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The Wessel Flute Design

by Stephen Wessel

The design was the result of a collaboration between John Webb, silversmith and head joint maker, and myself between the years 1982 -1984. We realised that many of the top London players at that time were using retuned Louis Lots in favour of the typical modern flutes coming out of American and Japanese factories. We also noted that the smaller British makers were carrying on the well-established “French” style but with increased weight and a strong adherence to traditional practice, particularly in regard to keywork. Apart from incremental improvements to the scale it seemed to us there had been no serious, practical innovation (discounting new fingering systems) for many decades. While much work had been going into head joint design during this period the flute itself seemed to have been forgotten. Perhaps the moment had arrived to reach back to the concepts behind those 19th century Parisian instruments and try to emulate their sound by the use of stronger, lighter materials for keywork combined with a handmade silver tube. The musical need was for expressiveness: a wide spectrum of tonal colour, the best possible scale, an evenness of tone and ability to project. 

After much experimenting with tube wall thickness we settled on .013” – .014”, all saddles and mouldings (rings) being silver soldered rather than soft soldered or drawn. Keywork would be made in stainless steel. Large areas of this such as cups and touches would be inlaid with a polished black acrylic both to further reduce weight and provide a secure feel for the player. We would stick to the use of traditional pads so that future replacement would be straightforward.

During development I came to realise the importance of good engineering and mechanical reliability for the benefit of both players and service technicians. Traditional cups were abandoned in favour of modern machined cups having flat seats for the pads while the general style of keywork took advantage of the tougher steel, displaying a unique elegance of its own. 

 Servicing the Wessel Flute

Ideally the flute should be returned to us for all maintenance work other than minor adjustments. Where this is not practical, due to high shipping costs for example, the following notes are for the guidance of repair technicians. It is assumed the reader will have a solid grounding in flute repair techniques. The notes highlight the differences between the Wessel flute and more traditional ones.

Description

The flute body is of 925 sterling silver and not plated. Tone hole saddles and mouldings (rings) are silver soldered to the body tube. The keywork is of stainless steel. All rods and point screws are also stainless and case hardened. The black inlay is acrylic. All threads are M2 x 0.4, except clutch adjustment screws which are M2 x 0.25 The mechanism is “pinless”. Two components, the F# key and the d# trill are locked to their rods by small socket screws. These require a 0.035″ Allen key. The pivot system is the conventional Boehm type using point screws. Open hole pad grommets fit inside the hole, making their removal easy using a small Delrin peg [see diagram].

A recent innovation is the redesign of the trill touches which do not require conventional cork bumpers. In place of these is a small rubber pad. This makes it possible to remove the trill key assembly before the right hand assembly when necessary.

Repadding

Pads are 11, 17.5, 18 and 19mm diameter x 2mm thick conventional type. Remove grommets by pushing downwards through the key hole using the peg. The grommet should be a tight fit.  The three small pads are glued in place using superglue gel. Never apply heat to remove them; instead they must be prised out if necessary and replaced.

Never use any kind of glue or shellac to hold the larger pads. These flutes have flat-bottomed cups which provide full support. Shim washers are not usually needed. ‘Hi tech’ pads with integral plastic cups are not required or recommended.

We highly recommend that padding should always be carried out by an experienced technician who should use a leak detector such as the Flute Ferret. 

Wear and tear

Looseness in the right hand section or the trill keys can be taken up by advancing the point screws slightly. The relevant pillars are: trill keys (2 or 4 if c# trill is fitted) and pillar nearest the D key. Looseness in the left hand section requires the c key rod to be shortened at the shoulder, usually by 0.1mm or less.

New flutes are given an allowance of about ¼ turn for this purpose. Should further advance be needed, it would be necessary to deepen the recess in the pillar. Use an extended 2.4mm or 3/32″ drill held in a small tap wrench for this, working it firmly forwards to remove the smallest amount of metal. Finish by running an M2 tap through. Do not be tempted to use a power drill for this job. 

The Allen socket grub screws should always be at maximum tightness. Their pointed ends create a small dent in a flat section of the rod. After removal, this dent allows the original positioning of the key to be found again. Make sure the Allen key fits the screw tightly with no play. Tighten hard until the key begins to take a permanent twist.   

Swedging of key tubing

This is very rarely necessary on these flutes but can be done in certain places. More force is needed however. Always ensure a piece of rodding is inside the barrel to prevent the bore from shrinking too much. The most likely key to need this treatment is the B thumb and here a slight shrinkage of bore may be required rather than a lengthening. This key is carried on a silver sleeve which is Loctited into the Bb key. If end play builds up on the B key it is easier to slide the Bb key along the silver sleeve towards it. This is best carried out by first applying local heat to the Bb sleeve to weaken the Loctite bond, then sliding the Bb key along to take up the wear. It should have fresh Loctite 290 applied if necessary.

General characteristics of stainless steel

Steel is much stiffer than metals more commonly used for flute manufacture. This means it is more resistant to bending. It does not easily corrode and therefore remains in its polished state unless heated or allowed to come into contact with certain chemicals such as sulphuric acid.

It has a very low heat conductivity, a property that is extremely useful to the repairer. It is easily silver soldered but not so easy to soft solder, requiring a special flux.

The relatively high yield point means that more force is required to bend or straighten a component. However steel is also much harder than silver, gold or nickel silver, so is less easily dented or damaged when gripped by a clamp, vice or pliers. Bending key cups relative to their arms is not recommended but can be done to a limited degree.

Following accidental damage to keywork it may or may not be necessary to remove inlays. The repairer should think how best to support a component prior to bending and work out how to apply the necessary force. If heat is required for resoldering, any nearby acrylic component can often be submersed in water to keep it cool. The flame can then safely be applied just above the surface and, thanks to poor conductivity of stainless steel, silver soldering temperature should be reached.

Acrylic inlays

These are intended to be permanent and cannot be removed without breaking up. Spares are available however. The cup inlays are glued in with Bondloc B3294. Should one of them need to be replaced it is important that the adhesive is spread evenly over the cup recess and the inlay pressed full home all round. The pad should be removed first. If this is done incorrectly, such as the glue applied in blobs, an air pathway could be created between pad grommet and the inlay edge. This would show up as a definite ‘pad’ leak.

Surface reconditioning. 

Minor scuffs and scratches can be removed without the need to replace the inlay. Remove pad and make a stub mandrel from plastic that fits the pad recess tightly. With this in the lathe plug the whole key on to it and ensure it runs true and is secure. It should be tight enough on this mandrel to stay in place. Depending on the length of the section of keywork choose a speed that seems appropriate and take great care. Small folded pieces of paper starting at 1000 grit can be held in the fingers and used to polish out small imperfections. Carry this process through to 2500 grit then finish with a small (25mm) polishing mop using any kind of compound intended for plastic. Work very gently at an angle and be careful the tool does not snatch or contact rotating parts other than the acrylic. It will not be possible to treat long assemblies such as trill keys or the low B key in this way as they cannot be rotated fast enough and may not clear the machine bed.

Inlay removal  

In cases of severe damage the cup inlay can be replaced. Start by removing the pad. For covered holes push a thin rod up through the screw hole and against the bottom of the inlay. Gentle heat may be required to soften the glue. For open holes the inlay is best levered out with a small screwdriver. Clean the cup recess thoroughly by scraping before installing a new inlay. Make sure it fits properly before applying adhesive. For covered hole cups temporarily replace the pad screw without its washer; this will prevent glue getting into the threads. Fit the inlay by pressing one side in first then work over towards the opposite side with your fingers; this avoids getting an air bubble trapped in the adhesive. Remove all surplus glue then remove the screw before the glue sets.

Bumper felts

A fine dense black felt should be used for all key tails (kickers). Trill key touches need a small square of 2mm nitrile rubber. Clutch plates are given nitrile rubber cushions approx. 0.5mm thick. Nitrile will accept superglue and is oil resistant, so is the preferred type of rubber. Soft pencil graphite should be rubbed over rubber to prevent stick. Cork can be used but wears badly and tends to be noisy.

Clutch adjustment screws

These are given a very fine thread and are fitted into a non-ferrous sleeve to help them turn smoothly. If any are suspected of being too loose a very small drop of Loctite 222 should be applied to the threads. Never use varnish over the heads. These screws allow extremely fine adjustment of key synchronicity and will save much time. They can be removed by turning clockwise.

Solder

Keywork components, including pillars to straps, are assembled using a silversmiths grade of silver solder containing 66% silver. A flux such as JM Easyflo must always be used for repairs and is removed by boiling water. Do not use pickle. Parts can be buffed up on a fine ‘scotchbrite’ wheel then polished.

A lead free soft solder is used for strap attachment and the head joint socket but not the foot joint socket which is silver soldered.