The last component to rebuild on the “head” section is a small valve box which is a primary booster for the Theme signal. The “Theme” feature is specific to certain types of player pianos, I will explain about that later.
For now we just need to be concerned that it works, although there is not much to it; just a pair of primary valves and pouches, inside a small box.
As per other operations, take it all apart, use a screw map to stow screws, carefully take apart the primary valves by chipping away glue blob at the top of stem, then a modest but firm blow with a small hammer (and punch, if necessary). It will come apart in two pieces.
Pull off what gasket material you can by hand, then scrape until you are at the glue residue level. Then lap surfaces on sandpaper over flat glass (or other dead flat surface). You don’t need to go to fine on the sandpaper, 120 grit is fine as a little roughness will help the glue joint.
Once it’s all apart and prepped, you’re ready to start rebuilding, with fresh materials!
Now it’s time to measure, mark, cut and glue some new gaskets. I mentioned about gaskets last time, so the method is described there. Once it’s all cut, glue in place, using enough but not too much glue, applying quickly if using hot glue –as you should!
Pull the old leather off the valve facings, resurface the top face (the bottom should not have been glued, if Standard style), and put new leather facings on, being quite cautious not to get any glue on the outside of the facings, which will render them useless. Again, enough glue, but not too much.
Reassemble the valves on the top section, using a gauge to space the travel gap at 1/32″, the default distance for Standard style outside valves. John Tuttle gave me a tip that you can make one from an old ivory keytop tail, so that’s what I did! It works! A little dollop of glue on top of the button at the stem will keep it locked in place. It doesn’t take much.
Put the box back together. It may look something like this ( I haven’t fitted the dust cap, as this is cosmetic and blocks the view of the primaries for testing):
Once reassembled, it’s testing time. You probably don’t need a suction pump from this, just a tube with mouth power (shallow breaths in!). When the valve is receiving atmosphere signal, it opens and lets atmosphere pass to the output. When the valve input is closed off (meaning that there is roll paper covering the corresponding holes on the tracker bar), it should receive nothing, and therefore output nothing.
The inputs should be the lowest horizontal row of nipples on the valve box, so when those are plugged and unplugged under suction, they should pop up and down accordingly.
It’s a little cumbersome to check all this in tight quarters, with a noisy vacuum cleaner as a test pump, but it can be done. Once you’re happy with the performance of this valve box, time to move on. In my case it means that the head of the stack is done, yes!
It’s a nice milestone to have the motor, transmission, spoolbox, tracker and valve box ready for final assembly. Now let’s dig into some peripherals!
Gaskets keep everything nice and tight. They keep the suction in where you want it, and the atmosphere out. Since all valve boxes are made of blocks of wood, and even well-mated wood surfaces are not airtight, there must be a membrane of some sort which is suitably compressible, but also durable.
The traditional candidate is split leather. When leather of proper quality and consistency is used, it does both jobs well, and leather to wood with hot hide glue is a match made in heaven. There simply isn’t a better way to work other than the original way.
However, there are alternatives. When I say alternatives, I want to stress I am not taking about the adhesive part! For my opinion on glues, see previous post here.
I was speaking of a “modern” gasket material of neoprene. Plastics get a bad rap in the piano industry sometimes, because in the beginning, the technology was inferior and the product didn’t age well (plastics were introduced into pianos as early as the 1930’s). However, plastic materials have come a long way, and like every product there is a range of quality.
Traditionalists will turn up their noses at this idea, but that’s fine. Tradition has its place, and I respect it where I feel appropriate, but this doesn’t prevent me from trying new things.
In the case of neoprene, for a material that was modestly cheaper, easier to source, slightly easier to work with and – most importantly!– well-performing as leather, that seemed good enough for me. Time will tell!
My main concern with this type of product in the long term would be elasticity (being permanently compressed and not expanding in drier weather), and structural integrity (starting to disintegrate over time). On the question of integrity, since a gasket is –by definition– always sandwiched firmly between two pieces of wood, the oxidization problems should be minimal.
The material comes in sheets and you just cut what you need, in the most efficient way you can manage. For cutting straight lines I use a steel rule and a rotary cutter, on a cutting board designed for the cutter (“self-healing”).
For punching holes I use a handheld punch, which works well for screw holes (the most common kind). For anything larger than that, you really need a punch set to do a neat professional job.
For small and medium surfaces mark all holes on a given side with chalk (lightly) and then dry fit the gasket to the surface. The perimeter outline can be rough at this point, doesn’t need to be perfect now. Release the piece and place the gasket on a punching board. The cutting board worked for me for this material, because it’s so light, you just press it out by hand. I would not have used a hammer to drive the punch on my nice cutting board!
Then do the screw holes, however you want. When all done check against the piece, and assuming it’s good, go ahead and glue it on real good (the neoprene I use has two different sides, it’s the “skin” side which gets glued down).
Finally cut away the perimeter edge with a pair of shears or long scissors. Easy!
The only thing to watch for is that the thickness tolerance is kept faithful, when you replace gaskets. If you are putting neoprene in place of a gasket that was originally designed to be leather or blotter paper, the compressibility will not be identical, so this is something to keep in mind. If you are not duplicating the original in terms of material, you should still attempt to match it in terms of dimensions, wherever possible.
Gaskets can be made from any number of things, but traditionally it has been leathers, cork, blotter paper or other cardboard type papers. You can choose to use any number of solutions, but don’t use the wrong material for the wrong reasons.
The thing about quality leather is that it is getting harder to source. It’s just another one of those commodities that has become more scarce, for several reasons. That was part of my decision to go with neoprene.
But using cheap and inappropriate materials only to save a few nickels and a few minutes is false economy. Spare a thought for the person who will have to do the next restoration, it may even be you! Trying to scrape off disintegrated plastics mixed with modern glues is truly drudgery of the worst kind. Don’t let it be you!
No photos this time, but I will illustrate gasket use in the following post!
This is going to be a lot shorter than the preceding post, for a couple of reasons.
Firstly, half the battle with a component like the tracking device is simply understanding how it operates. You can’t do proper rebuilding and testing/troubleshooting without this knowledge.
It took me a few days of fairly steady thinking on this topic, for it to start to sink in.
The other thing is that there is not a lot new here, in terms of components. I’ve covered pneumatics, I’m probably not doing pouches (however this is covered extensively in the Reblitz book), and I will specifically cover gaskets (simple) and valves in future posts.
Like the other components, good sealing is a must for proper function. This means the internal channels, the recovered bellows, the mating of the primary valve facings to the box, and good gaskets.
Once all this is done, it’s a matter of reassembly and testing. Here’s what it looks like back together:
And so let’s make sure it does what it needs to do.
First get a suction supply going, to test. In a perfect world you have a test pump from an old reproducing piano, but barring that, a regular shop vac will suffice (it’s what I used). Just regulate the suction so that you are in the 5″ water range (a vacuum dial gauge is good for this, or a home made water vacuum gauge). I made a laughably cheezy regulator, with a clothes pin and some elastics, to hold a piece of tubing a little bit outside the mouth of the vacuum. MacGuyver would be proud!
The drawback to testing with a vacuum is the noise. Apart from being generally grating, it also makes it difficult to hear leaks when troubleshooting. But, we must use whatever tools at our disposal.
Hook up the suction supply to the appropriate nipple on the box (it should be the one that is not otherwise identified). Then run the following series of tests:
1) Close off all 4 inputs (you don’t need to tube to an actual tracker bar to do this). Is the system balanced? You should see the pneumatic cloth get sucked in slightly in the bellows, but other than that, they should stay pretty much where they are. More on that in a moment. Assuming all good, continue.
2) Open the outer holes. Still balanced? Good!
3) Open the inner holes too, all holes open. Still balanced? Okay!
These tests check the balance of the pneumatics, if the bellows list to one side or another, or if they are otherwise not behaving identically to each other, we have a problem! The problem is a leak somewhere, so you’ll have to track it down and fix it. Do it now, show no mercy to leaks whatsoever. It will not ever work if it leaks, so if it means taking everything apart and checking each component separately, just do what it takes!
Once we have established balance in equilibrium, let’s check it in disequilibrium.
4) Close all holes again, then open just one outer hole. The bellows should track accordingly, moving smoothly in concert to one side. When you cover the hole, they should return to default halfway position. If they move quickly but don’t return reasonably quickly, this is a troubleshooting tip, likely a blocked bleed. Try the other outside hole in the same manner.
5) Same as step 4, but concentrate this time on only opening each outer hole (not at same time) just a little – halfway or less. The bellows should still react and begin to shift as soon as the hole is opened partially.
6) Cover only the inner holes, and repeat steps 4 and 5, one inner hole at a time. The bellows should again perform the same way.
Assuming it does all these things well, you should be good. But if there is something which makes you squirrelly happening now, just check again and again, repairing if necessary, until it looks like it should.
One thing I noticed on my first attempts, was that the right pneumatic would noticeable jerk when getting suction signal. It is a quirk of the design that the pneumatic is only mounted on the shift box with a single screw. This is not ideal from a “no motion” perspective, so I had to dismount it (which ruined my gasket, it had to be cleaned off and replaced), then check for flatness, and then make sure the pneumatic sits perfectly straight on the box, supported equally on both top and bottom, when you glue (or shellac) the gasket back on.
Thankfully the pneumatic had an access port for the screw, so I was just able to open that up to pop off the pneumatic, I didn’t have to ruin the the recovery job I had done.
This does remind me however, that there are possibilities for some real bouts of tedium and frustration when troubleshooting. What’s more is that the closer you get to the end, the chances of time-wasting increase, unless you take the time to really check your work at every stage. I must repeat this mantra to myself constantly!
Here’s a video of a testing session I did:
So, that’s basically it! Just reattach whatever mounting blocks or other hardware to the unit, and set it aside until whole action reassembly.
On to the next thing!
Actually, let’s take a quick side tour to gaskets….TBC
Although not as eye-catching as the motor, the auto tracking device is just as necessary and just as sexy. In fact the tracking device is usually the most mechanically elegant feature of the whole dang piano! In his introduction to the Standard Tracking Device (p 143), Art Reblitz calls the Standard in particular “one of the most sophisticated pneumatic mechanisms in any piano”.
The tracker in my piano is very nearly the same as a Standard, it operates on exactly the same design principles, especially in the valve box (also called shifter box). However in terms of appearance and layout, it is essentially an Autopiano tracker (see image below). Indicators are the bottom bleed chamber, as well as the vertical orientation of the pneumatics, plus another particular feature I will mention later on.
Note that while the general principles of the following information apply widely to most “automatic” pneumatic trackers, there are specific differences which may apply.
The tracking device keeps the paper rolling on the “straight and narrow”. This is vitally important, because if the paper becomes misaligned with the tracker bar as it unspools, the music becomes real bad, real fast. If we continue with an automotive analogy, the motor and the transmission are self-explanatory. The tracker can be considered the steering wheel. Imagine therefore, trying to drive your car, and the wheels did not follow what you were doing as you turned the steering wheel: it would be interesting, but not in a good way!
And so, let’s dig in a little bit and try and figure out how this thing works. I admit it has taken me some time to understand this thing. There is an awful lot to digest here, so understandably it may take you a while to get through it. Alternately you can watch a video by John Tuttle here. In fact, I recommend that you read all this, then watch the video, then do it all again!
Once it’s all taken apart, we see that it consists of two outside (primary) valves, six pouches and seven channels – three of which are almost too small to be considered true channels.
The 2 primary valves are paired with a set of primary pouches. There are two “wannabe” inside valves paired with what are called the “cutout” pouches. These are essentially two thick wooden discs (which look like primary valve caps) glued on top of the cutout pouches. Over head of the of the cutout pouches there are two slightly larger pouches, cleverly called “overhead” pouches. The overhead pouch has the power to override the cutout pouch, due to larger surface area (in my case 1 1/8 vs 7/8 diameter).For channels, we’ve got 4 “inputs”, which is where the four nipples on top of the valve box are tubed directly to the 4 specified holes in the tracker bar. Inputs 1 and 2 both lead to a matched but independent channel which runs underneath both the cutout pouch and the primary pouch. Inputs 3 and 4 are essentially direct feeds to each overhead pouch well (again, independent of each other).On the underside of the valve box (on my model, at least) there is a suction supply, which is just a small hole in the valve well with a nipple outside to hold the tube.Finally, there are two interior channels connecting the primary valves to the pneumatics. The primary valves determine if the pneumatics get suction or atmosphere, so these can be considered the “outputs” of the valve box.
Confused yet? I can’t blame you, after having read all that!A picture is worth a thousand words, so here is what the inside of the valve box looks like:
The first thing that will help simplify matters is to notice that the valve box is a stereo set. In other words, you really only have to understand “half” of what is happening, and the other half does the same thing.
The second thing is that even though the 4 inputs from the tracker bar can theoretically give up to 16 different permutations, for practical purposes it’s actually less than that.
If we work backwards and follow the path, we can see that the tracker linkage (which controls the position of the music roll, via the spool cam) is effected by the movement of the tracker pneumatic. The tracker pneumatic moves (e.g. opens or closes) depending on what “signal” (suction or atmosphere) it is getting from the output of the valve box. This signal is switched on or off by the primary valve. The valve is controlled by the primary pouch. The primary pouch is arranged inline with the cutout pouch, and both of these pouches are fed by the exterior hole of the tracker bar hole set (inputs 1 or 2, as labeled by me). The overhead pouches are fed by the interior holes of the tracker bar, which are again labeled 3 and 4 respectively on my box.
States of play, of one side of valve box (meaning one valve only):
1) Both (inner and outer) holes of tracker bar are open (no roll paper is covering). The inner hole triggers the overhead pouch, which overpowers the cutout pouch. Even though the outer hole is open, the cutout pouch is overpowered, so the valve is not opened, and the suction goes through to the pneumatic.
2) Both (inner and outer) holes are closed. The overhead pouch is not triggered, but it doesn’t matter because neither is the cutout or the primary pouch. Again, the valve stays down (closed), and the pneumatic keeps receiving suction.
3) Inner hole closed, outer hole open. The overhead pouch is not triggered; the outer hole allows air to pass to the primary pouch and lift the valve. The valve opens, closing the suction chamber and letting atmosphere into the pneumatic. This is what could be considered “default” setting
4) Outer hole closed, inner open. Unless the roll was damaged in a very particular way, this situation would never occur. In theory it would mean that suction continues to that pneumatic, as in case 1.
Note that for the first 3 scenarios, as long as the same thing is happening on both sides of the tracker bar (and valve box), the system can be considered balanced, which means the pneumatics are acting equally in concert, and not trying to move the piano roll left or right to compensate.
When there are differences between the sides, we will have an unbalanced system, so we have to revisit our scenarios.
5) One inner hole closed (on one side), other three holes open: atmosphere is fed to the open holes, for practical purposes it is the uncovered inner hole that leads to the overhead pouch, which will expand and let atmosphere pass to one pneumatic. The other pneumatic will still be getting suction, so it will pull the atmosphere pneumatic back into balance.
6) One outer hole opened, other three closed: the outer hole will allow atmosphere into its channel and open the valve, allowing atmosphere into one pneumatic. Again, the system will automatically rebalance.
7) One pair of inner/outer holes opened, other pair (on other side) closed: this would be an unusual situation, most likely resulting from a damaged roll. As explained by John Tuttle here, if both holes on one side are temporarily opened, the tracker does not try to correct, but just keeps status quo. Whether this was a planned design outcome, or just happy accident, I don’t know!
If that is not sufficiently confusing, another key fact is that the inner/outer holes are cross connected to the valve box inputs, so that the inner and outer hole from the same side of the tracker bar are not inline on the same input channel. Why? Because that’s the way it was designed, and that’s the only way it can work! I spent a bunch of time thinking about this, but John Tuttle gave me the above explanation, and really that’s what matters. It just is.
Other related facts:
The outer holes are for standard (or larger) sized piano rolls, standard size being 11 1/4″. The system will still work with slightly narrower rolls (i.e. the system can function using the inner holes only), but if there are rolls which are significantly wider than standard, the system is not well-equipped to respond to roll drift in this case.
Finally, the “particular feature” on my tracker is that there are no bleeds for the overhead pouches. This is related to the fact that my tracker bar scale apparently allows some air into the outer holes at all times, the holes are indexed this way on purpose. So not only is the overhead pouch larger, but due to lack of bleed it really comes down hard and fast, to override the cutout valve and keep the linked pneumatic under suction.
Furthermore, John reminded me that the self-cleaning bleeds are also self-regulating as well; the more that a valve pouch opens, the more the corresponding bleed opens as well, which means the resistance to opening increases concomitantly. Interesting stuff!
Your head probably hurts a little from having read all this, so let’s leave it there, and get into the specifics of rebuilding next time.
Sources: Player Piano Servicing and Rebuilding. A. Reblitz. Vestal Press, Lanham, MA. 1985.
“Player Piano Pointers”. Auto Pneumatic Action Company. New York, 1917. (Note: this is a public domain document, available from AMICA, with membership)
Let’s reassemble the motor and get this sucker running!
If you have been careful in documenting how you took everything apart, then putting it all back together should be a snap! If you haven’t….well, consider it a free lesson from the school of hard knocks. As we say around these parts: “that’ll learn ya!”
• stripped down the trunk, repaired any damage, sealed channels, lapped and lubed the face
• recovered, lapped and lubed slide valves
• repaired, rehinged and recovered pneumatics
• clean and polish all hardware
• replace and lube all bushings of various flanges, arms, valve guides
And so. After verifying each individual pneumatic independently for airtightness, let’s glue them back on to their home base. Probably good to get that out of the way, right off the top. You don’t need to get fancy or have an awful lot of pressure in this situation; here’s my solution:
Now with that done, test again, to make sure pneumatics are still tight. Close them and then seal all the trunk intake channels. If they offer stiff and continued resistance as you pull them open (firmly, but gently), and you don’t hear any hissing, leaking noises, you should be good. If ever you get the odd leak at this stage, you can probably bet (by process of elimination) that it is between the pneumatic and the trunk. If you can localize it you should be able to then neutralize it, with a few drops of Phenoseal — ask me how I know! (wink, nudge)
Now remount the hardware, again being careful not to bend the crankshaft as you reassemble everything. Next the slide valves. And you’re done! Or are you?
Last but not least, let’s check the timing. As with comedy, timing is everything! There is a mechanical sweet spot to be had, where the motor works at optimum efficiency (just like any combustion engine, including the one in your vehicle).
There are a couple of different ways to look at this, but basically you want all the valves set the same, and you want them all to begin the “powerstroke” just after the valve closes. You can refer to Reblitz 41 for more details, or also John Tuttle’s tidbits here, or here.
Once you feel confident, you can take it for a test drive! It should run fairly smooth, even at very low speeds. You can use a vacuum cleaner if you don’t have a test pump, but note that this is not the ideal testing device. It may make the motor appear to turn in a lurching manner. I have read that most of the good motors are overengineered to run even if not perfectly regulated, so as long as you get it as good as you can, that’s probably good enough!
Here’s what mine looked like, as an initial test run after rebuild:
One of the final tasks on the checklist before motor reassembly is rebushing. There are many, many bushings of different descriptions and purposes in a player piano (or a regular piano), but they are mostly variations on a theme.
A bushing is a piece of material (usually sturdy cloth) which creates a sort of “buffer zone” between a moving part and a stationary part. For example, anywhere there is a pin or rod that rotates, chances are good that there is a bushing around this part. A bushing must be the right size: too thick and it will induce unwanted friction, too thin and the moving part will not have sufficient support, causing inefficient mechanical motion and probably unpleasant noises as well.
For the present post, we are referring specifically to the bushings in the motor. You will want to redo all of these bushings, especially the ones that come into contact with the crankshaft (which is most of them). This motor has got to run a long time, so let’s freshen up those bushings and keep it tight!
Let’s start with connector arms and valve flanges. Remove the old cloth. Before we get too far ahead, you might as well clean out the bushing holes of old residue with a properly size drill bit. The fit should be snug, but don’t ream the hole any larger.
Now measure the old cloth. You will need to match the dimensions of the original bushing, the key word being original. There are two dimensions to watch for here: thickness and width.
The length of the bushing will not have changed, so when you cut a strip of cloth, the width of the cloth must match the length of the old piece. If ever the bushings are damaged or missing, you can approximate by remembering some geometry: the circumference of a circle is π x diameter. In other words, if you measure the span of the hole, multiply by 3 (and a smidge), and cut your cloth strip to this width, it should be a pretty close fit!
The thickness is tricker; measure the thickness with calipers or similar gauge, and then realize we must account for wear. Depending on wear, we may need to add ten to twenty thousands (of an inch) to replicate original cloth.
Once you’ve got something you can work with, tear a strip (good quality cloth will tear cleanly and evenly, just as well as cutting) of the proper width, as long as you need. For bushings that go in a hole (in a block of wood), cut a bit away to make a “tip” on the strip and pull it through the hole, almost the entire way through. If you look at the cloth sitting in the hole, the two sides should touch each other, but without having the cloth bunch up in the hole. If there is a gap, your cloth is too small. If it bunches: Too big!
Then put a reasonable amount of glue (you will figure this out on your own) on the cloth and pull it the rest of the way into the hole. Assuming you’ve used hot hide glue, let it set up for a few minutes (while you do the next, and the next), then double back before the glue hardens completely and trim the excess cloth.
There is a trick to this, and it involves a sharp instrument like a new razor blade. Nothing screams “amateur!” like sloppy bushings cut with a dull blade. To avoid dislodging your new bushing with the blade, insert a stand in mandrel (like a wooden dowel) of proper size into the bushing hole. Hopefully it goes without saying that you don’t use your crankshaft as the cutting mandrel!
For bushings which can be put in place without the above method (e.g. open cavities), you should be able to cut to size before gluing in place, as is the case with the following slide valve arm flange bushings.
And whadya know – John Tuttle has a video on this subject too! I’ll let him offer his perspective again – click here!
There are still more kinds of bushings, such as those for the side guides of the slide valves. These will be a snap, after having done the rotary ones. They are just strips of cloth!
Once your various bushings have all been done, collect everything (back in the correct order), and get ready to put the motor back together. Almost there!
You are of course welcome to read through the entirety of the following post (I assume that’s why you’re here), but if you would prefer to watch a video tutorial on the same topic instead, then click here. I don’t plan on going into as much detail as Art Reblitz in his book (pp 52-78), but I will at least furnish a proper introduction, to give you a taste…
First, some assumptions, pertaining to teardown:
That the pneumatic has been carefully removed from its trunk (whether gasketed and screwed, or glued).
That the cloth was slit lengthwise between the bellows, and then peeled back and removed.
That your boards are sequentially numbered in pairs, for easy identification, on the inside face of each. (the inside board should also be marked on the exterior in a suitable place, if it happens that a particular pneumatic needs to be remounted in a particular location)
That the hinge was removed from both boards, and the old hinge glue lightly sanded away.
That any remaining cloth was scorched or smoothly sanded off, and the edges all sanded smooth.
That all sides are square and true, and each board is precisely the same dimensions as its mate.
Starting with these two prepped boards, we will remake a pneumatic!
Let’s begin with the hinge.
First, flashback: after having removed the original hinge (perhaps long ago), you found a source of identical but new material; likely something in the ticking or twill canvass line. It really must be 100% cotton. Having measured the old hinges, you recreate them by cutting first to length (to create a strip for a whole section). You have paid proper attention to follow the orientation of the weave, so you cut in the right direction. You then crease the hinge by folding and running a warm iron over the surface. The strips may now be cut to width to create the pneumatic hinges.
Now, flashforward! Your pot of hot hide glue is at the ready. As are your pieces, organized and prepared. You may choose to insert a piece of wax paper in the hinge fold, to prevent gluing the hinge to itself.
Glue the end of each board where the hinge will attach. Pick up your hinge, place it on one board. Quickly take the other board and place it on top. Check positioning of the hinge (slight inset), and then clamp, with a medium spring clamp (I find large binder clips work well for this, and they are cost-effective!). Let dry, hinging is done.
To verify the hinge, once the glue is dry gently try to wiggle the open ends to opposing sides. If there is noticeable play, you have failed. Remove the hinge and start again, until the ends travel freely and easily to open or close, but resist any sideplay.
John Tuttle has a video on this, with a slightly different perspective. Check it out here
Now, the recovery with cloth.
Again some assumptions: you have the proper bellows cloth, with appropriate thickness for bellows size, a measuring tape, you have a nice, sharp, pair of scissors, glue pot at the ready, and if necessary a jig to speed up accurate, consistent production (e.g. this)
Cut strips for your bellows, the width of which will be slightly oversize the span of the pneumatic in question.
To recover: Lay out the strip of cut cloth (inside facing up). Position the handy jig for spacing, if you have one, over top of the cloth, offset the centre. Glue first side of the pneumatic, by which I mean both edges of the left side. Use enough glue, but not too much.
Wait. Turn. Glue end (open) edges. Wait. Turn again. Glue third side. Wait. Glue last side. Done.
This is a bit short on detail, but it is really meant as a procedural overview. There are other things to consider as well like carefully trimming the excess cloth from the finished pneumatic, to avoid knicking the cloth and wasting your work. Refer to Reblitz’s book or John Tuttle’s video tutorial for more in-depth information.
Now let’s look at the big picture of where we are with the motor, and what needs to happen. We have it all apart and documented, ready to begin restoration. So let’s go!
There is not an exact order, but any time is great to clean and polish the metal hardware (screwheads, brackets, crankshaft – carefully!!), and get it out of the way. For heavy greasy grime use a rag soaked in solvent (e.g. mineral spirits). Rinse or wipe off and then polish with a nice product like Flitz or Autosol. Nice improvement!
Again, if ever you find the hardware heavily corroded, then replating or even replacement may be necessary. Depending on your location, someone who is very good (and reasonably priced) at metal plating can be hard to find, something to keep in mind!
Apart from the cosmetics, the major items on the checklist are to rebush necessary bearing points (will post on this soon), as the motor will get a constant workout. Then it is all about recovering and air sealing. The motor must be tight else the music begin to turn with a loping, queer motion, causing the music to lurch and stutter unpleasantly.
In order to be robust overall, this means the bellows, the slide valves and the trunk interior must all be tight individually.
Pneumatic recovery is a specialized topic which will be needed throughout the restoration process, so I will cover that separately in the next post.
The slide valves are basically just miniature wooden frames, covered on one side with motor cloth. Like a pneumatic, the cloth side must be well sealed. However just as important is a good seal between the trunk face and the inside of the valves. This is why both the valves and the trunk face must be lapped (a specific sort of sanding) completely and evenly smooth, so that they are well-mated to interface with each other.
The preferred way of doing this, traditionally, is to adhere a piece of sandpaper to a solid, dead flat surface, such as a piece of plate glass or machined table (e.g. table saw). This ensures the lapping will give the desired result. Use a medium machinist’s square (6-12″ long) to sight across the valve surface of the trunk face. Depending on how much warpage or gap you see, you will need to lap accordingly. If there are significant gaps (more than a couple of mm), you will have to either begin with a rough grade of paper (e.g. 80 grit). Work your way up to medium (120-180). If there are only light distortions in the surface, then you can proceed immediately with a fine grit (250-320) to just even it out, and that should suffice.
Incidentally, there is a detailed video of this process by (guess who?) John Tuttle. It’s a longer one, but worth checking out here.
We then finish up with a nice graphite lubrication, making sure not to mix it too light (or too heavy!) or put it on too excessively. Also, for valves like this which are in perpetual motion, don’t EVER use a greasy or “wet” lubricant for this application. This will eventually cause binding and performance issues. There might even be a warning sign about this from the original maker!
The interior of the trunk should be proofed for leakage too; it needs protection from all leaks within and without!
Now here we would normally use a heavy shellac; the traditional choice for sealing internal channels. I am instead going to use a “modern” substance. This sealer, trade name “Phenoseal”, is a little like a thinned white glue. It has a water-like consistency when applied, and then sets up (but does not ever cure 100%) like a clear plastic membrane.
I would only agree to use this under certain circumstances: it is a significant time-saver, it does as good (or better) a job than shellac, it doesn’t cause other problems, in exchange for this convenience.
Given this criteria, It is vital that this type of product is never applied to a surface which needs to be glued or which contacts a moving part, and it is never used on a surface which will have to be refinished/resurfaced in the foreseeable future.
This is why we don’t ever, EVER, use a white or yellow glue for adhering parts which may need to come apart again someday. It is a bastard of a job getting these parts apart, unless hide glue has been used. Modern glues have many wonderful uses, but should only be used in permanent structural repairs to woodworking – that’s it!
So, we have covered prepping, lapping and sealing; I will discuss recovering separately. We also need to talk about rebushing, but as mentioned that will be a separate post as well.
Once the recovering, gluing and rebushing is done, your hardware is all clean and polished, you are ready for reassembly, then regulation!
Like Hide Glue, thick or “burnt” shellac is another “sorta kinda” natural substance, the use of which is traditional in this industry and has been sanctified by time.
While it is undeniably interesting and fun stuff, it’s also just as sticky and messy as glue, so we don’t want to get too playful with it!
As the name suggests it’s simply a very thick formulation of regular, everyday shellac finish. In player piano actions, its primary use is as a sealant. It sticks to absolutely everything, which is good if you put it only where you are supposed to! As the carrier solvent evaporates the shellac slowly cures to a hard shell.
So it can be “painted” inside of block channels or also around the junction of metal bits into wooden blocks, etc. Once cured it is airtight, and won’t come off, unless you want it to. And here again, it is wonderfully “undoable” like hide glue.
Burnt shellac is also good to reinforce a fastened joint, which can’t be glued but still need strength. An example of this would be for the arm flanges of a motor. The flanges attach to the bellows with small screws, but as they are under a constant load, they need a little extra strength as insurance. However it’s not a good idea to glue them (as they may need to be removed for repair purposes), so shellac is a good compromise.
This wonder substance can be made in two ways: additive or subtractive. Note that the finished product is not exactly the same in both cases, as explained in further detail here.
The additive way is slower, but safer. Buy yourself a bag of shellac flakes (from a woodworking supply store), and gradually add a minimal amount of solvent (e.g. mineral spirits), just enough to dissolve the flakes. If you can get it right you will have a thick goopy mixture.
The subtractive way is the traditional way, as the other name suggests. Premixed shellac is bought from the hardware store, then “burned off” by lighting the liquid on fire, and letting it burn for such time as that it thickens to a goopy mixture. It will cool to a thicker consistency than that which it burns, so don’t overdo it with the burn off!
For this method it is highly recommended that you do this out of doors away from combustible surroundings.
Disclaimer: I take no responsibility for any cataclysmic events that occur after the reading of this post!
Hot hide glue is the ideal glue for many applications in instrument repair and rebuilding, and it has been the adhesive of choice for centuries, until the rise of synthetic glues in the 20th Century.
For wood to wood or leather to wood applications, HHG in this context is hard to beat! A quick rundown of pros and cons:
sets up quickly, allowing a higher rate of productivity
depending on nature of joint, high tack means clamping is often not required
viscosity can be adjusted (somewhat) to purpose
dries to form a “brittle” joint, which does not creep
water soluble, so completely reversible
sets up quickly, so workflow must be organized beforehand and executed efficiently!
needs constant source of heat at steady temperature, to maintain working temperature
water soluble, subject to moisture infiltration and therefore not suitable in warm environments with elevated humidity
So we can see that HHG has a couple of characteristics which may either be good or bad, depending on how we look at it.
The property of reversibility is a huge plus, where restoration is concerned. It allows a rebuilder to dismantle and break apart wood and leather joints without excessive damage to the constituent parts. And by rebuilding in the same manner, it pays forward the same courtesy to future restorers.
To make use of HHG, you need three basic ingredients: glue granules (sold at suppliers to fine woodworking trade), water, and heat. The source of heat can be any number of things, but again it should be a source of steady heat.
For me personally I have gotten my glue granules from Lee Valley or from Player Care. For the glue pot I use the industry standard “Hold Heet” automatic glue pot, from Emco. It’s available at any number of places online, and it’s the only glue pot you’ll ever need.