Pinless bridges

[Jackknifegypsy]

On an old May-Bell I picked up, number one in the triage department, the new strings I put on were giving me a problem at the bridge. The way old strings didn't even have a little grommet on the saddle end. They were just tied into a knot and twisted so as to give the bridge pin some purchase.

The new strings were causing the bridge pins to sit about 3/8" above the bridge pin hole.

Lightbulb above head goes off.

I grabbed a small aluminum washer that would allow the string to pass through up to the grommet, added a small rubber plumbing washer and passed the string back thru the sound hole and up thru the bridge hole, omitted the bridge pin, and tuned it.

Not only did this eliminate the need for the bridge pin permanently (I'm contemplating how to fill the unsightly holes after I test it without filling them), BUT I had an annoying buzz that I couldn't get rid of. Now it is gone. I figure it was the grommet on the saddle end that was vibrating ever so slightly at a full strum, or pluck. v\

I'm sticking with this method until it doesn't work anymore.

[murrmac123]

Originally Posted by Jackknifegypsy

Lightbulb above head goes off.

I grabbed a small aluminum washer that would allow the string to pass through up to the grommet, added a small rubber plumbing washer and passed the string back thru the sound hole and up thru the bridge hole, omitted the bridge pin, and tuned it.

A lightbulb moment indeed, but what purpose does the rubber plumbing washer serve ?

[ZekeM]

My guess it he has them in the holes where the pins would go and the string is threaded through??

[John Arnold]

Afraid we will have to agree to disagree on this. it's all theory,

Actually, it is not theory at all. Like I said, a basic course in engineering statics is all you need.

[Go4aRyd]

Actually, a basic course in statics imposes the necessary assumption that all bodies are rigid and are thus constrained to newtons law. An acoustic top does not really behave this way. That actually requires a three-dimensional modal analysis. The shape of the bridge and HOW the forces are transmitted to the top changes the simple model significantly. As an example, something as simple as changing the size of the glued surface area of the bridge, all other things being equal, changes how stiff the top behaves - and thus how it vibrates with inputs through the imposed forces.

My only point being that simple statics alone is not sufficient to model nor predict a dynamic system. It can, however, be very useful in examining which design parameters have the most significant impact - such as string height and tension.

This is what makes the craft truly an art to me.


(..and now back to our regularly scheduled topic.....)

[527]

Originally Posted by Ken Donnell

A pinless bridge works just great for steel string. It changes the dynamics of how the strings pull against the soundboard, so that the bridge is rocked forward...

That happened on the two that I owned, the bridge seemed to want to rotate forward into the soundhole.

[Ned Milburn]

Originally Posted by 527

That happened on the two that I owned, the bridge seemed to want to rotate forward into the soundhole.

Were they Ovations??

[royd]

there are successful guitar designs with pinless bridges - Lowden et al. Why not take a look at what some of the successful designs have done?

Here's the top of a Lowden. I have no question that this is not the only way to do a pinless bridge, but George has come up with an effective way. I have seen a few Lowdens that have been converted to pinned... and there was not an obvious improvement in the sound. The guitar is designed for the differences in torque and a lower break angle and it works.

[royd]

Originally Posted by arie

well, however it is sliced and diced the bottom line is that you are establishing a basic lever.

thinking out loud about the physics involved here... if this is accurate, and it makes sense to me, then the saddle acts as a fulcrum and the tension of the string is trying to pull that string into a straight configuration. The larger the break angle, the more torque to lift the back of the bridge and twist it forward as the force is pulling up in the back of the bridge, over the saddle, and then parallel to the top. With a pinned bridge, the fact that the ball ends are actually pulling against the top mitigates that to some degree and spreads that torque through the belly of the guitar. But the force is still trying to twist the top with the saddle being a fulcrum. Make sense?

Now a pinless bridge with a lower break angle, there is much less force pulling up at the back of the bridge and almost all of the force is pulling more parallel to plane of the top so the lower break angle would actually decrease the twist of the bridge...

[Alan Carruth]

Boy: I _just_ posted a couple of long ones on another thread about this, so I don't want to have to do it again. The bottom line is that, having done the experiments, I can say with some assurance that, all else equal:
1) changing break angle makes a small difference in the way the top distorts,
2) the actual _amount_ of top distortion you see depends on the height of the strings off the top, which establishes the length of the lever arm, and
3) any small changes in the way the top vibrates due to alterations of the break angle are probably going to be inaudible, while changing the string height off the top does change the tone in ways that most people can hear. There are good reasons for all of this, but it would take a long post to even get started.

The saddle is supposed to be the 'stop' at the end that defines the length of the string. On a Les Paul you get pretty close to that, but on an acoustic not so much. Still, if the strings are moving much relative to the top of the saddle, say by rolling sideways or hopping off, you'll get problems in the tone, and these might be audible. So long as you are not getting those sorts of problems, what the string does behind the saddle probably doesn't matter much.

Swapping out pins can change the mass of the bridge, and it's pretty easy to show that changing the mass will change the way the bridge/top system works. I'm very skeptical about the tonal effects of different bridge pin materials other than their weight: I don't see how, say, titanium pins could 'transmit more vibration' since, if everything is working right, there should not be any vibration there to transmit. I'm willing to be convinced by objective evidence.

The bottom line, for me, is that a properly designed and built pinless bridge should work as well as a pin bridge. If you're trying to sell guitars, pinless might be a problem, but that's only because of all the mythology.

[527]

Originally Posted by HCG Canada

Were they Ovations??

No, I'm pretty strong in my anti-Ovation lifestyle. They were Harmony Sovereigns.

[Tom West]

A bit of a pain doing saddle adjustments with a pinless bridge.......!!
Tom

[pitner]

Originally Posted by Alan Carruth

Boy: I _just_ posted a couple of long ones on another thread about this, so I don't want to have to do it again. The bottom line is that, having done the experiments, I can say with some assurance that, all else equal:
1) changing break angle makes a small difference in the way the top distorts,
2) the actual _amount_ of top distortion you see depends on the height of the strings off the top, which establishes the length of the lever arm, and
3) any small changes in the way the top vibrates due to alterations of the break angle are probably going to be inaudible, while changing the string height off the top does change the tone in ways that most people can hear. There are good reasons for all of this, but it would take a long post to even get started.

The saddle is supposed to be the 'stop' at the end that defines the length of the string. On a Les Paul you get pretty close to that, but on an acoustic not so much. Still, if the strings are moving much relative to the top of the saddle, say by rolling sideways or hopping off, you'll get problems in the tone, and these might be audible. So long as you are not getting those sorts of problems, what the string does behind the saddle probably doesn't matter much.

Swapping out pins can change the mass of the bridge, and it's pretty easy to show that changing the mass will change the way the bridge/top system works. I'm very skeptical about the tonal effects of different bridge pin materials other than their weight: I don't see how, say, titanium pins could 'transmit more vibration' since, if everything is working right, there should not be any vibration there to transmit. I'm willing to be convinced by objective evidence.

The bottom line, for me, is that a properly designed and built pinless bridge should work as well as a pin bridge. If you're trying to sell guitars, pinless might be a problem, but that's only because of all the mythology.

I tried the titanium pins on several of my acoustic guitars and left them in the Olson SJ and my Alverez DMY96 with a noted improvement in the sound. No improvement in my Goodall or Martin D-18 was noted. I was going to change them all to titanium until the trial but just ended up doing the two guitars. Can't say why it worked on some and not others. Never did the 12 string but it sounds pretty good anyway so I will leave well enough alone.

[Alan Carruth]

There's another thread on pinless bridges in main guitar discussion area, so, again, I'm repeating myself. There is a pinless bridge design that does not thread the strings through a hole in a tieblock. Jeff Elliot used it on his harp guitar, and I've made bridges and archtop tailpieces this way. The ball end of the string drops into a tight fitting pocket on the top of the bridge, and there's a small pin in the bottom of the pocket that goes into the hole in the ball to keep it from rotating. The pocket is slotted up toward the saddle.

Increasing the break angle does not 'put more energy into the top', unless the angle was not sufficient in the first place. 'Sufficient' may be as little as six degrees, and certainly need not be much more than ten. That's enough to keep the string in contact with the saddle top throughout the full cycle of vibration, and as long as it's in contact, all of the force will be transmitted to the top of the saddle.

I set up a classical guitar so that I could change the break angle over the saddle by simply re-tying the strings. I used a 'wire break' setup to apply a standard pluck at a known spot on the strings in a known direction, and recorded six plucks for each open string for each setup case. My statistics guru and I then looked at the output levels, sustain, and harmonic breakdown for each string and case, and could see no real difference due to changes in the break angle alone. Altering the height of the strings off the top was another matter.

We also did a listening test. I constructed an 'artificial strum' using the beginning of a randomly chosen pluck from each string. These were played back through headphones in random pairs, and the listeners were asked if the two sounds they heard were 'the same' or 'different'. Again, they could not reliably discern a change in break angle, but could easily pick out a change in string height off the top.

USTs are an exception to the break angle rule. They work better when they see a larger static force, so more break angle can give a stronger signal. Even more effective is to angle the saddle back so that it bisects the break angle, which gives the maximum download on the UST that you can get for that angle. It also eliminates the tipping force on the saddle that tends to break out the front edge of the bridge.

[murrmac123]

Alan, nobody is disputing your findings regarding the breakover angle per se ..

The more salient question IMO is whether the same torque is being applied to the soundboard by a pinless bridge as by a pinned bridge.

I know that there are diametrically opposed opinions on this issue from equally experienced luthiers.

John Hall of Bluescreek guitars would maintain that the location of the ballend is a significant factor in the torque exerted.

John Arnold, equally experienced, would take the opposite view , namely that the only significant components in the equation are the height of the strings over the soundboard and the breakover angle.

My gut feeling is that John Hall's analysis is corrrect, but , at the end of the day, who really knows ..?