I am wondering whether 5/16" (7.9mm) OD tubing is too small for the mid returns on a bass drone, inside diameter measures 1/4" (6.3mm), or whether I should stick with 3/8" (9.25mm) OD tubing.
The problem is the bass drone keeps cutting out when playing the second octave on the chanter. I don’t think it is the reeds as that does not happen with the same reeds on a bass drone by another maker.
I have plans by Garvin, Sky, Ginsberg and Leo Rowsome, each vary here and there. Anyone recommend some good bore dimensions for a bass drone?
The bass drone on my set does not have a loop but has instead a “barrel” with three bores connected in series. The joining channels at each end are sealed with cork and measure about 5mm across which is less than the 1/4" you mention with the tubing. I do not know how deep the channels are as this would involve taking the cork out.
The was a thead mentioning barrel style bass drones about a week ago.
There is also a good description and measurements of a set of Taylor drones athttp://www.pipersgathering.org/Irish%20Uilleann%20Pipes/Uilleann%20Pipemaking/uilleann_pipemaking.htm#Notes%20on%20a%20set%20of%20Drones%20by%20the%20Taylor%20Brothers
For what it’s worth, I use 6.2mm for the midjoint in my bass drone without difficulty. The barrel drone design suggested by DMQ uses about 5.95mm for the middle joint.
8mm or larger for the mid joint is quite big IMO. But of course it depends on the rest of the bass drone bore dimensions, and the reed inner diameter as well.