All castings and even some of the steel componentry was rumbled to give a smoother finish, and round off the sharp edges caused during processing. The Rumbling Room was a noisy place .. you couldn't hear so had to shout in each other's ears!
Les Tunnecliffe was in charge. He was pretty deaf, and worked away in a quiet manner...with lots of noise!
Large steel drums were being turned over and over on special metal frames, with metal castings and steel components inside. Also in the drums were sand and stones. The concrete mixer-like action with the water and stones, gradually polished the products till they were acceptable. Les knew from long experience exactly how long they would need in the rumbling drums. There were even real concrete mixers being used with a little sand and water for small products that needing light rumbling.
Another exciting piece of equipment was a large oblong drum with a rounded base. This was mounted on heavy coil springs and shaken violently. When partly filled with small stones and some water, the castings would be added and the button pressed. With a deafening roar the shaker would start and the contents would roll around in a circular manner. After a while, the products would be sufficiently polished, or 'rumbled,' and would be hand picked out of the drum.
If any products were left in too long , they would be gradually ground away, and, if still not rescued, would be ground away to dust by the action of the shaker.
After sufficient rumbling, products would be rinsed and dried in a circular revolving drier, and then delivered to the next operation, which was usually drilling or painting.
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