Tips on replacing your nyckelharpa’s bridge
by Bart Brashers
If your bridge has become warped (not just leaning, but with an actual curve to its shape) or if too many of the ‘teeth’ between the slots for the strings have broken off, you may want to replace your bridge. Getting a replacement can be hard, but try contacting the maker of your harpa. Or make one yourself, or pay your local violin maker to make and install one for you. You can use the following list to evaluate your bridge, and decide if it needs replacing.
In the schematic above, all units are in mm (millimeters). It’s available as a PDF as well. The shape is one of many possible shapes, ranging from violin-like to the modern version of the “anvil” shape of the nyckelharpas from last century. Many thanks go to Sören Åhker for supplying the schematic! Visit his web page for to buy a full schematic for building a nyckelharpa.
The criteria for a good bridge are
- The feet should fit the top surface very well.
- The back (facing the tailpiece) should make a right angle with the top.
- The height should be such that the tangents touch the playing strings near the center of each tangent (halfway up).
- The width depends on the keybox and the nut. The distance between the strings is dictated by the distance between the tangents, and the desire for each string to be as close as possible to the tangents without buzzing.
- The thickness at the feet should be about 6.3 to 6.5 mm (according to Sören) or 6 to 7 mm (according to Esbjörn)
- The thickness at the strings (not the topmost edge) should be about about 2 to 2.5 mm (according to Sören) or 2.5 to 2.8 mm (according to Esbjörn). It’s important that the wood not be too thin, or the small bits of wood between the resonance string grooves will break off too easily.
- It should be made of maple (lönn in Swedish).
First of all, loosen all the strings and remove the tailpiece. Take the tension off the strings slowly and evenly, a bit at a time on each, to prevent having so much tension on one side of the bridge that it moves or cracks anything. You can leave all the strings attached to the tailpiece and just lift it off and out of the way (leave it on the workspace above the peghead). Throw some tape around the neck and nut before you start (taping the strings to the nut) to avoid a snarled mess at the peghead. Or you can remove all the understrings, it depends on if there’s a lot of other things that need repairing. If you do remove all the strings, one of those string winders available from any guitar shop comes in mighty handy for unwinding the resonance strings.
Start with a rough cut-out of the bridge, about 7.5 – 8 mm thick. It’s easier to sand if it’s a little thinker than the final product. Measure and make sure the outside width of the feet is less than the distance between the closest points on the f-holes, usually the holes at the top of each “f”. It’s usually about 58 – 60 mm. Take a scrap piece of hardwood about 2 inches wide and a few inches long and cut one end square with the bottom. Using a rubber band, attach the bridge to the squared end, with the tailpiece side touching the block. This will assure that the bridge’s tailpiece end will be square with the top of the harpa.
Here’s a good trick: buy some sheets of self-adhesive sandpaper from your local hardware store. They make them for electric sanders, both round and rectangular. I like the rectangular ones — they’re about 3 inches wide by about 6 inches long. Attach the sandpaper to the top of the harpa where your bridge will end up sitting.
Hold the block + bridge parallel to the length of the body of the harpa, in the center, where the bridge will eventually sit. This forces the back of the bridge to be square to the top. Press the bridge down with your finger (and maybe some pressure making sure it stays flush with the block) and rub it back and forth, sanding down the feet, until a nice smooth match is accomplished. It’s best not to move the bridge too far — use short strokes only. Make sure the bridge doesn’t lean one way with one stroke and the other way with the other stroke, as this will make the bottom of the feet rounded rather than flat. Start with a rough sandpaper, and switch to smoother and smoother as you go. The better this match, the better sound you’ll get. As you get close to done, take a pencil and put a bunch of lines on the bottom of the feet. Now sand until all the lines have disappeared. This assures a good fit, in that the whole surface has been sanded to match the curvature of the top.
Peel the sandpaper back off, and make sure the joining of the feet of the bridge and the top of the harpa is good. This greatly affects the sound of the harpa, and is very important.
Now you’ll need to check and adjust the height of the bridge. You can use the old bridge as a guide to get a rough cut on the new, though you may decide that the strings need to be in slightly different places. Put the A and low C strings back on, with just enough tension to hold the bridge in place. The tension should be approximately equal across the strings, so the bridge sits in the ‘middle’ of the harpa. Too much tension on one string will move the bridge to the left or right, which affects how close the strings come to the tangents. You must now adjust the height of the bridge such that the tangents touch the A string in the middle of the tangent. At the point even with the highest tangent, the low C string should be 4 or 5 mm above the wood of the keybox cover to avoid buzzing against it when played. The other two strings (the higher C and the G) should automatically be okay, touching the tangents at about their middles. You can shave down a little, but remember that you don’t want too flat a bridge. It’s more important to be able to play one string at a time than that the tangents touch the strings at their exact middle!
Now you can adjust the thickness of the bridge to be about 6.5 mm at the feet, graduated to 2 to 2.5 mm at the top edge. A sanding machine like a belt sander works well for this.
The picture is from Esbjörn Hogmark, of his own harpa, that he was kind enough to send me. Click on the picture to look at the full-sized (84 Kb) picture with less compression. Note the variation in the shape of the bridge, and the depth of the notch for the A-string.
You must now cut the notches for the strings in the bridge. There’s some art to this, in that you want the string to be just far enough from the tangents that it doesn’t buzz against them when being played. In the past, I’ve tuned all 4 strings up to their final notes, and played the harpa to make sure it doesn’t buzz and that the action (the distance the keys have to travel) is minimized. You may have to make tiny notches in the bridge to get the string to stay. The distance between the the tangents and the A string should be about 1 to 1.5 mm, and about 2 mm for the (higher) C and G strings.
Note also that the tension from the strings (including the rest of the resonance strings that you haven’t put back on yet) will press down on the top, making the bridge a little lower relative to the tangents! So don’t cut too much of the top of the bridge off before you put more strings back on.
The notches for the playing strings should be only half the diameter of the string deep. They should be rounded grooves, matching the radius of the string. For the resonance strings, use a small saw (I bought one at a hobby store) or a coping saw blade. The depth of the resonance strings should be about 3 or 4 mm. If they aren’t deep enough, then you will catch them with the bow. This happens to me especially when I dig deep and play loud — a lot of tension on the bow makes the playing strings deviate enough that I catch the resonance strings and it sounds awful. Here’s some more hints on cutting notches in your bridge (and nut).
