Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Problematic hammer alignment in bass section of old upright

Mark,

Thanks for the pics!

It appears that the bass bridge might have been re-attached to the apron. Notice the screws coming in from the top side of the bridge.

Also, notice that the lower edge of the bridge does not follow the bottom of the apron. (Edit: Also notice the gap between the bottom edge of the bass bridge and the edge of the apron.) It appears that the bridge may be misaligned. Or, maybe a new bb sometime over the piano's life that wasn't made correctly.

Joe,

On this piano, coming from this technician, nothing would surprise me anymore. I've wondered whether those screws could be original... and in fact, I think they are!

There are also a lot of screws going through the soundboard and into the ribs.
[EDIT: you can just make out some of the screw heads in this
Picture, just to the right of the highest bass strings.]
They look as though they were installed before finishing the soundboard, and the soundboard finish is definitely original. I have read that many German piano manufacturers made "tropenfeste Klaviere" (perhaps translated best as "tropic-proofed pianos") for certain export markets. And indeed, my old piano is actually called "Otto Bach", which was Zimmermann's export line destined for (South) Africa. Hence, it could well be that those screws in the soundboard and bridges are in fact original.

The strings, dead and dirty as they are, are original, I'm pretty sure of that. Somehow I doubt that someone would fit a new bass bridge but put those terrible old strings back. This would also indicate that the bridge attachment is original.

Nevertheless, the misaligment that you pointed out between the lower edge of the apron and the bass bridge intrigues me! I hadn't noticed this consciously. I'll have a closer look, perhaps shoot some more pics, and report back.

By the way, there are lots of original technicians' inscriptions and dates on various parts of this piano. With any luck, I might be able to date the bass bridge as original or replaced.

Be that as it may, Joe, even if the bridge had shifted slightly, do you really think this could account for a 2-3 mm lateral shift right up at the strikepoint? This would imply a much greater lateral shift, perhaps three times this amount, at the bridge!

Mark:

While we have our detective caps on, I wonder if the original hammers were thinner, and the replacements had to be pointed more to the right for clearance between them.

Regardless, I would bend the bottom of the shanks and shape the hammers for clearance if needed.

No Mark, I don't. Not based on the pics you posted.

If I notice misaligned hammers in only the bass section while servicing a piano, the first thing I check for is a failed bass bridge or apron. While the bass bridge on your piano is mounted strangely, it's not enough to account for 3mm error in hammer alignment.

Mark

The bass hammers in picture 6 of your Picasa album appear shorter, as expected, but all the felts seem to line up rather than the tails of the moldings:



Is this an optical illusion or the root of the problem?

Ian

Jeff:

Interesting idea. I do have six original hammers, albeit from the very top treble (partially visible in the picture Ian has shown here), because in Zimmermann's tradition, these carried the serial number and the tech/seller gave them to me as "pedigree proof". FWIW, I'll compare their width to the replacements.

Joe:
If you're interested, here are some more detailed pictures of the bridge and apron. Based on them, I don't believe that the bridge has shifted - and if it did, only minimally. It may, however, be a replacement bridge that was mounted somewhat strangely on the apron: closer to the pinblock. Also, the lower edge of the apron isn't varnished... Judging by the dust, cracks, hide glue residues and pins, however, the whole set-up looks original to me. I've added captions in the Picasa album.
Click here, then navigate through the next 4 pictures using the album arrows.

Also, I did notice a hairline crack in the apron, but nothing appears to have shifted or become unglued.

Admittedly, 3 mm misalignment only applied to the worst notes. On average, it was perhaps 2 mm, typically hitting the left string of bichords close to (or on) the left edge of the hammer when the flange was turned counterclockwise as far as it would reasonably go.

Ian:
It's an optical illusion in the sense that without using the zoom, the white felts tend to meld into one another. Here's a detailed crop:
Hammer line
Remember also that what you see depends on your viewing angle (like most everything in life...): the picture was taken looking diagonally down into the piano, roughly at right angles to the hass hammer felts. The bass hammers weren't evenly spaced when I took that picture in the seller's workshop. Hence, viewed from this angle, some tails appear to protrude further up. (Turning the flange clockwise shifts the hammer right, i.e. looking at this angle, it would appear further down; turning it counterclockwise shifts it left, i.e. looking at this angle it would appear further up. If one looks from the front, perpendicularly down at the bass hammers, the tails are in fact more or less all in one line, being held so by the hammer rail felt.

One exception was hammer no. 11. It was glued too high on the shank. You can see this in the picture (11th from the right.) I've re-glued this.

All:
I plucked up my courage last night, first re-seated all all the flange grooves in the action rail bead, then turned the flanges counterclockwise as far as the would reasonably go without unseating the groove, then heated and bent the shanks left, sometimes in two or three operations, also twisted the shanks where necessary to keep the heads parallel. This has largely corrected the mating, although the hammers are facing perhaps 2° left when striking the strings (checked this with a business card corner). One or two are still rubbing, but I'll sort them out too. I think this is the best compromise I can achieve for now.

Thanks for all the detective work and feedback.

Mark:

I think I know the problem, and it isn’t pretty. Ian’s post with one of your pictures tells the story.

The bore distance (from the strike point to the shank) on the bass hammers is incorrect. It is the same as the treble hammers. It should be much less to account for the plane that the bass strings are in. Ian is correct. The tails of the moldings should line up, not the strike points.

I don’t want to think about what was done to make the piano playable with this shallow blow distance in the bass. I am guessing the re-whatever-er bored the hammers himself and did not change the bore distance for the bass. I suppose you could remove the hammers, plug the holes and start over. You want to learn the trade, right?

This picture shows a correct hammer line:

Jeff:

Hang on, hang on. Things are not as bad. (But for a moment there, you gave me a good fright... )

1) What appears as a meeting of bass and treble strike point lines (in the picture Ian quoted) is mostly an optical illusion, to do with the camera position. Your picture was taken looking down perpendicularly at the hammer moldings, i.e. your camera was well in front of the action. Mine wasn't! It was directly (vertically) over the hammers. Think about it for a moment. You'll see that relative to the damper screws, at the tenor break, where the longer shanks are sitting, the hammer line appears to go back (away from the pinblock), and moving down the bass from C3 towards A0, it appears to come towards the camera (pinblock) again. That's at least partly because the camera is overhead, or even slightly closer to the pinblock than the hammers. It's also, in part, because...

2) The re-whatever-er had set his version of a "hammer line" using the capstans (negative lost motion). Once I slacked that off, using the hammer rail for a hammer line, things already looked better and more even.

3) The resulting blow distance, after introducing minimal lost motion, was generally too long (I wrote about that last year, enquiring about hammer rail shims), but generally, was not all that bad:
48 mm in high treble, increasing to...
50 mm at treble break (because the V-bar is actually slightly curved, being 2 mm closer to the pinblock at the treble break - don't ask me why, but I checked it with taut fish-line - I also wrote about this last year), decreasing back to...
48 mm at the treble side of the tenor break, changing to
46-47 mm in most of the bass, and...
44-45 mm only in the very lowest 4 or 5 notes, because of a bent hammer rail where the trapwork spoon is attached.
So, although the bass hammers aren't bored perfectly (about 2 mm too short [EDIT: too long]), they're not "wildly" incorrect either. I think the tech did this to get the bass and treble moldings to line up. Anyway, I've also read that a slightly shorter blow distance in the bass is actually quite common, because the bass hammers are often not quite short enough. This appears to be the case here. My Ibach, for example, does the same thing.

4) I re-felted the hammer rail recently, took out old shims, straightend it as best I could, and reduced the average blow by about 2.5 mm, by removing wood from the vertical end blocks where the rail is attached to the two action posts. Before, there was bobbling because of insufficient aftertouch - in spite of a full 10 mm key dip and minimal lost motion. In fact, to obtain lost motion with the original hammer rail, many capstans had to be screwed down so far that the threaded wire was protruding into the holes, blocking my awl. This is now much improved.

5) I still need to do fine adjustments for the bent V-bar in the treble break, using felt shims under the hammer rest cloth, but in principle, the blow is fine except for the lowest few hammers. I'm considering to try and straighten the rail by heating and bending it - not sure about that, though.

Whew! Sorry about the long text - just wanted to explain what's going on.

But yes, I do want to learn the trade.

Mark:

Sorry about my confusion. If the picture was taken without the shanks on the rest rail, then the hammer line doesn't mean anything. And sorry that I did not remember all the details you have posted in the past. The blow distances are reasonable and that is the important thing.

Ian:

Only after Jeff's post do I realise what you were actually asking. I had misunderstood you. I thought you were referring to inconsistencies amongst the bass hammers themselves, i.e. from one to the next.

Anyway, see my answer to Jeff.

I'll try to take a pic of the hammer line, from an angle like Jeff's picture, to put worried minds at ease.

Mark,

Thank you for the additional shots of the bass bridge. Unfortunately, they leave me with more questions than answers.

If the damper alignment in the bass section is OK, then you probably do not have a string alignment issue. Of course, this doesn't prove that the string alignment is OK; someone could have come along later and adjusted the dampers. But, it is telling if the dampers are also out of whack. The odds are that if the dampers are OK and the bass bridge alignment from left to right is OK, then the string alignment, in your case, is probably OK... IMO.

You are going to have to change your signature... soon. You hardly seem like a "Beginner Technician."

Mark:

Yes, I should have allowed for the gap between the bass and middle hammer banks.

Have you seen the Abel Hammer Katalog which shows the difference in total length between treble and bass hammers for a variety of German pianos? Most bass hammers are 8mm shorter and one might guess that's what they should be on your Zimmermann.

Congratulations on your progress!


Ian

Ian: no, I haven't looked at that catalogue. I'll check the difference in string height in my Zimmermann.

Joe: I'd be very interested in the extra questions you have about the bass bridge - if you'd prefer, you're welcome to send them by PM...

If this piano starts to sound, look and feel the way that I would like it to, AND my work gets a thumbs-up from a local (RPT-trained) technician, then I'll consider changing my signature!

Thanks for the support.

Hi Mark,

Thanks for letting me ask some more questions

1) It appears that the apron is finished above the bridge. Is the apron finished in the section below the bridge as well? If so, does it appear to be the same finish?

2) Since Zimmerman was exporting to S. Africa years ago, have you seen a similar bridge configuration on other Zimmermans? Other tropicalized pianos?

Thanks,
-Joe

Crappy hammers...Sets of hammers bought in bulk by S.A. technicians that haven't a bother for correct bore depth or distance.

I've seen this all too often in S.A.
Companies go for the cheaper option of buying 10 os 20 sets of hammers off the shelf with "general" dimentions for all modern pianos.


Having an older, more precise piano as yours is, replacing the hammers should have been a calculated affair. Samples should have been sent to a hammer manufacturer and exact replicas made with bore depth and angle and distance to be taken into consideration, but that would have meant a higher cost of the hammers.
I guess that if the hammers were planned and made to spec, they would have gone on beautifully by the hand of even an apprentice tech.

The Zimmermans that I've encountered here in S.A. of your age piano, are well made and allignment problems are rare. That is a good piano! 1915-1935, I,ve found to be good years for German piano manufacture and yours does fit into that category.

It would seem that from your discussions of your piano, that it has been "restored" in good old S.A. fashion....Do the bare minimum at the lowest cost to sell the damn piano.


And I've seen a hammer on Marks Piano in the flesh... Chinese mass produced and off the shelf bought in bulk happy-go-lucky set. No offence Mark!

I think you're doing great with what you have.

Joe:
Apologies for responding only now. I was at a choir music festival the weekend, playing tuba in a small guest ensemble. (A very nice Chinese tuba that was lent to me, by the way, made by Dalyan.) To get back to your questions:
1) Apron finishing:
Somewhere in my earlier posts (or in my Picasa album comments) I think I actually wrote about the apron finish. To elaborate somewhat: the "bearing surface" of the apron, i.e. the surface carrying the bridge, is not finished below the bridge. But the lower edge, facing the bottom board, is partially finished - especially the corner that faces the soundboard. It appears to be the same finish as the rest. You can see what I mean in this picture, where the string braid ends:
Partially finished lower edge of apron
Whether this is an original oversight, or a previous repair, I can't say. But judging from the appearance of the upper part of the apron, I'd say it's original.
2) Other Zimmermann "Otto Bach" pianos:
Unfortunately, I haven't inspected other "Otto Bach" Zimmermanns from this era. The technician who sold me the Seiler and then exchanged it for this Otto Bach, had another Otto Bach in his workshop, as yet un-"restored", so I didn't really have any reason to inspect it in detail. So, I can't say whether the bridge configuration and tropicalization on my piano was Zimmermann's standard procedure or not.

Brendan:
No offence taken at all. To the contrary: you confirm everything I've been told by previous technicians who've seen the piano:
"Do the bare minimum at the lowest cost to sell the damn piano."
That's exactly the point. The keytops, for example, tell the same story. Rather than filing the recesses for the sharp keys, just bang the balance rail pins of the sharps towards the pinblock, until the keys "fit". And rather than sanding all white keys level, and to the right thickness, before fitting the new keytops, just slap the keytops on, then bang the balance rail pins left and right, until the keytops appear even... and then put umpteens of shims underneath the sharps balance rail pins...
I'm just sorry that I didn't know in 2009 what I know now... But as they say: experience is the sum of all mistakes made up to date.
I'll be in touch with you (Brendan) about the hammers and all the rest. It's the sound I'm most worried about.

Ian and Jeff:
I tried to write earlier that the appearance of the hammer line depends on the angle from which you look at it. That may have come across somewhat muddled. Here are two pictures to show what I meant by that statement:
Looking from the front and top, i.e. more or less at right angles to the hammer moldings, it looks like this:

But looking vertically down, from directly overhead the hammers, it looks like this:

[Edit: Or even better, click on this link, then use the arrows above the picture to toggle back and forth between this picture and the next one in the album.]
In the first picture you can see that the hammer line is not too bad. Bass hammer strike points are definitely not in one line with the tenor/treble. The second picture, because of the incorrect camera angle, makes the blow distance of the bass hammers appear shorter than it actually is. The strike points appear to be almost in one line with the tenor/treble.

Mark:

Thanks for the extra photos. I've tried to estimate the length of the bass hammers relative to the others by counting pixels on screen. There doesn't seem to be much difference but I'm sure you've measured them anyway. Over to Brendan!

Ian

Ian,

I've not measured them, but that's easy enough to do. On the full-size original picture, the bass hammers are 126 pixels tall, while the tenor/treble ones are 136 pixels. At an estimated treble hammer length of perhaps 65 mm, that ratio of 10/136 comes to about 5 mm difference in length. Admittedly, that's less than the 8 mm you mentioned, but they are definitely shorter. And like Jeff wrote, the blow distance also depends on where exactly they were bored. I'll check this out when I'm next at the piano.

Mark,

A couple of somewhat obvious questions underlying my "Over to Brendan".

If the length of the hammers and/or boring are responsible for the 2mm to 3mm discrepancies in hammer/string alignment which started this thread:

1. What should the blow distance be on a Zimmermann? Can Brendan or owners and their technicians help?

2. If necessary and desirable - i.e. the hammers would produce a better sound - is it possible/practical to fill the holes and re-bore them to correct the geometry?

Ian

Ian,

Here are the measurements, just for "good measure".

Treble hammers: 73 mm
Bass hammers: 68 mm
Distance from tail to shank for ALL hammers: 4 mm
Resulting difference in blow distance: 5 mm (as calculated from photo pixels)
Distance between bass string plane and treble string plane along the strike line**: Just under 5 mm.

** Note: the two string planes are not parallel. At the point where the highest bass string crosses the treble bridge, the distance between the strings is 17 mm. In contrast, measured close to the V-bar, the distance is almost zero. So the bass string plane is leaning towards the pinblock. Also, as I wrote earlier, my treble string "plane" is not really a plane. The V-bar is recessed by about 3 mm at the treble break.

It actually appears as though the hammer geometry is quite appropriate for this piano, but possibly the bass hammers have been glued too high on the shanks.