Posted by Klaus on October 06, 2002 at 13:05:45:
In Reply to: Re: A historical helicon posted by Eric Lutz on October 06, 2002 at 09:32:38:
Disclaimer: Yes, this is a tuba forum, yes, the illustration has a point, and no, don't read this, is you are not interested in design patterns in brass instruments.
The direction of the airflow, in my opinion, has no significance at all. As long as it goes from mouthpiece towards bell.
If you are familiar with how to follow the airpath of a double horn, the above illustration of the King Eroica model will tell you that the air passes the valves of the F-side from left to right, whereas it passes the valves of the Bb-side from right to left.
Within our own range of instruments we also can see on 3+1 compensation instruments that the air passes the piston cluster with the main valve loops from left to right (seen from the players side).
But when the 4th piston is activated, then the air once more passes the piston cluster with the compensation loops, but now from right to left.
My point in telling of the reversed airpath in the Schediwy helicon was indirectly to point towards the fairly widebored straight branch (with a ferrule in its middle), that runs between the players belly and the valve loops.
That must be a very deliberate design feature intended to take pressure and weight away from the valve loops. They are vulnerable, as it is not easy to support them as much the larger branches (heavy ferrules and stays).
Klaus