Garry
Active Member
Posts: 45
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Post by Garry on Aug 16, 2004 10:32:57 GMT
I have just had my loco pass its boiler test (steam and hydraulic) and have run it under steam for a few hours but the problem is that as soon as it is running the steam pressure drops to very low. I can sometimes keep this reasonably high if I run with the blower partly on but that is not how it is supposed to be. The 1 in 3 and 1 in 6 angles look reasonably accurate so how can I test to see if there is a leak in the vacuum? or what other problems can it be? and how to solve/check them? The locos blower will pull the fire up from about 15 psi to 90 in a couple of minutes.
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Post by GeorgeRay on Aug 16, 2004 10:45:32 GMT
Is the blast pipe nozzle central in the petticoat and pointing straight up. If not this among other things would cause the symptoms you mention.
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Post by Phil Sutton on Aug 16, 2004 20:07:53 GMT
Have you checked to see if the smokebox door is sealing properly?It does sound as if there is n't enough draught on the fire.
Phil
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Garry
Active Member
Posts: 45
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Post by Garry on Aug 16, 2004 23:55:08 GMT
Thanks lads, The nozzles seem to be very close in line as best I can check with bars etc, and, I did have to take a little off 2 sides of the door where the machining did not line up after the first steaming when a small trickle of oil etc showed itself at the door bottom. This was not apparent after the second steaming. The door was turned and milled I think as it is round at the bottom with straight sides and top. If this edge is not flat, what is a suitable gasket that could be used? I have had to use a silicone sealer for all the gaps around the smokebox as per Modelworks instructions but it would be messy using it every time I had to open the door after a running session.
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Post by GeorgeRay on Aug 17, 2004 19:10:37 GMT
If it pulls round on the blower and not when the regulator is opened then I would think it's not likely to be a leak anywhere in the smokebox region. A leak there would affect the blower probably more than the blast pipe. So other potential areas to look at are the size of the nozzle and also is it fitting closely on the exhaust pipe so that no steam is being eject below the nozzle. Does the loco have a superheater before or after the regulator if after is it steam tight. Just a few of the more obvious things to have a look at.
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Post by Phil Sutton on Aug 17, 2004 20:13:18 GMT
Which Winson loco is it that you have built?Different models had different problems.
Phil
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jackrae
Elder Statesman
Posts: 1,333
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Post by jackrae on Aug 17, 2004 20:28:17 GMT
When you're running is the water pump continually feeding water to the boiler. This is one way to kill steamablity on the run
Another is to have the valves cut too far back so that little steam is used, hence less draught, hence low fire.
You don't say if you have the firebox full of dead coal when on the run. you need little and often rather than a lot infrequently in order to keep a good red fire.
jack
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Post by Deleted on Aug 18, 2004 7:21:57 GMT
Hi, Looks to me the blast nozzle is of the wrong size. Most probably to big. The result of this is a low velocity of outlet steam so the cones can’t do their work properly. Try with a smaller one and do check if there are steam leaks on the way to the nozzle. We do want all the exhaust there. Smokebox doors can be a nuisance best is to make the hinges not to stiff so they can flex a bit while closing the door. In this way giving it the chance to seat properly. Also check again for air leaks around the places where exhaust and intake pipes go true the smokebox. When my Simplex gives up usually it is there where the problem is. The blast created by the blower is usually strong enough to keep going but the exhaust is not. Also did you seal the joint between boiler and smokebox. This has been overlooked on several occasions in our club. Do check connections for steam in the smokebox as even the smallest leak destroys all the vacuum you would like to create in there. Such leaks would only show up when the engine is running as when standing these pipes are empty hence no leak and a good working blower. Just a few taught to keep you occupied. Regards Wilfried Vermeiren users.skynet.be/modelbouw.wilfried |
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Garry
Active Member
Posts: 45
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Post by Garry on Aug 18, 2004 11:59:25 GMT
Thanks again for replies lads and I will answer to everyone in this one letter. The loco is a Winson/Modelworks double chimney A4. The superheater is after the regulator. The boiler was sealed to the smokebox at the same time as fitting to saddle and using the same sealant both the nozzles were sealed. When I say sealed obviously I cannot tell if there was a slight gap anywhere I just hoped I had enough around to seal. The firebox usually has nice red glowing coal in it. The valves are to Modelworks dimensions so I would not know if this was a problem or not. All conections were in situ for the hydraulic test which was okay but maybe this could be different under steam due to expansion, how can I check inside this tiny and full of pipes smokebox when under steam? The axle pump is working most of the time but this has not been a problem on my other loco. I need axle pumps as I never have any luck with injectors. I have today had a phone call from Modelworks (they actually have acknowledged me) and they said the firegrate does need more holes in it as this could also be a problem.
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Post by davidimurray on Aug 18, 2004 16:30:49 GMT
Hello
One trick we use on the 'big' engines to look for steam leaks in the smokebox - Wind the handbrake on tight and block the wheels. Set the loco in mid gear and open the regulator. Then, use a long stick with some rag on end to look for leaks. Move it round all the elements, steam pipes, joints etc. if the rag flutters investigate further. I've never tried this method on model engines but it might work.
Another way to test for leaks is to do the following:- When cold fill the boiler with water, with the handbrake on, wheels blocked and drain cocks shut open the regulator with the hose still connected. This will fill all the superheaters, pipework and cylinders with water. Hopefully your water pressure will be high enough to get some pressure on. If not a squirt of compressed air may be needed. Leave under pressure for a while and examine all connections in the smokebox and an eye out for any water in the firebox. If you do this be very careful afterwards - drain the boiler water and open the draincocks and push the loco along very slowly to drain all the water out. Remember to do this with the regulator and boiler open to atmoshphere so all the water is drained.
Finally some other thoughts - is the valvegear set correctly and are the valves sealing properly. Try keeping the loco well forward, near full gear and seeing how it goes. Is the bypass valve on your pump shutting off properly.
Let us know how you get on.
Dave
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Post by davidimurray on Aug 18, 2004 16:33:01 GMT
Hmmm - appears that there's a filter on this as everytime I write drainthingys it replaces it with thingy's!!! - Seee it's done it again!!!
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Post by Andy Clark on Aug 18, 2004 17:27:31 GMT
Hmmm - appears that there's a filter on this as everytime I write drainthingys it replaces it with thingy's!!! - Seee it's done it again!!! How amusing to find the hidden admin features of this board in such a benign posting! I believe that I have resolved this problem so you can discuss draincocks to your heart's content now  |
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