Monday, 11 November 2013

Styrofoam Cutter

A styrofoam cutter made from spare materials I had lying around:

The arm can move so as to create an angle between the wire and the table and the temperature of the wire is varied by sliding the black wire up and down the cutting wire.

Voltage: 12V DC
Power: 10.5W
Throat: 20cm
Max Z: 20cm

Tuesday, 15 October 2013

First Cello Repair!

I looked into a possibility of repairing a cello that belongs to one of my friends. Its a Chinese Lark cello with a medium grained spruce table and plain maple ribs and back. As you may know, Lark cellos were one of the (worst) cellos you could get ten years ago and were found in school orchestras because they were cheap! This particular cello has seen service for over twenty years and sounds comparatively decent, probably owing to the fact that it has been played for so long.

This big guy came in with many problems due to its age:

1. The center seam on both the front and the back plate have opened, shown in the two pictures above and below:

2. There were two open seams on the treble side of the instrument:

3. The nut had come off and was only held in place by the tension of the strings. 

4. I also discovered that the fingerboard was coming off when I was about to put everything back together.

5. The endpin was damaged and was not at all parallel to the body of the cello, making playing awkward.

In any case, onto the repairs! (not in order of the problems listed)

1. Glued the nut back on since it was the easiest.

2. The open seams were next. I made new spool clamps for this job; this set of twenty can do both cellos and double basses!

3. The open center seam on the back was next. This particular repair was quite challenging as the two halves of the black plate did not align properly because the treble half had been pushed out by the pressure of the strings (acting through the soundpost)

This stage was rather scary as the wooden boards had quite a bit tension on them. If one of them slipped....

Anyway, I also glued some squares of maple veneer along the interior of the cello along the back center seam to reinforce it:

The spool clamps acted as a weight to keep the veneer squares down:

4. I did the front seam as I glued the reinforcing veneers onto the back:

The front center seam was another problematic issue; the wood in that area apparently shrunk, leaving a gap between the plates, causing them to come apart. The recommended repair procedure was to place wet tissue in the area so that the wood expands but I didn't want to do something so drastic.

I poured as much bone glue as I could into the area to fill it up. However, it was not to be and the seam opened up again a few weeks after I gave the cello back to my friend. If I ever get to see this kind of problem again, I would try putting a thin strips of maple veneer into the gap to fill it. That should prove to be a more lasting repair

5: The endpin hole on this cello was rather big and the endpin that I bought from Synwin was way too small for it. I tried to fatten the new endpin with maple veneer but two of the three pieces I put in fell out off the other side of the hole! The resulting endpin with the strings on was not very straight, but still an improvement over the previous one so I left it at that.

6. The last problem to be discovered and repaired was the fingerboard. It would probably have held on a few more years but since it was obviously opening up, I took the liberty of pouring some glue in:

7: I fitted a new soundpost into the instrument as the old one was a hair too short. The bridge itself was clearly not carved specifically for this cello; the treble side was too high and the bass side was too low. I could have turned the bridge around but then the feet would have fit badly so I just left it be and told my friend to scrounge for another bridge that I can try my hand at carving! The fingerboard also needed shooting as the scoop for the C string was not deep enough but I didn't bother with that as ebony is the hardest wood to carve and I didn't want to mess with it. I also sanded the pegs down as they were a little too big. However, I went a little overboard on that and the pegs are now too slippery!

Anyway, here are pictures of the repaired instrument:

For those of you who don't know what a nut is, its that small rectangular piece of ebony at the end of the fingerboard that contains grooves for the strings to pass through.

Overall, the (semi) repaired instrument sounded quite nice for a low grade cello, with the exception of the A string being a little thin due to the extra wood on the treble side of the bridge. The C string was fine but would buzz if played too loud due to it being way too close to the fingerboard but all in all, I was quite happy with my repair and setup :)

Tuesday, 13 August 2013

Regraduating a Viola

This is one of the most risky projects I have undertaken to date - especially since violin making is considered by most to be the 'pinnacle of woodworking'.

For those who don't know, the viola is a bowed string instrument pitched in between the violin and the cello, in terms of both sound and size. It forms the 'alto' voice of the orchestra but is rarely heard as a solo instrument due to it being able to 'blend' in so well with the rest of the orchestra.

This is a 15.5" Chinese factory viola from Yita Music that cost about $350 SGD, it could not project well (i.e. it was soft) so I upgraded to another instrument after a year of playing it in the SUTD Chamber Ensemble.

First Impressions
The tone and projection of a bowed string instrument is governed by a myriad of factors: the quality of the wood used, the shape, arching and thickness of the front and back plate, the thickness of the ribs, and of course, the final setup of the instrument.

The viola I had was heavy (too thick) and that was probably one of the reasons why it was not projecting well. The solution to this is to regraduate the instrument - which involves taking it apart and scraping off the right amount of wood in the right places:

1: Taking the instrument apart:

All bowed string instruments are put together using hide/animal glue. This glue is strong, but brittle and water-soluble. Although these traits are usually not very desirable, hide glue is used to construct string instruments as its properties allow the instrument to be taken apart for the occasional repair job. In addition, the glue joint formed is usually weaker than the wood used, which means that it would break in deference to the wood should the instrument experience excess pressure.

Taking apart a new instrument however, is not that simple as glue joint is still relatively strong. I spent quite a bit of time trying to break it without damaging the instrument. Once the glue joint is broken in one location, a chisel or a butter knife can be slid slowly around the instrument and the rest of the glue joint would yield to the pressure.

However, special caution must be taken when prying the top, bottom and four sides open. There are corner blocks in these locations and the glue joint is much stronger there. I managed to get the top of my first instrument open with one crack near the top (a good result by my luthier's standards; he expected three cracks).

2. Regraduating the Instrument:

The top plate of the viola shown together with my partners in crime: a 10mm plane, a penknife blade (snapped down to size) and a sharpened palette knife, which acts like a scraper.

Since this is a strad-style viola, I pulled off measurements made on the famed 'Gibson' Stradivarius from the internet:

In theory, IF i manage to get the thickness of the front and back plates down the the specifications, I would likely to have a relatively good sounding instrument.

Shown above is a custom-made depth gauge I constructed for this project, featuring a pair of digital vernier calipers. The supporting frame and all the components were lasercut to ensure precision. This device allowed me to measure the thickness of the top and back plate at any point to an accuracy of 0.01mm.

The top plate of a bowed string instrument is made of spruce - a soft wood. The original top plate was 1mm too thick in most areas - that's quite a bit of wood to take off! 

Unfortunately, I am not the most patient of souls. The end product was too thin, especially at the areas that were supposed to experience the most pressure when the entire instrument was put together (the middle)!

The back plate of the instrument is made of maple, which is a hard wood. Wood removal in this case was much harder than that of the front plate. Consequently, I measured the thickness more often and did not overshoot by much this time round. I even left some areas a bit thicker as I was too lazy to scrape off the remaining 0.2mm!

Note that the wood scrapings you see in the picture is probably a third of what I actually worked off the instrument!

3. Repairing the Damage:

Remember about the crack I made when removing the top plate? Not to mention the top plate itself being too thin! All this needed to be resolved before I put the instrument back together.

I managed to get some hide glue, varnish, a spruce dowl and some advice from the luthier and boss of Music Essentials, Mr. Chia Sin Teck.

Shown above in the ziplock bag is some hide glue; you have to mix the granules with hot water (about 75 degrees) in the right concentration. Upon application, you have about 2 minutes of working time before the glue cools and gels - at which point the glue joint (called a cold joint) formed is weak and useless.

I glued the crack together relatively easily. However, the hard part is reinforcement. Cracks on a string instrument are traditionally reinforced by gluing small pieces of spruce (called cleats) along the crack line and smoothing them down. The cleats must fit the contour of the area around the crack and be small enough not to affect the sound of the instrument. 

However, cutting the cleats out of the spruce dowl i was given was a rather impossible task for someone like me - no training, no proper tools, no patience. The small cleats kept on breaking as i tried to saw them off the dowel with a penknife.

The solution to by dilemma came in the form of maple veneer. I got a nice big roll of it (1" x 8") for $12 from Ban Heng Leong Trading. Veneer is by virtue flexible and thin and maple is a hard tonewood. This fulfilled my requirements of having something light and strong that fit the contours of the instrument easily.

Shown above is the big roll maple veneer; I cut a small semicircle out and patched the crack with it. I then cut two larger circles and used it to reinforce the middle of the instrument (one on top of the other). I used makeshift sandbags (aquarium gravel in a ziplock bag) and a book to weigh down and press the veneer onto the instrument as the hide glue dried over the course of a day.

Lutheirs would usually put their label on instruments they make. No exceptions here :)

4. Putting it Back Together:

Some people consider step this quite hard as you only have two minutes to spread the glue along the ribs, get the top plate on right (alignment wise) and clamp the corners of the instrument down tight. I rehearsed the individual steps in my mind a few times in the period leading up to this event to be sure I would do it precisely and efficiently.

The clamps used here are called spool clamps. As usual, all the clamps (30 of them) were designed and made by me specially for this project. And if you all are wondering how I got so many nice circles, yes, I did make good use of the lasercutter at school.

5. Setting the Instrument up and Final Repairs

Now my viola was back together again, it was time to set it up and put the strings on!

A soundpost is a wood dowel that is inserted into the instrument somewhere near the middle. It serves to transmit the force and the vibrations the strings exert on the top plate (via the bridge) to the bottom plate so that the instrument resonates as a whole.

I used a drill and sandpaper to thin the remainder of the spruce dowel given to me (that dowel was meant to be a cello soundpost. It was a crude method but it worked somewhat.

One final repair - I apparently shaved off a bit too much wood on one side of the top plate, which resulted in a big gap between a portion of the plate and the ribs. This was fixed with thin rectangles of maple veneer inserted and glued carefully into the gap.

5. The Final Instrument:

After I set the instrument up, I took the finished product to Mr. Chia for a little tweaking (I really need to thank him; his help and guidance was genuine despite his busy schedule; I learnt quite a bit!) . He mentioned that I could further improve the instrument by increasing the projection of the fingerboard and changing the bridge accordingly, but enough is enough. I consider myself remarkably lucky to have gotten this far without having caused any irreparable damage to the instrument!

The final instrument sounds much better than the original. For starters, it projects better (you can now feel it 'throw' is voice out). It has also adopted a more or less neutral tone (neither dark nor bright) with a slight hint of 'boxiness' (possibly due to the thin top). The original instrument sounded deceptively 'dark' and 'warm' due to the sound being 'trapped' inside it. This guy now sounds more 'open' and 'nasal', qualities you generally look for in a viola.

Monday, 12 August 2013

Plywood Bookshelves

This was done sometime ago in Feb 2012 and I thought it would be a good one to start this blog off.

Unfinished bookshelf ready for varnishing!
I ordered the plywood from Ban Heng Leong Trading, had to cut it down to size ($1/cut) and delivered. They didn't help me bring it up to my apartment though :(

These two bookshelves were built with the shortcomings of the cheap bookshelves IKEA sells in mind. They each have a solid one piece plywood back (no warping) and the shelves are supported from the sides and the back by plywood strips that are screwed into the sides and back (no sagging shelves). The irregularities were then planned off and the entire thing was given 2 - 3 coats of varnish to finish it off.

Bookshelf 1. The varnish brought out the layered texture
of the plywood well - an unexpected aesthetic result :)

These 2 guys took me about 2 weeks to finish and cost less than $200 SGD (excluding tools).