Wrekin disaster

MRail

MRail

16mm etc - Live steam, battery & trams
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Wondering if anyone has experience to share...

Enjoying a good run with plentiful steam plume, about 15mins in, Friday 13th struck.
Wrekin was pulling up 1:30 cab first, became rather jerky, and then emitted a loud "POP!" and clouds of steam.
Investigation revealed a plug blown out of the LH valve chest, later retrieved from among the ballast.
Presumably this indicates pressure OTT? S/V was feathering, actual pressure n/k, but >40lb.
c24904dbb44a42d79c43ba2b8ea0f65d.jpg

Unsure whether to push it back in & try again, or if it warrants more serious action.
 
Yup. It's just a blank. A TINY smear of loctite may stop it happening again. Probably got something behind the valve and it pushed it out.

Don't sweat it, it's not a disaster!
 
MRail said:
Wondering if anyone has experience to share...

Enjoying a good run with plentiful steam plume, about 15mins in, Friday 13th struck.
Wrekin was pulling up 1:30 cab first, became rather jerky, and then emitted a loud "POP!" and clouds of steam.
Investigation revealed a plug blown out of the LH valve chest, later retrieved from among the ballast.
Presumably this indicates pressure OTT? S/V was feathering, actual pressure n/k, but >40lb.
images

Unsure whether to push it back in & try again, or if it warrants more serious action.
Click to expand...

First of all how old is it. If within warranty then contact your seller of Accucraft UK. If out of warranty then the plug can be replaced with good quality locotite. I would however, check your safety valve on another locomotive because it may not be registering accurately. Have you had occasion to reset your safety valve recently because it appeared to be blowing off early?

Also check your timing on the scribed lines. If not sure give me a bell either now or saturday night and I will talk you through. Locktite plug in and leave overnight. My tel is 01752 845938

Bestest

Tag
 
Rob, I would add to the advice above that before you Loctite the plug back in make sure there is no oil around by giving the plug and the hole a good wipe with meths.
 
Thanks guys, Neil, Bob...
I was hoping it would "just" go back in. I was presuming an interference fit, and of course Loctite.
Tag, The loco is several years old, pre-owned & I've had her about 3 yrs.
I was test running after re-setting the valve timing, and it seemed fine both ways - just my luck!
Yes, I'll be checking the s/v before steaming again.
 
I'm just trying to think what made it blow out. Doubt it would be steam pressure, any idea how high the water was, had you just topped up? Perhaps a combination of a slug of water and a plug that wasn't very well gripped in the first instance?

Happy steamings,

John
 
Altering the valve timing makes me wonder if the valve is too far along the spindle and punched it out?
 
New Haven Neil 2 said:
Altering the valve timing makes me wonder if the valve is too far along the spindle and punched it out?
Click to expand...
My first thought was that as it was O.K. at the start of the run what caused it to pop later on? I suspect expansion rather than priming unless the valve has worked loose. This begs the question of optimum temperature for valve setting, or do the tolerances mean that the temperature is insignificant. All I know for sure is that with Gresley's conjugated gear the valve events varied a little with valve rod temperature.
 
Neil Robinson said:
New Haven Neil 2 said:
Altering the valve timing makes me wonder if the valve is too far along the spindle and punched it out?
Click to expand...
My first thought was that as it was O.K. at the start of the run what caused it to pop later on? I suspect expansion rather than priming unless the valve has worked loose. This begs the question of optimum temperature for valve setting, or do the tolerances mean that the temperature is insignificant. All I know for sure is that with Gresley's conjugated gear the valve events varied a little with valve rod temperature.
Click to expand...

I think it's more down to overall size Neil, these little bits haven't got that much mass to expand. Gresley's bits were a lot bigger. It's still not totally impossible though, but the valve would have to have been virtually touching the plug when cold.
 
CoggesRailway said:
Tag mate I wouldn't leave your number on there long - unless it is already public.
Click to expand...

Moderators would usually remove such a number from the posting. However, as Tag is involved in the commercial side of this hobby, I expect it is pretty well known and may well be published in his esteemed magazine anyway. I am pretty sure Tag understands the situation with putting a phone number in the public domain.
 
The loco has made several runs since last adjusting the reverser valve itself.
Back in September, while visiting the Mossala Hill Rly, it suddenly refused to reverse at all.

Having only just got round to investigating, the problem turned out to be the R/C link flexing and not pushing the cab lever properly. A more rigid link is needed, but a quick fix was made by bending the existing rod into better alignment. A brief indoor test seemed OK, so today it was steamed up for a proper run. All was well, with the loco pulling about 4Kg and running equally well in either direction. Locos always work hard on my tortuous, hilly line.

About 15mins into the session, and in reverse, it began to "hunt" with a noticeable jerkiness over the last few yards before the "blowout", on a 1:30 grade. After cooling, there was still a fair amount of water in the boiler.

So, present plans are to clean up and refit the plug tomorrow, then have a test run and report back.
 
Tag's number is posted on page 3 (contents page) of Garden Rail magazine under the masthead, so it is pretty much public.
 
Last year running my Accucraft " Edrig" named Spitfire , I had stopped to top the water. After a quick top up, the engine started off. At the far side of the loop the safety valve gasket inside let go. It blasted the entire contents of the boiler straight up 6 feet or so , this was over in about 5 seconds and then went DEAD ! I quickly turned off the gas , and checked for damage . Nothing was wrong except needing to replace a gasket. However the crowd at the fence line had all moved back about 3 feet and were all VERY QUITE . I had put on a great show for them . Nothing damaged except my pride .

Charles M :D
 
Continuing the saga....
This morning MR No 5 Pywr Ffas (Wrekin class) was moved into Mersey Lodge works for attention to its LH piston valve cylinder plug. No obvious problems were found - the piston is well clear of the end plug, and timing was correct.
The plug was cleaned and refitted. There is a very fine taper to the plug, which will only fit one way. As suggested, a small smear of loctite was applied to the leading edge, and the plug was refitted. This required tapping with a small hammer and drift to bring its face flush with the cylinder block.
At this time the outside temperature was -5ºC, and inside the works -2ºC.
By about 13:30hrs it was +2º outside, so a steam test was sanctioned.
Using the rolling road, No 5 was fired up on mixed gas (B/P 70/30), and the s/v feathered almost from the start, increasing as pressure built up, and blowing copiously at 50lb.
The loco was placed in gear and run back and forth for several minutes. No problem was evident with the plug.
On the track, general performance was quite poor. Using the same test train as yesterday, the loco could not make it up the 1:40 grade, and was worse in reverse. Without the train, it could not climb the grade light.
The trial was abandoned.
So, valve timing needs checking again, and some attention is need to the s/v.
Feels rather like back to square one!
 
CoggesRailway said:
Tag mate I wouldn't leave your number on there long - unless it is already public.
Click to expand...

Thanks Shipmate ? but my work number is available online and in print anyway...
 
I think plans for today (only -1ºC so far) will be to disconnect R/C from the reverser, and try the set-up manually.
Later...
Well, that went OK. Seems to run more or less equally both directions.
Modified the R/C rod by shortening to link directly to the rocker arm, instead of the cab lever.
Now moves the valve too far, so moved the link inboard on the servo arm & is slightly better.
4ºC pm, so steamed up & found rather poorer running in reverse.
So, more tweaking needed. The valve cylinder plug is OK though.
 
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