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So are you saying I can skip the next four pages cause there is no definitive conclusion?

there is a conclusion you are over looking

the failure rate is higher on pinless bridges but when done well and correctly they will work , but when they fail it us usually more catastrophic. Yes pinned bridged also fail but the rate is higher on the pinless.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

With a pinned bridge, it would seem that the since the ball ends of the strings are actually trapped below the sound board some of the string tension is being taken off the bridge glue line and distributed through the plate, soundboard, bridge assembly. On the other hand the pin-less style glue line takes all the load and leveraging. The exception would be the Doolin/Elliot design which actually has steel pins/dowels for each string angled back toward the tail block. These pins/dowels are buried into the sound board and bridge plate. Last time I communicated with Mike on this subject he was using CA glue to attach the bridge, I think after finish was applied.

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Ken Cierp

http://www.kennethmichaelguitars.com/

Meddling,

I would not recommend to anyone to not read the opinions and thoughts of others. I was personally disappointed with the all too typical circular conversation. It all reminds me of a couple instances in my early special effects portion of my film business career, the same scenario happened twice. Companies I was working for were trying to develop machinery to create a specialty product. Their engineering firms were unable to deliver any prototypes that worked at all, the mathematical finite analysis kept failing. In both instances I created working prototypes to use in the commercials in a few days. These ideas were later adapted to use in the machinery. I'm not an engineer, I have an MFA degree. The lesson here is simple, math is a great servant, yet a brutal master. Garbage in, garbage out, sometimes you have to get out of the box to learn anything. My brother is a brilliant aeronautical engineer with a stunning portfolio of achievement, yet he was useless figuring out how to build a very steep staircase to the water of the family lake home, he just couldn't "see" it in his head. IMO the ability to visualize in your minds eye what you are trying to achieve is the key to creativity and problem solving. To some it up, I saw a pinless bridge design in my mind. It was not just the bridge but the entire structure of the guitar top. The design is a success, it sounds very nice and unique and has held up. That in my opinion is what this forum should be about.

Tim

Here's some information off Mike Doolin's website note he does not want anybody to copy his bridge "shape" that is copyrighted and Elliot would like to be given credit for the concept.

http://www.doolinguitars.com/articles/bridgejigs/

_________________
Ken Cierp

http://www.kennethmichaelguitars.com/

I can see how anchoring the pins so close to the back of the bridge would be helpful...

That was kinda like trying to actually read and understand the iTunes user agreement.

The conclusions I drew were...

- nobody seems to be able to explain whether Pinless bridges are more likely to sheer than pinned bridges in a language that a mehum like myself can grasp.

- Grumpy is indeed aptly named.

- We could use a cleaner and better explained model to explain this to mehums.

- I will continue to use pinned bridges, if only so that people on the A... other forums can discover the wondrous tone enhancing properties acquired by switching from TUSQ to Magicked Muscox Balls...

LOL to be fair building stairs is not exactly intuitive. This one for my new shop took two tries.



I tried to find quarter sawn 2x12 for the runners but couldn't

Ok I give up do you pin the bridge or not?


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@jfmckenna

Are those pinless or pinned?

That is why when I built my stairs I bought premade stair stringers... I knew I would spend less buying them than 2 or 3 tries to get them right.




That all depends on who you ask... Much like everything else, there are multiple ways of doing things and no one single "right" way.


Cheers,
Bob

Thanks Bob. In John Bogdanovich's book he says only the cheaper guitars are pinned. Says it's not necessary. I'll just keep on reading maybe I'll get my answer.


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I did not read his book but did you mean "only the cheaper guitars are pinless"?

You will find that most guitars use the pinned bridge and only a handful use pinless. At least with the big manufactures. I stated somewhere in this thread that I though part of the reason is because of the customer. Customers are use to seeing guitars with pins so that is what they want to buy.

I do think that pinless bridged guitars are less expensive to produce from a production point of view so that may be why they have been seen on guitars of lesser value.

I certainly don't have the answer which is better or worse. But I know I prefer pinned bridges over pinless just on looks alone, so anything that I build will have pins. I own one pinless bridged guitar and really like it but it somehow just looks a bit odd.

Bob

I'd hardly put Lowdens in the less expensive category. Unless you mean less expensive than Somogyi or Tragout...

So Mr. Doolin is using a "pinned" pinless bridge. I doubt that the small metal rods or a few small metal bolts adds that much weight, once you subtract the reduction of mass that a smaller footprint would make.

One of the nice things about forums is the diversity of the people on them. We should celebrate that! And, indeed, Grumpy is aptly named, but also very knowledgeable!

So, the take-away is that there is no simple answer and the answer you get is dependent on the precision of the question that is asked.

If the question is about stress on the glueline, the level of shear stress is relatively unimportant, because unless heat stressed, commonly sized bridges rarely fail in shear. Baring things like cracks across pinholes and such, the predominant failure mode is a peel failure, best visualised as the flexible top peeling off a much more rigid bridge, like masking tape off a bench. The interesting thing is that the peel effect is the same (both carry the same torque) irrespective of whether the bridge is pinned or pinless, so pinned or pinless in itself is not the determining factor as both types can survive and both types can fail. So success turns on the detail of the design. If the whole top is made stiff enough to substantially eliminate the peel effect, it wouldn't radiate much sound. My rule of thumb is that bridge rotation should be limited to about 2 degrees under full string load. To put that in perspective, if the Golden Gate Bridge was designed for a 2 degree rotation (tilt/gradient) of the deck at the pylons, it would sag about 75 feet in the centre of the span, which is about 7 times what it was actually designed for. So in engineering terms we are talking large deflections on a guitar top.

So to get a bridge (of any type) to stay on, the peel effect at the bridge has to be reduced to a manageable level. This is done by making the top progressively stiffer as it approaches the bridge so that there isn't a large discontinuity in stiffness, which causes a stress concentration, which is the lead in to a crack, which is the precursor of failure. There are numerous ways of doing this: having the bridge plate overlap the back of the bridge; grading the braces appropriately, "softening" the back edge of the bridge itself, etc. etc.. The objective is to get that two degrees of rotation to happen over a good length of the top rather than it happen as a hinge at the back end of the bridge.

So if we believe the repair professionals (and why wouldn't we?) who tell us that there is likely a greater proportion of pinless bridges that fail, I would posit that that is due to things like omitting the bridge plate, without due regard to its deflection spreading effect, presumably in the belief that it is there primarily to prevent the ball ends pulling through and then not making adequate accommodation for its omission in the bracing/bridge design.

One should also consider the grain orientation of the bridge plate when used as a deflection controller. A number of the more erudite builders/repairers indicate that cross grain does little to spread the rotation and almost nothing to prevent bridges splitting through the pin holes. Both very valid points.

Anyway, that's how I see it, and I've never had a bridge come off despite allowing about double the bridge rotation seen in "main street" guitars and using bridges with a smaller than average footprint.


Structurally, either works (as we know), but the devil is in the design detail. Personally, I prefer pinned from a useablity view point.

_________________
Trevor Gore, Luthier. Australian hand made acoustic guitars, classical guitars; custom guitar design and build; guitar design instruction.

http://www.goreguitars.com.au

Screwed in with deck screws... Hmmm that gives me an idea about mounting ball end strings in a bridge!

Actually he said guitars of lesser quality were pinned. It's a very nice book though.


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Bogdanovich is strictly a classical builder, Almost all classicals are pinless other than historic instruments or their replicas.

Your right Jeff. Like all people he has his own take on things. It don't really make a difference. Pinned or unpinned kind of whatever floats your boat. Still a nice book. Hardcover,pretty pictures,etc.


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I have the book, very good for some things.
I don't recall that particular statement, but it would be irrelevant in the context of this discussion about steel string pinned or unpinned.
Steel string guitars have about twice the string tension of a classical.

Your absolutely right about steel strings vs classical. I've learned a lot from that book. My copy is very well done up. I'm building a baritone Uke and am getting dimensions etc from an old Lyra Uke I have here at the house. I was looking inside it and it looks like drywall screws holding the bridge on. I'm still up in the air about pinning or not. I did put a bridge plate of nice maple in there. Think I'll wait and see how this discussion comes out.


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Lonnie, I've only made 6 ukes, but I do not screw or pin the bridge. You can apply tape to the bridge footprint, then do whatever finish you do. When you remove the tape, put the bridge in it's place and apply some tape to the outer corners to help locate the bridge. I then use cam clamps on the edges to fix a flexible metal ruler (can use some thin cork underneath) so that it butts up against the front of the bridge location. This will help prevent skating and allow you to tweak the position when gluing. Then can use 2 or 3 of the Stew Mac mini cam clamps through the sound hole to clamp the bridge on. Soon as it's fixed, take the ruler off and Bob's your uncle

Thanks for that Beth. I appreciate the help. Yes I had an uncle Bob. He was a Korean War veteran. Highly decorated too. But how did you know? Lol


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