Cloned Wormwheel Is British Companies Largest



Largest Wormwheel from Renold Gears

Renold Gears has manufactured the largest wormwheel in the company's history and has done so by cloning a wormgear currently operating on a huge coal-pulveriser drive at a coal-fired power plant in the USA. The phosphor-bronze wheel is 2.4 metres in diameter and weighs in at just over four tons.

The coal pulveriser at the power plant grinds the coal to fine dust before it is mixed with warm air and blown into a furnace where it ignites.

The wormwheel was manufactured as a replacement for one that was coming to the end of its working life, but because Renold didn't manufacture the original the company had to 'reverse engineer' the tooth form of the gears in the USA for virtual cloning at its factory in Milnrow.

In a worm and wheel set the teeth must mesh to give a perfect contact, and the precise measurements of the profile of the teeth are critical. Renold Gears had to ensure that the worm and wheel manufactured at its factory in Milnrow would mesh precisely with the worm gear at the power plant in the USA.

Each gear manufacturer cuts its gears to its own tooth form and without having the details of this gears have to be copied using a very precise method of back engineering. This was achieved by taking an exact impression of the mating wormshafts thread profile in a perfect mould known as a 'slug'. The slug was then couriered to Renold Gears' factory in Milnrow where it was measured using the latest co-ordinate measurement machine loaded with Renold's unique software package. This maps the slug precisely and creates a computer model of the original worm's thread profile. From this model Renold Gears was then able to manufacture a master worm and the tooling with which the new worm wheel could then be hobbed. After hobbing, the wheel was paired with the master and adjusted to get the optimum profile in order to create a perfect clone of the original worm wheel in the USA.

Stephen Whitehead, Renold Gears' Sales Director for Holroyd gears, said: 'This is a major achievement for the company and we are all delighted to have been involved in this exciting project. It's an example of British engineering at its best and shows that the world's blue chip companies are still turning to the UK when they require high degrees of engineering skill and accuracy.'