Yes Tor: in the balance

This is the flag pole on top of Yes Tor on the Okehampton Range. It is balanced and designed to be tipped over. I estimate the counterweight on the bottom to be 4 plates of 15 cm x 50 cm x 1 cm = 750 cubic centimetres each. Say steel is 8 grams per cubic centimetre, then each plate has a mass of 6 kg giving a total of 24 kg. I estimate the triangular plate to be 50 cm across the base and 75 cm high. If it is 1 cm thick, it has a volume of 1/2 x 50 x 75 x 1 = 1875 cubic centimetres. That would give a mass of 15 kg. For simplicity, let's stick the total centre of mass at 55cm down from the pivot. The moment = 0.55 x (240N + 150N) = 214 Nm. This must balance the flag pole. Flag pole is about 2.5 metres long so centre of mass half way along at 1.25 m. 214Nm/1.25m = 172 N or 17.2 kg. Say it is a scaffolding pole of thickness 0.5 cm and radius r. Volume of steel = 2 x pi x r x 0.5 x 125 cubic centimetres = 157r cubic centimetres. Mass = 8 x 157r = 1256r grams = 1.256r kg = 17.2 kg so r = 0.07 metres or 7 cm radius. 14 cm diameter seems a bit high but given the estimates it's in the correct ball park.