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Re: Key not lifting properly

Author: Chris P
Date: 2009-03-16 23:46

The Ab-Bb trill linkage on most pro oboes is usually lightly sprung so the free end drops with the LH2 fingerplate, and it has to be spring very lightly so it doesn't hold the LH2 fingerplate down, likewise the LH2 fingerplate has to be sprung strongly enough to counteract the weight and friction of the linkage bearing on the small lug soldered to the lower side.

Depending on the make and model, this linkage key can either have a single key barrel or be in two parts joined by a clutch (with or without an adjusting screw), it can have a rod screw running all the way through it, it could be mounted on one of the trill key steels (usually the longer C-D trill key) or mounted between point screws. Some makes and models will have this linkage lightly sprung, though sometimes it's not sprung at all.

If it is sprung, either the spring on the linkage is slightly too strong or the spring on the LH2 fingerplate is too light.

While holding the joint laid down horizontally in front of you and holding the LH2 fingerplate closed with one finger, try lifting the linkage lever with another and letting it go to see if it falls under its own weight or spring tension. If it remains up, then it could be binding against the screw (or screws) or between the pillars.

Now try the same thing but this time holding the joint up above you horizontally with the main action keys facing the ground. If the linkage lever returns against the closed LH2 fingerplate then the spring tension is too strong and should be lightened by disengaging it and then very gently bending the spring in towards the main action fingerplates before engaging it back into the spring cradle.

If the lever remains off the fingerplate when turned upside down and still moves freely, the spring tension is fine. But if you then press the lever and it remains in the closed position, the linkage could be binding against the screw(s) or one of the pillars (possibly the lower one) may have turned slightly causing the linkage key to bind.

So check the spring tension on the linkage and LH2 fingerplate and the screws mounting the linkage to see if its binding and adjust it accordingly. If you can, remove the trill keys and then remove the linkage (or remove them all at the same time) to see if the screw is binding inside the key barrel, or if it's mounted between point screws, check there's a tiny amount of lateral play between the pillars.

Also check the condition of the cork on the underside of the linkage at the fingerplate end - sometimes the cork or other silencing material can exert too much friction on the small lug on LH2 causing the fingerplate to slow down or remain down once closed, and you can often cure this by coating the cork with graphite from a soft pencil. With natural cork, it can become compressed and distorted, or worn through the cork exposing the adhesive used to stick the cork on the underside with and that too can make things sluggish.

And check this linkage is also well oiled and not gummed up if the oil has gone thick. Remove and clean the screw(s) and key barrel, add a drop or two the key barrel and replace the linkage, then add a single drop to the end of the key barrel (in the gap between the end and the pillar face) where the screw goes in and work the key a few times.

Former oboe finisher
Howarth of London
1998 - 2010
The opinions I express are my own.

Post Edited (2009-03-16 23:51)

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Key not lifting properly new

ceri

2009-03-16 21:49