Slide Valves

[mott]

Hi Guys, Well the upshot of my visit to ModelWorks was that there were a number of problems , none very great in themselves but cumulatively could have caused the poor steaming. Firstly the reverser had a lot of play in it which translated into movement of the expansion links, secondly there was some slackness in the bolts fastening the expansion links to the brackets and the dieblock fastening to the valve extensions all of which didn't help. Furthermore the timing was in need of adjustment though the wheels would revolve under air pressure. Ian's view was that the 14XX was well sorted out and he had never experienced issues over the dimensions of the valves. There was some discussion as to whether to take out the valve chest but the decision was to correctly time the valves and then see. This was done, it took Debbie nearly an hour working away with the chassis on air at very low pressure 10-15psi, making minute alterations to the nuts on the valve rods, literally a flat at a time and with a screwdiver pressing either forward or back on the valve extension to see if the wheels turned more smoothly. I asked for and she fitted lock nuts in place of the outer nuts on the valve rods because I could see real problems if the nuts loosened in use. Eventually the chassis was passed fit for use and I could detect clear exhaust beat and cut off at very low pressure. Some binding of the crosshead in the slides, the one carrying the pump ram, was detected and the slides packed out with a washer at each fixing point to solve that one. 2 hours after arriving at ModelWorks I was back on the road. I have since run the chassis on air at home. The reverser is a nuisance, it doesn't turn smoothly and I have continued with plugs in the steam chest instead of the dreaded automatic cylinder drain cocks for the time being. ModelWorks corrected the problem on the boiler where the holes for the ash pan rod were too close to the bottom and were obviously going to give way quite soon.
So, so far a very successful visit. the loco has still to steam yet but really when boiled down it was slop in the valve gear and really hyper minute adjustment to the valve timing.As usual the tech support at ModelWorks couldn't have been nicer. Mott

[Phil Sutton]

Well done Mott,glad you're sorted.

Phil

[mott]

On the question of setting the valves I finally opted for removing the front cylinder covers to establish an accurate FDC for the piston and then using a plastic pipe stuck in the steam pipe used lung power to blow down whilst moving the valve rod to establish from the release of air into the cylinder the initial opening of the steam port. I then nutted the rods at this point. I know this would not be bang on accurate but the plan was to put the chassis on compressed air and the fiddle with nuts to improve smoothness of running afterwards. When we went on air forward running was jerky, but backwards was really smooth. I then found that even at mid gear the chassis ran in reverse. Funny. It seemed to be that the reverser screw was moving the expansion links in an unbalanced way, winding the die block to the end in back gear but not in forward gear . With the linkage disconnected and moved manually I could get smooth running forward and back . I extended the operating lever by 12mm soldering a section in and reconnected and so far have managed to have smooth and very slow running now forward and back. I was also able to notch up and the wheels kept turning. The total travel of the reverser was sufficient, it just seemd to be out of position to give balanced movement of the expansion link.
Whether the valve seating issue is now solved I will not know until I get into steam but I am hopeful as it runs so well on air. Mott