Bridges

between 1 29/32" and 21/4". Other tailpiece models are equipped with fine tuners (8).

There are expensive, heavy brass bridges available, too (9), which, with a bit of skill and the right workplace, can also be made at home.

Another type of bridge is fitted with piezo ceramic saddles (10). These make it possible to pick up each string separately and feed each one into a guitar synthesizer individually or to mix the acoustic piezo sound with the sound of the electric guitar.

Archtop guitar bridges (11) are placed and kept on the body solely by the downward pressure of the strings. The tailpiece is fastened at the side of the body, together with the strap pin.

Most bridges are available in chrome, gold or black chrome. String spacings vary from manufacturer to manufacturer and the figures given above apply to the models shown only.

Tremolos

A tremolo is a mechanical device allowing the stretching or loosening of strings by means of pressing an arm, thus raising or lowering the pitch of a tone.

The most common type of tremolo is the Strat-style tremolo. It is basically a bridge which can be tilted and is held in its resting position by three or more steel springs mounted in a cavity on the back of the body. By pressing or pulling the tremolo arm, the bridge can, to a certain extent, be tilted over its pivot. After the arm is released, the force of the spring pulls the bridge back into its resting position. The biggest problem with all tremolo systems is that they always have to reliably return to this resting position at which the guitar is accurately tuned. This being a problem ever more complicated and sophisticated mechanical marvels were developed over the years. Some systems pivot on six screws, others, with less friction, on only two. These latter systems have two knife edges which bear against two beveled posts that are screwed into the body. To keep friction as low as possible the knife edges should be slightly lubricated. In order to make the tuning more stable, the tremolo unit can be mounted in such a

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String pull

Spring tension counteracts the pull of the strings. The tension can be adjusted so that the tremolo “floats” or rests on the body in its neutral position.

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Photo: Stewart-MacDonald's Guitar Shop Supply

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way that it rests on the body when it is in its resting (“neutral”) position.

However, the main problem is that as the tremolo arm is pressed down the strings are loosened and unwind from the tuner shafts and do not wind up again in exactly the same way after the arm is released.

This is why on some tremolo systems the strings are clamped at the nut (1) and at the tremolo unit (2) after tuning. With the help of fine-tuning screws on the tremolo system the strings are then fine-tuned to the exact pitch as they will have gone out of tune after having been clamped. This system - which is rather expensive, but very effective - was invented and patented by an American named Floyd Rose. Fairly commonly a bit of wood is routed off behind the tremolo system so that it can be tilted further back.

Instead of using a clamp on the nut it is, as already mentioned above, also possible to use so-called locking tuners (3), where each string is clamped in the tuner shaft hole and thus kept from unwinding.

To keep the friction at the nut to a minimum, it is possible to use a roller saddle, where each string rests on a small roller. Nuts made of self-lubricating synthetic materials also serve this same purpose of minimizing unwanted friction.

By the combined effect of the number of springs used, the positions at which they are hinged and the adjustment of spring tensions a balance between string pull and spring tension can be found. The baseplate of the tremolo unit is suspended approximately parallel to the body surface and makes contact only at the mounting posts. This set-up allows the operation of the tremolo in both directions. Another possibility, which, however, only allows loosening the strings, is to mount the tremolo so that in its neutral position its baseplate rests on the body.

There are special systems which allow the adjustment of spring tension with one single allen screw (4).

On systems where the tremolo is mounted so that it “floats” players used to resting their hand on the bridge in doing so often unintentionally operate the tremolo. To prevent this from happening, a mechanical lock (sometimes called “Black box”) was invented which only unlocks the tremolo when a certain amount of pressure is exerted on the arm. Such systems are hinged between the tremolo block and the springs.

On all Strat-style tremolo systems the strings are fitted from the back and passed through the tremolo block.

Apart from the Strat-style tremolos there are a few others which do not require a body cavity. The Bigsby tremolo is the bestknown of these: here the strings are anchored in a low-friction, horizontally-mounted shaft. By moving a lever the shaft is turned and the strings are tensioned or loosened. Other tremolo models such as Mustang or Vibrola are less commonly used.

Other hardware parts needed

Depending on the type of guitar you are going to build other smaller parts may be needed. A peghead-end adjustable truss rod requires a cover plate for the adjustment nut (5). For mounting the output jack on the side of the body, a slightly-arched metal jack plate (6) is needed. String mounting grommets (7) are available for strings that are fitted through the body from the back, and string retainers which can be screwed on (8) are needed for guitars which do not have an angled-back peghead.

You also need parts for the electronics. Picture 9 shows an example of a passive electronics system: a pickup selector switch, pots with knobs, a jack, a capacitor and some wire. Pickups and electronics will be discussed later.

Potentiometer knobs have to be chosen according to the shaft diameter. 6mm (15/64" or 1/4")-shaft-diameter knobs are the ones most commonly used. The knob in the middle of picture 10 fits on a 4mm-diameter shaft, while all other knobs shown fit on 6mm shafts. Smaller shaft diameters, such as 4mm, are not very common in guitarbuilding.

Knobs can be fastened in three different ways: either you press them on a fineor coarse-knurled pot shaft, or you clamp them with one or two small, laterally-mounted screws, or you use a collet, which is the most reliable fastening method. Knobs fastened with a collet have a removable top and a hex nut or a screw under it that can be tightened to fasten the knob on the pot shaft. A scale on the knob can be very useful. And why not use knobs from old radios or other out-of-use appliances? They can look very good on your guitar, too.

I strongly recommend that you have all of these parts, smaller and larger ones, ready in front of you before you start designing or even building the guitar.

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