Monday, 13 June 2011

Sentinel 7109's Sandboxes

There are not unusually four sandboxes, one at each corner. However, this is where the fun starts regarding how they are operated.

An arm on the top of each box rotates a shaft when pushed or pulled. The shaft extends to the bottom of the box and moves a flap over a hole to allow or prevent the sand descending through the hole to the track.

The two front and the near-side rear boxes are all operated by one lever, the one to the left of the reverser lever. Oddly, the off-side rear box is operated by another lever, the one to the right of the reverser lever, via a vertical shaft.
LH lever operates 3 boxes via a cross shaft behind the boiler and below the coal bunker.
RH lever operates the offside rear.
Working on 7109, I sometimes wonder whether it really was a prototype with all the usual bodges to make a saleable first-off actually work. I can't see any reason why the same lever could not have been made to operate the offside rear as well. Is there anyone out there who knows better?

The sandboxes are heavy castings; one box's mechanism in particular had seized due to rust combined with sand over a long period.
Flap seized over the hole (the fluid is diesel to attempt to free it)
One attempt to free the mechanism freed only the end of the flap!
And so began the box repairs. Access is only via the small filling hole on top; a gas-axe being the only practical way to remove the innards!
Sandbox "remodelling" begins!
The front two and the near-side rear sand-box operating arms are having to be recast due to breakage or absence.

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