Bridge warping


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Hi all.

I'm curious as to what methods or precautions others use to prevent or alleviate bridge warping, particularly in cello bridges.

There seems to be no rhyme or reason to it.

I have made cello bridges that are still standing tall years later, and others, cut the same way, that are warping after a relatively short period of time.

There is one violin in particular that always seems to have a warping bridge, no matter how many times I replace it.

Other violins have the same bridge years on.

Are there setup/ construction issues that make an instrument more prone to warping bridges that I am not seeing?

Is it just the wood quality of the bridge?

Again, I am very consistent in my bridge cutting methods, so there is not a lot of difference between bridges, aside from opening the usual parts as needed.

Would it help if I held my bridge closer to the monitor? ;)

Thanks.

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Michael Darnton has an article on bridge cutting here...

http://www.darntonviolins.com/violinmagazine/book/setup.pdf

where at page 27 he describes the profiling of the bridge blank.

He doesn't leave the back of the bridge 90 degrees to the top, as lots of makers do, but relieves it slightly, with the effect that the downward pressure of the string runs an imaginary line through the centre of the feet where they meet the top. This seems to be a very stable, warp resistant design.

Best regards,

E

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I've altered the way I cut 'cello bridges over the years... especially the Belgian type. 'Cello bridges are especially problematic, as to get them to work properly, you need to balance the thickness and strength issues carefully (leverage). In addition, most 'cellists these days are using steel core strings and fine tuners, so the stresses from the strings are both in the "forward" and "backward" directions. I do leave a slight "chest" on the back side as well as the front. The style of Belgian I'm cutting now has proved rather stable and durable in the field, as long as the player takes care of the bridge properly. If the player doesn't pay attention, there's little if anything that can be done.

post-17-0-95095000-1318536959_thumb.jpg

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Thanks guys!

Jeffery, how much wood do you take off the back, percentage wise?

How much of a responsibility does the player have for maintaining the proper bridge position?

Do you explain to every customer how to adjust the bridge?

1) Never thought of it in terms of a %. The chest on the back side isn't nearly as severe as the front, but it's there.

2) No one else has that responsibility.

3) I know most of my clients pretty well. If they don't watch the bridge closely enough, I gently remind them how much a new one will cost. :)

would this apply to violin bridges as well?

For mine? Yes... more subtle, but yes.

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1) Never thought of it in terms of a %. The chest on the back side isn't nearly as severe as the front, but it's there.

2) No one else has that responsibility.

3) I know most of my clients pretty well. If they don't watch the bridge closely enough, I gently remind them how much a new one will cost. :)

For mine? Yes... more subtle, but yes.

cool, thanks...

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sorry but you guys with your slanted forward bridges seemed to have flunked physics, just look at the string angle over the bridge and bisect that angle right in the middle; the bridge is going to end up 90 degrees at the back on most violins

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the problem is the downward angle on the string sounding length side is usually a lesser angle than the downward angle towards the tailpiece, which has been traditionally compensated for by setting the centre of the bridge slightly angled back to compensate, which works out with the back flat side of the bridge at 90 degrees

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pardon me but i dont see anywhere where jeffrey holmes speaks one way or the other about bridges standing straight up, vs the back being 90%; 90% is very common in the industry, and if your having trouble with warping, first thing is only use expensive bridge blanks and two, if your standing them straight up, the tension of the strings is going to want to make the top curl forward, as the string tension doesnt push straight down, but slightly forward

as for leaving a chest, a thicker area in the centre of the bridge, i was routinely critisized for this from the picture of my bridge, because i add a heart and do a lot of cutaway near the centre of the bridge, i compensate by leaving the bridge thicker in the middle, if you do no extra carving at all, you can probably thin more than that in the middle.

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pardon me but i dont see anywhere where jeffrey holmes speaks one way or the other about bridges standing straight up, vs the back being 90%;

Hey Lyndon;

You are correct. I fit my bridges (before shaping) so that the back (tailpiece side) of the bridge blank runs about* 90 degrees to the arching... and correct again, I didn't say otherwise... but I'm having trouble finding anyone else who contradicted that in this thread. Did I miss something? Confused...

What we were discussing is a slight relief on the backside of the bridge as well as the usual chest on the front. I don't have a profile photo to share (not sure why, just have never taken one), but the relief, and the chest, are not so obvious when viewed from the side, as the edges are shaped so that they appear pretty straight (not bullet shaped), and are slightly thinner than the center... on a cello bridge this line (thinned outer edge) would start just above the feet and extend up to the string arch.

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thanks jeffrey, actonern was quoting michael darton and ive heard this before, that some makers make the centre of the bridge 90% so that both front and back angle in equally. melving was reccomending something like this, it appeared, then oded makes the ridiculous statement that everyone fits bridges the same, implying michael and melvings method is universal which its not, another case where people are trying so hard to be different from my method that they say things they dont really mean, maybe

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thanks jeffrey, actonern was quoting michael darton

Hi Lyndon;

I think this may be just some kind of misunderstanding. Here's a quote from the article by Michael Darnton that was being referred to:

"The final height of the two feet should be the same, unless something strange about the violin as previously discussed dictates otherwise, and the centerline of the edge of the bridge should appear to lean back just slightly from perpendicular to the plane of the ribs. Ultimately, because the bridge is tapered, this means the back is actually tilting forward just a bit, and the front of the bridge tilts back quite a bit. With most top archings, which aren’t parallel to the ribs at the bridge position, the bottoms of the feet will end up square to the back of the bridge. Refer to the photos for the appearance of a bridge standing at the right angle."

Some of the wording may be a bit confusing, as I'm sure some of mine is, but Michael references "the centerline of the bridge should appear to lean back slightly from perpendicular to the plane of the ribs". Pretty much the same thing as referencing the back of the bridge near to square to the arching of the top.

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I also relieve the back like Jeff describes. I often see bridges come in that are warping by the back curling toward the tailpiece. These bridges are usually straight in the back with no "slight chest" as Jeff described it. It doesn't necessarily matter what angle the bridge is in relation to the strings either. Do others find this as well?

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I also relieve the back like Jeff describes. I often see bridges come in that are warping by the back curling toward the tailpiece. These bridges are usually straight in the back with no "slight chest" as Jeff described it. It doesn't necessarily matter what angle the bridge is in relation to the strings either. Do others find this as well?

Oddly enough i don't and i mostly work on rental or school instruments. This is actually the first I've heard of the slight relief in the back. I will try it now though and see if the % of warped bridges goes down. Vary curious to me. I wonder if where in the country you live might affect weather (no pun intended) or not the "slight chest" is needed..

Jesse

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Hello,

I have learned bridge cutting in my apprenticeship with Alessandro Voltini, who passed me the methods he learned at J.F. Schmitt in Lyon.

This has been one of the most valuable experiences just after the violinmaking school.

I agree that sometimes the maker has to discuss and explain his views with customers, for two reasons: for lack of attention by teachers and (very frequently) for lack of information. I must say that I consider myself an average-level violinmaker, absolutely, but in my day-to-day experience with musicians a warped cello bridge occurred only once (6 years ago) and the customer didn't know that she had to watch for the bridge after changing all the strings, so her bridge became warped very soon.

By the way, I decided to change it to stop the complaints... and by making it a little thicker at the bottom we managed to adjust a wolf note too. I have learned a bit more and it ended "Tarallucci e Vino" the Italian way.

I frequently see extra quality bridges where the tailpiece side has become concave, so I always make a slight arching on the t.piece side on new bridges.

Student instruments nearly always have fine tuners, so I try to make their bridges well arched too, and occasionally I use a disc sander to be faster.

In violin and viola bridges, I use a Herdim half-round rasp with fine teeth to do this, rasp and file strokes always in a "Chinese fan" shape from bottom to top.

Since my right eye has a defect, it's useful for me to reverse the bridge on the bench and finish this shaping by working from top to bottom on the bass side.

This way I find it easier to make the step Mr. Holmes pointed out, that the finished bridge should have straight edges when viewed from the sides and not bullet-shaped.

I think that, apart from aestethics the aim is eliminating extra mass without compromising stiffness.

If I need to remove more wood I have no problem in filing the bridge stamp away. Sometimes I decide to plane away on both sides of the bridge to adjust the grain direction and not to make the starting thickness by planing only on one side (suggested by Christian Bayon).

But, I also have a question:

-When I make doublebass bridges with adjusting screws, I don't change my methods, so the finished bridge looks like a regular one when viewed from the side (first I shape the bridge then I cut it and put the screws, or Full Circle pickup, in). Should I make the "bisecting line" of the bridge go 90 degrees with the top in this case?

Giovanni

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