[modeleng] Re: Valve Problem
- From: "R.L. Roebuck" <rlr20@xxxxxxxxxxxxxxxx>
- To: "modeleng@xxxxxxxxxxxxx" <modeleng@xxxxxxxxxxxxx>
- Date: Sat, 30 May 2009 20:59:25 +0100 (BST)
Hi there Bede,
I might be wrong, but fundamentally I think there is going to need to be
some stripping down.
BUT there are four areas it could be that need stripping down - two
cylinders and two valve chests - so anything you could do to narrow the
problem down would be a good plan.
I'd avoid trying any further running until you have sorted the problem, as
if it is a lump of some clinker preventing the valve from seating onto the
port face then the more it moves, the more it could be scoring a line in
the port face.
Also I'd be tempted to make sure you fully sort the problem when you find
the cause (ie if it is clinker in the valve chest, then it will get in
there again if you don't make some kind of modification, do you have a
snifting valve for example, and does it work).
Now for checking things out:-
Do you have drain cocks fitted to the loco - if so this will make life
much easier?
If so, how about on each cylinder, unscrew the drain cocks (careful not to
shear them off). Set the loco in full forward gear, close the regulator.
Make yourself a fitting so you can pump water into where one of the drain
cock fittings was. Turn the loco wheels till the port corresponding to the
end of the cylinder where you have this fitting attached would be being
supplied with live steam. Now try pumping water into this end of the
cylinder. If I'm right - if that cylinder and valve are in good nick you
the pump should quickly become rigid indicating no leakage (well you might
get a bit) - don't pump too hard though. If water comes out of the other
drain cock hole on that cylinder or the blast-pipe, then the cylinder or
valve on that side is at fault. Try both sides of the loco to work out
which side the fault is on.
Next to work out whether it is the cylinder of the valve. On the fault
side, have your device for feeding water into one drain cock fitting
fitted, and plug the other drain cock fitting. If you now try pumping
again...if it goes rigid then the fault is the cylinder. If water starts
coming out of the blast pipe, then the valve it at fault (noting that one
could expext slight weeps as not a major problem).
What do you reckon everyone - will that likely work?
Yours,
Rich.
On Sat, 30 May 2009, bede@xxxxxxx wrote:
> Thanks all for your responses on this.
>
> I put the engine up on blocks and got the boiler up to working pressure
> on air. When I open the reg, the air whooshes out the blast pipe, BUT,
> the wheels do spin feebly about 10 or 15 revs before the pressure dies.
>
> So maybe the valves are seating and it's something else? Or one valve
> is unseated and the other is doing the work? or could this be piston
> ring issues? That would be more incremental it seems, and this problem
> occurred all at once.
>
> Any further thoughts as to what to look for as I begin to strip the loco
> down?
>
> Thanks as always,
>
> Bede
>
>
>
> On 5/26/2009, "bede@xxxxxxx" <bede@xxxxxxx> wrote:
>
>> Hi All,
>>
>> Looking for help troubleshooting my Martin Evans' "Conway", 3.5"
>> gauge narrow gauge 0-4-0.
>>
>> Tried to steam the loco over the weekend and it raised steam ok to
>> working pressure (80psi), but when I opened the regulator/throttle, the
>> steam just whooshed directly up the blast pipe, no power to the
>> cylinders at all in either direction, tried pushing the loco back and
>> forth, but no luck.
>>
>> I have to admit that I did an idiot thing- the smokebox was full of
>> cinders and ash and my steaming buddy and I took the lazy way out and
>> tipped the whole engine upright to dump the debris out. I'm thinking
>> now that this somehow caused one or both valves to become unseated which
>> resulted in the steam just going straight out the exhaust port. This
>> loco has outside cylinders with the steam chests inside the frames,
>> Stephenson gear with the slide/D valves vertical against the port faces.
>> But I can't imagine the valves coming away that easily, esp. as
>> they're vertical...
>>
>> Any suggestions on what steps to take to remedy this, I really hope I
>> don't have to strip the loco down...
>>
>> Thanks,
>> Bede in breezy Brooklyn
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