Piano World Home Page Forums Our Most Popular Forums Piano Tuner-Technicians Forum Grand Pianos w/Ribs on Top of Soundboard, instead of back

Del, do you recall the purpose of the "rib-like" strip of spruce atop the SD10 soundboard? I have forgotten.

It is not really a rib. It covers a joint in the soundboard. The SD-10 used a soundboard cutoff bar. To make gluing the edge of the soundboard to that cutoff bar easier and more reliable the board was cut so it could be clamped more securely to the bar. Then the remaining small triangle portion was glued in and the joint was covered by a thin maple wood strip.

Next time you're sitting in front of one of these pianos follow that strip to the front edge of the board and look down just below the damper guide rail. You'll see a slight gap in the edge of the board.

ddf

Wholly aesthetic, then. Thanks, Del.

As promised, here's another photo showing the top-ribs on the Bauer 6' grand, this time with all the wires & dampers removed for a better view:



This Bauer's design continues to present surprises. As you can see, the plate is a "full-perimeter" plate. The outer edge of the plate is not just a thin perimeter that sits on top of the soundboard dowels. The outer rim of the plate is a 6" deep "wall" of cast iron, bolted to the rim all around, as well as bolted down to the board.

I removed all the strings, dampers, and all the plate bolts visible from the top, to allow me to lift the plate up & off the board and out of the piano. But it wouldn't budge. Even lifting with my crane & hook, it just wanted to lift the whole cabinet up with it, as if it was stuck or there was one bolt I missed still holding it down. Turns out there were quite a few bolts still screwed in...under the soundboard.

That 6" vertical wall of iron that forms the outer rim of the plate, has "tabs" on the bottom, small extensions in the plate's casting for a dozen bolts to screw the plate to the cabinet perimeter just under the soundboard:



In 4 decades of rebuilding, never seen anything like it!

What an awesome project! I can't wait to see some finished pics.....that plate must be massive....rather ingenious design.

Several differences I see right off:

In my 9' JB there were relatively low laminated maple strips in the shape of the bridges glued to the soundboard with cutouts for the ribs. The actual bridges were [s][/s]mounted on dowels that were fitted into holes drilled into the top of this strip and the bottom of the bridges. In the treble the bridge was probably 50 to 60 mm tall By the time it got to the low tenor it was more like 140 or 150 mm. The bass was even taller.

The ribs underneath the soundboard panel were not quite as deep as those in your picture.

Does the piano have JB's "adjustable crown" feature?

ddf

Del, I've been unable to find any patents/diagrams in a Google search for "Julius Bauer" or "Bauer adjustable soundboard" or anything like that. The closest I've come is a patent by F. B. Long for an upright soundboard with adjuster on each corner: https://www.google.com/patents/US93...AbADVIz1A5CsogT5mYAY&ved=0CDIQ6AEwAw

So if you can post the actual link to the patent diagrams you saw for J. Bauer, that would be great.

Meantime, I not seeing any extra adjustment devices on this Bauer. And yes, the bridges have notches cut to accommodate fitting over the ribs, but the bridges appear to be one piece, plus a cap. A bit of a pain actually, as my bass bridge has enough thin diagonal cracks running right through the bridge-pin lines, to make it borderline as to repairing the existing bridge cap or needing recapping. I've never done my own bridge recapping, always sent it out to Schaff's bridge-maker. But with the notch-outs across the bottom, I don't know if he can match this.

The only patents I know of that were issued to Bauer listed "William M. Bauer" as the inventor. I'm not sure that particular feature was patented by Bauer, however. I thought I remembered it being described in one of his patents but I'd have to go back and read through them to be sure. When I have the time....

Edit: Yes, that was it. Search Google patents for US 1171921 A. <http://www.google.com/patents/US1171921>

ddf

I just want to say that those pictures represent one of the most sexy piano designs I've seen in a very long time. There are sooooooooooooooo many things "right" with that design. Modern manufactures would be wise to take serious note!

Freelife, when you took the plate out, was it distorted at all from the internal tension like some pianos, or was it pretty much flat? From here, it appears the design is really well balanced: I imagine it was probably pretty straight/flat if it were to theoretically be laid flat on the floor?

That looks like an interesting design.

What theoretical books say is that the ribbing is intended to install stress within the panel. (stress under the panel, between ribs and the underside of it, and stress on the outside, due to crowned shape.


this is somehow destructive to the panel itself with decades most probably

As we cannot know how where glued those ones it is very difficult to imagine.

Thanks for sharing that.

It was something that was already invented in the early 1800's and used in some french pianos.

http://www.palacepianos.com/en/uploads/pianos/1288966680_jean-henri-pape-grand-4188-4.jpg is one example

I think the idea being that it would resist the down bearing of the strings better.

but it's ugly-looking

The concept of the set screw to adjust crown seems okay, but looking at the patent drawings, I wonder about the execution. I'd love to see the actual product.



It looks to me that turning the set screw (16) would necessarily cause the screw (13) that fixes the soundboard (10) to outer strip (12) to tilt away from the setscrew as the outer strip moves inwards to increase crown. Either the screw will bend or it will unseat at the head slightly in the inset (into cast iron!). I'm guessing bend. If the screw were flat-head, with washers, and that hole slotted slightly to allow the inward movement caused by that set screw, no problem. I realize the amount of movement would be very slight to yield the crown, but that movement has to be accommodated somewhere and an inset screw of that type would seem to only allow the movement to occur with bending of the screw or tilting it out of the inset on one side at the head.

Also, what about the stresses on glue joints where (10), (11), and (12) meet, and what about compression deformation of 11 where it meets the flange when the induced tilt (if it can't slide as in a slotted screw hole) of (10), since one would assume this flange-to-strip joint by necessity is initially tight and without a gap.

To me, it seems a good idea not so neatly executed (at least in the patent drawings). I'd be interested in seeing if the final product accommodated movement better than the drawings do.

I think you did not get the location of the pushing bolt, which force the soundboard up without much problems with the screws, even if they warped a little that is not much a concern, but they probably do not suffer.

But the soundboard is somehow floating, with that system, hence may be the double ribbing

It would be rather hard to not get the location of the pushing bolt, since it's numbered and referenced in the patent.

It's that warp in the screws I'd prefer to avoid, even if, to you, it's not much a concern. My point is that slots and flathead bolts would prevent that warping. However minor, it's simply unnecessary.

Consider that an adjustment might be made that warps those screws (and compresses that wood strip). Then that just perhaps the additional crown turns out to have negative affect and the tech wants to back off the adjustment--will those warped screws prevent movement back to the original position? Will that compressed upper strip contacting the flange conform to that flange, after it's been compressed out of its original shape?

I simply think that with better execution of the same idea you gain an advantage without inducing problems from a poor execution. That's my only point. The basic idea seems quite good but if I were going to incorporate such a feature, I'd rather it be better-engineered.

If you were to remove the soundboard assembly—I did not—you would find that it behaves very much like a three-ply laminated (and rib-less) panel. The crown was forced into assembly in the press when the ribs were glued on. It is really quite a good idea, I think.

This could also be done with a three-ply wood veneer soundboard assembly but, to my knowledge, it has never been done. At least not commercially. I have tried to generate interest in the idea but, so far, without success.

In the 9’ JB that I had the inner rim was attached to the string frame much like it is shown in the patent drawing. The only difference I can see right off is that the underside of the string frame where the inner rim was seated was relatively narrow and appeared to be slightly curved. I did not remove the soundboard assembly so I don’t know this for sure but it wouldn’t be the first time an inventor left a few important details out of his application. I assumed this was to enable the top of the soundboard liner to rotate slightly when (if) the adjustment bolts were turned. In my piano I doubt they had been touched since the piano was originally built.

I played around with them some once I had the strings off of the string frame. They were adjusted to just contact the inner rim and, as far as I could tell, were doing nothing to add crown to the soundboard. When I backed the adjustment bolt—applying more force against the inner rim—out they did, indeed, force additional crown into the system. I didn’t go too far with this. I was only interested in finding out if they would do anything at all. Since there was already more than adequate crown in the system I ended up returning them to roughly the original settings.

(All of this is from memory. I sold the piano sometime in the mid-1980s so please forgive me if some details are a bit fuzzy.)
ddf

I like the idea of such a panel and realize it'd act like a three-ply laminated panel, with crown glued in. Probably would work well enough to make all but unnecessary that crown adjustment mechanism that I think might have been engineered a little better. With that panel, I doubt the shortcomings of the crowning adjustment system ever became an issue.

That was pretty much my thinking. The crown adjustment feature wouldn't work on a soundboard system that was less stiff and it wasn't necessary on a soundboard system that was this stiff.

ddf

The distance the bolt need to make to gain crown in the panel is incredibly small.
It was computed on this forum a few years ago. Showing how stiff the belt and plate assembly must be to avoid loosing crown. And why the glue may not give any deformation, in ribs and around the perimeter.

It work both sides.

Why would not work with a lighter soundboard, Del? You mean it would only deform on its edges?

Panels where almost as guitars on those pianos. Hence ribbing in all directions. I think 4 - 5 mm thickness on the 1840 pianino