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self-adjust bridge foot


tim2

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Here is some information I've put together concerning the self-adjusting foot used on one of my bridge styles, as I mentioned to someone here and others by e-mail that I would.

First here is a picture. The beads shown are jasper, but many other types of stone work just as well. I'm experimenting with hardening the seeds from the basswood tree for use as well. If you look closely, you'll see the elastic filament in the picture. I'm currently working on the use of some natural filament rather than the synthetic and a way to eliminate the use of the synthetic adhesive. I may come up with something different on down the road as some of you may have already assumed.

AdjBridgeBreakdown_small.jpg

Here is a link to a bigger picture in case anyone wants a closer look:

http://violinbridgeworks.com/Misc/AdjBridgeBreakdown.jpg

To this point I've had the best luck with the beaded stones, and an elastic filament to hold the mechanism together so it doesn't all fall apart when it's remvoed from the instrument. However, just the lubrication and close fitting of the ball and socket pretty much holds it all together without any further assistance. However, I sure would hate for one of those feet or stones to go rolling down inside someone's instrument while they were putting the bridge on, so I figured I'd secure it a little better.

Although all of the holes in the beaded stones aren't the same size, I use only the ones with the smallest of holes. I position the stone in the socket that I've created in the bridge and using a wire drill, make a hole through the portion of the bridge that it's attached to. I then insert the elastic fiber through the stone and the hole in the bridge and use a drop of cyanoacrylate glue to hold it in place.

Next I have to secure the filament to the stone so the stone is held in place against the socket in the bridge with enough elasiticity to allow minor movement. To do that, I simply pull the fiber (while holding the bead against the socket) until it's somewhat stretched and then force a wood sliver into the hole in the bead beside the fiber and add drop of the cyanoacrylate. Once dry, I shave it off smooth. Now the stone is secured within the socket which has been lubricated for smooth movement. This is the socket where the actual movement will occur.

Finally I place the foot on a form which is similar to the top of a violin and glue the bead to the foot so that in the relaxed position, with the bridge off the instrument, the foot falls naturally into place.

Tim

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That looks pretty clever, Tim. I like the striped figure in that particular bridge, too.

Just speculating out of my imaginiation, I would think the stone beads might be better than basswood seeds in that they would tend to be more consistent in size and more perfectly spherical. You wouldn't have to worry about them breaking, either.

If beads of that size were available in a suitably hard wood, wouldn't they carry vibrations between the bridge and feet more effectively than jasper?

What about carving balls on the bottom of the bridge that would fit into the sockets of the feet? Would that be too tedious to be practical?

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Hi Nicolo,

Your suggestion about the integrated beading may be workable and something that I've been pondering. The problem is still keeping everything together as a unit when the bridge isn't installed. Using a reversal of your idea, and carving the ball into the foot so I could still use the fiber attachment method may work. The fiber needs a certain length in order to offer the elasticity. I would not be able to put a hole in the foot for the fiber to run through even if I were to make the foot a little taller bacause it would then be weakened and likely to split with the downward pressure of the ball. As far as the carving that shouldn't be a problem since I'm currently investing in a CNC machine for the production making of this particular bridge in order to distribute it in the many music stores and dealers. As you may already be aware of, a CNC can carve hundreds of these as well as conventional style bridges each day which is pretty much necessary to be competitive - which I plan to be. I will still offer a custom hand-made version of this particular bridge with special carvings and color, which I'm currently working on as time permits. Handmaking of these things is where I pride myself so that will always be a very important part of my bridge-making.

Using the current socket and bead, I can jig-up for carving of the sockets, and the actual installation of the bead and all takes less than a minute for each bridge so that too isn't a problem.

Concerning the transfer of the vibration, the beads work very well. That may not be the case as the string angle over the bridge is increased and very light strings (like light gut) are used, as is the case with some instruments, in which case wood or similar material may need to be used. However, that's more of an exception than a rule.

I'm still testing the seeds from the basswood tree. Due to the shape of the mating surfaces, the strength of the seed becomes less of an issue than one might think. However, an "untreated" seed won't work even with that concideration, while just the slow baking of a seed adds conciderable strength - proportionally so.

Thanks again for your comments and suggestions.

Tim

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Hi, Tim

Have you tried it on your violin? I think the bridge is a very tricky thing. Making it work is easy, making it work WELL is tricky. I have just spent $20 to cut down my bridge by 1mm and got it work slightly better. Its weight and angle and those holes and feet have a lot to woth the sound ? I don't understand how it works. One time a luthier told me my bridge wasn't right and he eplaced it with another (without cutting to fit, not even look good on my violin but..). It worked three time better than my old bridge. I could not figure out how could he tell so fast and so correct. Experience?

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Hi yuen,

Thank you for your question and other input. I test my bridge designs on my violins and other's as well.

Yes, the bridge is a very tricky thing. You are correct that just a small reduction in height can make a difference, and lots of other things can too.

I'm glad that your bridge is now working slightly better than it was - show us a picture if you can.

Tim

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Hi, Tim2

Your picture worths a thousand words. It is very impressive in deed. I am very glad you have shown that photo. I am sure now that you know very well what you are doing. I don't have a camera for taking picture to post mine . Your idea of self-adjusted kind of bridges is very interesting. I hope to hear more about it as time comes, especially in regard to the sound(or the tone). Thank you.

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Won't you (or somebody) still have to fit the bottom of your feet to the violin so that it fits well? Otherwise you'll have a poorly fitting bridge foot, and that's not gonna be good.

If you're having to fit your bridge feet, don't you lose whatever advantage you might have had by using the beads?

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Seth,

That's a good question. The feet of my self-adjusting bridge have a slight curve across the bottom, as well as allowance for the normal bridge vertical angle. The required curvature of the feet at the bottom is pretty standard for most violins due to the short distance that the foot spans. The main thing that needs to be compensated for is the slight arching differences (that goes the entire width of the bridge) which isn't something that can be readily predetermined, and the reason for the self-adjusting mechanism.

Take a close look at the foot of any bridge including mine and realize how much of the actual surface area on the botttom of the foot is bearing the load. Due to the design of mine, more of the foot carries more of the load since it's stronger at the ends, but the amount of meat at the ankles, bead, or whatever still has a lot to do with how much of the foot will actually carry the load and the distribution of the load will determine how much the curve (mininal as it may be) even needs to be concidered or compensated for.

Tim

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Michael,

You may have missed the point. That which is at the ends of the feet, be it my bridge style or the conventional style bridge, isn't load bearing unless the arch of the individual foot is extreme. In a case where the arch would be excessive the ends would bear the load only temporarily until the centralized weight created by the design of the ankle caused it to settle.

The ends of the feet on my bridge being heavier serve no real function anymore than they do on the conventional style bridge with whatever type of treatment you decide to give to them - other than being decorative.

Tim

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Johnson & Courtnall make it a point to emphasise that the bridge's feet "must fit the arching perfectly" at the bridge's position. They even suggest the use of chalk as a final step in order to achieve a perfect fit. I doubt self-adjusting feet would do as good a job, but I'm not a luthier.

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The book you refer to suggests that method as a means to achieve a smoothness of the feet bottom but not necessarily in relation to the top surface of the instrument although the assumption is typically made that the surface where the feet will fit is smooth. A fit as they suggest is assumed and agreed upon. Others suggest a similar method of using carbon paper placed between the top and bridge to show variation. In the past I suggested the slight moistening of the bottom of the feet to follow those and all other methods for an even finer fit which like many things has found it's way to the various message boards and been debated both pro and con.

The feet of a bridge can be made to fit the top absolutely perfectly, yet it has been debated as to whether or not an absolutely perfect fit (as suggested with my final "moistening" method) is required since with time the actual graining effect of the top can create an imprint in the feet even on feet that were originally scraped flat. There is much discussion of this issue perhaps because it is one of the few aspects of tuning and fitting that can be realized as definitive and visually so.

Tim

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I presume the reason for using the chalk is to eliminate irregularities caused by the cutting of the feet to match the arching, but the importance of using the chalk is not really my point. My point is that, according to the book, the feet must fit the arching perfectly, which I presume is not what happens when the feet are shaped independently of the arching.

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It's easy to think that there is more of a curvature to the bottom of the foot than there actually is because the overall curve across the bridge is quite a lot.

Here is a bridge that I just removed from a violin that fit quite nicely:

bridgeFootCurvatureSmall.jpg

closer view: http://violinbridgeworks.com/Misc/bridgeFootCurvatureMed.jpg

The card placed against the bottom gives a visual idea of the curve at the foot, but the actual deflection is about .1mm and that's taking into concideration the entire length of the foot area. Even if the curve of the foot was slightly more and the top remained the same, the foot would naturally flex to fit the top perfectly.

This issue is something that often just goes around in circles with the final conclusion being that the feet aren't really actually cut to fit since the one who's doing the cutting never takes into concideration the deflection of the grain or even the varnish imperfections that are under the foot and relies on the foot settling in at least a little bit to compress the grain and varnish imperfections or if the feet are moistened, the reverse occuring. That being said, if my point is still not made, I could pretty much argue this point until the "cows come home" with yet no resolve.

The best I can offer with my self-adjusting bridge is a guarantee that it if it doesn't fit as well as one thinks it should and doesn't sound better than their conventional style bridge, or if unhappy with it for any reason whatsoever it can be returned for a full refund.

I'm really not sure what else to say about this subject.

Tim

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Just to make it clear: the people who argue about if the feet should fit or not and how well are rarely the ones who make them fit the best. :-) Those of us who make them fit happen to think that it matters quite a bit, and don't count on time to make things better, either. I've never seen the point of arguing that shooting for less quality is desirable. :-)

By the way, are you setting this up so the bridge can rotate forward and backwards on the joints, then? Most setup people take that angle and the transmission of vibrations through the feet in that direction pretty seriously. Or are you locking it in place after it's "fit"?

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Hi michael,

Here's some of my thoughts on what you wrote:

Quote:

Just to make it clear: the people who argue about if the feet should fit or not and how well are rarely the ones who make them fit the best. :-) Those of us who make them fit happen to think that it matters quite a bit, and don't count on time to make things better, either. I've never seen the point of arguing that shooting for less quality is desirable. :-)


I think that sometimes the way that you use words, you make certain skills such as this seem more complicated than it is. The more complicated it appears to be and the better and easier you (or I, or anyone else) can do it the more skilled you or the rest of us would appear to be. I hope that's not where you're going with this. I'm not saying or implying that you're not skilled but getting a bridge to fit perfectly really isn't one of those things that one should be giving themselves too much credit for being able to do well. Those who may be struggling with it and reading this, you may later find that what was causing you the problem wasn't a lack of skill.

Quote:

By the way, are you setting this up so the bridge can rotate forward and backwards on the joints, then? Most setup people take that angle and the transmission of vibrations through the feet in that direction pretty seriously. Or are you locking it in place after it's "fit"?


I agree that angle is important. I also know that people rarely get their bridge back exactly where it goes in it's upright position after adjusting their strings. A double visual clue afforded by a fitted bridge would appear to be an aid in getting it positioned back into it's correct upright position (by an obvious gap along the long edge of the foot) but giving it just a little more thought, one would quickly realize that it's not that good of an aid at all since even what one might think to be quite ridgid is also flexible and if a bridge is tilted out of position, the foot will eventually settle into place due to the flexibility in the ankle, but will first do damage to the top surface. Additionally, under that scenario if the bridge is left in that position, the next time it's adjusted and the same visual clue of a gap along the long edge of the foot is used to assist in alignment, the bridge is now positioned into the wrong position but all appears to be okay.

One of the bad qualities of a ridgid foot is that everytime the strings are adjusted the bridge is rocked forward and the long edges of the feet cut into the top varnish and sometimes the wood itself if the varnish is thin, so basically the first time someone replaces their strings they begin a process of damage to the top surface with very little obvious visual clues that they are doing so. With time, part of this scenario contributes to the wear and occassionally even very deep pockets below the feet. I find it interesting that issues such as this haven't been addressed even after hundreds of years. I'm not saying a self adjusting foot like this is the best solution but it's not as bad of a solution as some may make it out to be.

I think it's important to educate people about correct vertical positioning of the bridge, and that they learn to position based on the vertical angle rather than something that may "look" incorrect such as gaps at the bottom of the feet. Under no circumstance should someone be made to feel comfortable thinking that their bridge is in the correct vertical position becuase it "feels right" because the cut of the angle at the feet has caused it to fall into a particular resting point.

Tim

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I think you misunderstood. I'm saying that the fixed joint and the angle built into a bridge is a potentential tonal issue.

Players can learn to set their bridge correctly--they don't usually attempt to fit a bridge foot that the maker didn't bother to try to fit, however, regardless of your implication that it's an easy job and any guy off the street could do it. I would agree with you that either way, physical damage is an issue, which is why I think bridge feet should be fit properly, and players should learn to place the bridge correctly.

Do we assume now that you've lost faith in the ability of players to keep their bridges straight and that you're discontinuing your bridges with the fixed feet?

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It's not my bridge--it's a relatively recent one, by one of two people who are in the shop now. The shop style runs, to some extent, through all of us who've been there, though.

...On the fit issue: I thought the last step was going to be to put a drop of superglue on the bearing, to lock it all into place. That would take care of one issue, at least.

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Michael,

In response to your words:

Quote:

I think you misunderstood. I'm saying that the
fixed joint
and the angle built into a bridge
is
a potentential tonal issue
.


I thought I was clear what you meant by this comment until Marie's comment. Please clarify whether you think there are tonal (not necessarily meaning that my design is the solution) issues associated with the the fixed foot design.

Quote:

Do we assume now that you've lost faith in the ability of players to keep their bridges straight and that you're discontinuing your bridges with the fixed feet?


No I have no intentions of doing away with the fixed foot of any of my bridge styles, but am currently working on adding a self-adjusting mechanism to those without. Both options will continue to be made available until I think there is a reason to do otherwise. I believe that there are a lot of players that have a good understanding of proper bridge positioning and plan on finding ways to better educate those who do not. Perhaps one way of doing so is by including some information concerning the damage that can occur if the fixed-foot bridge is allowed to tilt too much while tightening the strings - usually more of problem during complete replacement of a set of strings.

I should also mention here that the fancy style I made prior to this is still "alive and well". I've had an overwhelming response concerning that bridge due to it's appearance and am working on making some improvements to it's functionality that I think are necessary. Different people have different tastes and I think they deserve some options in the appearance - but most importantly the functionality.

Quote:

On the fit issue: I thought the last step was going to be to put a drop of superglue on the bearing, to lock it all into place. That would take care of one issue, at least.


Whatever type of bearing is used, it will be permanently fixed to the foot whether it is actually carved into the wood, or attached as a separate entity

Tim

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Quote:

Whatever type of bearing is used, it will be permanently fixed to the foot whether it is actually carved into the wood, or attached as a separate entity


It will be permanently fixed to the foot, but will it be permanently fixed to the bridge? If not, the bridge would pivot back and forth around the bearings and therefore transfer less of the vibrations to the feet in that direction.

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Quote:

It will be permanently fixed to the foot, but will it be permanently fixed to the bridge?


I may or may not make it possible to be permanently fixed to the bridge once the bridge has been installed. However, at this time I see no reason to do so and lots of reasons not to.

Quote:

If not, the bridge would pivot back and forth around the bearings and therefore transfer less of the vibrations to the feet in that direction.


If you really take a good look at the bridge and give it some thought you may come to realize that's not really the way it works. Whether a foot is allowed to pivot or not, it's still being forced into the predicament to do so - not anywhere close to the degree that some may think. There really isn't a significant amount of that type of forced movement or the ridgid foot assembly would either quickly fall apart or if the lower bridge including the ankle and foot combination were stout enough, begin to work it's way into the top wood of the instrument. The ankle is a very weak member through the path of movement and really isn't designed to be an element with the amount of control you may be thinking about.

Tim

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