Don Noon's bench

[Don Noon]

6 hours ago, HoGo said:

How long did it take to cut the back as shown?

The only thing I actually timed was the clearing off of the central area, as it was noisy and I left the shop until my timer went off.  The cutting took about 8 minutes per pass, and I took 4 passes.

Most of the time is taken in setting up and checking the results; the cutting goes pretty fast.  But even with all the setup, it's infinitely faster than I can go by hand (but maybe not faster than Burgess).

These were my first plates, so caution slowed things down, I think.  With more practice and less caution, I can probably wreck plates in a flash.

3 hours ago, scordatura said:

Fusion 360 only has loft. Rhino has curve network. 

If you loft using "rails" (as I did), I think the result is similar to the curve network.

[scordatura]

18 minutes ago, Don Noon said:

If you loft using "rails" (as I did), I think the result is similar to the curve network.

I am going to do an A B comparison. My gut tells me that Rhino will have the edge on Fusion 360 when it comes to skinning from rails.

[HoGo]

The most important on the curve network in Rhino is that it allows to create new surfaces with smooth transition to adjacent surfaces (and at two levels - tangency or curvature continuous). But still the result is VERY dependent on which curves you create for your network. Planning ahead is a must and sometimes you need few differing attempts to get it working.

[Michael_Molnar]

Nice job, Don.  I also enjoyed the surface modeling posts and agree to move them to a CNC thread.

[Don Noon]

A few things happened in the last 2 months...

Violin #27 is with its new owner after its re-varnish job.

#16, which was my VSA2016 entry, also is with its new owner after a re-varnish and some fairly extensive modifications:  large patch added to the back C-bout, and much heavier (but not stiffer) bass bar.  I am over my lightweight phase, as I find that mass is needed in certain places.

#30 also is with its new owner after a re-varnish of the top.  Hopefully I can get better at varnishing the first time.

The viola twins are coming along; the garlands and backs are done, and one top is nearly done.

With the flurry of sales, I naturally had to sink some of it into a new tool:

I am REALLY impressed with this new machine.  The previous version (with round guide rails) had a stiffness at the spindle of ~670 lb/in, the new one with linear guides is ~5000 lb/in.  The wireless handwheel is convenient too.  Further playing with the new toy will have to wait until I finish the violas.

Annelle Gregory made a new video that is perfect for this period of pandemic panic and enforced isolation.  I think my violin is better suited for a large hall (as in her performance I went to last month), but I can't fault the playing.

 

 

[Don Noon]

I guess Annelle has been busy at home making videos.  I like this one, and the sound seems to be better... the previous one had what sounded like strong room acoustics.

 

[Jim Bress]

That was nice. 

[Wood Butcher]

On 3/27/2020 at 11:22 PM, Don Noon said:

With the flurry of sales, I naturally had to sink some of it into a new tool:

I am REALLY impressed with this new machine.  The previous version (with round guide rails) had a stiffness at the spindle of ~670 lb/in, the new one with linear guides is ~5000 lb/in.  The wireless handwheel is convenient too.  Further playing with the new toy will have to wait until I finish the violas.

I guess this is a CNC machine. Is it a particular type or model, or something you have created yourself Don?

[Don Noon]

5 hours ago, Wood Butcher said:

I guess this is a CNC machine. Is it a particular type or model, or something you have created yourself Don?

It is flattering that you think I could create a machine like this (or more likely, you aren't all that familiar with this kind of machinery).  I suppose I could make a similar one, if I wanted to spend a few years and many thousands of dollars doing it.  This is one of the latest models to come out of China, a standard "6040" size (approx. 60cm x 40cm travel).  As I said, a very  impressive machine.  The instructions and documentation... not so much.  But that can be overcome.

[Don Noon]

After verifying the alignment of the new CNC and fabricating a new spoilboard (the wood that goes on top of the bed), the first major project was to fabricate pre-grafted neck/scroll assemblies for violas (which naturally needed a fixture that I had to design and fabricate).  It turned out that I have zero viola neck blocks of full size, but some short blocks wide enough for the scroll and plenty of narrow blocks for the neck.  All these are torrefied... except for the fixture.

[Don Noon]

It has been slow going; I figured that since the pandemic has slowed down the music performance side of things, I'd get some more stuff done on the CNC vs. the usual hand work.  That takes a LOT of time for the first one, with all the design, CAM, fixturing, and testing that has to be done.  So the delivery dates are slipping near-term, but hopefully this will speed things up down the line.

One of my least favorite tasks is shaping and lighweighting ebony fingerboards, so that was one thing I really wanted to have offloaded to the CNC.  I had to make up a vacuum fixture to hold down the blank for shaping the top surface (first photo), and another fixture to hold the fingerboard for hollowing the underside (not as snazzy, so no photo).  Before risking ebony, I tested all the fixtures and operations by making a fingerboard out of scrap maple (next 2 photos).

I closed the body on my new viola design (40 cm) a while ago, but lots of final scraping and detail left to go.

 

[FoxMitchell]

It's looking good!   

I know there are threads out there discussing lightening of fingerboards, but I figured I might ask here since you brought it up, and you do all the acoustic measurement stuff so you might actually have empiric evidence: Does it actually make any difference as far as the sound goes, or is it simply a matter of making the whole thing a few grams lighter for added comfort?

[Don Noon]

3 hours ago, FoxMitchell said:

Does it actually make any difference as far as the sound goes, or is it simply a matter of making the whole thing a few grams lighter for added comfort?

I have never been able to find any significant sound effect from the fingerboard... but my measurements are all with either open (and damped) strings, or in 1st position bowing.  I don't play out there on the far end of the fingerboard to tell, but I have heard that the mass makes a difference to how it plays in the high positions.  I can always glue a bit of lead under the fingerboard end if necessary (as I have seen on a Burgess violin); it's more of a pain to take off mass once the instrument is completed.  This is regarding lightweighting on the free end, where my thickness is very close to the "normal" treatment.

As far as lightwighting where it glues to the neck, I think there is less concern about reaction mass in playing, but should be more important to player comfort because it's cantilevered farther from the player and takes more effort to hold.  A few grams there can be noticed, and for violas I think it is much more important than on violins.

[FoxMitchell]

Awesome!

[Don Noon]

Just another video of Annelle Gregory, pre-pandemic... 

 

[Don Noon]

My new model viola is still far from done, but the varnish is on and partially antiqued.  At this ugly stage, I won't post any photos, but I wanted to string it up and see how it played and sounded, in case some internal adjustments were needed.  I think it sounds and plays very nicely.  The bridge is still too high and way too heavy, but here's a comparison with my VSA2016 viola, using bowed semitone scales:

Construction-wise, the new model is not as wide, the arching is ~2mm lower, and the plates are slightly thicker.  Top (with bar) and back weighed 78g and 124g respectively, a few grams heavier than the previous one.  A major difference is the garland; on the VSA instrument, I had very large endblocks and cornerblocks, as well as thicker ribs than usual.  The new viola garland is almost 20g lighter (!)  Projection is also ~2mm higher.

Technical acoustic observations... viola CBR output seems very strong, and is the strongest output of the new model.  At this lower resolution, the CBR and B1- peaks blend together.  The new model also has extremely strong output in the 1 - 1.5 kHz range, where the previous model had a dip.  I attribute this to the lower arching, although I could be wrong.

In playing and listening to recorded comparisons, the new one seems noticeably more powerful, and I think sounds more like a viola.

It will be a while before this is really complete and I can get a good demonstration with somebody that can play it.  Hopefully this (or and even better one) will be in the VSA2022 competition.

[Bill Merkel]

On 8/4/2020 at 1:01 PM, Don Noon said:

Just another video of Annelle Gregory, pre-pandemic... 

what are some things you consider the recording to not capture?

[Don Noon]

5 hours ago, Bill Merkel said:

what are some things you consider the recording to not capture?

Actually, I think this is a very good recording to showcase the power of the violin to be heard over a loud piano in a large hall.  Of course, Annelle has something to do with it.  She's great.

[Don Noon]

Before I post the more interesting thing, here's a 1-day project that I've been meaning to get to for quite a while (it was a very long day).  I had a cheap, noisy, dusty belt/disc sander from Harbor Freight, but couldn't stand the noise and dust, and found better ways to make parts.  So I salvaged the motor (kinda neat TEFC 1700 RPM item), disc, miter, and power switch.  After boring the disc to fit the motor, adding some magnets and some 6" diamond discs, I finally had my diamond disc sharpening machine.  The final motivation to make this was turning pegs on my lathe, where I could only get one peg done before the HSS bit went dull.  Something like this is a necessity for sharpening carbide bits.

[Don Noon]

FINALLY finished the first viola of my new design (5th viola overall, all different).  I know it's all subjective, but the sound came out the way I think a viola should sound... not like a violin.  Technically, I suppose that means having its response peaks where a violin has dips, or something like that, and as much power as possible in the lower frequencies.  I'm satisfied with the varnish, but not 100%.  It's still not exactly what I want, but presentable.

Some details:  40 cm (15 3/4"), 458 grams full setup, without chinrest.  

And, of course, the test drive:

 

 

[Andreas Preuss]

458g is really light. 

Interesting f-hole design to drop the bridge position below the center of the f-hole. 

And comparitively long f-holes.

I guess all made on purpose with having the viola sound in mind.

how hifg are the ribs?

 

[scordatura]

Viola sounds great Don. Seems from the video very responsive. The strongly sloping upper bout should make upper positions easier to reach. Do you mind sharing the densities of the top and back?

[Don Noon]

6 hours ago, Andreas Preuss said:

458g is really light. 

Interesting f-hole design to drop the bridge position below the center of the f-hole. 

And comparitively long f-holes.

I guess all made on purpose with having the viola sound in mind.

how high are the ribs?

Long F's to get A0 up to ~C, to give maximum power to the 1st harmonic of the open C string and slightly more power overall.

F's are positioned about the usual geometry relative to the body, but getting the 375 mm vibrating string and 3/5 stop position put the bridge where it is on the 40 cm body.

Rib heights 36 - 32 mm.  A bit on the low side (?), to keep air volume down and A0 frequency up.

1 hour ago, scordatura said:

Viola sounds great Don. Seems from the video very responsive. The strongly sloping upper bout should make upper positions easier to reach. Do you mind sharing the densities of the top and back?

Yes, the curve of the upper bout was made with high position access in mind.

Top wood:  .335 g/cc, speed of sound 6040 m/s,  RR=18

Back wood:  .534 density, 4650 m/s

These kinds of properties (lower density, higher RR) I think work best on violas, but not so much for violins.  And these are pretty extreme pieces.

[Geigenbauer]

19 minutes ago, Don Noon said:

Top wood:  .335 g/cc, speed of sound 6040 m/s,  RR=18

Back wood:  .534 density, 4650 m/s

Hi Don,

beautiful viola. Thank you for sharing!

Just to confirm: Are these density/speed of sound measurements taken before or after torrefication/torrefaction (not sure what the right term is)?

Thanks

[Don Noon]

Those values are after torrefying and many months of stabilization.  The original properties were .355/5740/16.1  for the top, and .575/4415 for the back.  Most of the mass loss is bound water.