Search found 195 matches

by Craig Bumgarner
Tue Jun 11, 2013 1:37 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Testing good examples
Replies: 26
Views: 32534

Re: Testing good examples

Hi, Just wanted to say that the instruments I would be gathering data on are vintage instruments 50-70 years old and their builders are now departed. To me, to gather and publish information on these does not seem inappropriate. The festival I'm attending is a players festival, not a builder's festi...
by Craig Bumgarner
Thu Jun 06, 2013 6:36 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Testing good examples
Replies: 26
Views: 32534

Re: Testing good examples

Mike, Yes, those are all important physical characteristics I usually document. Break angle of the strings over the bridge is something I also measure as it is functional end result of neck angle, fingerboard thickness and bridge height, and it is quick & easy to do. I usually take a neck section pr...
by Craig Bumgarner
Wed Jun 05, 2013 12:18 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Top Deflection rig
Replies: 41
Views: 76211

Re: Top Deflection rig

I've been thinking of switching to lead shot in a plastic bag for weight. Sooner or later, I'm going to drop the weight and a solid disc of metal will not doubt damage the top.
by Craig Bumgarner
Tue Jun 04, 2013 10:44 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Testing good examples
Replies: 26
Views: 32534

Testing good examples

I'm going to a festival in a couple weeks where there will be a LOT of good examples of the Selmer style guitars I build and I would like to document as many as I can using the principals in the Books. I've only just read them and begun using the methods so I'm inexperienced, but I don't want to mis...
by Craig Bumgarner
Tue Jun 04, 2013 10:25 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Top Deflection rig
Replies: 41
Views: 76211

Re: Top Deflection rig

Here is a picture of the rig I've been using. The weight is not shown, a barbell weight goes on the spindle at the top in the middle. Except that my gauges are offset from the load point, I think it is reasonable accurate and stable. For the sake of simplicity and easier transport, I'll probably mod...
by Craig Bumgarner
Tue Jun 04, 2013 4:30 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Top Deflection rig
Replies: 41
Views: 76211

Re: Top Deflection rig

Interesting. First deflection jig I've seen other than the one I cooked up and like the simplicity of yours. I'm interested in how you are applying the load. Is there a spindle hiding behind the gauge? A picture from the side would be interesting. In my jig, things get crowded eithe the load and the...
by Craig Bumgarner
Thu May 09, 2013 11:16 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Re: Equation 1.7-1

It looks like K has been calculated in N/mm (instead of N/m) which in turn has modified m, which looks like it may have given a result in s/kg x 10-3 to line up with the units in the graph? Steve Yes, that's right. In order to get the zero count right compared to the graph, I used Newtons and milli...
by Craig Bumgarner
Thu May 09, 2013 1:31 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Re: Equation 1.7-1

I see in my last Excel screen shot, the formatting of the column for m was only to 4 places. It still calculates correctly, but looks better when formatted to 8 places.
Specific Mobility, screen shot 3.jpg
Specific Mobility, screen shot 3.jpg (39.16 KiB) Viewed 28563 times
by Craig Bumgarner
Thu May 09, 2013 12:10 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Re: Equation 1.7-1

Okay, thanks for these ideas, sorry if I'm being a pest. I too have been skeptical of the mobility number as the Selmer tops for the same reasons you state, they do seem stiffer than most and the mass is probably not a lot less. I say probably as I really don't know what the tops on other styles wei...
by Craig Bumgarner
Tue May 07, 2013 11:31 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Re: Equation 1.7-1

On second thought, maybe better to use Newtons and mm:
Specific Mobility, screen shoot 2.jpg
Specific Mobility, screen shoot 2.jpg (38.43 KiB) Viewed 28611 times
Thanks for everyone's help on this!
by Craig Bumgarner
Tue May 07, 2013 11:16 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Re: Equation 1.7-1

Okay, I'm going to assume then that my calculation is basically right. Being metric, the zero count will depend on whether one uses Newtons, Kg, mm or Meters. From here out, I just need to be consistent. As the graph in Figures 1-7.8 and 1-7.9 uses a scale of 0-30 on the Y axis, I'll use what gives ...
by Craig Bumgarner
Tue May 07, 2013 7:19 am
Forum: Instrument Builders Forum
Topic: Binding jig router setup
Replies: 6
Views: 7433

Re: Binding jig router setup

Here is a picture of my setup. Actually the router is a Bosch Colt, but I should think the Makita base is just screwed on too. I use the same holes as the original base. My guitars have a lot of arch, so I want the minimum of contact area, the small curved part. The larger part underneath is more of...
by Craig Bumgarner
Sun May 05, 2013 3:54 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Re: Equation 1.7-1

I don't understand the units of the results shown in Fig. 1.7-8, s/KG^-3, ..... Well, first, that should be s/KG x 10 ^-3, but I still don't understand the units. :? Second, maybe it would be a help if I posted the data I working with: Deflection load: 5 pounds, I input 22.241 Newtons Deflection: ....
by Craig Bumgarner
Sun May 05, 2013 1:33 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Equation 1.7-1
Replies: 33
Views: 36853

Equation 1.7-1

I'm a bit stumped on the units for Equation 1.7-1, both for input and results. I inferred from the text that K is the load in Newtons over the resulting deflection in mm. I don't understand the units of the results shown in Fig. 1.7-8, s/KG^-3, in particular what is "s". Elsewhere "s" is pluck lengt...
by Craig Bumgarner
Sat May 04, 2013 8:00 pm
Forum: Instrument Builders Forum
Topic: Binding jig router setup
Replies: 6
Views: 7433

Re: Binding jig router setup

I'm away for the weekend and can't check until Monday, but my recollection is I took the Makita base off and made a custom base to with the LMI jig. I'll check and post pictures Monday.

BTW, I like this jig, it works very well.
by Craig Bumgarner
Sat Apr 27, 2013 12:07 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Collecting data on good examples
Replies: 5
Views: 7836

Re: Collecting data on good examples

Okay, thanks Trevor. I did some tests taps this morning on one of my older guitars, strings off, strings on. I was a little concerned that with a Selmer type guitar, floating bridge and tailpiece, that I might get significantly different results if I could not tap in the center area of the top made ...
by Craig Bumgarner
Fri Apr 26, 2013 12:26 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Collecting data on good examples
Replies: 5
Views: 7836

Collecting data on good examples

I'm going to an annual gypsy jazz festival where the Selmer style guitar I build will be in abundance, many of which are some of the best in the world for this style music. I'd like to be able to collect data on the best of these guitars without too much intrusion. It seems like a great opportunity ...
by Craig Bumgarner
Thu Apr 25, 2013 3:10 am
Forum: Instrument Builders Forum
Topic: Setting up Visual Analyser and capturing a frequency plot
Replies: 22
Views: 33292

Re: Setting up Visual Analyser and capturing a frequency plo

Yes, it works that way in VA 11, thanks.
by Craig Bumgarner
Sat Apr 13, 2013 1:51 am
Forum: Instrument Builders Forum
Topic: Setting up Visual Analyser and capturing a frequency plot
Replies: 22
Views: 33292

Re: Setting up Visual Analyser and capturing a frequency plo

Thanks Trevor and Marcus, I'm using VA-11 and I don't see the option to save as a .wmf file, only .tee or .txt. , but maybe it is there somewhere. No big deal, I can use Alt+PrtScn to copy to clipboard, pasting into a graphic program and save as .jpg if and when I need that. For now .tee files and t...
by Craig Bumgarner
Fri Apr 12, 2013 11:39 pm
Forum: Instrument Builders Forum
Topic: Setting up Visual Analyser and capturing a frequency plot
Replies: 22
Views: 33292

Re: Setting up Visual Analyser and capturing a frequency plo

Hello from Maryland, USA. I'm a new member and joined at the recommendation of the good folks at MIMF to further my understanding of Trevor Gore & Gerard Gilet's terrific book set. I read most of the Build volume last year and at the encouragement of MIMF have started in on Design. I've set up VA an...