Tuesday, 18 July 2017

Operating Experience (2)

Joyce has taught me (and continues to teach me) a thing or two about operating a heavy piece of steam machinery, particularly the bits I didn't address during restoration.

This innocent looking axle box oil filler cap is one example (right front).
Filler cap with original fitting (1)
The lid can be swung out of the way for filling. The cap bracket is peened on both sides to a pin which passes through the oil filling pot.
Filler cap with original fitting (2)
The problem is that the pin has become loose in its 'pot holes' over the years and leaks out any oil which is above the lowest level of the horizontal pin. This is not only a waste of oil but not nice environmentally.

Three of the axle box pots are like this and leak whereas a fourth one (right rear) which doesn't leak has the bracket rotating around its pin firmly fitted in its 'pot holes'.

I decided it would be prudent to convert the pins to threaded short pins which should prevent further leakage.

In advance, I made these short pins about 18mm long, 8mm in diameter with an M8 thread. The original pin diameter was about 1/4" so M8 was an ideal size.
M8 Short pins
I removed the original pin and threaded the holes for the M8 short pins. This photo shows them in place with the bracket suitably adapted to rotate around the pins.
Short pins with adapted lid bracket
So how did I prevent the metal filings from the tapping tool from getting into the bearing, I hear you ask? I blocked the hole to the bearing with a cloth and used a magnet on a stick to fish out the filings produced.

I've topped up the oil level to where it would have leaked previously. Fingers crossed it will be successful.
Level topped up above the new pins.
Here's the finished job (one of four). The bracket is a bit tight and the cap has to be rotated to the correct position to make it seal properly. I also had to reshape the bracket to enable the (90 year old) spring to push the cap home.
Finished job
Three to go. (Technically the non-leaking original one can be left but I would prefer them to all be the same).

One small point that I'd been mystified by for some time is whether the axle boxes use a pad to 'wick' the oil to the bearing surface or the bearing simply dips into the oil bath. I found an old photo from when I was making a new axle box cover gasket. It clearly shows a pad beneath the bearing.
Axle bearing showing oil pad

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