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Standard bridge radius?


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#1 polkat

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Posted 01 June 2010 - 12:48 AM

Lately it seems that all the bridges I cut are a bit too flat. I keep hitting adjacent strings to the one I'm playing, when I don't want to. This is fairly new for me. This might be great for a bluegrass player who plays a lot of double stops, but I'm a jazz player and it's no help! Am I correct in remembering that the standard bridge arch is cut to a 42mm radius? And how does this relate to the arch of the fingerboard? Thanks!

#2 Nicolas Temino

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Posted 01 June 2010 - 02:24 AM

Lately it seems that all the bridges I cut are a bit too flat. I keep hitting adjacent strings to the one I'm playing, when I don't want to. This is fairly new for me. This might be great for a bluegrass player who plays a lot of double stops, but I'm a jazz player and it's no help! Am I correct in remembering that the standard bridge arch is cut to a 42mm radius? And how does this relate to the arch of the fingerboard? Thanks!


As long as the strings fit a 42 mm radius circle, the shape of the bridge is less relevant. I have two tamplates with different top shapes, but strings allways fit a 42 mm circle.

But sure there is a better way. Maestri have the word.
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#3 robertdo

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Posted 01 June 2010 - 03:57 AM

On the C&J book they give 42mm as being the radius of the fingerboard itself. But then I suppose, given that the E string is only 3.5-3.8 mm above the fingerboard end while the G string is about 5mm, shouldn't the radius of the bridge might be slightly below 42 in order to avoid hitting 2 strings? I also thought the radius of the bridge was better determined by a direct measure from the fingerboard shape at it's end rather than relying on a given value.

#4 polkat

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Posted 01 June 2010 - 04:30 AM

Maybe this pic will clear up what I'm asking. What I'm asking is if the pic is correct? I downloaded this a few years back (probably from this website, so I apologize for using it if someone here owns it!).

Bridge_arch.gif

With the above idea, the bridge is first marked with an arch using a 42mm template at a height that, if cut there, would lay the strings perfectly flat along the fingerboard (assuming that the fingerboard is also shaped with a 42mm radius-I understand that is standard). This could be traced with a pencil, then the arch is drawn at half the pencil diameter lower. Then marks are placed on the bridge above the first line at the standard string heights (above the end of the fingerboard) as shown. Then the 42mm template is used to connect these dots while drawing another arch, and that is the bridge height cut to be made.

In other words, what is the best way to cut a new bridge with a classical arch placing the strings at the proper height? You'd think this would be an easy question, but for some reason lately I'm having trouble with it. Don't get old!

#5 Brad Dorsey

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Posted 01 June 2010 - 07:26 AM

I don't recall offhand what the standard bridge radius is, but I believe that setting up the instrument so that it it works the best for whoever is playing it is more important than adhering to any standards. I recommend that you experiment with it and figure out what works best for you.

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#6 Ken Pollard

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Posted 01 June 2010 - 08:07 AM

Maybe this pic will clear up what I'm asking. What I'm asking is if the pic is correct? I downloaded this a few years back (probably from this website, so I apologize for using it if someone here owns it!).

Bridge_arch.gif

With the above idea, the bridge is first marked with an arch using a 42mm template at a height that, if cut there, would lay the strings perfectly flat along the fingerboard (assuming that the fingerboard is also shaped with a 42mm radius-I understand that is standard). This could be traced with a pencil, then the arch is drawn at half the pencil diameter lower. Then marks are placed on the bridge above the first line at the standard string heights (above the end of the fingerboard) as shown. Then the 42mm template is used to connect these dots while drawing another arch, and that is the bridge height cut to be made.

In other words, what is the best way to cut a new bridge with a classical arch placing the strings at the proper height? You'd think this would be an easy question, but for some reason lately I'm having trouble with it. Don't get old!



The sketch looks like one of mine, though I don't recognize the text. I think it came up in a discussion a couple years back on this topic with Stradofear posting much of the good stuff. I was just trying to understand. It is possible to get different heights of strings (such as the e and G) with the bridge radius matching the fingerboard radius -- you just offset the two arcs, as in the sketch.

You really don't even need the curve in the wood to get the 42-mm radius string placement --

roofbridge.jpg

Again, a suggestion of Stradofear's. Here, the strings are on a 42-mm radius curve. The shape in the top of the bridge is incidental. By the way, it is more difficult to cut the top this way, and its only purpose seems to be to start arguments with people who believe that the arch in a violin bridge and the arch in a river bridge (actually negatives of each other) serve the same function in support. It was a fun experiment, and after taking the photo, I finished the bridge in a conventional way.

So my first suggestion would be to examine the string postions on the bridge to be certain that they actually are a 42-mm radius. Don't be fooled by the arc between the strings. If the strings aren't on the arc, but close, it should still be possible to play, though tougher. As Brad states, you need to make it work for you.

Cheers,

Ken

#7 Nicolas Temino

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Posted 01 June 2010 - 09:12 AM

That picture Ken has posted is exactly what I meant in my post. It is not so imoprtant the final shape of the bridge but the 42 mm radius. I say 42 mm because it is the normal radius of the fingerboard, if you had a different fingerboard radius I think you should keep that radius in your bridge.
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#8 Ken Pollard

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Posted 01 June 2010 - 09:29 AM

That picture Ken has posted is exactly what I meant in my post. It is not so imoprtant the final shape of the bridge but the 42 mm radius. I say 42 mm because it is the normal radius of the fingerboard, if you had a different fingerboard radius I think you should keep that radius in your bridge.


Nicolas -- Yes, I should have mentioned your prior posting in mine, but I was agreeing with it. It's easy to be distracted by other parts of the shape, parts that aren't in contact with the strings.

I think that if, on a violin, the fingerboard differs much from the 42-mm radius, one should examine the reason for that and if none is found, then fix the fingerboard first.

And it's also worth noting that a flatter bridge doesn't aid in double stops, but it does aid in shifting between pairs of double stops on adjacent strings -- common in bluegrass or old-time American fiddle music, as polkat mentioned. See "Orange Blossom Special." Having said that, though, most folks in fiddling seem to do well with a standard radius. I have only a couple requests per year for a flatter bridge.

I know for me, it's not the shape of the bridge that's limiting my ability to play double stops, shuffle patterns, or even single notes! :)

#9 David Burgess

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Posted 01 June 2010 - 09:47 AM

41.5 to 42 is pretty much considered the standard. That's not the shape of the top of the bridge, but the radius measured on the upper surface of the strings, the playing surface. The curvature at the bottom of the string will vary depending on whether different diameter strings, such as a silver D, are used. It's the upper surface which matters to players. When they need a string, most of them want to know exactly where to find it and when it will start making noise. :)

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#10 Ken Pollard

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Posted 01 June 2010 - 09:55 AM

41.5 to 42 is pretty much considered the standard. That's not the shape of the top of the bridge, but the radius measured on the upper surface of the strings, the playing surface. The curvature at the bottom of the string will vary depending on whether different diameter strings, such as a silver D, are used. It's the upper surface which matters to players. When they need a string, most of them want to know exactly where to find it and when it will start making noise. :)


Hi David,

I've heard this and wondered about the concept. Given that the G-string sits a bit deeper in the bridge than the e-string, and strings vary in diameter depending on type, it gets complicated to think about. Do you use an above-the-strings template when finishing up a bridge? Or do you use the more common under-the-bridge template which has been adjusted to get where you want?

Since I do mostly student instrumens, on a practical level it probably doesn't matter much to me, but I am curious about.

Thanks,

Ken

#11 David Burgess

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Posted 01 June 2010 - 10:14 AM

Do you use an above-the-strings template when finishing up a bridge?

Yes. The bridge starts too high, and I deepen individual string grooves until everything is just right. Then I remove the bridge and trim the top to remove the excess depth from the grooves. One needs to allow for the thickness of the E string protector when doing this.

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#12 Ken Pollard

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Posted 01 June 2010 - 10:20 AM

Yes. The bridge starts too high, and I deepen individual string grooves until everything is just right. Then I remove the bridge and trim the top to remove the excess depth from the grooves. One needs to allow for the thickness of the E string protector when doing this.



Thanks!

#13 Bruce Carlson

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Posted 01 June 2010 - 02:44 PM

Thanks!

The first time I ever saw the string radius method (versus the bridge crest line) being used by David when we were at Weisshaars I immediately incorporated it into my bridge cutting routine and never looked back.

Measuring up from the fingerboard is only going to work if by chance the fingerboard radius is good. You can see right away that if the measurements were to remain the same that switching from an aluminum wound D string to a thinner silver wound string would necessarily give you a flatter bowing curve relative to the A and the G. With the bowing curve adjusted on top of the string it is going to be the same.

I now have a series of radii which allow me to duplicate any bridge curve I please, flatter for better players with bow control and somewhat rounder for students. It is especially useful if you are trying to get the curve right for a viola d'amore, a viola da gamba or other instruments with more than four strings.

To avoid confusion on this point I like to call it the bowing curve or the string curve as the actual line of the bridge crest is not a radius.

Bruce

#14 Jeffrey Holmes

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Posted 01 June 2010 - 03:00 PM

The first time I ever saw the string radius method (versus the bridge crest line) being used by David when we were at Weisshaars I immediately incorporated it into my bridge cutting routine and never looked back.


Yup... David got me with that one too. Been using that method since I worked with him. Troublemaker! :)

#15 das928

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Posted 01 June 2010 - 06:01 PM

What is the standard curvature or string radius for a viola bridge, is it also 42 mm?

#16 Alan_Coggins

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Posted 01 June 2010 - 11:35 PM

"The first time I ever saw the string radius method (versus the bridge crest line) being used by David when we were at Weisshaars I immediately incorporated it into my bridge cutting routine and never looked back.
To avoid confusion on this point I like to call it the bowing curve or the string curve as the actual line of the bridge crest is not a radius.


Yup... David got me with that one too. Been using that method since I worked with him. Troublemaker! :)


Sounds like it should be known as the 'Burgess Curve' :)

#17 Bruce Carlson

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Posted 02 June 2010 - 02:05 AM

QUOTE (Bruce Carlson @ Jun 1 2010, 03:44 PM) *
The first time I ever saw the string radius method (versus the bridge crest line) being used by David when we were at Weisshaars I immediately incorporated it into my bridge cutting routine and never looked back.

To avoid confusion on this point I like to call it the bowing curve or the string curve as the actual line of the bridge crest is not a radius.

Sounds like it should be known as the 'Burgess Curve' :)

Hi Alan,

I first saw the string curve radius through David and personally I am not aware of anyone doing this before him, but in a world where everything has already been thought of and attempted the idea may already have been out there. It is nonetheless ingenious and revolutionary. It is much more accurate than measuring angles on top of the string at the bridge or measuring up from the end of fingerboard.

I usually do only 3 strings at a time like E,A,D and then A,D,G for example on a violin. Knowing that any three points can define a radius (on a bridge these are - or should be - equidistant points). Usually I have the bridge virtually finished with the E and G very close to final height and with the radius still rocking when pivoted on the A or on the D. Then I bring the A and the D down alternately, as one three point curve influences the other, until the radius touches the three strings in question. You can place the dry parchment temporarily under the E string during this process to get the correct curve.

Before a musician begins to complain that a bridge curve is too flat, I have noticed that they sometimes have negative comments about the sound or playability of the A or D string; not realizing that they are compensating for a flat string curve that doesn't allow them enough free bowing clearance without touching one of the adjacent strings. The curve has to be just enough to take full advantage of the sound palette, obtained by pressure or distance from the bridge. If it is not this way, they find themselves forced to play nearer to the bridge crest and cannot really dig into the string when required. Once the curve is corrected the "sound" problem often goes away.

If the string curve is excessive then you have to introduce unnecessary bow arm movement and playing three strings becomes impossible. For young students who do not have a lot of bow control the string curve can be increased (reduced radius) to compensate for their lack of bow control.

The flattest string curve I ever saw was Ruggiero Ricci and he also had the strings right down close to the fingerboard. As the strings are lower you can use a flatter curve because the string will be deflected less to reach the fingerboard. Ricci's setup is unplayable for many musicians but he said that it drastically reduced the time to stop the string against the board when playing fast passages.

Bruce

#18 Guest_erich_zann_*

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Posted 02 June 2010 - 03:27 AM

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#19 Roman Malamant

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Posted 02 June 2010 - 03:42 AM

Lately it seems that all the bridges I cut are a bit too flat. I keep hitting adjacent strings to the one I'm playing, when I don't want to. This is fairly new for me. This might be great for a bluegrass player who plays a lot of double stops, but I'm a jazz player and it's no help! Am I correct in remembering that the standard bridge arch is cut to a 42mm radius? And how does this relate to the arch of the fingerboard? Thanks!

The way I am doing the bridge curve is like this.

First I make a bridge higher than what it is supposed to be. Since I don't check at this point the curve on top of the strings (I make the curve of bridge itself), my bridge template has a bit higher curve at the D string in order to make sure silver D strings will be high enough. Actually, I make the top of the strings curve a little bit higher at the D in final bridge too because D has a bit less tension than A. So, in order to have the same curve when playing forte, D have to be slightly higher (its especially noticeable when playing in high positions).

With the higher bridge on the violin with strings in tension I measure by how much the E and G need to be lowered to make proper height over the fingerboard. It is very important to have, at this point, strings close to proper pitch as some violins tend to pull the fingerboard a little bit downwards when in tension. Sometimes by mm or even 1.5 (especially on violins with "bully" arch). I don't measure the height at the middle strings as this is a function of proper fingerboard curve. Bridge curve should take care of comfortable bowing only, it's the fingerboard curve should take care of making middle strings in proper height with relation to E and G.

Next thing, I mark on the bridge how much E and G need to be lower, using previous measurement. I avoid method of cutting string grooves until string height is right, as some people do, because, while doing this, distance between strings can change. I just measure how much bridge too high at E and G and mark on the bridge. Than using my bridge template I draw the new bridge line aligning with marks for E and G and cut the rest of the wood away. Now that I have the right bridge height I make the last finish put the bridge on the violin, check the sound and do adjustments as needed.

The last thing I check the curve on the top of the strings. Actually its not a curve, that I am interested in, but proper clearance for A and D. What I do, I look at the bridge from E side, with back of the bridge aligned flat so that you actually don't see it (the violin is in my hand in horizontal position, the bridge is on top in front of my eyes, the head to the right). When I look at it I align the tops of E and D strings at the bridge so that I see the D exactly behind E. When tops of strings E and D aligned you can see precisely the clearance of the A string above the E and D.

Using this method I compare the clearance of the D and A. As I said before I give the D string slightly more clearance as it has slightly less tension. Clearance something like 2 mm for D and 1.7 mm for A (I do it by eye never really measure it) should be ok - but it can change of course, depending on player preferences. At this point I cut the grooves under strings deeper in order to adjust the proper clearance. The last thing, to make sure each string sits only half of it's diameter inside the groove, I file the top of the bridge to remove all the wood above that point.

That's all, hope it was clear but please ask if something was not.

#20 Roman Malamant

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Posted 02 June 2010 - 04:13 AM

Just to illustrate what I mean by aligning the E and D in order to see clearance of A, here is the photo (I assume it's obvious but just to make sure - in order to see clearance of the D string you need to align A and G :) ):
IMG_6124.jpg
This is my template:
IMG_6130.jpg




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