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British inventor`s variable speed belt drive challenges gears

01 September, 2000

British inventor`s variable speed belt drive challenges gears

A British inventor have developed a new form of mechanical speed control that, he claims, can replace gears and even conventional electric motors. John Hammerbeck says that his SCRAM (Simple Continuous Ratio Adjusting Machine) will lead to a rethink in the way motors are used in mechanical systems.

The SCRAM system is a simple, low-cost device that uses an extendable belt to provide reduction, clutching, continuously variable speed control, and an automatic response to power demand. Its reduction ratio of between 15:1 and 25:1 makes it ideal for use with motors, Hammerbeck suggests.

Unlike existing gear systems which work by the interaction of differing circumferences, SCRAM uses a fixed period belt that is lengthened to increase the speed of an output wheel over which it runs (shown below in patent application). The result, says Hammerbeck, is a drive system with an exceptionally wide, continuous ratio range, that is easily controlled without having to disengage the drive power.

One version of the drive uses a tension coil spring as the belt. This is driven around its endless path by lugs mounted in a hollow drive shaft that interact with the spring`s windings. Turning the shaft causes the lugs to move the spring forward. Because the number of windings does not change, the belt passes the drive point in a fixed time for a given input speed. If the coil is extended, the speed of any wheel it runs over will increase, and if it is shortened, the speed will decrease.

Hammerbeck, who came up with the SCRAM concept after working on a design for variable speed moving walkways, demonstrated two prototypes at the recent Tomorrow`s World Live event in London (one is shown below). He reports that reaction at the show was "tremendous" with several visitors suggesting potential applications for the technology including machine tools, cement mixers and textile machines.

One possible application for the technology would be a novel form of electric motor with a variable ratio. The idea is to use an elastic belt containing magnetic elements and to drive this using a series of phased solenoid coils. Hammerbeck admits that this is still a theoretical concept and he has not tried to build one yet.

Hammerbeck - a history graduate who has worked as an art dealer - describes SCRAM as a "dislocational technology" which could make some conventional products obsolete. "It may well destroy some businesses," he admits.

He has already applied for global patents for SCRAM. He plans to apply for a series of national patents next Spring and estimates that this will cost at least £250,000. The cost could rise to as much as £1m if the patent authorities decide that he needs different patents to cover different aspects of his technology. He says he has already had offers of funding.

Hammerbeck does not intend to put the system into production himself. Instead, he plans to grant development licences for a nominal charge and hopes, eventually, to receive royalty payments from sales of products based on the SCRAM principle. He says that to offer exclusive licences, "would not be socially responsible".

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