88 STEAM TURBINES
less if the problem of oblique impingement were out of the way. Fig. 12
shows spacing for tangential buckets to secure an easy discharge at 20 de-
grees.
In the Riedler-Stumpf turbines, the angle of discharge is 180 degrees.
In other words, the discharge is opposite the jet, but this calls for in-
creased surface, more width and weight for the revolving member, and
expensive work in construction, which are hardly offset by countervailing
advantages, and which certainly prevent a cheap and general manufacture
of the machine.
Mr. Richards then contends that buckets of steam turbines
should be curved in all planes approximately as shown in Fig. 13,
taken from a form of water buckets of an advanced type by W. A.
A
0
SECTION ON Ty
Fig. 13. Buckets Suggested by Richards,
Doble of San Francisco. These are of double concave or cup form,
in order to permit direct and balanced impingement at the various
angles in which they are presented to the jet, and have a central
dividing wedge to permit tangential application. The bucket is
notched at A, following the construction of certain water wheels,
to permit the passage of the jet beyond and through the buckets
as they come into position, so that it will impinge against the
buckets in advance which have reached a position where the jet
will act upon them efficiently. He estimates that about one bucket
for each 8 degrees of arc will be sufficient for wheels from 20 to 40
inches diameter. This is less than one-fifth the number now em-
ployed for wheels having the ordinary type of buckets.
Zoelly's Patents. In 1900 a patent was taken out by Heinrich
Zoelly for a turbine wheel of the Pelton type, but with radial arms,
the outer ends of which serve as vanes for the wheel. These arms
decrease in cross-section as they approach the periphery of the
