Doug,
Thanks for posting the material on the WDA carb patent application. One thing that I would like to share that may not be completely apparent is the reason for the conical springs. We are used to looking at carbs that have pulse passages that connect the pump systems in our carbs directly to the crankcase so the system sees alternating positive and negative pressure pulses. The alternating pressures cause the pump membrane to move back and forth in very small deflections in synch with the movement of the piston in the engine. In some applications the WDA carbs were fitted to engines where the pulse source is upstream of the reed cage so the pump system will only get alternating negative and nuetral signals. In the absence of the positive pressure pulse the carb is fitted with the conical spring and the pump membrane is drawn toward the spring by negative pressure and pushed back by the increased tension in the spring thus mirroring the movement of the membrane produced when the system is tied to the case.
Here's a link to some sample photos of the actual parts from the single pump version.... https://www.dropbox.com/sh/odx9zk6bb4v78...LVTVa?dl=0
Steve O'Hara
Thanks for posting the material on the WDA carb patent application. One thing that I would like to share that may not be completely apparent is the reason for the conical springs. We are used to looking at carbs that have pulse passages that connect the pump systems in our carbs directly to the crankcase so the system sees alternating positive and negative pressure pulses. The alternating pressures cause the pump membrane to move back and forth in very small deflections in synch with the movement of the piston in the engine. In some applications the WDA carbs were fitted to engines where the pulse source is upstream of the reed cage so the pump system will only get alternating negative and nuetral signals. In the absence of the positive pressure pulse the carb is fitted with the conical spring and the pump membrane is drawn toward the spring by negative pressure and pushed back by the increased tension in the spring thus mirroring the movement of the membrane produced when the system is tied to the case.
Here's a link to some sample photos of the actual parts from the single pump version.... https://www.dropbox.com/sh/odx9zk6bb4v78...LVTVa?dl=0
Steve O'Hara