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| Bridge Thickness... http://luthiersforum.com/forum/viewtopic.php?f=10101&t=35210 |
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| Author: | sdsollod [ Tue Jan 31, 2012 5:42 pm ] |
| Post subject: | Bridge Thickness... |
Here are photos of a stock rosewood Martin bridge and one I made of ziricote (the first after a practice one that turned out fine...). Mine is a little thicker than the stock bridge. Mine measures 0.400". The Martin bridge is 0.350". Should I reduce the thickness or is it okay? |
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| Author: | StevenWheeler [ Tue Jan 31, 2012 6:08 pm ] |
| Post subject: | Re: Bridge Thickness... |
Steve, I shoot for a bridge thickness of .375". I set my strings 1/2" above the sound board and that leaves .125" of saddle showing. Gives some room for adjusting saddle height and keeping a decent break angle for the strings. So, yes, you could trim yours down a bit. The other thing I notice about your bridge is that it appears flat across the top. You would be well served to put an arc in it to match your finger board radius. Doing this maintains saddle height above the bridge and string break angle. Because of the higher action on the bass strings, I try to leave that side of the bridge a little thicker so the amount of saddle showing stays consistent across the width of the bridge. Steve |
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| Author: | sdsollod [ Tue Jan 31, 2012 8:10 pm ] |
| Post subject: | Re: Bridge Thickness... |
Steve, You have some very good suggestions. ![[:Y:]](./images/smilies/smiley20.gif "Thumbs Up") You are right, the top of the bridge is flat and your comment to put a radius in the top is a good one. Perhaps I should wait to chamfer the holes until I bring the thickness down and radius the top...? Thank you, Steve |
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| Author: | Tom West [ Tue Jan 31, 2012 8:11 pm ] |
| Post subject: | Re: Bridge Thickness... |
Steve: Another big consideration is "how much does it weigh".....?I like to keep the weight down to enhance responsiveness and to help support the treble output of the guitar. A digital gram scale is great for checking the weight of various parts. Tom |
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| Author: | gozierdt [ Tue Jan 31, 2012 9:38 pm ] |
| Post subject: | Re: Bridge Thickness... |
+1 on Tom West's reply. The weight of the bridge is a major factor in how the top of the guitar responds. As he said, an overly heavy bridge damps the treble output of the top (think of trying to shake a baseball up and down in your hand vs a bowling ball). So most of the better builders I try and follow try and keep bridge weight down as much as possible. It goes along with the whole effort to build a light, responsive instrument. So I personally would follow Tom's suggestion and radius the top of the bridge, plus whatever thinning will leave you a reasonable saddle exposure above the top. You'll need to have the neck set to figure out a final thickness. If you radius the soundboard of the guitar , don't forget you'll need to take some thickness off the bottom of the bridge, so don't overly thin it until you've got the radius on the bottom of the bridge. I don't ream the chamfer on the pin holes until I'm doing my final setup on the guitar, so I can make sure all the pin heights come out the same. |
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| Author: | sdsollod [ Tue Jan 31, 2012 9:54 pm ] |
| Post subject: | Re: Bridge Thickness... |
These are great comments. What should I shoot for in weight of the bridge? |
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| Author: | StevenWheeler [ Tue Jan 31, 2012 9:55 pm ] |
| Post subject: | Re: Bridge Thickness... |
In grams, high 20's low 30's. |
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| Author: | grumpy [ Wed Feb 01, 2012 12:37 am ] |
| Post subject: | Re: Bridge Thickness... |
Mid to high teens.... 
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| Author: | theguitarwhisperer [ Wed Feb 01, 2012 12:58 am ] |
| Post subject: | Re: Bridge Thickness... |
Anybody ever excavate wood from the bridge to lighten it up some? Maybe carve some channels in it lengthwise? |
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| Author: | David Malicky [ Wed Feb 01, 2012 3:43 am ] |
| Post subject: | Re: Bridge Thickness... |
I've heard a few theories on bridge mass. Some say a relatively heavy bridge is good -- I think the argument is that it helps define the end of the string (more impedance), so that the string resonates with a more stable endpoint, which gives more sustain and maybe cleaner string harmonics (?). Others say a light bridge is best, maybe as light as possible -- Trevor G's argument is that less mass gives more soundboard acceleration and responsiveness. I'd love to hear a discussion between the camps... in a new thread? I think most would agree that adding mass to the bridge gives more bass balance, a smoother tone (many would say less responsive), and more sustain; reducing mass gives relatively more treble and attack. For steel strings, I think 'heavy' bridges are typically 30-40g, while 'light' bridges are as low as 15g -- huge range! |
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| Author: | sdsollod [ Wed Feb 01, 2012 10:20 am ] |
| Post subject: | Re: Bridge Thickness... |
There seems to be some differing philosophies on bridge weight. David makes some interesting comments... Quote: I think most would agree that adding mass to the bridge gives more bass balance, a smoother tone (many would say less responsive), and more sustain; reducing mass gives relatively more treble and attack. For steel strings, I think 'heavy' bridges are typically 30-40g, while 'light' bridges are as low as 15g -- huge range! Do others have an opinion or any other thoughts on the matter? The thickness of my stock Martin bridge is 0.350". Steve Wheeler shoots for 0.375". I assume that dimension correlates to weight, to some degree, depending on the species... |
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| Author: | CharlieT [ Wed Feb 01, 2012 10:24 am ] |
| Post subject: | Re: Bridge Thickness... |
grumpy wrote: Mid to high teens.... Hi Mario - what do you find are the advantages of a bridge that light? Thanks! |
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| Author: | StevenWheeler [ Wed Feb 01, 2012 10:18 pm ] |
| Post subject: | Re: Bridge Thickness... |
So you know 15 grams is really light and 40 grams is heavy. 27.5 grams is right in the middle and that's what I used when I first started paying attention to bridge weight. I hope you weren't expecting any deep scientific theory from a guy that rides a 100hp turbo charged motorcycle with no rear suspension. Thin that bridge down and radius the top. Get a scale that measures in grams (I purchased one from Harbor Freight for $15) and weigh it. Weigh the stock one for comparison. You won't get a belly bridge down to 15 grams, but if yours is heavy, lighten it up. There is a bit of weight in your bridge wings as they use a softer transition than the stock one. There is a lot of mass that can be shaved behind the string holes. I use a belly bridge on my guitars. The last was made from Ipe, it that was so heavy I had to cove that area instead of rounding it over. Mario knows a whole lot more about guitar building than I do. If you want your bridge to be that light, you have to change your shape to be like his (see also: Burton LeGeyet, Martin pyramid, typical classical). Maybe I'll try this on my current Dread. Steve |
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| Author: | StevenWheeler [ Wed Feb 15, 2012 8:46 pm ] |
| Post subject: | Re: Bridge Thickness... |
StevenWheeler wrote: You won't get a belly bridge down to 15 grams, Whoops! I should know better than to speak in absolutes. This is a maple bridge shoe polished black. The Ebony one weighs in at 24.1 grams. |
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| Author: | Steve Saville [ Thu Feb 16, 2012 12:21 am ] |
| Post subject: | Re: Bridge Thickness... |
sdsollod wrote: ......Do others have an opinion or any other thoughts on the matter?......... Seriously?? I think one reason that there are different opinions is that a heavy bridge might work better for one builder and the way he builds and what he wants from a guitar while another guy gets the results he is looking for using a light weight bridge. Then these two guys talk about their truths for their guitars as if it was universally true. Maybe it is, and maybe it isn't. You need to find out what works for you and not listen so much to others. Try a like a light, medium, and heavy weight bridge on the same guitar and see what you notice and what you like. Does that make sense? You can get bolts from Stew make that will allow you to try different bridges by just bolting them on. http://www.stewmac.com/shop/Tools/Speci ... Bolts.html theguitarwhisperer wrote: Anybody ever excavate wood from the bridge to lighten it up some?.... Ervin Somogyi, to name one. I also do it. Here is mine - 
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| Author: | dberkowitz [ Thu Feb 16, 2012 11:29 am ] |
| Post subject: | Re: Bridge Thickness... |
Lost in this discussion is that guitar making is a system of components, in that folks are talking about bridge weight in the abstraction. I found my guitars improved with a heavier bridge. I think that the opposite is true on a classical which has strings under less tension and a propensity to provide low frequency information. Consequently one should want a lighter bridge on a classical because we're trying to get out the trebles, whereas on a steel string there isn't generally the same need. Again, I can't emphasize this enough that bridges are part of a system of components that all have an effect on sound production. Given a particular set of design parameters you may want to try a lighter or heavier bridge. A lighter bridge in and of itself is no panacea. |
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| Author: | Kent Chasson [ Thu Feb 16, 2012 11:49 am ] |
| Post subject: | Re: Bridge Thickness... |
The other thing that gets lost in this discussion (that Steve alluded to) is that this is about the easiest thing there is to test for yourself on your own guitars. Start with the heaviest bridge you might use and pare it down and see what happens. Go until you've gone too far, take it off and put on a new one the weight that you liked. The bridge bolts Steve mentions might work but I would be inclined to glue it down to get a more accurate idea. Good chance to practice bridge removal in the process. |
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| Author: | Alan Carruth [ Thu Feb 16, 2012 12:55 pm ] |
| Post subject: | Re: Bridge Thickness... |
Yes: as the Brits say, it's 'horses for courses'. Mario gets the response and tone he likes with a really light bridge, and that's great. One of my students got a little carried away carving hers, and it ended up at 22 grams, iirc, which was too 'bright' for her. We ended up adding some weight inside the top when it was in the white. Later, with some finish on it, it no longer needed the added weight; whether it was the extra mass of the finish, or the damping, is hard to say. I always look at the main function of the bridge as working with the top to tell the string how long it is, so that it will know what note to make. You have to see it as part of the whole system of stiffness and mass that establishes the impedance mismatch that terminates the string. I tend to use 'tapered' bracing, which makes the top stiffer in the bridge area than 'scalloped' bracing would. With this system you need a certain amount of mass at the bridge to avoid too much of a 'high pass filter' effect. When you get it right it's reasonably responsive, with good sustain and headroom. With scalloped bracing you might find a lower bridge mass would be OK, although it's possible that the combinationm of low mass and lower stiffness could be subject to more 'wolf' notes, and would need to be carefully handled. In return you might get more responsiveness, a stronger attack, and better bass response. There's no one right way to do it in every case: all categorical statements are false. |
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| Author: | bluescreek [ Thu Feb 16, 2012 1:02 pm ] |
| Post subject: | Re: Bridge Thickness... |
Just to set the record straight , Martin uses a few different size bridges for the production line. .250 to .410 They don't weigh the bridges and yes they are a production factory. A bridge is a brace that is outside the guitar . What works for one may not work for another as Alan points out well. It is a part of the guitar that can be manipulated for tone and sustain. |
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| Author: | Steve Saville [ Thu Feb 16, 2012 8:51 pm ] |
| Post subject: | Re: Bridge Thickness... |
Kent Chasson wrote: ...... The bridge bolts Steve mentions might work ....... I have used them. The do work. Tone was virtually unchanged between bolting it down and gluing it. |
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| Author: | Trevor Gore [ Thu Feb 16, 2012 9:48 pm ] |
| Post subject: | Re: Bridge Thickness... |
A guitar's responsiveness (sensitivity, capability to produce high volume, call it what you like) is directly related to monopole mobility, where monopole mobility is proportional to 1/SQRT(k*m) where k is the effective stiffness of the top and m is its effective mass. The bridge mass directly affects m and so the monopole mobility is directly related to bridge mass. Put another way, for a given drive force produced by a string, a low mass top will accelerate more and therefore produce more sound. However, whilst making a really light top is not that hard, it is very hard to have it light and responsive with even loudness over the fretboard, no wolf notes and an alluring sound. To do that, you have to distribute the modal frequencies correctly, where a mode's frequency is dependant on SQRT(k/m). So you can see (maybe!) how the bridge's mass and stiffness directly interact with the rest of the system. A heavy bridge might seem to "smooth things out". It does, but by attenuating everything, particularly the mid/higher frequencies, so you tend to loose a lot of responsiveness, too. I've yet to build a bridge so light that I can't "smooth things out" by other means. For me, a typical low mass bridge is ~15grams. It's hard to get lower. The factories use different thickness bridges (which are consequently of different mass) so they can get a decent action with a set amount of saddle protrusion, to leave enough for adjustment (usually lowering) later; clear evidence (if you needed any more!) that the factories build only to mechanical tolerances rather than acoustical ones and why custom builders can do so much better. |
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| Author: | grumpy [ Fri Feb 17, 2012 2:07 am ] |
| Post subject: | Re: Bridge Thickness... |
e used them. The do work. Tone was virtually unchanged between bolting it down and gluing it. The less responsive an instrument is, the more you can change one or more details and have no response/change. The better the instrument, the more responsive it will be too minute changes. If you added bolts to the same guitars that previously didn't have bolts, and didn't hear a change, well, sorry, but your hearing is lacking(happens), or the instrument simply wasn't that good/respnsive to begin with. |
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| Author: | Joe Sallis [ Fri Feb 17, 2012 8:23 am ] |
| Post subject: | Re: Bridge Thickness... |
This is a very interesting discussion which I'm not experienced enough to add to but I would like to ask; what about the bridge plate? You've talked about redusing mass on the bridge and we've seen one method from Steve for doing that. does anyone have any methods for redusing bridge plate mass (putting holes in it, for example). The bridge and the plate must work as a coupled system can anyone elaborate on this? |
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| Author: | Trevor Gore [ Fri Feb 17, 2012 6:10 pm ] |
| Post subject: | Re: Bridge Thickness... |
Yes, the bridge and bridge plate do work as a system. My objective is to design the system to spread load from the bridge as efficiently as I can, without causing stress concentrations, so minimising the material that has to be used, and hence the overall mass. So, for example, the front and back edges are curved to help reduce the "hardness" of the bridge edges. The bridge is also a cross grain brace, so has to be designed with that consideration in mind, too. So I use carbon fibre in the bridge and bridge plate when I want extra stiffness (not usually required on X-braced guitars). The traditional thinking on X-braced guitars is to run the bridge plate grain perpendicular to the top plate grain. I struggle to see the sense in that as it provides little extra stiffness in the long grain direction, which is where you want it on that design (never mind issues like bridges splitting along the perforations). So I typically set the grain of the bridge plate obliquely. Bridges/bridge plates for falcate bracing follow the same design philosophy, but the execution is different. My bridge plate/cf assembly comes in at 10-11 grams. The six holes I drill in it helps reduce the mass. |
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| Author: | Jmc2010 [ Sun Feb 19, 2012 11:29 am ] |
| Post subject: | Re: Bridge Thickness... |
I was a master class yesterday featuring Steve Klein. Someone asked him if there was a mechanical or structural reason for the shapes of his bridges, or if they were just for looks. His basic answer was that there is more mass on the bass side of his bridge to aid in bass sustain, and that the less mass on the treble side brought out more crisp highs. It definitely made me want to think a bit more about my bridge design, and what the end result of mass or lack thereof will bring. |
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