Tuesday, January 24, 2017

Harmochord restoration with a 3D printer (mostly Dad's work!)

In the summer of 2016, we stumbled across an interesting find at a pawn shop in Verdun:



It's basically an accordion with an electric pump instead of the manual bellows, designed as a table-top instrument! Single bank of reeds for the keyboard, and a relatively small array of bass notes compared to the full size accordions

After trying it out in the store and verifying that at least every key makes a sound, we decided it was worth the $20 and the effort to lug it back home on the bus (it probably weighs around $15kg or so...)

The things that were apparent immediately:

- It was "Made in West Germany", which makes it probably the most interesting instrument I have owned thus far...
- pump appears to work fine
- 3 black keys are missing
- a few of the bass notes would stick when pressed

Things we found out afterwards:

- The "briefcase" actually was supposed to contain 3 legs, which allows the instrument to be self standing. Those were missing as well. (oh well...)
- slight leakage in some of the bass notes, causing either weaker sounds or other tones when some notes were pressed

As a keyboard player, the first thing I wanted to do was to get replacements for the black keys. Never got around to it with busy school and family schedule, but when my dad stayed with us for a bit, he took on the project.

This is mostly a documentation of the result of his efforts!

Here's a close-up of the missing keys:


A 3D printed model was made in SketchUp:


It was a basic 2D profile that was pulled upwards, and then a small rectangular extrusion was added (top left of picture).

Here's the key being printed and the finished product:



Here are keys in their final location. Note that the key bed (not 100% sure if that's the right term here) isn't in the best of shape, so things aren't super aligned and some of the existing keys also aren't completely straight either.



Finally, a short demo of how it sounds:



There are a few more things that need to be fixed. My dad managed to get rid of the sticky behaviour of the bass notes, but the leakiness of some of the notes are still there. Here are some shots of the mechanism when it was open, for curiosity's sake:




So at some point, I might tackle that... (but there's also a good chance it won't happen until the next time Dad visits! ;)

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