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Old 04-27-2020, 01:26 PM   #1 (permalink)
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Default Accucraft K-36 burner problems

During this COVID19 stay-at-home time, I've been running, fixing and improving the performance of most of my locos.

I have an Accucraft K-36 which has been a "shelf queen" since I purchased it. Along with some other issues perhaps due to its long period of non-operation, I've been struggling to get the dual gas burners to work properly and consistently, I've cleaned the jets and cleared the supply line from the tank to the jets with blasts of butane from the tank.
What I found was the gas would not "pop back" from burning in the smoke box to proper burning in the poker-type burners unless the air supply was heavily throttled using the sliding sleeves over the air intake holes at the rear end of the burners. Even with this adjustment, the flames are very unstable and one or the other burner often sputters or goes out. I've checked the flame color to be sure that the burners aren't running lean (indicated by a greenish flame).

I have other Accucraft locos with single and dual burners that are stable and consistent and none of them require any intake air throttling at all.
So, my question for other K-36 (or perhaps K-37) owners is whether they have had to deal with this problem.
I was wondering if perhaps the jets are the wrong size, although they are not marked so I'm not sure what size came with the loco.
I appreciate any help or suggestions.
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Old 04-27-2020, 05:58 PM   #2 (permalink)
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Jeff, my K37 is the best running loco I have, it lights immediately and runs strong. That said I have other Accucraft engines that have had issues in the past. Here are things I have done.. by the way I am an amateur at this...

- Check for blocked jets, run butane through the jets in reverse, don't try to use a tool to poke through (looks like you did this)
- Make sure the jets are tightly sealed in the supply line, I use liquid thread sealant so no errant air is getting in
- Check the fuel supply lines and validate they are not leaking (use liquid thread sealant there)
- Use warm water around the fuel tank to make sure the gas is not liquid
- Check to see that the burner is not clogged
- If one is more consistent than the other check the super heater tube to make sure it is not too close to the burner
- Try butane/propane mix if cooler out
- Pull burners out of the engine and test fire them outside engine to see if they light there

Hope some of those ideas help
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Old 04-27-2020, 07:15 PM   #3 (permalink)
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Thanks for your suggestions, but I've done all of those except pull the burners and mess with the superheater tube. I guess those are next.

Also haven't used butane-propane mix since it's been 75-85 F outside every day this week.

I tried putting my K-27 jets into the K-36. It seemed to run a little bit better but not much.

Question: Do you have to throttle the air supply to the burners using the sliding sleeves that close off the air supply holes at the rear of the burners, outside of the boiler?

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Old 04-27-2020, 07:17 PM   #4 (permalink)
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On some engines, yes I have to adjust those sleeves. That said, once I have found the right position I don't have to change it.

My next step would be to remove the burners and try to fire them outside the boiler to see if that works
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Old 04-27-2020, 08:39 PM   #5 (permalink)
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Hi Jeff, I have found with all my twin burner Accucraft gas engines and especially the K36 that on first light up I need to restrict air to get the burners to 'pop' back. I do this by placing my fingers over the top air holes when lighting ( or when flame is just lit as I can't do both at the same time ) and only take my fingers off when they get hot or after about 30 to 60 seconds. I also have a stick with a bit of cloth wrapped on the end to do the same thing as my finger. Sounds silly I know but I find this choking down of the air at first light up when cold makes the flame pop back easily and when the boiler tubes are warm it will stay alight. I set the air adjusters when its hot for best running, blue flame etc
The air adjusters are essential for fine tuning and I have mine set at half air hole exposed on LH side and a bit more than half hole (5/8ths open maybe) on the RH side. It stays lit unless gas tank pressure drops as water bath gets cold or near the end of a run where one burner drops out.
The main issue with these double burner engines is the huge gas tank that needs to immersed in warm water (not hot) to keep pressure up and stop the gas from becoming liquid so start with warm water in the tender. The K36 has a 'water warmer' valve (like a whistle valve) that takes steam from the boiler to the tender water when you press the valve lever. I would get in the habit of using this now and again to keep the gas tank warm and up to pressure. The water needs to be warm even in warm weather as the gas is used the tank can get very cold.
A few other things I have found that may be of assistance but maybe not in your case, is when you take the burner out is it straight? I have found two burners that with heat have a bend in them and that makes for a poor burn. Straightening them out fixed it.
I also found some jets were drilled poorly and not to size to promote even spray. I hooked a jet up to a syringe of water one day ( the burner problem followed the jet when swapping from loco to loco) and when I squeezed gently the water through the jet it came out not in an even spray but a curly jet like a pigtail. Obviously drilled improperly so that one is in the bin. Also check the usual things such as is every thing straight with the jet in the holder then the burner and no air leaks around the jet. The jet size I think was a number 5 from memory but don't hold me to that.
These large engines need warmth in the boiler tubes to be stable to light up and definitely warmth in the water bath around the gas tank. Hope this helps.
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Old 04-27-2020, 08:47 PM   #6 (permalink)
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Green flame is an indication of running far too rich a fuel mixture. I would be suspect of the burners not being at a dead 90* angle when seated against the backhead (so they run parallel in the flues).

Blue flame is better and a blue-violet flame is pretty much the optimal (stoich) ratio in these locos. Green will result in some fairly obnoxious fumes out the stack and poor performance.

I would suggest starting with known numbered jets (available from Accucraft as well as The Train Department)as a baseline and swapping them out systematically to achieve an optimal burn with the air collars wide open. Also, important to make sure the superheater tube is not fouling the flame path of the burner (often the case) as the turbulence can cause uneven burn and even self extinguish the burner.

Lastly, it is worth shining a flashlight into the burner tubes to check for any foreign debris or objects that would impeded the fuel-air mix.

I've had a loco with literal cobwebs inside one of the burners before, which happened overnight. Quite the puzzler to figure out.
SA #1361
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Old 04-29-2020, 10:14 AM   #7 (permalink)
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Interesting story about the cobwebs/cocoons.
I have to clean them out every year on my gas barbecue.

Before I converted everything to ceramic burners, I made little levers to slide the rings around the jet holes back and forth. One could then choke them off for lighting and then open them up for optimal operation.
Bill Allen
Woodside CA
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Old 04-29-2020, 03:52 PM   #8 (permalink)
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As an add on to the other comments here there is some benefit in having a supply of gas jets to swap will find that the tube with the superheater will need a different jet than the one without....and it seems no two of these jets have the same actual hole size in spite of having the same number stamped on them. It all comes down to the manufacturing process for the jets that does not hold precise hole tolerances.

I know there are manufacturing processes that can drill tiny precise holes that would allow perfectly matching jets, but I'm not sure folks would be excited about paying $50 per jet! we live with the jets we have in our hobby.

I keep 8-10 spare jets available for "matching" with dual burner boiler others have said here once the right jets are found and the air mixture air holes set it is common to not have to touch them again.
Cliff Ward
Cary, North Carolina
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Old 04-30-2020, 03:54 PM   #9 (permalink)
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Not to derail the thread too far but...

Bill, you have ceramic burner experiance.

I now have Accucraft's new 7/8" Forney. Had problms with steaming out of the box. We replaced the accucraft jet with a #8 from the train department (one burner tube on this one). Big improvement.

Did the same with a freind's also improved, BUT after a while running the fire popped under the ceramic. Loud roar, bright glowing ceramic and poor steaming. Any suggestions about why? Is it back to the air collar?

I could go on with questions and thoughts but lets stop ther for now.
Eric Schade
Winnegance and Quebec Railway
SA #5649
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