A lot has been said recently in regard to taking valve blocks apart. I will be the first to acknowledge that there is no single "right way" to do it, as I have done it several ways in the past. But there is a way now that we take valve blocks apart in our own shop, after having done over ten-thousand of them. It is the safe and sure way, but first I will also explain why we don't use a microwave to disassemble them.
It would seem the quick and easy way to do it, and frankly, the method works for some blocks, but not for others. It is also a much more time-consuming way of doing it. The heating alone requires two minutes. In that time, I can have three blocks split perfectly my (better) way.
In most later valve blocks there is a hard black inside valve seat, made probably of carbon and shellac. These are shellacked into their holes and should be removed and reglued. But only a percentage of them can be broken out of their holes from the outside of the valve block. The rest will have to be very gently scraped from their shellac and pressed out from the bottom. That requires you to disassemble the valve.
The reason you do not want to microwave these valves is two-fold. First, the valve seat will often warp and then bust when remove it and then start reinserting them. This is because it softens the seat which conforms to its own hole, then it is no longer reinsertable in some cases, and will be domed or warped on its sealing surface, too. Second, if the wood has entrained moisture, it will cause the pouch board to warp concave, and what looks on the surface like an easy reassembly will become difficult.
Also, the idea of glueing them back under clamping pressure will only work momentarily. The joint will fail sooner or later from the continual force on the joint added to the pressure of the spring clamps when reinstalled. You may have a set of blocks with a minimum of moisture, or you may have a set with just a little more, and all it takes, it seems, is "some" moisture to do the damage. There is no way to tell which valves you will ruin. Microwaving works quite often, but when it doesn't, you're in trouble. It isn't a safe procedure.
If your valve blocks are Ampico B blocks, you will have to remove the ball bleed and replace it. It is a waste of energy to clean them, even in a sonic bath cleaner, because they have been microscopically pitted from acids and chemicals in rubber particles which have lodged around the ball inside. This has actually been checked under a microscope in a laboratory. They only way to make them work is to replace them.
Regarding the ball bleed removal, this can be done two ways. Once the valve has been disassembled at the pouch line (not the lower filter screen line), you can press them out using the proper size drill bit. Or, by grinding a "V" into one end of a piece of thin blued desk spring material, you can lever them out from the output hole itself.
Do NOT reuse the old ball bleeds. Here's why:
The old ball bleeds are going to stick, both open and closed, because of the dirt and moisture that is again going to circulate through them from the air. If they are still tight, it is probably because of the dirt pack around the ball. But that pack will eventually increase the risk of balls sticking as they are used.
The reason ball bleeds were used was an attempt (successful, too) to allow the valve to start up with a #70 bleed hole, and hold itself on with about a #56 equivalent bleed hole. That larger "on" bleed hole size makes for a very quick return, since the pouch can deflate so much faster. (It has absolutely nothing at all to do with the valve's noise or anything else. It was designed to get rid of a primary valve stack.)
Now, back to disassembling the valve blocks.
Remove the cork gasket, outside valve seat and poppet. Dump all the outside seats into a jar of shellac thinner alcohol and cover. Remove all loose inside valve seats that are ready to fall out. On a belt sander, carefully remove the old shellac around each block first.
Now here is where so many people louse up their valves. The reason is because they don't use a belt sander correctly. They "oversand" at an angle, at that, and the block is no longer true square.
In order to prevent destroying the valve blocks' squareness (easily done), using a 50-80 grit belt, and realizing that the leading edge will sand twice as fast as the trailing edge, touch the block on the moving belt by holding the block between the thumb and 2nd and 3rd fingers of one hand, and immediately examine it.
Each time you put the block back down on the belt for a moment, examine it. You will see that part of the shellac is removed, and part isn't. Place your index finger directly over that part of the block that needs more sanding, holding the block between your thumb and middle finger. Very soon you will get the hang of it, without ruining ANY blocks at all. Do not sand the side that had the cork on it yet. Very important!
Split the blocks apart, using a rather thick-bladed knife (rather than a fillet blade). You want some support. You don't want the blade to deflect even a little and follow a soft grain line, because the blade will take the path of least resistance.
The easy way is to begin anywhere you see an opening or a well-defined seam between the pouch line and the upper block (the body of the valve). Lay the knife down at a low angle and tap with a very small, light hammer or a handle. Let the seam itself guide the blade. Let the block's construction do the work for you. On some blocks you may need to start somewhere else. Don't try to break a block open from one direction, only. Do it gently and gradually, and you'll very soon get the knack, and it will start taking far less time.
If you split wood or break out pieces, use always hot hide glue to repair them with because carpenter glues creep under pressure and do not glue back well with hot hide glue.
If you cannot repair a broken block that way, try body filler from the auto supply store. It glues easily with hot hide glue. just pile it up, let it harden, and sand it flush with the sander. Voila-- new valve block.
Removing pouches can be a problem. Don't leave the old glue ring. once the pouch is sanded off, dampen the old hide glue in the valve body, let it soften, and carve it out of there. This gives you a recess for the new pouch to sit into. (Not absolutely necessary, but it helps when sealing down Ampico B blocks, especially.
Broken inside valve seats are repaired using something like "Hot Shot" super glue. Next, surface them all on fine sandpaper laid on a glass or saw table top. Don't take any chances with these. If they aren't round, due to valve block compression, throw them away and buy new replacements. Reglue them back in with some form of PVC-E white glue, which allows for the movement of wood without cracking, as does shellac.
Repouch the pouch boards with very very thin pouch leather-- sometimes hard to find. Most skins, however, contain some. You have to select it from the edges of the skin and not use the center of any skin for Ampico pouches. The originals were .005-.007 thick. But even .010 new leather will be more flexible than the old .005 pouches because Ampico used rubber cement and talc to seal. This made them hard and stiff, after awhile. It was really the main downfall of the Ampico system for later rebuilders, who didn't understand the principles of unprotected latex in the open environment.
Now for a little trick. When glueing down pouches, use thin hot hide glue, and wet the entire top of the pouch board with it. Then gently center your pouch in the glue and press with a proper pouching tool that dips the pouch shallowly try one with a lifter and a valve body to make sure you dipping tool places the lifter disk about 3/32" away from the valve stem felt. When replacing the lifters on the yet unsealed pouches, first, place a little 1/4" dia. spot of pouch leather (thick) down in the center with some hot hide glue or fish glue. Then glue the lifter just to it! Don't use too much.
You don't want to glue a pouch down to the edges of the hole, so once the pouch is down and dipped, just very gently blow at its pouch nipple hole and inflate that pouch upward, so it can dry in that position, first, before you attach those lifters. It's these details that will give you a very responsive valve, later on.
The valve leather must be a beautiful example of fine suede. If your skin isn't nice enough to make you a fine coat that you would be proud to wear, then buy some more!
Cutting off the lower inside valve leather reveals a tiny little brad which attaches the valve to the stem. Be careful. Save those brads. That means, you clean your work area, so when you drop one, you can find it. If your new valve leathers aren't well centered, neither will be your stems, and that valve will have problems. Might as well do it right the first time, and get them perfect. It will take a lot less time in the long run.
When glueing back the valve blocks (no, we still haven't sealed the pouches, yet) use rather heavy hot hide glue and nothing else! If it isn't nice and thick, add some to it. Then warm up your valve blocks in a cardboard box at about 150 in the oven, put the box on a warmer tray, get a box of the smallest rubber bands for clamps, and start glueing and clamping them together. Be especially careful with Ampico B blocks, that you are 100% sealed between the bottom of the ball bleed hole and the pouch board hole. If it can leak there, the valve will play very weakly.
And another thing to be sure and do with the Ampico B valve block: After each is clamped in both directions to dry with rubber bands, take a pipe stem cleaner and clean out the ball bleed hole by curving the cleaner down into it through the output hole of the valve.
The time has now arrived to seal the pouches. using Dow Corning 111 Pure Silicon Grease (found at the transmission supply houses like IBT) dilute this grease in a solvent like MEK, acetone, etc. Get a consistency that is about like coffee cream (not whipping cream). Say, just a bit thicker than milk. Try some on a sample, first. Let it fully dry! Talcum it.
To test pouch sealant, here's another trick. Take a plastic film can and drill a 5/32" hole into it, insert a nipple, seal with some hot melt glue stick, and suck down some unsealed leather first, by punching a hole or holes in the lid, snapping the leather between the lid and the seal of the can, and feeling the tightness by mouth. Now have several sealed pouches, one with one coat, one with two coats, etc. and test them that way. They don't have to be cartridge tight. Putting too much sealant reduces their flexibility, too.
Get a nice balance between soft and flexible, and tightly sealed. Remember, your fixed bleed is a #70. You can test this with a bubble jar adjusted for so many bubble/second, then you can compare that to the overall pouch leakage. You will have to decide for yourself the optimum tradeoff here with your particular leather. If you wonder, then finish a valve, seal it's block around twice with heavy bodied Phenoseal, and when fully dry, test the valve's sensitivity, operating a pneumatic. An Ampico B valve will operate at about 3.5" smartly.
From here on separates the men from the boys. We hope you have marked out all the pin holes in your leather skin first, before cutting pouches, because now is when you will find the differences.
By building a little test stand with a pneumatic and valve mounting of some kind, but before replacing the cork gaskets yet, you will press each finished block against the test gasket, drop your test vacuum to the very lowest level that the most sensitive valves operate on, and check sensitivity. As the valve rises, adjust the gap by pressing down the outside valve plate and watching the action of the pneumatic. There will be an optimum place where it closes quickest. That will be the gap you will want, ultimately. But you are going to have leaks around the outside seat, so by using some hot melt glue, you can preseal this. Then keeping it warm, you can adjust it.
Once you have about twelve of them done, blow through their outside seats with your mouth. This gives you a feel and some samples to use in setting the rest of your valves if you wish. You can get them very close that way. Just trust your senses. If you wonder, then put them back on the tester.
Now, if you don't want to seal all the outside valves with the clear hot melt glue, you can use a fresh batch of thick shellac or whatever else you want. Hot hide glue doesn't work in this application, however. And of course, before you start setting valves, you must seal the blocks very well with (I recommend) Thick, full-bodied Phenoseal. It is the best there is. After that, if you want the color of shellac, put some over the Phenoseal.
Shellac doesn't last long as a "perfect" sealant. Because it is so brittle, and because wood is constantly challenging it, it is constantly breaking and getting more and more porous with the years. Even the heavy shellac found on the original Ampico valve blocks leaked like a sieve through the end grain sides.
On Ampico valve blocks without a bleed, you may simply set these vlave clearances to between .035 and .045 with a springbow gapper tool, like you would find at Player Piano Co. Or, make your own. By sticking some aluminum ductwork tape to the shimming tool and trimming it, then burnishing down the aluminum for smooth edges, you can increase the gap.
The reason a gapper works fine on double valve actions, is because the critical valve in that case will be the primary stack valves (outside valves), or "driver valve." You won't have to "blow" your valves unless they belong to a finely tuned reproducer action.
When placing the gasket on the block valves, use thick hot hide glue only. Time it so that after they are tested and set, but before the gasket glue is glass-hard, coat the gaskets with pure Silicone Grease, and install them on the player stack. Use ONLY Ampico valve block springs (Bob Streicher or PPCo) because the old steel bars once used by Ampico distort the blocks too much. They do not accomodate wood shrinkage during winter months, and the block gaskets often leak, eventually, after many winters, making one think they have a valve problem. Instead of the bars springing, the valves simply crush in. The gradual indent loses its resistance, and the valve drops loose.
So this is another use of the grease. The grease on the cork gasket allows you to seal the valve without even using a spring. Nice for testing. until you are finished testing, you don't have to keep replacing the spring clamp.
Hope these hints are of some use.
E-Mail to: Craig Brougher
Design by Player-Care
407 19th Ave, Brick, NJ, 08724