Thursday 1 October 2015

Maintenance Update (felt, small end, nut)

Saturday 26th
This was our AGM day.  It was good to see so many (mostly familiar) faces.  After the AGM, many of us took a trip behind 2807.

There was some discussion (in the TPO) about the loss of oil from the RH big end.  It really is a puzzle.  The oil pot has a vertical pipe within it that has a restriction through it.  Oil should splash around as the loco moves, and some will go down the pipe.  At the bottom of the pipe is a felt pad.  This should restrict the flow of oil and make the pot full last all day.  So, why doesn't it?  The decision was to remove the con rod on Wednesday and have a look at the pad.

I did suggest that replacing the cork (a plug in the top of the oil pot, which has a cane breather through the middle) with a solid one should create a partial vacuum and thereby restrict the oil flow.  This purely as a temporary measure until we could remove the rod.

Monday 28th
I went over to Todders to do some chair painting - we have two or three boot scraper orders that need progressing.  2807 was in the yard, and the RH side con rod was positioned exactly at the angle that it has to be when being removed.  The position is fairly critical, because the step gets in the way, and also the small end has to be backwards of the slide bar bracket.  This was either a stroke of luck, or a deliberate act by the driver - who knows?!  So, I took the decision to fit a Not To Be Moved board on the loco!

In this low position, the oil pot is easily accessible, so I filled it up.  Let's see how much runs out over the two day period.  The oil level can be expected to fall to that of the top of the pipe (but no motion = no splashing, so the level should not drop below that … unless there's a serious problem in the pot!).

I checked the Issues Log for new reported issues from Saturday.  Two:

57 [JC] LH lifting link top pin loose.  Pin tightened & new split pin fitted.  {Thank you, JC}

72 [anon] @ cork had no core.  Refitted cork.  Oil usage decreased.  Continue to monitor.  {so much for the solid cork test - driver spotted it and replaced it with a breathable one!}

The numbering is up the creek .. it was young Jon W's fault!  ;-)

Wednesday 30th
Gil, Bruce, John G & I (aided from time to time by Loco Dept chaps) tackled the removal of the RH con rod.  The oil level had dropped to the top of the restrictor tube (as one would have expected), so that gave no clue about why it loses so much so quickly.  It transpired that the wheels were not 100% perfectly lined up … we had to push the loco back by about 2".  This wasn't too difficult, once the three of us were pushing in the same direction.

The vacuum pump has to be disconnected first (because it is linked to the cross-head).  The big end came off easily.  The little end is always a challenge, and needs an extractor.  So, it took Bruce & Gil a bit longer to get that free.

Sliding the rod off was easy.  We then turned it over to be able to see the felt pad.  It was in place and intact.  We could see nothing wrong at all.  Nevertheless, it was decided to replace the felt in both ends.  I ran a wire through the constrictor, just to be sure it was not blocked.  It was fine.

Today was 3850's last day in service before its Heavy General Overhaul, and John G took the opportunity to ride behind as far as Winchcombe.  He was able to report that Fred, Ray and Bill were working on the siphon restoration.  They had completed the construction of a new pair of doors and were just making minor adjustments to its fit.  They have the wood ready for constructing the other doors, but will test this one in each place first, just to verify that the doors are all exactly the same size!

Bruce cut new felt pads.  These were inserted and then the con rod was fitted back.  Once again, it was the small end that caused trouble.  Getting the castellated nut lined up with the split pin hole took for ever.  It was either the nut being too slack, or too tight.  Some fiddling of the washer, nut, its castellations and the split pin finally got it all to fit together.

We are none the wiser as to why the oil should have run out so quickly (i.e. after each single trip), unless … did the driver realise that the level will fall rapidly to the level of the top of the constrictor, and then very slowly thereafter?  Maybe he thought that the pot always needed to be full above the constrictor top?  Who knows?!

During a couple of slack periods, John G and I managed to restock the Flag & Whistle (they having sold five boot scrapers) and do a little more on the production line.

2807 is on Fire & Drive duty on Fridays during October.  She's not rostered to be in public service now until next year.


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