Steam Department

(With a couple of corrections 2/4/2013.  Thanks to Bob for spotting that one of the links was wrong !!)

The snow resulted in a limited turn out at the steam shop this weekend but a small and determined group kept things moving forward.

On 1630 I worked with Phil, Dave and Cameron to continue the tube fitting:

Progress in fitting fire tubes

·         All the remaining ends were fully expanded on the fireman's side. 

·         We also removed one remaining tube where the ferrule had slipped, replaced it, and fully expanded the firebox end. 

·         This leaves a number of tubes in the center, below the super heater flue holes that were set but not fully expanded.  Unfortunately, while expanding these, one moved forward removing the ferrule from the back sheet.  It will have to be replaced and, having been substantially expanded, proved a bear to remove.  By end of day we have largely cut the end off to enable removal and should complete that next weekend.

For the first time we were able to get clear pictures of the tube expansion process so can now show rather more clearly what we have been doing for the last few weeks.

Tube end expander

This is the expansion tool.  The central steel pin is octagonal and drives the segments outward as it is driven between them.  Several tools of this general type are used in the overall tube fitting process but this one is unique in having projecting "feet" on alternating segments.  When in use, these bear against the tube sheet.  This means that, as the tool is hammered, outward force is applied to the walls of the tube but the substantial forward force is not applied to the tube, but born by the tube sheet thru these feet.

Dave locking the smokebox end

There is a careful process of adjusting the projection of the tube to 1/4 inch minimum thru the rear sheet then, before anything else, the tube is locked at the front.  Here Dave is applying  the clamp.

Smokebox end locked

This tube is now clamped into place to, hopefully !, prevent it shifting as the rear end is expanded.  This clamping should hold the tube against a certain amount of forward pressure as the tube expands against the ferrule.  However, the feet noted above are critical in ensuring that the force of the air hammer itself is not applied to the tube.  Were that to happen, this clamp would be thrown off at the first impact !.

Place tube expander

The expander is then inserted in the firebox end after confirming, by shining a flashlight down the tube from the smokebox end, that we are working with the same tube at each end.  Important as it is a real bad idea to hammer a tube that is not the one secured at the smokebox end.

Hammer to lock

The pin is then hand hammered to expand the segments sufficiently to lock the expander into the tube end.

Apply large air hammer

The air hammer is then applied

Until the pin is driven home

... and power applied until the pin is fully driven home.  You can see by comparing this to the previous view that the travel and therefore the expansion of the segments, is quite substantial.

Then hammer to loosen the pin

Then the pin is hand hammered at the end to loosen it.  Regular application of lard to the pin is important to ensure that it releases.  It is a finely balanced process.  Substantial force is required to release the pin, which is initially locked into place by the force of a substantial; air hammer.  It can often take many substantial blows to initially free the pin but, when it does free, the slope of the lubricated faces of the pin tend to drive it out.  So it is real important to listen for the change in sound as the hammer it the pin.  There is a real change in tone as the pins starts to free and if you do not notice this and keep hammering the pin can easily shoot out.  Then you have the fun of groveling in the bottom of the firebox to recover the tool and pin!.

The tool is then turned in the tube, secured and air hammered twice more and you have another tube fully expanded into the rear tube sheet.

On 428:

·         Jerry continued grinding old braze metal from the boxes to prepare the surfaces for Dennis to weld in the reinforcing plates;

·         Tom continued planing the wedges used to adjust the axle boxes in the frames.

So a good day's progress with a small team.

Nigel