Thursday, 18 October 2018

Gearbox update

KS4415 Update 11/10/18

Images by Rob Bishop

The blog entry December 2017 described a trial fitting of the gear box in the frames. The deliberations from that trial fitting led to the drawings in the 5th March 2018 entry which illustrated the proposed repair, using plates which bolt to the annulus around the bottom bearing housing.  The new components have been manufactured and are seen here with the cleaned up gear box.

The annular ring for the RHS plate is to allow it to be fitted outside the frame stretcher, as space in this part of the loco is at a premium.

If it all goes to plan it will assemble like this:

Before painting, the gearbox has been given a very thorough wire brushing; what a thing of beauty! Note the line of brazing on the rear face, bottom left.

This is a brazed repair to a crack in the casing; the crack is still visible on the inside.

Inside the gear box the drive from the (upper) forward/ reverse shaft to the lower (high/ low gear) shaft is via a chain drive (see below). If a link comes off the chain, the still rotating upper shaft brings all the chain up in the box and piles it onto the top shelf.  There isn’t enough space for this, the result is evident.

In the view below the gearbox is lying face down and the damaged lugs which support the gearbox on the layshaft can be seen, hence the new supporting plates. The next task is to replace the studs which fix the lower cover with some longer ones that are able to pick up the plates.

Progress on the new mounting plates is illustrated below. One pair of blocks which will secure the two halves of the mounting plate around the layshaft have been machined and drilled. The tack welds are temporary.

Finally, because we know that watching progress on the project is like watching paint dry, here is a picture of some paint drying. The green panel is the front cover to the gearbox, the grey components are the covers to the external gears (on the outside of the gearbox and on the layshaft). Some work to do before they are re-fitted!

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