Test-mule guitar teardown

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Test-mule guitar teardown

Postby Chuck Tweedy » Sun May 26, 2019 7:17 pm

Hey y'all, I've made a quick tear-down/build-up guitar so I can quickly take it apart, make changes, then put it back together.
The neck is all bolt-on -nothing terribly new there.
The headstock is my standard headstock joint, which I've always wondered if I could leave un-glued. Sure can. String tension pulls it on tight and solid.
Bridge joint is potentially a unique technique. The bridge is also held onto the top purely by string tension. It has ten 1/16" dowel pins that both hold the bridge down, and act as string anchors (well, 6 of the 10 are anchors).

HERE is a 4 minute video of me taking it from a playing guitar down to the individual components.

let me know if you would like to see more (i know you do, but i'm just too damn lazy right now to post anything more :P )
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Re: Test-mule guitar teardown

Postby Bob Francis » Sun May 26, 2019 8:50 pm

That's really impressive!
I would like to see more detail on that lever headstock joint.
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Re: Test-mule guitar teardown

Postby Peter Wilcox » Sun May 26, 2019 9:22 pm

That headstock joint is really something. But I was waiting for you to take the back off. :o
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Mon May 27, 2019 10:44 pm

Seems the interest is mainly in the headstock joint. I've been doing that headstock joint for at least 7 years, tho my building has really slowed down in the past 5 years so its only on a half-dozen guitars.
It is a 3-sided pyramid tenon in a matching mortise. It's basically what i though Martin did back-in-the-day but found out otherwise in a GAL quarterly. After that i decided to make what i had in mind, and it works great.
I always wondered if it could hold string tension without being glued on, and it sure does.
Attachments
g-mule-hsJoint-mortise.jpg
g-mule-hsJoint-top.jpg
g-mule-hs-back.jpg
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Mon May 27, 2019 10:45 pm

And this is what it looks like fully carved and finished.
Attachments
g-coco-hs-back.jpg
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Mon May 27, 2019 10:48 pm

Really, nobody cares about the bridge joint?
The bridge is slammed down tight on the top purely by string tension.
well ... OK
Attachments
g-mule-bridge-below.jpg
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Re: Test-mule guitar teardown

Postby Barry Daniels » Tue May 28, 2019 11:27 am

Just got the chance to view the video. Lots of cleverness there, Chuck. The bridge attachment is the bomb.

I do a bolted on fingerboard extension similar to yours but the bolts are accessible from the inside and hidden on the outside. I'll show some photos of how I do it on the next build.
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Re: Test-mule guitar teardown

Postby Bob Francis » Tue May 28, 2019 2:02 pm

I think both of those connections are brilliant Chuck. I was so impressed with the headstock that I was preoccupied. I did notice your pulling the pins from the bridge but couldn't see well enough on my tablet to tell what was happening.
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Re: Test-mule guitar teardown

Postby Barry Daniels » Tue May 28, 2019 2:36 pm

Chuck, would be tempted to use the bridge connection method on a non-mule, normal guitar?
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Tue May 28, 2019 5:10 pm

Thanks for looking guys.
Barry, the big cap screws on the fingerboard go into threaded inserts in the heel-block. The small screws near the end of the FB are just wood screws going into the top/brace. They are there to keep the extension from buzzing. I would be interested to see how you attach to the very thin FB. Not much meat for an insert.

The bridge connection is pretty good - better than I thought it was going to be - but right now I'm pinning directly into spruce. All the stress is at that interface between pin and spruce. You notice the bridge has an underlining of garolite fiberboard - that was because the rosewood bridge was cracking. In the top my pinholes are starting to oval a bit - so the fit is deteriorating every time i mess with it. To make this a real, long-term, bridge mounting system, some more R&D needs to be done to figure out how to make it last.
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Re: Test-mule guitar teardown

Postby Clay Schaeffer » Wed May 29, 2019 7:44 pm

Hi Chuck,
If you have trouble with the strings tangling when you take them off one solution I have found for that is to modify a bag clip to keep them in order.
Although the peghead joint you are using is not Martin's modified bridle joint, it is an old method of joining the neck to the peghead. I believe it is called a "covered V" joint. Originally the "V" didn't come through the face of the peghead and no peghead overlay was used. They did angle the sides of the joint but generally didn't have a "volute" on the back of the headstock. Your's looks very well done.
One Question - why would you want to use your bridge mounting system for long term use over one that securely glues the bridge to the top?
Attachments
bag clip.jpg
bag clip.jpg (59.23 KiB) Viewed 1001 times
bag clip 2.jpg
bag clip 2.jpg (69.74 KiB) Viewed 1001 times
covered V.jpg
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Wed May 29, 2019 11:01 pm

yep - very similar - thanks for pointing me to that Clay.
funny, mine comes up if you search google images for "covered v headstock joint"

and i enjoy untangling strings :P
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Re: Test-mule guitar teardown

Postby Barry Daniels » Thu May 30, 2019 10:57 am

You could inlay a small strip of rosewood into the top under the bridge to prevent wear on the pin holes.
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Thu May 30, 2019 12:41 pm

Barry, yep, that is the beginning of R&D.
And there is optimization of the angle. I'm at a sharper angle than the free-body diagram suggests - which makes the stressed part of the material a sharp little wedge, BUT it also makes lifting of the back edge less likely - so i would need to find a balance there. It goes on an on - but i'm not really wanting to dive into the engineering of this joint right now.
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Re: Test-mule guitar teardown

Postby Barry Daniels » Thu May 30, 2019 12:49 pm

By the way, my bolted extension design uses 6-32 T-nuts buried in a recess on the bottom of the fretboard that is covered with a homemade carbon fiber plate glued into a recess. It's working so far.
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Re: Test-mule guitar teardown

Postby Bryan Bear » Thu May 30, 2019 1:10 pm

What is it you are trying to test with a removable bridge? inlaying something into the spruce may alter the function of the top enough that your results may not translate the way you want. I assume you want it easily removable so you can switch bridges quickly to test without waiting for clamping time. If you are testing bridge mass, could you glue a think layer of rosewood to the top and pin bridges to that (thinned by the amount glued to the top)? Just thinking our loud.
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Thu May 30, 2019 1:54 pm

Barry - i think i get it. I assume this is mostly up in between frets around 17, 18 or so?
Bryan - this is so i can easily pull the top off and change thickness, bracing, SH size, whatever. What I'm trying to do now is avoid spending all my time fussing with the bridge attachment and get some work done on the guitar body as a whole.
My motherinlaw will be with us for a week or so, so ... you can expect a lot of posts and hopefully a lot of work in the shop coming up. :-)
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Re: Test-mule guitar teardown

Postby Barry Daniels » Thu May 30, 2019 6:32 pm

Chuck Tweedy wrote:Barry - i think i get it. I assume this is mostly up in between frets around 17, 18 or so?


Yes. I just used two of them. T-nuts are much more shallow than threaded inserts and more secure. The extended part of the T-nut also serves as location pins by going though equal sized holes in the top. A rosewood plate glued onto the inside of the top serves as a reinforcement for the bolt heads.
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Re: Test-mule guitar teardown

Postby Chuck Tweedy » Thu May 30, 2019 9:12 pm

totally got it - i was going to ask if the threaded portion stuck down and registered with the top - guess it does.
i like it - may steal it if that's ok
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Re: Test-mule guitar teardown

Postby Barry Daniels » Fri May 31, 2019 10:18 am

I would be honored if you borrow this. One other thing: I used torx head bolts to make turning them inside the guitar easier. My carbon fiber plate was about 1" long 1-1/2" wide and about .050" thick. It gets glued into the fingerboard recess with epoxy amended with chopped polyester fibers.
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