Orientation of Wood in a Standard Bridge


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No responses so far. Let me ask in a different way and describe why I am interested ---

I want to make several bridges for the same instrument. After reading about the effect of bridge thickness, various options for trimming in various places (the kidneys, heart, etc.), and various chemical treatments of the wood, I want to do a series of experiments to try to understand these things better. I know much of this could be "reinventing the wheel", but it will still be a good learning experience. And I simply can't afford to go out and buy 50-100 bridge blanks. So I want to make my own.

I do have access to some large, dry maple (several species). So a first question is whether the standard for bridges is maple, and if so, which species of maple (if it matters)?

Second, I think I remember hearing that 'good' bridges have a lot of medullary rays running through them. Is that true? Do the medullary rays run from north to south, or east to west, or top to bottom through the bridge as it sits on the instrument?

Third, I'm not sure which way the medullary rays run through a tree. If you were to take a bridge and place it back into the tree from which the wood was cut --- which way would the feet of the bridge be facing --- toward the tree center, toward the bark, toward the sky, or toward the earth? Which way would the front and back surfaces of the bridge face?

Hope these questions are clear. Wish I knew how to post a drawing but I'm not skilled with computers. Thanks for any replies.

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I do not have absolute confirmation of the following orientation, but it must be true by logical deduction of appearance, strength maximizing, and yield.

Imagine cutting a slot in a tree trunk parallel to the ground with a saw. Now imagine that you take a bridge blank and try to hammer it into the slot as a wedge, but because you decided to do this before having your morning coffee, you hammer it in feet first. This is the position from which bridge blanks would come from the bole.

I do not imagine it would matter whether the face points up or down with respect to the tree.

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GMM22, are you sure? I thought the faces were on the quarter, not end-grain - maybe I misunderstood you.

On-the-quarter would signify that if you were to split the trunk into quarters, eights, sixteenths, et cetera, the bridge is cut wih the grain running side-to-side, and most are probably cut with the feet pointing out.

A word on borax treatment - I don't do it anymore on bridges or soundposts. I may try it on an instrument in the future, but for the time being, I prefer a bridge that is more flexible, and borax discourages that. However, if you are going to experiment, it would certainly give some results of value. It may yet be a candidate for "Strad's Secret". But I don't really think so.

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I think you misunderstood. They would indeed be on the quarter. Having the feet pointing out has two down sides. One is maximum yield, as this position does not take into consideration the tapering of the edges. In addition, wood is stronger toward the outer portion of the bole, so it would make sense to have the thin top section from the stronger part.

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Collin, I want to make sure I understand the orientation you suggest --- using GMM22's terminology you're saying to makd a slot perpendicular, rather than parallel, to the ground and hammer the bridge in (probably top first) --- is this correct?

Re: borax, yes I'll probably try this and other things. I'll let you know if there are any worthwhile results. As far as finding the "Strad Secret" (assuming one exists) --- I'm not naive enough to think that someone with my experience level will find it. I have just come to believe that setup is one of the most important factors in violin sound quality and the bridge is a major factor in the setup. Therefore I think I will advance more by spending more time working on understanding bridge characteristics than by carving more plates, scrolls, trying new varnishes, etc., etc.

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Mind you, bridges could be cut the way I mentioned, and while they would offer less yield than the method in the link, my intuition is that such a method would at the very least offer a completely different (and perhaps interesting) set of mechanical properties, all other things being equal.

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Thanks both for the link to Paul Hostetter's description. A picture really is worth a thousand words.

But I have to ask one more question --- if the bridge is cut according to the diagrams in that article, why do the "dots" appear on the faces of the bridge. I thought these were the medullary rays and that they went straight through, front to back. Are these dots something other than the medullary rays described in that article? Thanks again.

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The medullary rays run radially out from the center of the tree, and are seen as the "stripes" on one side of a good bridge-- the dots are the side not exactly on the quarter.

Unless the tree is of precisely such a diameter that BOTH sides of the bridge are exactly on the quarter (unlikely), then by necessity, at best, ONE side will be exactly on the quarter-- and the plane of the other side must cut through the medullary rays, leaving the "dots" you describe...

Chet

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quote:


Originally posted by:
GMM22

Imagine cutting a slot in a tree trunk parallel to the ground with a saw. Now imagine that you take a bridge blank and try to hammer it into the slot as a wedge, but because you decided to do this before having your morning coffee, you hammer it in feet first.

The way you describe, is the way my bridges are cut - opposite the cello bridge shown inside the log at the link provided. And yes, as you suggest, there is less yield.

For final cut, I suggest that the side with the rays face away from the player. If a bridge were cut as shown at the link, I would suggest final cut with rays facing towards the player.

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Nice post, Chet.

"tim2", a bridge cut the way you describe would be end grain on the front and back surfaces. While this may be viable, it's not he way bridges are usually cut. Normally, end grain is on the sides of the bridge.

If a bridge were cut as shown at the link, I'd suggest that the rays face away from the player. The surface with the long rays should have better structural continuity, and be stronger. Normal warpage is toward the scroll, so I'd think you'd want to have greatest compression resistance on that side.

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quote:


Originally posted by:
David Burgess

"tim2", a bridge cut the way you describe would be end grain on the front and back surfaces. While this may be viable, it's not he way bridges are usually cut. Normally, end grain is on the sides of the bridge.


Hi David,

Did he really write "parallel to the ground"? I'm sure that he knew better, and was right about the coffee thing -

Tim

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Of course it would have no practical use, as sustained flight would require far too much energy, but the question remains, could an apparatus be constructed that would allow a human to leave the ground vertically (it has been done horizontally, first by the Gossamer Condor in 77) under ones own power for an agreed time, say twelve seconds, which happens to be the length of time the Wright brothers Kitty Hawk spent in air on its maiden powered flight.

I have had a working mental concept for fifteen years, but to actually execute it would require partners and serious financing, but if anyone wants to trade in their Strad for entry into the Aviation Hall of Fame, I'm game.

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quote:


Collin, I want to make sure I understand the orientation you suggest --- using GMM22's terminology you're saying to make a slot perpendicular, rather than parallel, to the ground and hammer the bridge in (probably top first) --- is this correct?

Yes. With a violin bridge, I don't think it makes that much difference which way the top is pointing, as so little wood is used. With a 'cello or bass bridge, however, it may be better to have the top pointing away from the center.

quote:


Re: borax, yes I'll probably try this and other things. I'll let you know if there are any worthwhile results. As far as finding the "Strad Secret" (assuming one exists) --- I'm not naive enough to think that someone with my experience level will find it. I have just come to believe that setup is one of the most important factors in violin sound quality and the bridge is a major factor in the setup. Therefore I think I will advance more by spending more time working on understanding bridge characteristics than by carving more plates, scrolls, trying new varnishes, etc., etc.

Thanks! You may be intereted in Joseph Curtin's "Some Principles of Violin Setup". I should also add that having a perfect fit, both in the soundpost and bridge feet, is critical. I was doing an adjustment of my violin, and the soundpost fit pretty well, but there were some spots that weren't making full contact. I carefully cut those down, moistened the ends, and reinserted the post. The effect was very suprising. It really brought out the brilliance of the instrument.

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Curiously, a google search turned up an unanticipated plethora of human powered vertical flight enthousiasts. Two things were notable. One is that the American Helicopter Society has offered paltry prize of $20 000 for a sustained flight of one minute. The other is that the rules stipulate the craft must be rotary based. It is hard to understand why there would be such a limitation, as it seems to exclude an entire class of possible constructions based instead on oscillation. Perhaps I will just stick to violins. At least the pay is better.

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quote:


If you moisten with the tongue, the proteins in saliva will also help strengthen the wood when it is dry and compressed (as Mr Nigogisian indicates in the Curtin manuscript).

Curious. I wouldn't have thought of that.

GMM22: Perhaps the limitation that the craft must be rotary based is because it would then be a helicopter, and thus gain publicity for all the helicopter manufactuers with which the AHS is likely under contract with. Much like any violin has to be based after a Strad, Guarneri, or Amati to sell.

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