Working through the list of jobs on my Snapdragon 24 “Jupiter” purchased in 2005 I had come to the roller reefing. The unit appeared to be original with the boom being rotated by a geared system, which in my case was seized solid. Applying oil and trying to coax the mechanism into movement did not work, so it was decided to remove the boom and strip down the assembly.
To begin with, the pinion gear into which the winding handle locates needs to be removed. This is done by removing the three screws retaining a location bush, which can then be withdrawn either by turning the pinion with the handle or if the pinion is seized lightly tapping on the opposite side of the pinion gear. Next it is necessary to drill out the pop rivets holding the casting to the aluminium spar, and then separate the two. On the end of the casting a nut holding the assembly together can be seen, the nut is locked in position by a split pin, which must be removed prior to undoing the nut. Be careful when taking the split pin out as it is made from brass and so will easily shear off.
With the pin out and nut removed the assembly should come apart, in my case however the gear wheel had seized onto the centre spigot locking the two together. Thus it was necessary to remove the four screws — originally hidden under the nut — to separate the rear part of the casting from the gear wheel. With the rear casting removed it was clear that the gear wheel had corroded onto the central spigot on which it was meant to rotate, the cause of my problem.
To extract the gear wheel from the spigot four longer screws were found with the same thread and used to push the wheel out. With the assembly now apart all the components
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where cleaned and inspected ready for re-assembly. In my case the gear wheel had damage to the teeth probably caused by attempts to rotate the boom with the gear wheel seized. As the gear wheel is made from tufnol it is the weakest part of the unit.
Enquires through the club revealed that the reefing unit was originally made by Barton and that the likelihood of finding spares today was remote.
Without a hobbing cutter making a new gear wheel would be difficult, so it was decided to attempt a repair of the original wheel. Being involved in Horology I have sometimes seen broken gear teeth replaced with pins arid so decided to try this approach. The wheel was placed in a vice on a bench pillar drill and a radial hole drilled at the broken tooth base into the body about 5mm deep. The hold diameter was a few thou (0.002”) less than the steel rod diameter to be inserted, thus ensuring interference fit. The steel rod had the protruding end rounded prior to fitting. Pin insertion was carried out using the pillar drill, the pin gripped in the drill chuck and pushed home using the down feed. This procedure was carried out for each of the broken teeth taking care to maintain the original tooth spacing and height. Once completed a try assembly confirmed that the system worked smoothly and so items were well greased and assembled. This time a stainless steel split pin and screws to replace the pop rivets were used. Hopefully the repair should keep me going for many years, however I would be interested to try and produce a gear wheel so if anybody has a scrap assembly from which I could remove a pinion gear to make a gear hobbing cutter I would be grateful.
Paul Comley (Bedfordshire, Tel 01462 730639)
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