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Deflection tsting calculations
http://luthiersforum.com/forum/viewtopic.php?f=10101&t=47963
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Author:  Colin North [ Thu Jun 30, 2016 4:42 pm ]
Post subject:  Deflection tsting calculations

Can anyone give me, or direct me to a website which will give me, a formula for calculating long grain Modulus of Elasticity from deflection testing, preferably in metric units?
I've spent a fair bit of time looking and have turned up nothing, although I'm sure I've seen it before somewhere.

Author:  Trevor Gore [ Thu Jun 30, 2016 6:27 pm ]
Post subject:  Re: Deflection tsting calculations

Design P1-24 or P4-39/40.

Author:  Colin North [ Thu Jun 30, 2016 6:40 pm ]
Post subject:  Re: Deflection tsting calculations

Got it, thanks and duh
The volume was actually at my elbow as I read your post, I'd looked it out to search.

Author:  jfmckenna [ Thu Jun 30, 2016 8:51 pm ]
Post subject:  Re: Deflection tsting calculations

You got that? I didn't :)

The P's and Q's that is.

I just started deflection testing too and tried searching as well for others methods and so on. I finally came to the conclusion that it's a big secret and you have to figure it all out yourself. So I have a brick with cork glued to it, a dial caliper, some blocks to raise the top up on and just add the weight, repeat 3 times, take the average, and record it. I guess after about 20 more guitars I will have a personal data set that will start to provide results.

Author:  Trevor Gore [ Fri Jul 01, 2016 12:59 am ]
Post subject:  Re: Deflection tsting calculations

jfmckenna wrote:
You got that? I didn't :)

The P's and Q's that is.

Page references for the book. A lot easier than trying to write out math formulae on a text-based forum.

jfmckenna wrote:
I just started deflection testing too and tried searching as well for others methods and so on. I finally came to the conclusion that it's a big secret and you have to figure it all out yourself... ... I guess after about 20 more guitars I will have a personal data set that will start to provide results.

No need to re-invent the wheel. According to Charles Fox (referring to the book) "This is exactly what you want, and you can begin wielding this valuable knowledge almost immediately instead of waiting a lifetime to attain it."

Thank you Charles!

Author:  jfmckenna [ Fri Jul 01, 2016 8:23 am ]
Post subject:  Re: Deflection tsting calculations

Oh I see! Yes, been meaning to get the books for some time now. My problem is I buy books, shelf them, and never read them. That or I spend all my money on wood :D

Holiday weekend coming up might give me time to finally sit down and finish the Somogyi books and then move on...

Looks like it's out of stock? Is there a digital version?

Author:  Trevor Gore [ Fri Jul 01, 2016 7:08 pm ]
Post subject:  Re: Deflection tsting calculations

jfmckenna wrote:
Looks like it's out of stock? Is there a digital version?


It's not really the sort of book that lends itself to digital. I'm currently proofing the 2nd edition pre-prints from the printer. Should be back in stock toward the end of August, if all goes to plan.

Author:  CharlieT [ Fri Jul 01, 2016 8:45 pm ]
Post subject:  Re: Deflection tsting calculations

Trevor Gore wrote:
I'm currently proofing the 2nd edition pre-prints from the printer.

Trevor, will there be significant differences between the 1st and 2nd editions?

Author:  Durero [ Sat Jul 02, 2016 12:03 am ]
Post subject:  Re: Deflection tsting calculations

CharlieT wrote:
Trevor Gore wrote:
I'm currently proofing the 2nd edition pre-prints from the printer.

Trevor, will there be significant differences between the 1st and 2nd editions?


+1

Also very interested to know.

Author:  Trevor Gore [ Sat Jul 02, 2016 12:35 am ]
Post subject:  Re: Deflection tsting calculations

CharlieT wrote:
Trevor, will there be significant differences between the 1st and 2nd editions?


Probably greater than 98% the same. I've changed out a few of the "free standing" photos for better/more interesting ones; the photos in Build are all a little bit larger and better colour balanced; there's a bit more on intonation/compensation, there's a better double-acting truss rod. There's minor changes to some of the equations so that they are easier to check (there was a residual error of ~0.5% (iirc) that was driving people mad when trying to check their calcs, but of no consequence in real life). There's the new foreword by Charles Fox (referred to above) and a commendation by Tommy Emmanuel. Otherwise, it was about correcting typos and re-wording a few explanations to help reduce the possibility of any ambiguity. So if you already have Edition 1, I wouldn't be rushing out to update to Edition 2, unless you have plenty of spare cash that you want to throw in my direction!

Author:  Bob Shanklin [ Sat Jul 02, 2016 9:41 am ]
Post subject:  Re: Deflection tsting calculations

Trevor, are you going to have the updates online for those of us that have the first edition?

Bob

Author:  Trevor Gore [ Sun Jul 03, 2016 4:11 am ]
Post subject:  Re: Deflection tsting calculations

Bob, quite a lot up of updates came as a consequence of discussions in "the book" section of the ANZ Luthiers Forum. So in a sense many of the updates are already on line.

Author:  printer2 [ Sun Jul 03, 2016 10:57 am ]
Post subject:  Re: Deflection tsting calculations

Trevor Gore wrote:
Bob, quite a lot up of updates came as a consequence of discussions in "the book" section of the ANZ Luthiers Forum. So in a sense many of the updates are already on line.


Are they complied in one thread?

Author:  Trevor Gore [ Sun Jul 03, 2016 6:25 pm ]
Post subject:  Re: Deflection tsting calculations

They are all in one sub-forum. Just follow the link above.

Author:  CharlieT [ Mon Jul 04, 2016 10:01 am ]
Post subject:  Re: Deflection tsting calculations

Trevor Gore wrote:
Probably greater than 98% the same. I've changed out a few of the "free standing" photos for better/more interesting ones; the photos in Build are all a little bit larger and better colour balanced; there's a bit more on intonation/compensation, there's a better double-acting truss rod. There's minor changes to some of the equations so that they are easier to check (there was a residual error of ~0.5% (iirc) that was driving people mad when trying to check their calcs, but of no consequence in real life). There's the new foreword by Charles Fox (referred to above) and a commendation by Tommy Emmanuel. Otherwise, it was about correcting typos and re-wording a few explanations to help reduce the possibility of any ambiguity. So if you already have Edition 1, I wouldn't be rushing out to update to Edition 2, unless you have plenty of spare cash that you want to throw in my direction!

Thank you Trevor!

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