Hi all,
In this part, we will take care of stringing the instrument, installing the action, and taking care of the little odds & ends that are necessary. We’ve come so far in this project that this series would be incomplete without talking about strings and jacks etc. However, detailed descriptions of the techniques involved would be useless to you unless you were going to build your own instrument. So, in the interest of brevity and sanity (mine and yours), I’ll briefly tell what was done without getting into the nuts and bolts of the procedures.
Odds & Ends Gap Spacers – 3 maple gap spacers are installed between the upper belly rail and the pinblock. The pull of the strings tends to pull the bellyrail into the gap. This can narrow the gap, sometimes to the point where the registers will be frozen and unable to move. The gap spacers help to eliminate this tendency.
Register Rest Blocks – The 2 upper registers sit in the gap. The ends of the registers sit on the register rest blocks glued to the case sides on the cheek and spine.
Buff Stop Rail - The buff stop rail is a thin wooden rail that sits behind the 8’ nut and is held in place by a few escutcheon pins. After the strings are installed, little buckskin pads will be glued to this rail. When the rail lever is turned on, these pads lightly touch their neighboring strings and change the tone to sound more like an acoustic guitar or lute.
Register Levers – The two upper registers and the buff stop rail are moved left or right to turn them on/off. This movement is controlled by the register lever which are fabricated in the shop from 1/8” thick, 3/8” wide brass bar stock.
One end of the brass is bent 90 degrees to form the handle. This is done using a vise and a c-clamp.
The far end of each lever has a hole drilled into it which accepts a pin imbedded into the register or, as in the next photo, the buff stop rail. Moving the lever left or right will move the register or rail in the opposite direction.
Hitchpins – The far end of each string is looped around hitchpins which are imbedded into the 8’ hitchpin rail and the 4’ hitchpin rail (which is underneath the soundboard). When we built it, (
see Part 19) we punched dimples into the soundboard to show the position of the 4’ hitchpins. We now punch similar dimples into the 8’ hitchpin rail (taken from the blueprint) to locate those pins. Then we drill the 104 holes using a 1/16” drill bit and install the pins. Here the hitchpins are being installed into the 8’ hitchpin rail.
And through the soundboard into the 4’ hitchpin rail.
Bridge Pins – Dimples were similarly placed on the 8’ bridge in
Part 19. We drill these holes with a #56 drill bit to accept pins with a diameter of .049. The holes on the 4’ bridge will be located and drilled after the 8’ strings have been installed.
The white material you see at the base of the pins is soap which has been applied to the pin to make its insertion into the bridge easier. Keep in mind that the soundboard is only 1/8” thick and we don’t want to push the pins in with such force that we crack the soundboard. That would really spoil my day.
Stringing the Harpsichord
There are 104 strings to install – 52 on the big bridge and 52 on the small bridge. Nine different sizes (diameters) of wire are used ranging from .020 in the bass to .009 in the treble. Three different wire materials are used – red brass in the lowest bass, yellow brass for the rest of the bass, and low-tensioned steel for the rest of the instrument. Each of the 104 strings are cut to length from a coil of music wire and have a loop turned into the far end. This loop is turned by hand using a vise into which is placed a hitchpin. While this loop looks somewhat complicated, it’s pretty easy to do after you’ve done a few hundred of them. Each loop takes about 30 seconds. Here’s what a completed loop looks like.
The 8’ strings are put on first. Pins are installed into the 8’ nut which terminate the speaking length of the strings and cause the strings to cross over the registers in the correct position.
Once the 8’ strings have been installed we drill holes on the 4’ bridge and pin that bridge. Then we can install the 4’ strings and pin the 4’ nut.
After the 4’ strings have been installed and the 4’ nut pinned, the stringing is completed.
Installing the Jacks
As there are 104 strings in the harpsichord there will be 104 jacks – one for each string. Here’s a photo of an assembled jack, complete with its plectrum (plucker).
At this stage the jack is far too long and must be cut to size. The jack goes through its slot in the upper and lower registers and sits on the end of its corresponding key. The jack must be cut so that, when installed, the plectrum will sit 1/16” below the string it is to pluck. It would be nice to be able to determine this length and gang-cut all of the jacks. However, you may remember that the bridges and nuts taper in height from bass to treble, so each jack must be cut to fit separately. We drill out the bottom of each jack to accept a small machine screw which gives us a way to fine-tune the height of the jack.
Each jack is labeled so that we can remove it and replace it in the same slot.
Finally it’s time to install the jacks. If everything to this point was done accurately – if the registers were cut correctly – if the pinning of the bridges and nuts is dead on – if the tuning pin holes were drilled in the right place – if the coils of music wire on the tuning pins leave the pins at the correct angle – if the plectra are cut to the correct length – then the installation of the jacks will proceed without a problem. In other words, if perfection was achieved then the job is easy. Of course, perfection is never achieved, at least by me. Hopefully, any errors will be minor and can be compensated for. Over the years I’ve learned that almost any error can be fixed or compensated for, but not without a lot of pain and several sleepless nights. Five months of work all comes down to this. Fortunately, nothing went wrong with our instrument and the jack installation went without incident. Here’s some 8’ jacks being installed.
After all of the jacks are installed, they must be regulated to work correctly. The plectra must be voiced by scraping their undersides with a sharp blade so that the volume of sound produced by the harpsichord is even throughout its range. The plucks of the 2 jacks controlled by each key must be staggered so they don’t pluck at the same time, which would make the feel of the keys very heavy. All of this takes time – it’s not at all unusual to spend a couple of weeks on this regulation and still not be satisfied.
Part of this regulation has to do with the jackrail that we built in
Part 11. The jackrail, which has cloth installed on its underside, is vital to the proper functioning of the action.
The downward movement of the keys stops when the jacks hit the jackrail. This downward movement is called key dip and is adjusted by adding more cloth into the jackrail or by shortening the jacks above the plectra, which is the method I use.
The last step is the installation of little buckskin pads onto the buff stop rail.
That done, the stringing and action have been completed.
Except for some nit-picking, which I love to do, the instrument is now complete – and playing. In the next post, which will be the final post in this series, we’ll summarize the project and show the final photos.
Till the last time,
Ernie
04-02-2009, 01:01 AM
.gif "Drogar BigGrin(DBG)")
You not only did an outstanding job of building the instrument, but did an equally impressive job of documenting the process. 
Truths: There is no such thing as a 25 hour day, so why do I keep trying to cram so much into every day so it seems that way! 
.gif "Drogar Laugh(DBG)")
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