Fay Reid
From:
Orono, Ontario, Canada
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Posted 16 Oct 2007 12:25 pm |
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Adding Raises (or Lowers) to a Changer
Please read the suggestions under a recent submission by Ken Crisp. These solutions involve the manufacture or parts supplier. My discussion harbours around the do-it-yourselfer (the drill press and hacksaw crew) and the last-resort gang. Another guitar with the desired options is always another solution.
You need another change on the changer for one reason or another. Perhaps it’s to be added to another pedal or it’s the result of a split tuner that you wish to add, but you don’t have it available on your guitar. Perhaps you could get the desired parts but, for the moment, would like a quicker fix. In other words all the positions at the changer for the string in question have been exhausted for an additional change (either raise or lower).
There is at least a couple of methods that I can think of at the moment. One would be to suspend a 5/16” hinge-like structure from the under side of the deck of the guitar to the nut side of the changer. It would have three 1/8” or slightly larger, say 9/64”, holes to accept three 1/8” pull rods. The one nearest the deck of the guitar should logically be connected to an available slot in the changer (one that is already being used). We’ll reassign it later. The other two pull rods are connected in the usual fashion at the bell crank after having been threaded to accept a nylon tuner that screws on ahead of the “hinge”. One is the reassigned pull from above and the other, the new change. A non-functioning nylon tuner is attached at the changer on the first pull rod as well as on the far side of the “hinge”. Tuning is done on the two pulls independently from under the guitar using the two tuners attached to the other two pull rods. I have not used this method since I’m not sure what form the “hinge” would actually take. The hinge setup is nothing more than a basic reproduction of the fingers in the changer. Theoretically, more than one new change could be added by drilling a 4th hole and adding the appropriate hardware.
The second method is one that I have used on my guitar in a couple of places for many years. As long as the aluminum parts are constructed properly, there are no differences in function from the regular changes. Like the method above, tuning is done, at least in part from underneath the guitar. Generally, this is not that difficult since the “tuners are permanently attached, fairly large, and always in the same spot.
The basic idea is to connect the “new” bell crank for the added change to another pull rod making the same change, of course since we have no other place to connect it. The railroads have been doing this for years. They just hook on another car on the end. So, it all becomes a series connection. (Note that the connections using the “hinge” method are parallel connections.) We run the one (and only one) pull rod through the first brass “wristpin” and on through the second, securing each with a setscrew. Your setup will have to be modified if you have the “hook” arrangement on your guitar (Carters, for axample) to something similar to the one suggested.
We get back topside and tune the first change at the endplate. It’s tuned. We do the same for the second change. Oops! We will be detuning the first change if we tune the second. Not only that, but all changes on both associated pedals change when one of the pedals is activated. For instance, if we had connected the two B to C# changes on pedals A and C, pedal C with B to C# and E to F#, would also move when pedal A is depressed.
The two pedals have become one. We must find a method of making them act independently.
Don’t fret! If you have a guitar with bell cranks similar to those used on the modern MSA’s, the above discussion doesn’t even apply to you. The back sides of the bell cranks have been removed (creating slots instead of round holes) such that the brass ”wrist pin” is free to slide rearward without activating the other pulls on this pedal (say, pedal A) when pedal C is depressed. If your bell cranks can be modified to the shape of those of the MSA, go ahead. All that needs to be done, now that we have the two pedals (and changes) acting independently, is to find a method of tuning them independently.
Don’t fret! Actually, all we have to do to tune independently is to have a mechanical means of varying the linkage distance between the two bell cranks (and their wrist pins) on the separate pedals. To do that, we’ll remove the setscrew of the wrist pin of the most distant bell crank, thread the pull rod beyond the wrist pin, place a “spacer” on the rod after the wrist pin, and add a nut on the end that can be used to tune this change. The spacer can be round stock aluminum, drilled slightly oversize, and concaved to better fit the shape of the wrist pin. Topside, we tune the change closest to the change, firstly, then the other. To do it the other way around will leave the second change out of tune after tuning the one closest to the changer. Now you have 3 raises (changes) instead of 2, 4 instead of 3, 5 instead of 4,…for the same string!
If you can’t adapt the bell cranks as suggested above, (not enough structural material on the front side to cut the slot), you’ll have to do something similar to the construction on my machine. (See Diagram) Essentially, you’ll have to create a “substitute” slot for the first wristpin. Taking a look at the diagram, you’ll see that it’s a block of aluminum with an elongated hole (slot) drilled crosswise to accept a moving wristpin that is set screwed to the pull rod. The elongation of the hole is determined by the amount of movement necessary to accomplish the desired change by the far pedal. On first observation it looks as if a simple spacer (similar to the one described above) could be employed, but this arrangement would allow the wristpin to spin when we tried to tune at the changer and at the second change position (the nylon nut). This aluminum block must have an extension on the changer side to fit into the slot of the bell crank and against the “idler” wristpin in the bell crank to keep the pull rod from spinning during tuning. It may be wise to include a setscrew collar after the block to keep it from extending beyond the back edge of the bell crank. If it slides beyond, then the tuning of either change is impossible since the pull rod would spin. My guitar doesn’t have the collar and I haven’t had this happen. When assembling, the wristpin in the slotted block must be positioned as close to the changer side of the slot as possible, including the running of the block against the wristpin. Otherwise, you are losing “slot” travel and the block is more likely to slip beyond the far side of the bell crank. In both cases, don’t shave too much material that slides into the bell crank slots and against the wristpins. This area could be weakened to the point where the “ears” could break off. Making the block and the spacer a little taller, if there is room to work it, would be a good idea.
The construction of the tuning nut on the second change is quite simple. Using an old snow mobile slider (about ½” thick), heat a 12 point socket of appropriate size with a torch or stove element just hot enough to be pressed into the nylon. Let it cool, place it in the lathe chuck if you have one and drill the centre undersized. Thread it onto the end of the pull rod without its having been threaded. A friction fit is desirable.
Fay
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