New Dora Owner needs help!

JimmyB

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When reassembling the gas system always use some PTFE tape on all the threaded joints to stop any unnecessary minor leaks

I hate hearing reading this, unless the joint is a taper thread joint, then you should NOT use PTFE tape on the threads, this prevents the actual sealing faces sealing. I have had to repair no end of leaks that have been caused by PTFE tape incorrectly used. So what is the method of sealing the joints there are three primary ones, though may variations:
  • Flat face that has a washer or grommet NO PTFE.
  • Olive type arrangement that mates directly with the "nut", there are compounds for these, but a turn of PTFE on the olive only.
  • Taper threads, there are where the seal is made by the threads, and two turns of PTFE on the male thread in the direction of the thread, however often users end up blocking the hole with over enthusiastic use.
 

maxi-model

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I hate hearing reading this, unless the joint is a taper thread joint, then you should NOT use PTFE tape on the threads, this prevents the actual sealing faces sealing. I have had to repair no end of leaks that have been caused by PTFE tape incorrectly used. So what is the method of sealing the joints there are three primary ones, though may variations:
  • Flat face that has a washer or grommet NO PTFE.
  • Olive type arrangement that mates directly with the "nut", there are compounds for these, but a turn of PTFE on the olive only.
  • Taper threads, there are where the seal is made by the threads, and two turns of PTFE on the male thread in the direction of the thread, however often users end up blocking the hole with over enthusiastic use.
I am only referring to the gas system on these locos and I am only relating what I have been shown/told by my local, very experienced, Accucraft service agent. But it is interesting to note your comments, I will keep them in mind in the future and use them. I think I have covered the "over enthusiastic use" bit but not quite so eloquently as you :) Max

You have got me looking at my locos again Jimmy. All the Accucraft locos I have, both UK and US marketed, use what I assume to be, olives throughout with a nut on their gas systems. Fibre washers on their products are only used on their steam/water plumbing. Roundhouse though do use fibre washers mixed in with olives/nuts on their gas systems.
 
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Paul M

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Gas jets can and do get blocked, sometime there may be tiny bits of dust left in the assembly that inevitably get into the jet to block it. My solution has been to unblock it with a tiny bit of wire that usually pushes out the blockage, you need really fine fuse wire or a bit of fine multicore separated wire. It does need to be very fine. If this does not work then a new gas jet may be required.
Be very, very careful poking wires into gas jets, one scratch and it could be ruined. Blast it with your gas in the opposite direction in which the gas would normally go. Are you sure you're completely filling the tank?
I must admit my one can be very temperamental when lighting, it will sometimes go out for no reason
 

Phil_Vincent

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Thanks for the replies. I don't think the wire option will work the hole is super small.

Would holding a gas cannister up to the the hole clear it ok? (I'm just using a cigarette lighter refill bottle at the mo until the adapter for the larger cans arrive.) I mean just holding the gas jet to the dispenser over the hole and pushing it down. I don't really have any other tools like a compressor etc yet.
 

Phil_Vincent

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Be very, very careful poking wires into gas jets, one scratch and it could be ruined. Blast it with your gas in the opposite direction in which the gas would normally go. Are you sure you're completely filling the tank?
I must admit my one can be very temperamental when lighting, it will sometimes go out for no reason
I can only assume I'm fully filling the tank, I go until I can't hear any has leaving the can and it splitters a bit. Worked brilliantly all last weekend and then today it stopped. I did manage to get it to light again but it was more of a greeny yellow flame like a Bunsen burner not on fierce mode!
 

Paul M

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Yes, just use a squirt. What sort of gas are you using, lighter gas? Are you sure it's Butane gas not liquid?
 

maxi-model

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I can only assume I'm fully filling the tank, I go until I can't hear any has leaving the can and it splitters a bit. Worked brilliantly all last weekend and then today it stopped. I did manage to get it to light again but it was more of a greeny yellow flame like a Bunsen burner not on fierce mode!

Correct. The flame colour seems to indicate the flow is not correct or the jet is damaged in some way. Is your gas can empty ? Did you fill from the right supply - it happens. Again check the gas valve on the tank, press it down manually a few times in case it has got stuck, happened to me a few times. The Train Station do all these spares as will Argyle (I forgot you were in Aus). Roundhouse do a handy multi tool that has heads to remove gas tank valves and adjust safety valves among other things - Argyle stock that https://argyleloco.com.au/product/roundhouse-multi-tool-complete-set/ but check it works with Accucraft spec'ed parts. Max
 

dunnyrail

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Be very, very careful poking wires into gas jets, one scratch and it could be ruined. Blast it with your gas in the opposite direction in which the gas would normally go. Are you sure you're completely filling the tank?
I must admit my one can be very temperamental when lighting, it will sometimes go out for no reason
Yes I knew there would be dire warnings about using wire, but as I said it needs to be the finest fuse wire or a strand of something very small so will be quite flexible. And yes it is the last resort after blowing with air etc. butane gas is in a liquid form and transfers to the gas tank as such, any seen billowing around has turned back to a gas. As for using the gas tank to clear the jet, this may work but needs to be done outside.

The other problem may be that the loco tank is not fully filling due to the hot weather a known problem that also raises its head when the loco tank gets warm after a run. That is why some locomotives have a tender with water in to keep the gas tank cool. What may work is to keep both loco and gas replenishment tank in the shade for an hour or so, thus giving better chance of a successful refill.

Another thing worth remembering is Water, Oil, Gas in that order when replenishing a loco. That way you do not forget one of the vital options IE Water and Oil, with no gas things will go nowhere but a gassed up loco can do damage to an empty boiler. If this is followed between steam ups the tank may have cooled somewhat to allow a refil.
 

Phil_Vincent

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Well a quick reverse squirt with the butane into the jet nozzle and she lights as before. A good trick to have up ones sleeve.

Re gas, I'm currently using the one on the left of the attached picture. Waiting for the correct adapter for the one on the right as I have a load of these from camping gear. Im pretty sure these are correct for the trains we use.
 

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maxi-model

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Yes I knew there would be dire warnings about using wire, but as I said it needs to be the finest fuse wire or a strand of something very small so will be quite flexible. And yes it is the last resort after blowing with air etc. butane gas is in a liquid form and transfers to the gas tank as such, any seen billowing around has turned back to a gas. As for using the gas tank to clear the jet, this may work but needs to be done outside.

The other problem may be that the loco tank is not fully filling due to the hot weather a known problem that also raises its head when the loco tank gets warm after a run. That is why some locomotives have a tender with water in to keep the gas tank cool. What may work is to keep both loco and gas replenishment tank in the shade for an hour or so, thus giving better chance of a successful refill.

Another thing worth remembering is Water, Oil, Gas in that order when replenishing a loco. That way you do not forget one of the vital options IE Water and Oil, with no gas things will go nowhere but a gassed up loco can do damage to an empty boiler. If this is followed between steam ups the tank may have cooled somewhat to allow a refil.
Jon, unless you have the exact size wire size (and a set of calipers accurate enough to measure) to match the broached hole on the jet (and you know its exact size) you are either not going to clear it properly or you are going to render it useless, Just do not attempt this method, Spray through with gas under pressure, clean with thinners or replace.

As to the the water bath in the tender bit - I always thought that was to warm the gas tank up so as to ensure a decent gas flow to the burner throughout a run. It is usually only applied to larger gas tanks remote from the warming properties of the boiler they will usually be sited near to in most loco designs. The self same Accucraft service engineer, I mentioned earlier, even went to so far as to install a valve on the back head of my NG/G16 so steam could be bled off to ensure an even temperature in this vital warm "bath". Cooling the gas this way will risk reducing the gas pressure to negligible levels as the tank empties impairing its firing qualities. Over heat your gas and you risk a "blow back" or ruptured tank. If you live somewhere hot just make sure you stick to butane and not mix with propane, or even pure propane, that some resort to in colder climates. Max
 

JimmyB

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I am only referring to the gas system on these locos and I am only relating what I have been shown/told by my local, very experienced, Accucraft service agent. But it is interesting to note your comments, I will keep them in mind in the future and use them. I think I have covered the "over enthusiastic use" bit but not quite so eloquently as you :) Max

You have got me looking at my locos again Jimmy. All the Accucraft locos I have, both UK and US marketed, use what I assume to be, olives throughout with a nut on their gas systems. Fibre washers on their products are only used on their steam/water plumbing. Roundhouse though do use fibre washers mixed in with olives/nuts on their gas systems.
Taper threads these day are normally only used in low pressure (100 psi) compressed air systems, similar to that used in garages, and so the threads are taped, the problem is often the "mechanic" is not taught the correct use, and goes on to use PTFE tape on all pressure threads. :)
 

dunnyrail

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Jon, unless you have the exact size wire size (and a set of calipers accurate enough to measure) to match the broached hole on the jet (and you know its exact size) you are either not going to clear it properly or you are going to render it useless, Just do not attempt this method, Spray through with gas under pressure, clean with thinners or replace.

As to the the water bath in the tender bit - I always thought that was to warm the gas tank up so as to ensure a decent gas flow to the burner throughout a run. It is usually only applied to larger gas tanks remote from the warming properties of the boiler they will usually be sited near to in most loco designs. The self same Accucraft service engineer, I mentioned earlier, even went to so far as to install a valve on the back head of my NG/G16 so steam could be bled off to ensure an even temperature in this vital warm "bath". Cooling the gas this way will risk reducing the gas pressure to negligible levels as the tank empties impairing its firing qualities. Over heat your gas and you risk a "blow back" or ruptured tank. If you live somewhere hot just make sure you stick to butane and not mix with propane, or even pure propane, that some resort to in colder climates. Max
Sorry Max I have been using this method for years going back to 1983 when I got my first Merlin. So long as the wire loosely fits it is not a problem.

Oh dear another rage of disagreement on GSC, when will this nonesence ever end?
 

PhilP

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I don't think rage comes into it?
More, it is down to knowledge and experience..

If you have that knowledge, then using a 'pricker' back into the jet (from the output side only) may be a valid modus-operandi..

Poking 'a bit of wire' into the taper, is very likely going to end in needing to purchase a new valve.

If the OP does not have the experience to know this, the urge to 'stuff something down the hole' could be very great, and would in all probability, wreck the valve.

PhilP
 

Phil_Vincent

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gentlemen fill me with your knowledge.

From reading between the many lines here, it sounds as though the jet nozzle bit, is more than just a piece of metal with a hole in, which gets narrower. That being said, the hole looks to be incredible small, so I can't imagine there is a valve in there? Or am I wrong?
 

PhilP

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gentlemen fill me with your knowledge.

From reading between the many lines here, it sounds as though the jet nozzle bit, is more than just a piece of metal with a hole in, which gets narrower. That being said, the hole looks to be incredible small, so I can't imagine there is a valve in there? Or am I wrong?
The jet assembly goes down from 'gas pipe' size, to the tiny hole you see on the output..
The valve part, is a very fine tapered hole, and into this is an equally fine needle... When you operate the gas valve, you are screwing this needle in/out of the tapered hole.

As you say, a teeny-tiny hole, and a scratch (or tiny bit of anything) can ruin the valve..

Hence, your gas can, to blow backwards through the valve..
If you try/force something through the hole, a scratch will leak gas around the needle, so the valve will not turn off..

PhilP
 

JimmyB

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Though technically correct being called a valve "a device for controlling the passage of fluid or air through a pipe, duct, etc.", most people think of a valve as something to manual or automatically control (tap or faucet) flow, or something to prevent back flow non-return valve, so using the term jet is often preferred, as it is a pre-calibrated orifice.
 

dunnyrail

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I think we are in danger of getting slightly confused here with the gas Regulator and the gas Jet. The gas jet is at the end of a pipe that comes from the gas regulator. It is the gas jet that sometimes gets blocked with tiny particles of dust.

In the picture below taken just now of my Roundhouse Jack, I have labelled the regulator as the valve. The jet is clearly seen connected to the pipe that feeds the gas to the jet which is where the flame ultimately comes out inside the tube in the boiler. The jet itself is actually screwed into the brass assembly so is not able to be seen with the burner in place in the boiler.
2F55AF9D-322E-452E-A2A9-BAA18245D85E.jpeg
To hopefully clarify:-
The valve (or gas regulator) is a device that allows the flow of gas to be turned on, up or down, this is Phill says has a fine valve to adjust the flow of gas.

The jet is the device that works a little like a jet engine in that it compresses the flow of gas from the pipe emitting it as a gas that lights and then heats the water in the boiler. This jet is where blockages can occur as indeed the exit on the jet itself is extremely fine.

There have in the past been available fine wire devices available whose purpose was to clear occasional blockages in the jet, they have been akin as I said earlier to very fine 5Amp fuse wire. Below I show a demonsteration (as Fred used to say) of the 5A wire passing through a No.6 Gas Jet. There is no force needed to get the wire through so it shows that if fits just fine, but I should caution that there are differing jet sizes available. It would not go through the No.5 jet that I have but happily went through the No.10. So it would appear that the higher the Gas Jet No. the larger the hole.
1B3A1800-D441-486C-A99B-5F158B4C12B8.jpeg
Oh the No. is stamped on the jet itself that needs a 4ba spanner or very fine pliers to remove it from the pipe union. When putting it back on it should not be overtightened to plumbers tight but enough so that gas does not leak. It would be good pratctice before putting back on to turn on the gas for a second or two to possibly remove any crud in the pipe before replacing the Jet.
 

maxi-model

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Oh for gods sake ! - Just do not poke things through the fine broached appature on a gas fired loco's jet. There are other ways, previously mentioned on this thread, that describe guarenteed non destructive methods of clearing a blocked jet, suspected or otherwise. Just plain good practice. Jets can become blocked for a number of reasons not just "dust". Jon, you even say yourself that without knowing the actual size of the jet's broaching the wire method cannot guarantee success. Why do you persist in promoting this technique that risks a users kit, without the depth of knowledge you may have ?

Anyhow, in the world over we are using electrical service units in our houses, instead of the old fuse boards. The knowledge around fuse wire and its availability has dwindled somewhat. I will say no more. Max
 

dunnyrail

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Again we will clearly have to disagree here, how odd. Yes fuse wire is pretty difficult to obtain these days but a good old style ironmongers are likely to have it. I am lucky that there is such a beast at Kimbolton not far from here. I think poking wire indeed should be the last resort.

Thats it from me and sounds like thats it from him.