes clearer. The current belly with 13 deg angle, much more precise drilling, and epoxy lam cap is miles better than this 7 deg patient regarding falseness.

By the way, I have always endeavored to string as you describe in your earlier thread with the pic above in this thread, and re-stringing has not improved recalitrant beating, at least in the case I described above. Sometimes its hard to read where the natural curve will end up, but often it lays down correctly. So I'm interested in why your results are conclusive and mine are not. This is not a challenge, but rather an attempt to understand.

Jim Ialeggio

One reason I decided to try a piano with reduced distance between the front and back row of bridge pins was to increase the holding power of the pins without increasing the side forces. Since the stagger offset string angle is kept the same-having the string segment shorter between them increases the apparent stiffness of the termination due to the stiff nature of piano wire. I believe it makes it harder for the speaking length to "vibrate" the string segment on the top of the bridge. Of course any motion of this segment that is separate from the bridge motion is bad.

Also, since I use the copper plated pins, the string is able to indent the plating and this also helps hold the string from climbing the pin.

Another reason is to keep the neighboring rows of pins as far away from each other as is practicable.

My FTDS implemented in the way my license requires, produces a high treble tone that is very, very good. Better I think than any piano that has ever been made. Upon hearing how clear, dynamic and full the tone is, you may start to think about adding notes above 88.

I have done a couple of bridges where the side bearing stagger angle of the strings was low. These pianos are more difficult to get the string to stay exactly in perfect tune when hit very hard. They just keep "wandering" a very slight bit. More false beats too.

Finding just the right balance betwixt makes all the difference. Conversely, one maker of a lesser Korean grand of the day, 4'6" I think, had a penchant for adding way too much side bearing at the bass bridge. Perhaps to help stabilize the tuning of an inherently unstable design? or just sloppy work? After only a few years ruptured bass bridges were not altogether unknown. Seemed like an eternity to get a new bridge shipped from Asia. An unexpected surprise: when we installed the new bridge with proper side bearing we expected a trade-off manifested in a lack of tuning stability. That didn't happen. It tuned up just fine. And so, maybe it was just sloppy work after all.

Jim, here is another question:

Kudos to you for the great care that you are taking to make sure the bridge pin holes are centered and drilled straight. As you have described it, I see no reason why you would not have greater consistency and less likelihood to abuse the hole in the act of drilling, and achieve a better result.

We all drive the bridge pins in by hand using a punch and a hammer. With approximately 500 pins to drive in, the opportunity to have an off target blow with the hammer is there. I certainly have, and sometimes I have even bent the smaller bridge pins. I may be clumsier than the average bear, but I suspect we all have done this at one time or another.

That misplaced blow can distort the top of the hole, making otherwise careful work for naught. What are you doing to minimize this? Have you created a dedicated arbor press to push the pins in to depth, since you are doing your bridge work outside of the piano?

Will

I do this by hand...early in my career, as a site finish carpenter, I was known far and wide to have the worst hammer aim this side of Spokane. So I feel your pain...literally...ouch

I do have a dedicated series of brass punches I made, which allow you to insert the various size pins snuggly into the punch to accurately start the pin at the appropriate angle, and drive it most of the way...errant hammer strikes are well removed from the top of the cap. I also place a smaller size pin in adjacent holes to help me eyeball the actual angle that I want to start the new pin at.

But no, no press. And yes I have bent a #6 pin ...arghh...cludgers unite!

I'm not sure a press would help, because aligning a press shaft travel to the precise angle of the already drilled hole would be very difficult to pull off. A CNC where a rotating multi tool head drills then inserts at the same position, would be ideal. As I mentioned before, in field service, I routinely notice how clean sounding machine pinned laminated caps are, even if the instrument is cheap. They have plenty of other issues but falseness often isn't one of them.

I don't know what the actual physics of this is, but my sense is that a #6 pin is exerting less distortional force on a hole than a large pin, particularly if the pin is started off coarse. Can any material science guys out there address this?

Jim Ialeggio

The quarter-sawn maple bridge cap has a certain elasticity. So it can tolerate a certain amount of mis-directed hammer force without compromising the tightness of the hole on the pin. The highly laminated caps would actually have less of this. So they would require a higher degree of pin driving accuracy. I use a regular nail set to install the pin after I start it in the hole with the hammer alone. I do bend a #6 pin or two, at the start-I just pull it out and stick in a new pin. Very slight vertical bending can be done after driving in to further align the pins or remove any slight bending the driving produced.

And another cludger comes out of the closet.....

Are some of the laminated caps densified in the glue up process? (such as a falconwood block would be). Otherwise I don't see that laminating the piece would make its external surface any harder, if it is made of the same materials (rock maple)

Will

How tight a fit are people striving for with the bridge pins? What observations do you use to ascertain if the fit is too tight/loose? Any follow-up hand reaming, or just machine drilling?

For those that prefer a tighter bridge-pin fit, one can freeze the pins beforehand to temporary reduce their size upon installation. It helps prevent excess friction and accidental bendings, but it also allows for a more consistent and tighter fit of the pins.

Freezing also works well with the installation of tuning pins and consistency/feel of hammer at the pin.

If you can pull the pin out without making definite dents in the pin from the pliers-it is loose. But many pianos have pins that loose and they can sound quite clean regarding false beats. But the piano has to start out tight or they get too loose for good tone in a few years.

A little from Fenner :
t remains to say something about the bridge pins. If possible, the pins thickness should not be less than 2.3 mm in the treble, which is sufficient even in the medium range. For small little piano, equipped with the above mentioned reduced Bass bridge, this strength is enough there, too.
For larger instruments with strong core wire and heavy bars bridge pins are thicker in the bass of course as required.
Some manufacturers use bridge pins made of brass, which looks nice at first.
It is well remembered that in countries with a humid climate, these pins can not rust . But they can corrode, and this is much worse. Experiences, for example, from England confirm this dilemma. It must be remembered, too, that brass pins with the same dimensions are less stable than iron pins.
Also, pins made of stainless steel, as used in needle roller bearings have been sometimes already used.
This promises to advantages, especially when these pins are harder than usual from ordinary iron. There are, however, not been enough experience with the use of such bridge pins before to assess what the results can be.