All,
Yet again I am looking for inspiration from the group!
Towards the end of last season it became more and more difficult to get Mouland (a 7.25" Narrow Gauge Locomotive) to go in reverse. It never was that easy, but it got to the point that if you hadn't got more that
60psi on the clock, there was no way that she was going backwards!I should also add that mid gear on the reversing lever was in fact 2/3 of the way back!
So, it was one of my winter tasks to try and sort this problem out.
Stage one was to re-fettle the valve gear to remove the excess movement. It had been designed well and all I had to do was re-bush two pieces of the valve gear. All other movement was horizontal and that didn't bother me too much.
Two days ago I stripped Mouland so that I could get at the top of the steam chests and observe the valve events (a major exercise involving removing the cab and both side tanks, let alone all sorts of plumbing.) I tweaked the valve gear, tried it on air, it seemed OK, so I put her back together. Last night I tried her on air again and it looks like one of the return cranks has moved. So I needed to get access to the steam chests again. When it is all set up and running sweetly (if ever!) I plan to pin the return cranks)
(Wasn't I glad that when everything had been removed I had chopped the running boards in two so that to access the steam chests it was just now just two screws each side!)
So, I spent a very frustrating night trying to set it up. (The valve gear is Marshall/Hackworth Outside Admission - there's a model on Charlie Dockstader's site). I only seem to have two variables, the position of the return crank on the drive axle and the position of the slide valve on the valve rod.
Regardless what I do I cannot seem to get a smooth transition of events. I have played with both the return crank and the position of the slide valve and nothing seems to give what I would expect (and it certainly doesn't run that well). At best it just about runs forward and won't run backward!
If I get one side set up, the other isn't. If I get both just set up in forward, it is hopeless in reverse (the events are way out)
In my re-fettling I have not changed any element of the valve gear apart from these two bushes. Also, there is no sign of damage, bending etc., to the valve gear.
So the questions are;
- How do I reset the valve gear to get mid gear as "neutral", THEN
- What do I move to get smooth valve events in both forward AND reverse?
One logical answer I am expecting is to plug my valve gear figures into Charlie's model and see what gives. I shall try that tonight.
I look forward to the responses
Regards
Peter