  We present 30 GHz Sunyaev Zel'dovich (SZ) observations of a sample of four
galaxy clusters with a prototype of the One Centimetre Receiver Array (OCRA-p)
which is mounted on the Torun 32-m telescope. The clusters (Cl0016+16,
MS0451.6-0305, MS1054.4-0321 and Abell 2218) are popular SZ targets and serve
as commissioning observations. All four are detected with clear significance
(4-6 sigma) and values for the central temperature decrements are in good
agreement with measurements reported in the literature. We believe that
systematic effects are successfully suppressed by our observing strategy. The
relatively short integration times required to obtain these results demonstrate
the power of OCRA-p and its successors for future SZ studies.
