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by Charles Darley

Development of the Ship's propulsion system Part 4

The motor mounting is reaching its conclusion. There is to be a hoop of timber over the motor which will sandwich a piece of rubber to the based plate. The based plate will be held in place by some 6mm studding though slotted holes in the based plate.

The motor is now installed behind a water tight bulk head. The temporary structure shown above has been made secure.

Looking down on the fixed position of the motor. It is located below the after removable deck cover so that access can be made to service the motor. There was no need to use the heavy weight fixings!! Brass screws have been more that adequate.

However, in December 2000, following running the craft for several hours it has been found that the craft required greater speed. A new driving system has been developed as shown in the next pictures.

Flat belting is now being used. This has meant that I have been able to make up the pulleys in the work shop. The one on the left of the picture was the first test piece. It has a suitably curved profile where the belt would run. The raised surface enables the belt whose natural tendency is the ride to the highest point to run round the centre section of the pulley.

However in early test switching from forward to reverse throw the pulley belt off. The second pulley was then designed. Still with the raised centre section but with a flange at one end he result was that no matter how quickly I moved the motor motion from forward to reverse of vice versa the pulley no longer left the pulleys.

So this is now the pulley system. The centers of the shafts have stayed the same but the upper pulley is 25mm diameter and the lower pulley is 62mm diameter. Originally the ratio of drive to driven was 6:1 now the ration is 2.5:1
The addition thrust given by the propeller is significant, now that it is turning faster, when tried in the garage test tank. It is hopes to soon have the craft back on the water.

The flat belt used in the drive system has been home made from a piece of semi elastic chair webbing, supplied by Martin. A strip of it was cut off 15mm wide and then one end was chamfered in its thickness from full to none. The belt was then placed around the pulley system and measured. To allow for the elasticity 5mm less belt was used than found by placing is round the pulleys. The belt was then stuck together using super glue until two complete thickness were built up. The outer part was then similarly chamfered down. So far the belt has worked faultlessly in the test tank but now has to with stand the riggers of the system under operational circumstances. From the picture above the belt looks very even all round - and so it is !!!!

Eventually the flat belt might well give way again to toothed belting when the ratio has been decided upon, and I am in funds to buy the pair of toothed pulleys and new belting. We are still in the experimental stages of the development of the drive system.


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