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by Charles Darley

Change to the motor unit and other updates

Following much testing over a distance of 100 feet it has been found that up to now the craft did not have sufficient speed to match it calculated scale speed, unless with revised pulley ratio the original was run at a current draw higher than the rated maximum. It needed to run at 1.5 amps over its designed maximum and became very hot, too hot to handle and took nearly 30 minutes to cool down to ambient temperature. Thus I came to the decision that a different motor was needed. David had just purchased new motors for his boat and test were carried out with one of the motors which looked very favourable.

One of the motors mentioned above has been obtained (6th March 2001) and has been fitted to the craft. Trials in the garage based test tank have shown very promising results and it is hoped that trials on the open water of the mast pond in Chatham Historic Dockyard will prove we now has sufficient speed.

With the change in motor has come a change in the pulley ratio. the pulleys are now 15:60 a ratio of 3:1, and we have also made a new propeller which is more balanced that the original and gives more equal push in each direction and at a lower current draw than expected.

To ensure that the motor temperature does not rise too much its temperature is to be monitored and an electric fan switched on should the case temperature rise above about 30 degree C. The ship's funnel will be used, as intended, to allow warm air to escape.

A rev counter is being developed by Trevor, another of my electronic specialist friends. The first prototype has shown that the motor has a top speed of 9000 rpm which is close to the estimated max of 9778 rpm. Eventually we hope to have the speed of the motor sent back to the control point by radio telemetry, together with other data such as motor temperature and battery condition.


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