Ask Dave: How Can I Raise the Conn 8D Thumb Lever?

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Suzanne asks:

I have a student with a Conn 8D mechanical Bb valve.  Is there any way I can raise this valve?  His hands are huge and could use some extra space?  Thank you.

Dave replies:
Conn has made many changes to the thumb lever mechanism over the years.  Since its manufacture in Eastlake, Ohio, they have worked to make the levers more accessible for smaller hands.  The large reach of the valve levers was always a complaint about the older 8Ds.

The current mechanical linkage lever on the 4th valve can be made longer by removing the linkage from the rotor stop and unscrewing the two linkage armature parts at the connecting screw in between.  This will lengthen that lever and move the thumb paddle closer to the other levers.

But your student needs to accomplish the exact opposite, which is not an easy thing to do.

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The paddle must be modified in some way, and this almost certainly means taking it to a competent repair tech who will evaluate what best to do for your student’s situation.

Modifications could include:

  • Cutting the mechanical linkage armatures and connecting screw to shorten the armature length.
  • Soldering on or brazing on to the thumb paddle an extender of some kind.  Many people use bent quarters.  (Be sure to use an pre-1965 single alloy quarter rather than a newer bi-metal version.)
  • Cutting and moving the entire thumb paddle to a more comfortable position, which requires brazing.
  • Or, some combination of the above.

For a large handed person, my first inclination would be both to move and extend the thumb paddle.   I don’t believe that modifying the mechanical linkage armature will accomplish much.

I do not recommend simply bending the thumb paddle unless you are prepared to replace the part should it break during bending.

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