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Bridge options

 
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Dave Chandler
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Joined: 31 Oct 2007
Posts: 691
Location: Mt Mitchell in North Carolina

PostPosted: Sun Nov 18, 2007 9:54 pm    Post subject: Bridge options Reply with quote

I just completed a violin, on which I put my usual thinned and cut down bridge (4.5mm at the feet, 1.3mm at the strings). After five or six different post relocations, I continued to have a thin metallic quality to the sound. The best location for the post ended being a bit inboard but still under the right foot, and about 6mm toward the tailpiece.

On a hunch, I tried a half dozen old bridges, same sound. then I took a full size unthinned, uncut bridge and put it in place. Of course, it was not very playable beyond 1st position because of the height of the strings above the soundboard (fingerboard projection to bridge is 27.5mm). But the sound was clean and clear, but a bit muffled by the amount of wood on the bridge. I cut the bridge about 2 mm higher than I usually like to play, and did not thin the bridge or remove any other wood from the bridge, except enough to fit the feet. The sound is wonderful, but I have this thick bridge. Is there an alternative that would be less noticeable? If I thinned the bridge is there some way to add some mass to it? Is there something I should do to the violin so that a normally cut and thinned bridge could be used (thinking of my next violin)? Thicker plate under the bridge? Heavier strings (currently med. Dominants)?
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
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jethro
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Joined: 07 Apr 2007
Posts: 178

PostPosted: Tue Nov 20, 2007 4:45 am    Post subject: bridge mysterys Reply with quote

Dave: I have had similar troubles with thinning bridges. they sound better and better and then suddenly - wham- the sound and the feel under the bow just collapses.

Try this fix:

start with blank bridge.
cut feet to fit top(or sand)
cut underarch and trim top of feet.
open the side holes up towards the outside of the bridge- a little
trim the points so they don't have any arrowhead
lower the heart hole a little - maybe 1 mm
sand the lower half of the bridge off by about 1/4 or 1/5 of its thickness-
(I think this is .200 inches- whatever the books say)
draw a line across the upper arc of the bridge paralell to the top edge
and about 3\16 or 1/4 inch from the top. draw on both sides.
gouge or scrape or sand a fascet starting at the line you just drew and ending at the top edge. you are trying to taper the upper edge along a stripe near the top edge but not down in the middle of the bridge.
taper both sides. Shoot for having the top edge be about .050 inches
and the cut you made going back maybe 1/4 inch back from the edge.
you can thin the area below here but only just a tiny bit. you can thin the
G side a little just above the hole on that side.
put it on and see how it sounds. If one of the strings sounds tight then
thin the area under that string but only thin in that upper stripe area.
You can taper and blend the adjustment into the area of the neighbor
string position.
I think if you keep the bridge relatively meaty in the middle and bottom
and do most of the thinning in the upper 1/3 you will be keeping the
overall bridge frequency up (good) and allow the edge to flex more freely
up at the upper edge.

I think I have an intuitive idea how to do it but it seems to be hard to relate in words.

If this wasn't clear ask me more Q's !
I could find allmost no information how to do bridge adjustments...........

Tim
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Dave Chandler
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Joined: 31 Oct 2007
Posts: 691
Location: Mt Mitchell in North Carolina

PostPosted: Tue Nov 20, 2007 12:46 pm    Post subject: Bridge adjustments Reply with quote

Jethro:
Thanks for the hints, and I think I understand your instruction. I'll give that a shot! In the past, I had relied on trimming the bridge down to a basic shape first before ever putting it on the violin, and then trimming down to where I was satisfied with the sound. This time, it seems I've got to start with a full size blank.
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
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jethro
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Posts: 178

PostPosted: Wed Nov 21, 2007 2:10 am    Post subject: Reply with quote

chet:
I was doing the same thing initialy. Then I started thinning the whole bridge and then playing, thinning the whole area a little more and playing again. I was thinning from the bottom arch to the top edge. Some of my bridges were REALLY thin and had all most a concave shape to the faces.
I think this was the problem. Get a basic collage physics book and look up the part on moment of inertia. You might immagine the bridge as having its feet glued down to the top plate and the top edge free to
"ring" like a tuning fork. (no strings involved) As you remove material from the bottom or middle more - the moment increases and the bridge
frequency goes down. as you remove wood from the top more the
freq. would go up. so instead of me making my bridge thick at the bottom
and thin at the top with the area in between concave, I make the area in the middle more convex and do the thinning on the "stripe" which is the
last little area just below the strings.
I will measure one of my bridges and give you the thicknesses at top ,
bottom and middle. I can send you a digital pic if you want me to
E-Mail it to you. I don't think I have any way to post one here--
(at least that I have figured out !)

I probably cut and tested 30 bridges just experimenting to get where
I am now -- which is barely anywhere !
I tried some beautifull oak which had beautifull rays just like the good
auberts. It worked but the wood was noticeably more rubbery than
maple and it seemed like it attenuated a lot of the sound.

Tim
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Dave Chandler
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Joined: 31 Oct 2007
Posts: 691
Location: Mt Mitchell in North Carolina

PostPosted: Wed Nov 21, 2007 12:20 pm    Post subject: Bridge thinning Reply with quote

Tim:
I tried your suggestion, and it worked out real well. I was able to get the string height down to where I am accustomed, and more volume as well without losing the quality of the sound.
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
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jethro
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Posts: 178

PostPosted: Wed Nov 28, 2007 3:54 am    Post subject: russian roulette now ? Reply with quote

Now that you see what has worked more or less, you can experiment and
see how much more performance you can wring out of the violin.
You don't want to add weight to the bridge. What you want is for it to keep
a relatively high resonant frequency and also be as thin as possible.
( take your new bridge and one of the old ones which wasn't working--
and drop each one on you benchtop. You will hear each "ping" with a
specific pitch. See if you can hear the new one being higher than the old one....) Generaly what will keep the bridge frequency up is to keep
the stiffness high, and the mass LOW . Since the bridge is stationary at
it's feet and moving with the strings at the top you want the "rotational
moment" to be as low as possible. If you carved the bridge up sice down
with the feet thin and the upper edge 4 mm wide this would send the
moment the opposite direction.
If you want to live dengeriously........ slightly thin the middle of the sides
from the the bottom of the holes to the top of the heart - having a little
taper as you go up. Correspondingly re-thin the upper edge a bit more
to keep the demarcation line about 1/4 inch away from edge. ( as you thin
the middle the old line will move up)
You might do this adjustment with a scraper or maybe a tiny sanding block. You may get a noticeable increase in vollume and ease of playing.
But I think there is a point at which it will it will self distruct. You just have
to experiment to see where that point is.
I have thought of making 2 identicle bridges. Keep the 1-st one trim ahead
of the other. As the first starts to get worse you know the 2-nd is close
to optomised.
Just an idea !!!!!!!!!!!!!!
There is also something to be said for not screwing with success !

Tim
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Dave Chandler
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Joined: 31 Oct 2007
Posts: 691
Location: Mt Mitchell in North Carolina

PostPosted: Wed Nov 28, 2007 11:18 am    Post subject: Bridge options Reply with quote

Tim:
I really appreciate all the detail, I've printed out your suggestions and put them into my loose-leaf with other set-up articles.
I've love to get into a course on set-up that really goes through this process for each type issue. I also don't see any really good resources on the internet. If someone knows of a great book on violin set-up and bridge shaping/tuning, I'd appreciate that info. A full understanding of the bridge's action under a variety of scenarios is something I need to understand much better. I think the mechanicals of shaping the violin is one thing, but getting a great sound is far more challenging.
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
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Jack H.
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Joined: 24 Mar 2007
Posts: 346
Location: Israel

PostPosted: Wed Nov 28, 2007 1:36 pm    Post subject: Reply with quote

just a few words on bridges from master maker.
http://www.josephcurtinstudios.com/news/tech/journal_vsa/principles.htm
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jethro
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Posts: 178

PostPosted: Fri Nov 30, 2007 2:36 am    Post subject: bridge cutting Reply with quote

WOW - thanks Jack for that T-Bone steak-quality bridge and setup page
from Curtain. I had been there but had not found that page ! I have not read it all yet but it looks like it really hits the spot !

Dave C. : Yes I too am thirsting for a good understanding of the
functions and dynamics of bridges.
Here is a thought I had while thinking about bridges ......
The bridge is the sole (I think) conduit to transmit energy from the strings
to the body of the violin. All the energy available to the top plate has to
go THROUGH the bridge. Therefore I have to conclude the bridge has
the function of being a FILTER - for better or worse. I mean a filter in
the sence of filters used in television and radio circuits. There is a whole
spectrun of stuff going in , but what gets out through the feet is only what
makes it THROUGH the bridge. The bridge will have resonances and
modes and standing waves and dispersions and frequency cutoffs and Q-factors and absorption peaks and everything else a vibrating mechanical object could have. So it seems like to me ---- you never really know how
good a violin you have made (what it is capable of) untill you know that
the bridge is as good as it can be made (I don't know how you know that
!!!!!!!!!!!!! )
I came to the conclusion that the bridge and to a lesser extent the post and rest of the setup is in some ways harder than making the whole rest
of the instrument !

If you agree with my filter analogy then I think you have to agree on how
important it is to squeeze EVERY bit of performance out of the bridge or
you never really know ho good you did making the instrument !!!!!
And THAT is what I need to get better at every time I complete one
and move to the next.

I'm off to read and print the Curtain piece now (thanks jack !!!!!! )

Tim
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Dave Chandler
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Joined: 31 Oct 2007
Posts: 691
Location: Mt Mitchell in North Carolina

PostPosted: Sun Dec 02, 2007 11:18 am    Post subject: A bridge too far Reply with quote

Thanks for the link to the article. Once I got there I realized I had that article already, so it was back to that for a re-read. Actually, after fiddling with the bridge and soundpost I ended up taking the top off. My conclusion was that the top was too stiff to respond to anything but the highest bridge height, leaving me no room for properly adjusting the bridge. I made sure my top graduations were as even as possible, took some height off the bass bar, then sealed it all back up. I'm getting terrific response, volume, timber especially pleased with the G &D, still needing to get a little more volume from the A, and need a little better response from the E. Thanks for all your encouragement.
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Dave in the Blue Ridge
Southern Violin Association

"Success is the ability to go from one failure to the next with no loss of enthusiasm" Winston Churchill

"I took the road less travelled, and now I don't know where I am." Marco Polo
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violinbridges
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Joined: 10 Jan 2008
Posts: 10

PostPosted: Fri Jan 11, 2008 1:04 pm    Post subject: Reply with quote

Dave you may find our site has some usefull links and articles

http://violinbridges.co.uk/ref.php


Since this forum has been upgraded we have added a few hundred more bridges, now at almost 1000 online, most recently some lovely Italian and Swiss makers. We have added a page where you can query the database to return minimum-average-maximum measurements and weights for most bridge widths and types.

Due to many requests we have asked dick.biz to set up an online shop which you now can choose from 1400 different types of bridge blanks to buy.

Also you can track auction results of any of the makers in our database via links to the "Red Book"

Many Changes and Additions, with a few more planned for the future.

As always we are always looking for more to add.

Gerard

www.violinbridges.co.uk
shop.violinbridges.co.uk
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