Keeping 26043 alive.....the good the bad and the ugly
Entry posted by pheaton
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Hello All
The good 
26010 after a lengthy stay at the GWR, finally made it home, all 4 of its traction motors repaired, and a suspension bearing re-white metalled, i went up there a few weeks ago to help them sort out a few final bugs before we did a very basic test run
Everything went very well indeed, and its fantastic to see the loco running again.
Because the owners had not driven a class 26 in over 2 years and i was (just) in competence on the type my final task of the day was to re-assess the owners inline with there safety management system to be passed fit to drive class 26s again. Of course i couldn't resist having a drive myself 
26010 will hopefully have a long career yet in preservation.
The Bad and the Ugly
Back home work continues on 26043s engine repair, this is the first time in nearly 40 years these components have seen the light of day
The pistons have now all been cleaned and De-ringed ready for measuring to decide what rings need to be renewed, and what pistons will need to be sent away to have the grooves machined, there are tight tolerances on the piston rings and the new rings must be a good fit, initial measurements show the the compression ring groves (top 4) on many of the pistons have worn to close to and just over 7mm the maximum wear on the compression grooves is 7.5mm, which means these pistons are now really close to be being end of life, they are good enough for this overhaul but its likely they would be too worn for another overhaul afterwards. The groves with the holes are for the oil scraper rings, engine oil under pressure is fed up the up the conrod from the crankshaft and around the piston interior this keeps the piston cool relatively 
, and also lubricates the bore, the scraper rings then push this back to the sump to prevent too much oil being burned on combustion. The cylinder liners now cleaned externally and internally can be seen in the foreground.
compare this with the previous photo
A locomotive never keeps its original components and pistons are no exception, the crown of the piston has a lot of information stamped into it.
For example....this piston when it last went through works had an A ring groove width of 6mm but more interestingly it has the number of its previous owning locomotive in this case 25075 and this was piston No6
https://derbysulzers.com/25075.html
This piston has come from D5405 a class 27 and again it was piston number 6
https://www.rail-online.co.uk/p942129668/h2654723F#h2654723f
And this piston has come from of all things a class 45 D65 and we can see it was from B bank and it was piston number 6 this is more interesting because obviously peaks had a 12lda and not a 6lda as fitted to the 25s 26s and 27s you can also see that this piston has had groves A opened to 7mm and B and C groves opened to 6.5mm.
so we can see a lot of long deceased locos live on in some form
Next we move on the the liners, i touched in the last blog the liners were not in as good condition as they could be.
Here we see external pitting on the outer heat transfer surface of the liner, the pitting is a result of cavitation and corrosion, cavitation causes shockwaves that form when water boils and they literally erode the surface of the liner and form little pits, if the pits are allowed to get too deep they will affect the integrity of the liner and cause water to leak into the bores, all the liners have this issue, and will need to be repaired with a high temperature chemical metal. English electric engines tend to suffer from this far more than sulzers.
A close up the liner seal grooves which show advanced pitting around the sealing lands, this is corrosion and is a result of water being able to sit behind the top two seals, again this will need to be fixed and carefully profiled with high temperature chemical metal.
An internal view of one of the worst affected cylinder liners the direct cause of this is water ingress into the bores (via the exhaust) the water has sat around the rings which can clearly be seen marked on the surface and then water has run down the ring gaps, the cris-cross marks are as result of honing the liner over 40 years ago....and demonstrates how little wear the liners actually suffer, if it wasn't for the pitting its possible this liner could be re-honed to remove most of the defects you see there, however its likely this liner will have to be renewed. However the engine was running with the liner for over 8 years with no ill effects noticed, and this was evident on the pistons, so it was clearly not affecting the engine that much. The pistons and rings were all carefully checked and showed no evidence of gas blow-by.
Two more views of liner damage caused by water ingress, although it looks severe, it looks worse than it is, and if you were to run your finger nail over the surface you would notice and damage in the surface, these marks will need to be carefully polished out with a de-glazing brush.
All of this damage is caused by a locomotive that has sat idle (pre-restoration) for for too long, even without the rain water going into the exhaust, naturally damp air will find its way into the bores via open valves and cause the damage seen.
The next area is the heads.
3 of the 6 heads having there valves removed for inspection of the valves, and valve guides, on the left is the head having its valves removed on the right the valves have already been removed from the head and the top of the valve guides can be seen, although the locomotive was not burning oil, all of the valves guides bar one have been found to be worn beyond the acceptable maximum, and all are being replaced. The plate seen on the left compresses the valve springs so the collets can be removed, then the springs and upper assembly and then the head and be turned over and the valve pushed out. All of the heads have been de-coked and paint has been removed ready for repainting.
After the valves have been removed, looking directly at the flame face on the left is the inlet valve and on the right the exhaust, the rust was caused by the steam cleaning the week before, you can see the bottom of the valve guides and the valve seats which are in reasonable condition but will require re-lapping with the valves when the head is re-assembled. The valve guides will need to be pressed out on a hydraulic press. The hole in the centre is the fuel injection hole, the hole at the top is the decompression hole. Another round of cleaning is required before then though. Each valve hole is roughly 4" across.
an inlet valve.
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A badly damaged exhaust valve needless to say this will not be going back into the locomotive, its thought incorrect tappet clearance has caused this damage sometime in the past, the valve was still sealing however as evidenced by the lack of blow by on the valve. This valve will be made for sale shortly as a souvenir, with all proceeds going to 26043s engine rebuild.
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