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

Leaky Axle Box Gasket

Each of Sentinel 7109's axle boxes supports its corner of the loco on a plain bearing and has an oil bath in the bottom. A large sprung pad sits in the oil bath and is spring loaded against the lower surface of the axle bearing. The pad acts as a wick to lift the oil to the lower bearing surface. As the axle rotates, oil is carried round from the pad to the weight carrying upper surface.

Some time ago, I'd noticed that one of the axle boxes seemed to be retaining its oil level much better than the other three.

I checked whether there was any water under the oil in the offending box using an oversized horse-syringe (for want of a better name).

One of these

There was a lot of water!

On removing the covers from the two right hand side axle boxes, the oil retaining one showed signs that its gasket was split at the top. On further inspection, both the right hand side gaskets were in poor condition and weren't helped by being disturbed.

New gaskets were made for both of them. (As no problem has been apparent with the LHS boxes, they have been left alone).

Front RHS gasket of 1.5mm Rubberised Cork

With the cover on, the axle boxes look like this.

Assembled (complete with missing stud!)

The missing stud will be replaced, of course (and the wheels will be painted).

Note: These photos have been cropped. If there are any modellers wishing to copy the axle box detail, leave me a comment below. I have other photos with more detail that I can supply on request.