# Ceramic Gas burners on Locos



## doubletop

I'm using a commercial ceramic gas burner on my Rob Roy loco for the first time and I am having trouble getting anything like a good steam pressure.

http://www.homemodelenginemachinist.com/index.php?topic=9516.0








I've worked out to start with a low flame to get things heated up before slowly opening the gas valve to get more heat. Should I have the fire door open or closed and should I be using the blower to get some air flowing through the system.

With the fire door open I can have have flames shooting out the door, so I've closed it. I then open up the gas to the point there's probably to much gas and it flashes over and either goes out or I have a moment and shut down, just in case. Sometimes the burners ceramic block glows orange other times I'm just getting a blue flame. Is it the orange glow or blue flame I need. 







Any clues on how I should be doing this please?

Pete


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## lordedmond

Pete 

I hate to say it but the burners are not big enough. most people just use open jets with out the ceramic bit, yes use the blower

you will need enough heat to lift the safety valves with ease and keep them blowing off for at least 10 mins ( for the accumulation test ), note that your boiler is flued for coal not gas fired , ie the flues are to small 

a Rob Roy in steam on the track needs a good fire going to maintain its steam any way


Sorry I cannot be more help , I have driven but not owned a Rob Roy , I did have a "William" which also have to be fired to the bottom of the door 



Stuart


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## steamboatmodel

Hi Pete,
Ceramic burners generate radiant heat when they are glowing orange, and should produce the maximum amount of heat in that condition.
Regards,
Gerald.


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## doubletop

Stuart

I think you've confirmed my suspicions; this burner just isn't going to do it. I was having these concerns running in my garage, our club track is on the beach in sunny windy Wellington.






So its out with the ceramic burner and re-install the ash-pan and grate. That saves me a bit of time I could have wasted trying in vain to get it to work. The guys in the club can show me how to fire it up.

Gerald

I had thought that may be the case it just wasn't consistent enough to rely on it. Any bit of a draft and and the flame was all over the place and at times more outside the firebox than in.

It's gone

Thanks guys

Pete


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## steamboatmodel

Hi Pete,
Most of the ones using the Ceramic Gas burners that I know are in Gauge 1 Locos or in Model Boats. I think that the air supply has to be very well controlled and brought in with the burner. There have been a number of them around here (Toronto, Canada) that have gone to gas burners, but I haven't looked too close to there designs as they are too large for my models.
Regards,
Gerald.


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## doubletop

I had given up on the ceramic burner idea and refitted the ash pan and grate when one of the club members gave me a call and put me in touch with a group of Kiwis who are successfully running their locos on propane. One of them another Rob Roy and one a large 5" gauge loco.

I went round to Dave's place and we got the ceramic burner running and he was pretty happy with what he saw. Eventually we got it up to 80psi. The result of the session was a series of mods I had to do to improve things.

I've been getting better at getting steam pressure up and keeping the whole lot alive. Yesterday I managed to get a cold engine, with a cold fill, up to 80psi in about 10 minutes. It was outdoors with a bit of a breeze going. So pretty encouraging.

I'll post the pictures back on the Rob Roy thread when I get a bit of time this week.

Pete


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## doubletop

I got a PM from Tups (Cris) for more details on the replacement ceramic burner I have made. This one works and if I dont forget to open the blower before I stop running it doesnt go out.

Some of this is a repeat from the Rob Roy thread but for completeness Ill do it again here and hopefully by the end it will all make a bit of sense;

The problem I had been having with running my loco successfully on gas was although I could get the engine up to pressure relatively easily maintaining it was a problem so I ended up going round the track in short runs followed by a recovery of pressure then on again. On the assumption that the more heat you can get into the engine the more steam you make and keep up the pressure. I have been experimenting with burners and learned something from the exercise. Some of it is blindingly obvious but it has helped me understand what is going on, or not as the case may be. 

The basics being.
·    To get more heat you need to burn more gas (I said it was blindingly obvious stuff)
·    The amount of gas you burn is a factor of jet size and jet inlet pressure.
·    You need the right balance of primary and secondary air to ensure complete combustion (its about a ratio 1:24 gas:air for propane (4%:96%)
I made myself a test rig so I could see what was going on. Regulator on the gas bottle, Input pressure gauge and output pressure gauge after the gas tap

Gas Control Rig









The assumed problem with the ceramic burner was that it couldnt get enough secondary air. If it is running on the electric blower its fine, on the steam blower its fine. But add more gas and the engine whistles like kettle as it tries to draw air through the holes on the firebox door. If the pressure is too high, and the blower is off, it flashes back with a huge pop or just goes out. If it goes out there's no indication as you can still hear the gas flowing. Not good

My starting pint was the local guys who had given me a lot of advice based on the success they had with gas firing their locos. 

First was to put a baffle on the front of the burner to keep the flames in the firebox for a while rather than shoot straight down the fire tubes. This keeps the heat where you need it and stops you melting the paint on the smokebox. Believe me it works, I ran the loco once with it out and the smokebox paint job looks a bit sad now. 

Stainless Baffle on original burner







Baffle in the firebox, note its at the fire tube end not the fire door end.







(_I am convinced this is a major contributor to success)_


The next was make a new burner I started with making a new burner based on some old magazine articles, the intention being that the gaps between the tubes would allow enough secondary air.






This didnt work too well and made a couple of versions but they just didnt give the heat and there was lots of un-burnt gas.

*New Burner*

I then turned to resolving the secondary air issue with the ceramic burner I had seen a version of a burner with tubes running through it. I wasn't about to hack my burner about in case I was wrong so set about making a copy

All the parts alongside the original







New and old








New burner with the lid off






Installed in the loco you can see the baffle in the front








Make sure that the burner is as high up in the firebox as the jet holder will allow e.g hard against the foundation ring.

The dimensions for mine is 26mm high, 42mm wide 85mm long. This just fits in the firebox allowing for the ends of the stays and a little bit of room for the baffle 

Through the middle are 2 x 12mm tubes for the necessary secondary air . To hold up the ceramic there are 2 x 15mm sleeves around the air tubes and strips of copper soldered on the inside edges of the body.

The jet holder is 38mm long 12mm dia brass drilled 8mm for the jet assembly, It is cross drilled with 6 x 5.6mm holes set at about 60degrees. The jet is a #15 held in with 6BA screw. The jet holder is mounted as low as it can be in the burner body. I'm sure it can be longer, as your installation would require.

My original was stainless steel, this one is copper, as thats what I had. Im sure brass would be just fine. (either way16-20swg)

I got my ceramic from Bruce Engineering (Polymodel) in the UK

http://www.pollymodelengineering.co.uk/sections/bruce-engineering/index.asp

It cuts really easily; I did the holes for secondary air pipes by using an offcut and twisting it slowly as it worked through the material.

See these drawings from Sandy C his burner gives a good view of a similar sort of burner albeit smaller and no secondary air holes. However it give you a good idea on sizes. Most of my burners have had some basis on this burner from Sandy and there does seem to be some commonality with parts.

http://www.homemodelenginemachinist.com/index.php?action=tpmod;dl=item155

*Running with it*

As with any loco a blower is needed to get the burner running otherwise youll get lots of flame out of the firebox door. I start at about 5-7psi gas pressure with the blower going, it doesnt need much of a blower, I use a computer fan in a cut down plastic funnel on a long coper tube so the whole lot doesn't melt. That said with the baffle it not like there's flames shooting out of the loco flue.







Once a bit of steam pressure is available (5-10psi) the steam blower can be opened and the external fan removed. As steam pressure comes up more gas can be applied. I find that 20psi max is good for my burner on this loco. It takes only about 10 mins from cold to full steam pressure (80psi), my boiler takes about 500ml of water.

OK I understand theres a but of reluctance to go to gas burners, but when they work they work pretty well, and clean up at the end of the day is just about zero in the firebox area. And if you have a problem with water, as I have been having on my small loco, no grappling for the dump pin. Just shut down, sort the water, if you've got steam pressure and bit of steam blower and re-light.

Hope that is of use to somebody

Pete

PS

For those of you who missed it, here it is running

[ame]http://www.youtube.com/watch?v=iugzOVs-73E[/ame]

Dodgy track at the end caused it to slow and stop


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## tups

Thanks very much Pete, that is exactly the information I needed to get started on my own gas burner, hopefully without my usual progression of buying lots of stuff, finding it doesn't work, buying more stuff, finding it still doesn't work, etc etc ad nauseam. My grate is 67x 55 mm, which gives it nearly the same surface as yours, and the boiler is also 500 mL, so performance should be quite comparable I would guess.
In any case, firing a blowtorch through the firebox door just isn't cutting it 

Again, thanks a bunch, and enjoy your beautiful loco! 
If I manage to actually make something, I'll post onhere.

Cris


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## doubletop

I thought I'd add a bit about gas supply.

The biggest problem I've had with any of the burners I've done, including those for my little engines, has been controlling the gas supply so I know what is going on.

For my small engines I used camping gas cylinders with the 7/16 screw on connector. Primarily because I had a control valve for these cylinders that came with the original Rob Roy ceramic
burner.







This didn&#8217;t work very well with the loco for two reasons.


You have no idea what pressure you are supplying to the burner and you can&#8217;t really see what is going on, as the fire door needs to be shut.
The gas in these cylinders is 60/40 butane/propane, you really need propane as it provides more heat.

The light began to shine when one of the club members loaned me his driving trolley that is fitted out for gas running. It has gauges so you know what is going on and carries a 2Kg Primus gas cylinder.











The Primus cylinder is ideal as it is a nice size and has a low profile. We get these filled at the local BOC depot and the gas they supply is guaranteed 60/40 Propane/Butane.

You can see the cylinder has a regulator (orange knob on the right) to control the gas pressure and of course the gauges up front to see what is going on. (the grey cylinder on the left is the accumulator for the vacuum brakes.

This led me to get my own set up like this for testing. (I use the loaner trolley for the track)







This has a bottle mounted regulator with a POL connector and input (post regulator) and output (jet) pressure gauges. In addition there is a cut off valve and two gas control valves in parallel. The idea of the parallel valves is one is preset for idle or pilot burning and the second for the main control of the gas supply. The main control can be shut right down without the burner going out. If there is a major issue the cut off valve can be used.

Of course the problem with this is the use of the LPG type bottles with POL (or whatever connectors) they are generally too big and the wrong shape for carrying on a driving trolley. 

The other option is the disposable propane cylinders with the &#8220;MAPP&#8221; connector. I had one of these for a portable barbecue but had no way of dealing with the regulation issue until I started searching on Ebay and found the Turbotorch STK-R regulator. The trouble was they were expensive (~US$60) and the shipping prohibitive in comparison. 

http://www.thermadyne.com/IM_Uploads/Literature/lit_302_05_56-1252.pdf

Then I stumbled across this guy in Hawaii who does these and ships worldwide.

http://ultimatespudgun.com/propane-mapp-regulator-p-220.html

US$27 and $12 shipping. It regulates 0-40psi which is ideal when I am trying to get 0-20psi for the burner.







This regulator combined with a pressure gauge now gives me a compact solution for gas supply and control. 







The regulator itself provides enough control of gas feed but building this into a driving trolley should really also have a cut off valve and two gas control valves in parallel readily available to the driver rather have them fiddle about with the gas cylinder which can be hidden in the trolley.

There are some issues with these small cylinders


They are probably only suitable for smaller locos.
They wouldn&#8217;t supply enough gas at the right rate for larger locos. They&#8217;d cool right down and the pressure would drop off
These small cylinders are not refillable and they are more expensive than bottle gas. For example one of these 450gm (1lb) cylinders is NZ$11 whereas a refill of the 2kg Primus bottle is NZ$2.50.
Although these regulators fit MAPP bottles I&#8217;d suggest don&#8217;t even thing about using MAPP gas for your loco.

Of course my other option is the Primus cylinder but I haven&#8217;t found a suitable regulator for one of these and these cylinders don&#8217;t seem to be current in NZ. I do have a Primus to POL adaptor but when the cylinder, adaptor and POL regulator are coupled together it&#8217;s a really cumbersome. Maybe I&#8217;ll get something sorted in this area but for now it looks like I&#8217;m going the small cylinder route.

Regulators side by side









*PUBLIC SERVICE NOTICE &#8211; You are on your own with this. It&#8217;s up to you to make sure you do things safely and within the bounds of your local regulations *


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## bambuko

From my days in G1 I seem to remember dire warnings about using propane!!!
Only butane was recommended. I will try to find more - but in the meantime I suggest you research it as well.
It would be a shame to not to learn from the mistakes of other people.

Chris


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## shred

bambuko  said:
			
		

> From my days in G1 I seem to remember dire warnings about using propane!!!
> Only butane was recommended. I will try to find more - but in the meantime I suggest you research it as well.
> It would be a shame to not to learn from the mistakes of other people.
> 
> Chris


Propane can create much higher tank pressures and a non-professionally-built tank (eg: G1) needs much more testing. Using a commercial tank and regulator designed to be used with Propane should avoid that problem.


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## tups

Hello Pete,
Hello forum,

I pm-ed Pete in december to ask him about the experiences he had with the gas burner he made for his Rob Roy, and he updated this thread with a wealth of details. I've had little time in these past few months, but I finally did succeed in building a gas burner for my OS rocket.
It doesn't look pretty, but now I know that the geometry works, I could make a second, prettier one. The shapes on the copper on this burner are a little more challenging ... but it glows bright orange in use, there is no unburnt gas (I feed it liquid butane which evaporates in the copper feedpipe) and the loco lifts the safety valve easily when stationary.
The pressure buildup seems a little slow though, and when running fast (on a rolling road) steam pressure plummets pretty fast. I have not added a baffle yet - maybe the hot gases leave the firebox too fast. I can't wait to see what it does on the track... next weekend we have a running day.

Some pictures:































And the burner in place - space constraints necessitate a bit of a back-asswards mounting, but it works!





I really can't thank you enough for the guidance and advice!

Cris


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## doubletop

Cris

Your burner looks perfect but what you describe is exactly the scenario I had, which then proved to be disappointing on the track. In fact I was out running this weekend and my experiences contribute to my growing understanding and help me answer your question.

Pressure building seeming a little slow would indicate not enough heat to maintain the steam pressure. The problem is you can't just push in more gas without means of drawing the air through the boiler. So my suggestions, in some sort of order.

Your loco looks pretty new. It needs to be loose to enable this to work. I was told to run mine on air for a long time to run it in. I ran it for 6 hours plus keeping it well lubricated all the time. Varying speed, reversing etc. It should only need 5-10psi of air pressure to do this, so its not a case of thrashing it.

Put in the stainless baffle, unless you do, once you get enough heat it will ruin that beautiful paint job around the smoke box.

If you haven't already got it rig up some means of including a pressure gauge in the gas feed after the regulator, before the jet, so you can see the jet pressure. That way you'll get to learn what works and what doesn't. A 0-60psi gauge will do. I use guages from Norgren http://www.norgren.com8BSP 40mm gauge. They are off the shelf in NZ so wherever you are I'm sure you'll be able to get one.

Use propane if you can otherwise you'll need more butane to make it work and you may not be able to get enough gas through your burner to make enough heat.

Use an electric fan on the flue to start with, you'll see I use an old fan from a computer.

Put in the fan, start the burner on a low pressure (2-3psi) to warm things up a bit. leave the blower, regulator and drain cocks all open to let heat through the system.

After 2-3 mins shut the blower and regulator and open the gas pressure up to 5-10psi and wait for the loco pressure gauge to rise to about 20-30psi. Crack the loco blower just enough so you can hear it in the flue. Leave it like that for a couple of mins. Boiler pressure should keep rising.

Remove the electric fan. Increase gas pressure to 15-20psi. Boiler pressure should come up pretty quickly and the safety valve blow off.

With gas pressure at about 20Ppsi and running on the rollers without a load, and blower shut off it should be possible to run the loco and maintain boiler pressure to the extent that the safety blows off while you are running. If it doesn't try more gas pressure, but make sure its burning all the gas. You'll smell it if it isn't.

If you shut down the regulator remember to open the blower and reduce gas pressure to about 3-5psi otherwise the burner will go out and be at risk of flash back when you try to relight.

The gas pressures quoted are what works for me. The jet size plays a big part on the gas pressure required. I have a #15 jet. If you use a smaller jet you'll need more pressure and vice versa as the gas has still got to get to the burner at the right rate.

I also had an issue with pressure loss when running. I ran it on air, upside down, and used soapy water to trace leaks in glands unions etc. Try that

My experience this weekend re-enforced all this. My gas bottle was getting empty, which means the pressure dropped off and as I can only get propane/butane mix (LPG) the propane tends to go first leaving the less efficient butane until last. Once the bottle pressure got below 25psi and I couldn't maintain 30psi gas pressure, when running, the loco just packed up and I was back to where I was a few months ago. Its a fine line between right and hopeless.

Please re-post your question to me on the main thread and I'll copy my reply over as well for all to see.

Good luck

Pete
_
(just had another look at you pictures, beautiful!!!_


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## tups

Thanks for the suggestions.

About the Rocket, I have no merit in its construction, it is a ready-made model by OS Live Steam. In the mean time, I took it to the track, and while it runs very well on its own, I don't think it will keep up steam when it actually has to pull things. The advantage of butane is that you don't need pressure gauges, it is consistently self-regulating - but when the canister cools down too much from the evaporation, it regulates itself too low unfortunately. 

Before switching to propane, I'll try one more thing, which is keeping the canister in a bucket of water to keep it warm. I think, hope, that that will do the trick.

The weirdness with gas is all these different threads and fttings that don't fit into each other, so switching to a different canister is a major pain in the ass while I figure out what I have to make up now in the way of fittings ...

And jets. I would love to find a source of jets. It seems impossible here (Belgium). I have a number 16 which I bought in the UK, and that of course leads to more thread compatibility madness.

Thanks, again!

Cris


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## doubletop

I had the same experience at the start with the engine running by itself OK. I even thought of adding radio control as I didn't expect it to get any better. In the end I proved myself wrong.

I don't know what you mean by self regulating? You do need to be sure you are getting enough gas out of the jet. The bottle pressure will drop off as the gas depletes. I've just taken my cylinder to BOC for a refill. They told me it was 1/4 full. It may be, but there isn't enough getting to the jet to generate enough heat.

So, I'd suggest that your main problem is lack of heat not allowing the boiler to maintain pressure. At risk of sounding patronising, its a chain of events. The bottle needs to feed the gas at the right rate, the gas has to be the right calorific value, the burner has to convert the gas to heat, the boiler uses the heat to create steam at pressure, the engine converts the steam to mechanical effort. As the effort is expelled the gas needs to provide the replacement energy, preferably at a rate higher than it is being used.

I know what you mean about standards, It is a nightmare. In the end I found a local source of off the shelf 1/4" flare and 1/8" BSP fittings so its now easy to mix and match. With a 1/8" BSP tap I now make up my own adapters. It is confusing though as 1/8" BSP actually has 3/8" diameter thread. I've got jets from Bruce Engineering in the UK. They use BA threads and fortunately I have BA taps and dies. After a while I did notice a bit of commonality between threads being used and things from different sources started to fit together. 

The biggest problem is the gas canister fitting, but I've now got examples of most so can switch between POL, MAPP, Primus, and disposable cylinders. I have found disposable butane and MAPP type canisters (with Propane) just don't have enough go in them so I am settling on Primus right now. We don't have GAZ in NZ.

Pete


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## tups

Hello Pete,

I understand pretty well what is involved in getting water to evaporate, and also the direct link between the combustion heat of the gas and the resulting work from the engine - I teach thermodynamics to industrial engineers. But it is good to see others come to the same conclusions independently ;D

My main problem is that I have difficulty understanding and/or am unable to find good literature on the venturi effect in burners. No-one seems to have researched that properly, and the relation between air holes, their location and size, the jet size, feed pressure and mixing tube length is muddy to say the least - which is why I was so happy to find working starting values for a comparable boiler and burner size in your post. I had to lengthen the mixing tube a bit and provide more holes closer to the end of the jet for it to work better, but now it seems OK - on butane. I'm curious to see what it will do when I increase the pressure and use propane. They have pretty much the same caloric value, it is just that the pressure in a propane canister is much higher than over pure butane. 

If the gas evaporates, the liquid cools down. The boiling point of propane at atmospheric pressure is -44°C, for butane it is 0.5°C. Once the canister gets that cold, no more evaporation takes place. That is why I wrote butane is self-regulating - in the end the amount of evaporating gas is only proportional to the heat flow that is possible from the outside world through the canister wall. This is what limits the amount of gas the burner can burn in the end. The problem should be solved with propane, as this can go much lower in temperature without losing too much pressure, and if the temperature difference with the environment increases, so does the heat transfer to the canister. I found some canisters today with propane-butane mix, which I plan to use when this butane canister is empty.

Another way around the problem is to turn the butane canister upside down, so it feeds liquid butane to the line to the burner. This then evaporates in the line, unless you're unlucky and it makes it all the way to the jet, in which case the spray will get you bad flare-ups of the burner. On the track I had to leave the canister right-side up on the tender the whole time, and thus performance was paltry.

In the end I'll buy a small bottle of pure propane and see how I need to change the air hole geometry to cope with much higher feed pressure - but the shop handling that was closed on modays.

Once more, thanks a lot!

Cris


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## doubletop

tups  said:
			
		

> Hello Pete,
> 
> ................ - I teach thermodynamics to industrial engineers. But it is good to see others come to the same conclusions independently ;D
> 
> ...............
> Cris



OK so I'm the one who should be asking the questions 

On the "How much air" question I found somewhere that the gas/air ratio should be around 4%/96% and there should be a similar amount of secondary air as primary air. Primary air being the air introduced in the mixing tube and secondary air at the point of combustion. That's why I added the through tubes to the burner to increase the availability of secondary air .

How you achieve this seems to be empirical from our point of view. Air vent adjuster on the mixer tube, observation of the flame, combustion smell and in my case a pressure gauge on the jet pressure so there is a means confirming gas feed rate (jet size and pressure being proportional to gas feed and hence the BTU's that can be achieved from that gas.

I did find this site with a lot of information for propane engineers which helped my understanding. The long link takes you to a series of documents that includes details on troubleshooting systems.

http://207.200.58.35/Resource%20Library/Forms/AllItems.aspx?RootFolder=http%3a%2f%2f207.200.58.35%2fResource%20Library%2fGas%20Check%2fCETP%206.0%202001%20Gas%20Check%20Cross%20References&FolderCTID=0x01200016E31ECAED4C8E4AAEB16325DB5F5979

Also take the time to look around the rest of the site lots of stuff there.

So now my question which you may be able to answer Cris. If we were to look at this question from the "how much heat do I need" point of view we should be able to work back to "how much gas do I need to shove into the system" getting it to burn efficiently then becomes a secondary question. If we can't feed the gas its never going to work.

I know there will be a whole lot of factors that would need to be fed into any equation but we should be able to make a start.

We know boiler dry weight and it is copper, we know how much water needed to be heated to 80psi so how much heat does that need? We are now going to vent the pressure at a some rate so how much more heat has to be added to maintain our 80psi. Then we have some losses, how much heat should we allow for that? If we can define the need.

Maybe a case study for your students? You have the ideal means of putting their theorectical results to a practical test.

Pete


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## tups

Dear all, 

Well, here is a quick back-of-an-envelope calculation on how much gas you should need in an ideal world, not based on efficiencies, but simply on the amount of steam the engine goes through at a particular speed.

Lets assume (for my Rocket) a 14 mm cylinder diameter, and 35 mm stroke, with 120mm driving wheels, and 5,5 bar (80 psi) boiler pressure.
This leads to a stroke volume of 5390 mm³, four strokes per wheel rotation, and a distance travelled of 377 mm, so in order to travel 377 mm, we use up 21,6 cm³ of 5,5 bar (80 psi) steam when the throttle is fully open and the engine is performing a maximum amount of work.
If the engine would do that under maximum load while travelling at a fast walking pace (6 km/h), it would do 8.8 strokes per cylinder per second, and thus 17.6 total strokes per second.
This corresponds to 525 cm³ of steam per second, converted to atmospheric pressure. For this we need to vaporize 0,0234 moles, or 0.42g of water per second.

Since the heat of evaporation of water is 2.27 MJ/kg, we use 0.95 kJ/s of energy. This needs to be compensated by the burner.
In order to generate 0.95kJ, we need to burn 0.0203g of propane  per second. This corresponds, in an ideal world, to 73g of propane per hour.

Obviously, there will be (a lot of) heat loss. On the other hand, the full power of the engine will not be used all the time, and when the throttle is closed more, less steam will be used. This is equally true if a cutoff is used, but the Rocket wasn't that sophisticated :

I wanted to attempt a small calorimetric experiment on the loco tonight along the lines of what Pete suggested, but this was cut short by the lack of a suitable balace to figure out the amount of water in the boiler. I'll see if I can find something useful in the next few days. For now, I generated the following tables, consolidating the drill size to BTU/hr table (which was also a theoretical calculation based on simple assumptions btw ... the numbers follow a second order polynome perfectly) and the jet size data that Pete found links to, into a table that gives grams of propane going through a jet of a particular size:






I did do an experiment where I measured firebox wrapper and stack temperatures versus times and weight of the gas bottle - I had to do this with an analog kitchen scale, so that didn't exactly help accuracy, but for now it's the best I could do.






I have the safety valve blowing off at 80 psi 7 minutes after a cold startup.

By juggling the butane can and switching it between an upright and upside down position, I can control the burner perfectly. The temperature of the butane can falls to 6,5°C, which is too cold for providing a good gas stream, which is why it needs to be turned upside down for liquid butane to be fed into the line. My troubles at the track sunday were clearly related to temperature issues with the can which had to remain upright on the tender during the entire run. The ceramic element then shows a dull reddish orange glow instead of bright yellow orange. 

Some more worthless data (because of course it depends on the amount of water in the boiler - that is why a good scale would have been so very worthwhile):

With the loco stationary, I can go up from 3 bar (140°C on the firebox wrapper) to 5.5 bar (155 °c on the firebox wrapper) with the safety blowing off in 37 seconds.

I can do the same thing with a bit more water in the boiler from 2 bar up to the safety blowing off in 56 seconds.

I can keep the loco rolling while putting a load on the driving wheels by pushing down on the front end, with the safety blowing off almost continuously.

And finally, perhaps the most interesting number of tonight: I used a total of 88 grams of butane for exactly one hour with the burner running - minus a few minutes of burning my finger while trying to correct the mixture - that would be a ballpark figure corresponding to 5 psi of butane pressure with a nr 16 jet in the table above.

I'll try and locate scales that are sufficiently precise to get a better idea of the weight of the loco and the gas canister, and then I can come back with more definitive results on heat loss.

From what I observed this evening, I am quite convinced that the loco will do well on Sunday, and should be able to pull me around the track without too much trouble with this burner.

Now if only I could solve my problems with the water level showing in the sight glass being strictly unrelated to what amount of water is present in the boiler ...that would be fantastic.

Cris


----------



## doubletop

Cris

This is fantastic thanks and helps the understanding of what is going on. The only unqualified aspect is the table I provided, the inclusion of a pressure gauge in the setup would help confirm that the gas pressure was 5psi. I'm going to go and re-read in detail and see if I can reproduce the results and include jet pressure data.

From your graph below it appears to stabilise at about 220secs. I'd assume that's the system warming up?

Although I can get my boiler up to 80psi on 5psi gas pressure (#15 jet) it isn't going to go anywhere. Running with 20psi gas pressure the boiler doesn't recover and is soon down to 20psi boiler pressure and fails to negotiate a small rise on the track. With 30psi gas pressure the boiler pressure can be maintained an with nurturing get back to the safeties blowing while running. 

It may have to wait to the weekend its raining at the moment and doing this sort of experiment anywhere but outside is frowned upon.

Thanks again

Pete


----------



## tups

doubletop  said:
			
		

> From your graph below it appears to stabilise at about 220secs. I'd assume that's the system warming up?



That is actually a good question, I suppose it could be ... water will start condensing everywhere over the water level inside the boiler at this point and flow back cooler, so until the entire boiler is at the normal boiling point of water, the temperature will not rise any further. You also see the residual water in the safety valve begin to sputter and boil at this point, as well as the water in the blowdown line.
It may also be a mixing effect, where convection from the firebox into the rest of the boiler really starts going. As you perhaps know, the firebox of Rocket is a bit of an oddball design, being outside of the actual boiler. It has two tubes at the top leading the boiling water back to the boiler, and two tubes to the sides of the firebox bringing in colder water from the bottom of the boiler.
This circulation starting up by the firebox boiling over into the boiler may be the cause of this effect. The inner firebox liner is typically hotter than the flue tubes.

By the way, I've done all this without a blower or fan - due to the high smokestack the loco drafts very well, and there are no problems at all as long as you keep the firebox door closed.

The temperature of the smokebox and chimney does not get over 65°C when the burner is running, due to heat soak it heats up to 85°C when the boiler is off. This is not hot enough to damage the paint job, even without stainless steel baffle in the firebox, which on this loco is extremely difficult to fit ... I think I'll try without for now.

Cris


Cris


----------



## doubletop

Cris

On the subject of blowers I can run without one up to about 5psi of gas, once the gas feed pressure is increased above this the smell of unburnt gas can be obvious. Adding the blower aids the combustion and higher gas pressures can be used. When I'm running at 30 psi of gas pressure I must get the loco blower on before the regulator is closed otherwise there will pop as the burner goes out. Normal running sequence for coming to a stop is blower on, regulator shut off. If stopping for an extended period I turn the gas down to 5psi and shut the blower off.

On a restart, blower on, gas to 20psi, recover pressure, normal starting procedure with drain cocks etc. Once I'm running blower off, and gas to 30psi. As I've said before it will loose boiler pressure if running at only 20psi gas pressure.

By being patient the loco can be started without an external blower; 5psi of gas to get up to 12-15 psi boiler pressure open the loco blower gently and then gas pressure can be increased as boiler pressure increases and the blower goes harder. 

By the way, adding the secondary air tubes to the burner markedly improved it and flame outs now rarely occur if I follow the procedure above. The original ceramic burner was hard to keep alight when pushing a lot of gas through it.

With your calculation showing a burn of 73g/hr and the Little LEC results indicating say a typical efficiency of 0.4% am I correct in saying that would indicate the loco would really require 18.250Kg of gas to run for an hour? Which I know would be excessive I've just about managed two weekends with a 3Kg bottle when I went for a refill it had 750gm remaining. I now have a cycle trip meter on my new driving trolley, last weekend I did a total of 3.6km, with 53min of run time (in motion) and an average speed 4.0 km/hr. There was also a considerable amount of standing around time with the burner going.

Like you I need some scales so In can properly measure bottle use.

You may find this useful http://webspace.webring.com/people/ib/budb3/parts/ste.html there are many web pages with this formula, this is the first one I found. I was reading the same in a 1929 copy of Greenley's book just the other week. 

Pete


----------



## tups

doubletop  said:
			
		

> ...
> 
> With your calculation showing a burn of 73g/hr and the Little LEC results indicating say a typical efficiency of 0.4% am I correct in saying that would indicate the loco would really require 18.250Kg of gas to run for an hour? Which I know would be excessive
> 
> ...
> Pete



Hi Pete, 

No, I have calculated steam use at full throttle for a particular engine speed, assuming all heat from the burner is converted to evaporating water at 155°C/80psi.

This has nothing to do with efficiency, which is the conversion of the total heat of combustion into actual mechanical work, i.e. "what is the force integrated through time needed to move the train as it did over a trajectory". The main contributors there are rolling resistance and pulling weight up gradients. This is also why the Little LEC results are not so transparent - they have calculated the necessary constants for driving trolley resistance and the track profile, probably from a run with a dynamometer car at some point (or anyone's best guess, which is less work, but also gives less accurate results), and use these numbers for arriving at the efficiency. The numbers are not given in the article, which says "contact the organisers if you want to see the details". 

Whether the loco can actually attain this speed the calculation is based on and stay at it for extended periods of time is a different matter entirely - chances are it won't, and the difference is largely due to heat loss.

The upper theoretical limit for the efficiency of any heat engine is given by input and exhaust steam temperature. Our small engines operate at reduced steam pressure from their large cousins (typically 8, 10 or 12 atmospheres) . In addition, heat losses are far more important in our small locos. In any steam loco, part of the potential mechanical work is blown out the stack due to the lack of a condenser. The ideal scenario would be something akin to a high speed Newcomen engine, where high pressure steam is injected into a cylinder and then perhaps cascading to a few compound engines, in the last of which the steam is condensed so the cylinder reaches vacuum prior to the next injection of steam.
In practice, this has never been feasible for a locomotive.

There have been some experimental high pressure engines working at the optimum pressure for steam of about 60 atmospheres (the benefits of any additional rise in pressure are marginal compared to the draconic design requirements) , but they have never been a great succes, due to their propensity to kill their operators at some point. High pressure technology was not quite what it is today in the first part of last century. 

The 73g/h I calculated should be pretty close to the actual figure for normal running, that is, with the throttle partially shut or the cutoff reduced when the train is moving, and with periods of standing still. These times when less steam is used compensate for the heat loss, comparing for example my 88 g/h on what could be an emulation of a "typical run" compared to 73 g/h theoretically. My gut feeling is that a large part of the heat loss happens in the steam pipes to the cylinders and cylinders themselves, as well as from boiler appendages, and perhaps a minor part radiating from the boiler itself. Another large part of the heat loss is the hot flue gases blown out the stack.

Have a look at this test: 
http://www.whitetrout.net/Chuck/844/Tests/Lagging/Index.htm

The heat loss from the boiler (which has a much larger surface area than our small boilers obviously) is 13,9 MJ in one hour, corresponding to a continuous heat output of 3,8 kW.
I'll look into doing a similar experiment at some point - it could be improved upon to provide more data besides the sense and nonsense of boiler insulation.

As an aside, since the heat of combustion of 73g of propane is only 3,4 MJ, our little burner couldn't even come close to keeping this large boiler up to temperature. With 73g of propane/h a burner is equivalent to 0,9 kW (that means, it puts out 0,93 kJ per second for 3600 seconds to arrive at 3,4 MJ in an hour).

Now, if on Sunday, I find results wildly different from my guess for the gas usage, I won't hesitate to let you know 

Cris


----------



## doubletop

Cris

Thanks again for a comprehensive explanation. While you were doing that I took a look at the Little LEC results published in ME 4389 to see if I could make any sense of them. With the help of parameters from conversion websites I was able to derive the same efficiency results. See the attached it shows the calculations for each of the values.

I then looked at the results from the 2008 Little LEC available here http://www.stationroadsteam.com/LittleLEC/2008/index.htm they don't have all the parameters such as run time but realized that time wasn't required to derive the efficiency as it cancels out in the power out/power in calculation.

The track constant used by Little LEC remained a mystery until I found http://www.littlelec.co.uk/home/

In our case weighing the gas bottle before and after should allow the input BTU's to be established by way of a comparison.

Pete




Attached  

View attachment Little LEC.pdf


----------



## doubletop

This may be a bit off topic but to support gas burners you need to be able to drag the gas bottle around with you. I'd been using a riding trolley, fitted out for gas, on loan from a club member. I needed to make my own and had some basic parameters I wanted to achieve.

be lighter than the 39Kg of the loan trolley.
be able to carry me (100Kg)
be able to carry primus gas bottle
have gas controls and gauges.

This is what it turned out to be












Its made out of aluminium 20mm x 40mm x 3mm box section as we have a supplier 10 mins from the house. Once I'd machined it all up they welded it for me.







I got the bogies from One Inch Railroad in the US http://www.oneinchrr.com/index.htm. They'll supply with 119mm back to back spacing for SMEE standard tracks rather than the 4.75" used in the US.







I fitted my own design brakes as the One Inch Railroad brake kits only fit 4.75" spacing






Gas controls

Gas cutoff - red lever.
Regulator pressure - left gauge
Pilot control - small knob
Main control - large knob
Jet Pressure - right gauge






I got a bit carried away with 'features'. Once I had the loco running well my next problem was water supply so I fitted a water tank (lunch box) and pump run from 12V SLA battery. The red button on the control panel operates the pump.






The orange unit next to the battery is the gas regulator. The gas pressure being read on the left hand gauge

You'll also see from the photo a cycle computer has been installed and that proved to be very successful. However, it only measured in units of 100mtrs so is being replaced with a home made computer and display using a PIC micro. That measures distance in units of 1 metre. It's up and running and just needs to be installed.

I hope that's helpful

Pete


----------



## tups

Dear forum,

I have, over the past few weeks, tweaked my little homebrewed ceramic burner according to Pete's recipe a bit more, and I have arrived at this result:

[ame]http://www.youtube.com/watch?v=EcjDqTTnx78[/ame]

Crucial in the success were the use of propane instead of butane, allowing to push a lot more gas through the burner, and careful tweaking of the mixture by a moveable and fixable shroud over the (too many) air holes in the mixing tube.

All is peachy now - I love that little loco! Scale speed is on average 55-60 mph in the video. On the real thing, that would be beyond scary.

Some thermal efficiency testing will be done later, until now, with several test runs of about 2.5 hours total, I have used around 300g of propane.

With best regards,

Cris


----------



## Charles Lamont

tups  said:
			
		

> All is peachy now - I love that little loco! Scale speed is on average 55-60 mph in the video. On the real thing, that would be beyond scary.



Very nice little engine - goes like a Rocket? Just one thing; if the original had springs they would have been much stiffer than yours. I think the roll induced by the angled cylinders is far too much.


----------



## doubletop

Cris

I be you are pleased with that? It was going really well and I noticed the safety blowing off while under way, so plenty of steam being created. That tall smoke stack wiggling about looks a bit scary but no doubt it wasn't as bad as the video would suggest.

I'm keen to see your calculations so I can judge how inefficient mine is and maybe do something about it. As you know I tried the 450g Coleman cylinders but didn't think they held enough gas so moved up to the 2Kg Primus cylinders. You may prove me wrong and get me to move back.

Congratulations and well done.

Pete


----------



## tups

Dear all,

The picture server I used for the pictures in this thread has gone belly-up in the mean time. I tried editing my posts, but that does not appear to be possible - hence here a repost of the pictures that used to go in my messages earlier in this thread.

propane data chart





loco data





and some burner pictures





























As for Rocket, I still have not gotten around to efficiency tests, because I'm having too much fun running it!


----------



## railroader

Hello everyone,

Thanks again for your posts.  I am learning a great deal about ceramic burners, and I greatly appreciate your comments and photos.

I wanted to show a picture of my 1/8 scale locomotive, a model of the 1830s vintage Invicta, one of the first locomotives made by the Stephenson Company in the UK.   Eventually I plan to install some type of ceramic propane burner. 






[/IMG]

The model was made by an excellent machinist by the name of Jim Zeeler, who lives near Columbus Ohio.  I found it for sale on www.discoverlivesteam.com.  His shop is remarkable.  He had twenty of the same model engines on display, awaiting sale.

The engine is designed to run on coal.  I'm experimenting to make it run on propane.  Before I discovered this forum (and the Unofficial Mamod and Steam Forum), I knew nothing of ceramic burners.  My experiments have been with modified "Marty burners" which are fashioned from a coffee urn.  Below is a photo of the Invicta lifted from my work bench with a chainhoist.  






[/IMG]

The next photo is a closeup through the bottom of the empty firebox.






[/IMG]

The next photo is of the burner with fittings from two coffee urns.  It has a flame deflector, which I installed after learning from this forum.






[/IMG]

The last photo is a closeup of the burner fitted into the firebox.






[/IMG]

Please feel free to let me know what you think.

Eventually, I'll enter the world of ceramic burners with this engine.  I haven't met anyone who has done this in a 1/8 scale steam locomotive (at least not in my little world of Michigan, USA).  You guys could teach us a lesson.

In the meantime, I'm having fun running this little engine.  Here is a brief YouTube video.

[ame="http://www.youtube.com/watch?v=MQ1ZqE9IxRE"]http://www.youtube.com/watch?v=MQ1ZqE9IxRE[/ame]

Cheers


----------



## doubletop

Chris

Apologies for not replying. It appears that the new site doesn't notify contributors to posts from the old site.

That's  a great loco and I somehow suspect that your burner is the best option for a loco of that size. The trouble with ceramic burners is they fill the firebox space and getting secondary air into the flame area becomes a problem. I sort of dealt with it by putting tubes through the burner. But if you take that to its extreme you end up with a burner like yours. 

At some point I'm going to try a "Marty Burner" which are similar to yours.

http://www.discoverlivesteam.com/magazine/186/index.htm

Pete


----------



## railroader

Hello

In my last post, I showed a propane flamethrower-type burner for my 1/8 scale steam locomotive, the Invicta.   It had a baffle plate.

My goal was to open up the bottom of the firebox as much as possible, in order to let plenty of air flow in.    This was a mistake.   
The flames blew out whenever I opened up the throttle.  Too much suction from the fire tubes.  I had the same problem after removing the baffle plate.


----------



## railroader

I prematurely hit "submit."  

Sorry.

The locomotive was originally designed to run on coal.  I guess this is why so much draft was needed through the firebox.   I fixed the problem by enlarging the hole size on the exhaust port directly beneath the smokestack.  Here is a picture of the smokebox, with its door open.  You can see the blower on the left side. 






I also set a steel plate directly beneath the flamethrower jets.   I got this idea from reading the posts on this forum and the Mamod steam engine forum.







The plate is smaller than the firebox, making a 3/4 inch air gap between the plate and the firebox walls .  When the throttle opens up, suction from the firetubes pulls air through this gap, keeping the high velocity away from the flamethrower outlets.  Here is a view of the underside of the locomotive, with the flamethrower installed. 






This weekend I drove the hell out of this locomotive and the flamethrower never blew out (until I ran out of propane). 

Here is a side view of the flamethrower. 






And here is a view of the flamethrower upside down.







One last view of the flamethrower, also showing my latest creation:  the beginnings of a cow-catcher, made from a chunk of steel cut out of a piece of full-scale railroad. 






I'm addicted now. 

What does this have to do with ceramic burners?  I'm still interested in making one.  My sense is it'll perform better than the flamethrower because it uniformly produces heat across a large, flat area.....much like a bed of coals. 

Cheers


----------



## tups

Looks like great progress, Chris.
If you are happy with locomotive performance as it is, I would keep what you have, and forget about a ceramic burner.

I forcibly redesigned my ceramic burner after the mixing tube started to look like Swiss cheese from experimenting with the jet location and the location of airholes. I designed a new mixing tube with 4 elongated (about 10mm) 5mm wide slots milled into it, and the jet just shy of the rearmost edge of the hole. That worked very well last weekend, running the loco all day long, and going through 2.5 lbs of propane, without running too rich, as had been a problem earlier.

However, from my experience, having the ceramic glowing like a bed of coal is an illusion. It will do that, on low burner settings. If you crank up the gas to the volume needed to sustain high speed running, the gas flow and secondary air from the exhaust suction cool the ceramic so much it will simply be dark with blue flames - but it will put out the maximum amount of heat.

Cris


----------



## doubletop

I'm with Cris on this 7.25/7.5" guage is a big loco for a ceramic burner. If you aren't getting the heat you need with the 2 "flamethrowers" why not make an array of 4. If that's too much adjust the jets or gas pressure to suit.

If I was to make a burner for my 5" gauge Simplex on gas I be trying those Marty Burners.

No doubt Cris could quickly do the maths on how much heat would be required to be generated for such big locos but I believe with the pressure and jet sizes I'm using for the Rob Roy I doing 11KW/hr and the Northumbrian about  8Kw/Hr and I don't think its enough. I somehow doubt a ceramic burner would do the job for the larger scales, although Cris has been quite successful with his Rocket.

Pete


----------



## RickNayor

doubletop said:


> Cris
> 
> Your burner looks perfect but what you describe is exactly the scenario I had, which then proved to be disappointing on the track. In fact I was out running this weekend and my experiences contribute to my growing understanding and help me answer your question.
> 
> Pressure building seeming a little slow would indicate not enough heat to maintain the steam pressure. The problem is you can't just push in more gas without means of drawing the air through the boiler. So my suggestions, in some sort of order.
> 
> Your loco looks pretty new. It needs to be loose to enable this to work. I was told to run mine on air for a long time to run it in. I ran it for 6 hours plus keeping it well lubricated all the time. Varying speed, reversing etc. It should only need 5-10psi of air pressure to do this, so its not a case of thrashing it.
> 
> Put in the stainless baffle, unless you do, once you get enough heat it will ruin that beautiful paint job around the smoke box.
> 
> If you haven't already got it rig up some means of including a pressure gauge in the gas feed after the regulator, before the jet, so you can see the jet pressure. That way you'll get to learn what works and what doesn't. A 0-60psi gauge will do. I use guages from Norgren http://www.norgren.com8BSP 40mm gauge. They are off the shelf in NZ so wherever you are I'm sure you'll be able to get one.
> 
> Use propane if you can otherwise you'll need more butane to make it work and you may not be able to get enough gas through your burner to make enough heat.
> 
> Use an electric fan on the flue to start with, you'll see I use an old fan from a computer.
> 
> Put in the fan, start the burner on a low pressure (2-3psi) to warm things up a bit. leave the blower, regulator and drain cocks all open to let heat through the system.
> 
> After 2-3 mins shut the blower and regulator and open the gas pressure up to 5-10psi and wait for the loco pressure gauge to rise to about 20-30psi. Crack the loco blower just enough so you can hear it in the flue. Leave it like that for a couple of mins. Boiler pressure should keep rising.
> 
> Remove the electric fan. Increase gas pressure to 15-20psi. Boiler pressure should come up pretty quickly and the safety valve blow off.
> 
> With gas pressure at about 20Ppsi and running on the rollers without a load, and blower shut off it should be possible to run the loco and maintain boiler pressure to the extent that the safety blows off while you are running. If it doesn't try more gas pressure, but make sure its burning all the gas. You'll smell it if it isn't.
> 
> If you shut down the regulator remember to open the blower and reduce gas pressure to about 3-5psi otherwise the burner will go out and be at risk of flash back when you try to relight.
> 
> The gas pressures quoted are what works for me. The jet size plays a big part on the gas pressure required. I have a #15 jet. If you use a smaller jet you'll need more pressure and vice versa as the gas has still got to get to the burner at the right rate.
> 
> I also had an issue with pressure loss when running. I ran it on air, upside down, and used soapy water to trace leaks in glands unions etc. Try that
> 
> My experience this weekend re-enforced all this. My gas bottle was getting empty, which means the pressure dropped off and as I can only get propane/butane mix (LPG) the propane tends to go first leaving the less efficient butane until last. Once the bottle pressure got below 25psi and I couldn't maintain 30psi gas pressure, when running, the loco just packed up and I was back to where I was a few months ago. Its a fine line between right and hopeless.
> 
> Please re-post your question to me on the main thread and I'll copy my reply over as well for all to see.
> 
> Good luck
> 
> Pete
> _
> (just had another look at you pictures, beautiful!!!_


Can you give us a little schematic of the gas buggy/car? It is interesting but it will not blow up enough to read the gauges. It looks like you need one gauge for the tank, one for the post regulator and one on the jet?


----------



## doubletop

Rick

I was going to have a gas bottle pressure gauge but it wasn't necessary







The gas bottle connects directly to the regulator and the regulated pressure fed to the control panel






From the regulator the feed goes to the red 'T' handle which enables the gas supply to be cut off quickly. 

Then to the left hand gauge (0-60psi) to indicate regulated pressure. This should remain constant when the pressure drops the bottle is getting empty. I set the regulator at about 40psi.

Then two valves to control the jet pressure. These are in parallel the smaller one to just give a low level 'pilot' flame with the jet pressure gauge reading something below 5psi. This allows the main control to be shut off without the flame going out. The larger knob controls the main jet pressure. There aren't two jets just two means of controlling the gas flow.

The second gauge is the jet pressure gauge, between the two control valves and the jet. This is 0-25psi gauge. of course the jet pressure is dependent on the size of jet you are using and the amount of gas you can get your burner to burn. I run a #15 jet at about 15-20psi. As the boiler is coming up to steam I slowly increment the jet pressure in 5psi steps. Once steam pressure is about 30psi I use the loco steam blower and remove the electric fan and the jet pressure at 15-20 psi. Boiler pressure comes up very quickly from this point.

The push button is for a water pump for the reserve tank I have on the wagon.

Hope that helps

Pete


----------



## doubletop

Photos reinstated following the Photobucket problem 

More to do

Pete


----------



## Artieclark

Has anybody tried building a set of Walchaert gears to control the steam more efficiently?   I built such an engine several years ago but have not applied it to anything as yet.

Tom


----------



## doubletop

Artieclark said:


> Has anybody tried building a set of Walchaert gears to control the steam more efficiently?   I built such an engine several years ago but have not applied it to anything as yet.
> 
> Tom



Tom

Posted on the wrong thread???

Pete


----------



## doubletop

It’s been a long time since I posted on this thread as I've moved to loco's that are coal fired However, I still get the occasional query and it seems that this thread has become bit of a reference so I'll post this here.

I got my jets from a model engineering supplier but recently I've purchased a 3D printer and sought a supply of extruder nozzles so turned to Aliexpress. They arrived today and my immediate thought was "these are gas jets". I hadn't noticed the similarity before. It’s understandable really, hobby 3D printing gained a foothold with RepRap and where else would they get nozzles? 

Barely US$8 for 22 "jets" with shipping.

US $2.58 11% OFF|22 Pcs Nozzle MK8 Extruder Head 3D Printer for creality CR 10 CR10 Machine Heads 1.75mm|3D Printer Parts & Accessories|   - AliExpress






Pete


----------



## Donrecardo

doubletop said:


> It’s been a long time since I posted on this thread as I've moved to loco's that are coal fired However, I still get the occasional query and it seems that this thread has become bit of a reference so I'll post this here.
> 
> I got my jets from a model engineering supplier but recently I've purchased a 3D printer and sought a supply of extruder nozzles so turned to Aliexpress. They arrived today and my immediate thought was "these are gas jets". I hadn't noticed the similarity before. It’s understandable really, hobby 3D printing gained a foothold with RepRap and where else would they get nozzles?
> 
> Barely US$8 for 22 "jets" with shipping.
> 
> US $2.58 11% OFF|22 Pcs Nozzle MK8 Extruder Head 3D Printer for creality CR 10 CR10 Machine Heads 1.75mm|3D Printer Parts & Accessories|   - AliExpress
> 
> View attachment 120401
> 
> 
> Pete


Under where it says  22PCS it lists the sizes like  0.02   0.04 etc  but they are not , they are 0.2  0.4 ( ten times bigger ) its stamped on each jet  . Also the thread will almost certainly be 6mm   where normal gas jets ( at least in England) are I believe 1BA


----------



## Steamchick

Hi Guys,
I have been making ceramic burners for 25 years or more, on and off. But the technology is limited by the laws of physics, so really a surface glowing the size of a firebox cannot provide enough heat to power the loco - if the firebox has been designed (sized) for coal. The coal fire, as well as providing the "red surface of coals" also gives huge amounts of hot gas - to transfer heat in flue tubes, PLUS the hot coals radiating sideways into the firebox lower walls ( a cold gas-air mix in a box for the ceramic). AND there is the soot... These soot particles, id incompletely burned in the fire box transmit with forced draught into flue tubes and continue to burn - and radiate heat - as well as provide extra heating to the gases - in the flue tubes. All in all as designed by George Stevenson, a jolly powerful heat source!
But the ceramic burner - if adjusted to a glowing surface - ONLY provides the radiant heat from that surface, as the gases are completely burned so the Carbon monoxide is consumed - which stops burning below 300deg. C -and the exhaust gas only has the small amount of residual heat from 300deg. C to steam temperature to impart as it passes up the flue tubes. 
OVER fuelling ceramics - as explained by users - gives huge amounts of burning gas, but that is all, as the hot (not burning) exhaust in the flue tubes only has the residual heat of the gas (maybe 650deg C to steam temp) to impart. So you need a Lot of burning gas - and very fierce (fast combustion in the confined space of the firebox) to generate the heat and exhaust - that then needs the blower to drag it through the flues....
However: A solution is at hand, though only recent technology:
In steps:

Ceramic: 950deg C max.: 120kW/sq.m.
Stainless steel (wire wool) matrix: Metal fibre knitted matrix:1050deg.C. max.;200kW/sq.m 
High Temp. Stainless (ferro-chr. alloy)matrix (Sintered surface) 1050deg C max.; 250kW/sq. m.: 
Porous Ceramic burners: (Silicon Carbide porous matrix, or other modern clever materials):*1450deg*.*C max*.; *1000kW/sq.m.*

Infraglow seem to sum it up in their on-line brochure: - worth a read:




__





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					infraglo.com
				



Go-Gas have an interesting technical comparison table and clues about design.




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						GoGaS Goch Dortmund - Home
					

GoGaS Goch ist Hersteller von Produkten aus dem Bereich Prozesswärme, Heizungssysteme, Desinfektion, Wasserstoff und Gas.




					www.gogas.com
				




Also, search for "CREMADOR - Joan Lluch": as he has made a big and powerful firebox burner... - wire mesh type: - but he has a resonant noise problem to overcome.
Note: Regular stainless steel wire wool burns-up quickly: Special alloys are used by the Burner Manufacturers.
The porous matrix materials cost $100 per small block - so I haven't bought any to make myself a burner, but the 1000kW/sq.m capability is big enough to make firebox burners suitable for boilers designed for coal firing. (8 x more powerful than ceramic burners.).
Over to you guys!
K2


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## Steamchick

Just spotted this one:








						Radiant Burner Stoves: Ultimate All-Weather Stoves | MSR Blog
					

Learn more about the performance and efficiency benefits of radiant burner stoves, and check out MSR's Reactor and WindBurner stove systems.




					www.msrgear.com
				



Also,I understand - from various sources - that the preferred medium for a porous gas burner is CORDIERITE porous foams. The burner comprises an air inlet at the jet, venturi, mixer tube (as "normal") - then with the mixture entering a low-density (high porosity) matrix for cold gas mixing and heating the mixed gas, followed by a higher density (lower porosity) matrix where combustion takes place: Combustion is COMPLETED in the matrix: NO extra air is required for post combustion. But the whole of the high density matrix glows brightly at 1400deg.C. (ish) with the internal combustion taking place inside the material. - like 1 big hot coal! The exhaust is supposed to be very clean. - So loco drivers will not get headaches from the CO normally blasted up the funnel in great quantities.
Bring it on?
K2


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## fcheslop

A big advantage with a radiant burner. The velocity through the flue is slower giving a greater dwell time  to absorb the heat
I have recently built a simple marine centre flue boiler and comparing it to a water tubed flue of the same size the flue with no tubes heats the water faster and the outlet temp is nearly 80c lower .Also the temp along the length of the flue is reasonably constant at 510c to 620c
Its very 16mm loco in form and for my toy boats no idea how it would scale up
Often wonder if in larger loco fittings doing away with the blast system would make a more efficient set up
Another benefit is the amount of gas used drops by about 1/3 reducing freezing and cooling of the gas tank.Using just butane with an ambient temp of 6c the plant will still run a 1/2 by 1/2 double acting wobbler at 300rpm
radiant material canbe bought from the jewellery suppliers like Cousins
For mesh you really need to consider nichrome mesh as it last far longer than stainless but I tend to get around 12 or so burns from stainless. The likes of Wilko in the UK sell frying pan cover for a couple of quid and the wire just happens to be the right size to make number 3 jets double bonus for the penny watchers like me
cheers


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## Steamchick

Good stuff! But I wonder if there is really much heat flow from the gas to the boiler in the flue tubes? - The temperature should drop from around the 600 degrees (post combustion) to nearer 200 degrees (beyond boiler) if the heat is being "sucked" from the gas into the boiler. I would be tempted to put a wire coil inside the flue, not touching the side walls, to gain heat and radiate it into the side walls of the flue. (Black infra-red can't be seen but is still very effective). Also install some very loose stainless steel wire wool inside the wire coil. - The hottest gas will be in the middle. The coolest gas at the surface of the flue tube. You should heat the "wire wool" (or other) in the hottest gas so the heat can radiate across to the walls of the flue. That should increase efficiency of the heat flow into the boiler....

 I have made Ceramic (and other) burners ranging from a no. 3 jet (0.2mm) (for Mamod boilers) to a 0.49 jet: - which was for Propane on a ceramic for a 9" dia boiler - 2 ft. tall. - That one was "short" of a lot of flue tubes, so needed the ceramic to create most heat suitable for heating the bottom of the vertical boiler, rather than the (Stevensons) loco multi-tube boiler that maximises the heat flow in flue tubes. I did some very crude calculations and decided the 9" dia boiler had very little flue CSA to take a 7kW or so simple gas burner. So I made a rectangular burner about 7" x 5" powered by 15psi Propane. - Rated at around 4.4kW. (see "International Toy and Model Steam Hospital" for the boiler). I've not seen many ceramics on models this big.
By comparison, a friend has researched the "heat" required for his 4" vertical boiler to drive his Clayton Wagon: 27kW: So it explains easily why radiant ceramics just don't have the rating to achieve the power density required for Coal-fired loco fireboxes! a 4" circle  of radiant ceramic is only a single kW or so! - Good for making Tea....
However, as used in domestic central heating boilers, a 5" x 3" plaque can be used (non-radiant mode) as a surface diffuser for 25kW or so of gas flames in the water-tube boiler. - I understand  successful 5" locomotives usually have around 30kW (or more?) of gas combustion in the firebox - using some very fierce multi-nozzle blow-lamps. (look-up J.E.Nystrom).
K2


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## fcheslop

All good stuff and very interesting
The idea for the small plain flue is to keep gas velocity low allowing more dwell time. It seems to work from the rough ars££ experiments I can conduct
Using different burner ideas the flue exhaust has dropped about 140c and the gas consumption has also gone down. The engines rpms have gone up to near what I need for this wee boat. May have to take it to Roker for a test run when she is finished although a Stirling engine based on the Glasgow engine is on the bench.
Nothing new the loco guys have used the idea for sometime in the small scale stuff
The Clayton is greedy for steam or at least my engine is. Although she has not been steamed for over 20 years and needs a full rebuild. Maybe someday it will happen.
I only build the smaller stuff now just cannot afford the big toys and no longer wish to be in a model engineering club
keep well


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## HMEL

Gentlemen:
I have been fascinated by these series of posts.  I spent a good deal of my career doing combustion/ steam calculations.  So I will comment.  If you know the required steam flow per unit of time you can calculate the heat input.  The flue gas heat loss is significant due to the water of combustion.  So when you calculate the heat required for steam generation you must divide by that efficiency  to get fuel actually fired.  Its very difficult to get efficiencies above 85% unless there is a condensing heat exchanger involved in the unit. Only in modern furnaces are you likely to find that.  Dividing the calculated steam heat requirement by the efficiency gives the minimum burner size for the system.  After that its a matter of how well the boiler is designed to capture the heat, and how much excess air you are using in the combustion chamber.


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## Steamchick

Tell us more... I use "Model boilers and boilermaking" for a basis of my calculations, along with some theoretical gas consumption tables per jet size, and a huge fudge factor (<70% of expectations become reality). The biggest difficulty I find is in estimating heat losses... so I really go to town with complex insulation on my boilers. (Just a sheet of "bought insulation" is laughable to me!). I feel boiler and pipework losses are the most neglected areas of model engineering.
Any advice is welcome!
I am also a believer (as an ex-design-engineer) in calculations predicting optimistic results in the hands of the inexperienced. I spent some of my life being inexperienced  in most things! (Now I reckon I'm inexperienced  at everything). 
Ta, K2


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## Steamchick

K.N.Harris advocates the only air in the fire-box should be primary air, as any un-used secondary air will reduce efficiency of the boiler. Many (especially people converting coal-fired boilers to gas) want lots of excess secondary air... ceramic burners lend themselves to zero secondary air when we'll designed and in a suitable boiler. But (Imho) boilers designed for coal firing seldom offer optimum heat transfer for gas firing. Not being a chemist, I can't calculate the volume of gas passing through flues for gas and coal fires of the same thermal output, but I guess the coal fire produces denser gas with all the carbon dioxide produced...so can get "more power" from the same flue CSA. Alternatively, gas needs bigger flues for the same power as a coal fire. - Is that correct?
K2


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## wazrus

A most interesting thread. I had come to conclude that gas burners as applied to model steam locomotives were something of a black art, even given that there's a gentleman in Finland who has used 'in flue' burners, which I realise aren't necessarily the subject of this thread. I have two 'gas specific' boilers in 4mm copper, flanged and almost ready to silver-braze. Both have 38mmx3mm copper tube flues. There are two flues in one boiler, three in the larger. The larger boiler is about 180mm diameter. I have fiddled for ages with all sorts of burner lashups and I feel the stainless steel mesh, as a sort of 'glow cone' in the flue works, but is perhaps not the way to go. Interesting, though is the idea for nichrome mesh, but just where does one get that? Nichrome wire I do have, but mesh?
I've made many and varied gas jets for all sorts of positions and I've become fairly adept at drilling 0.4mm holes in brass jets. But 0.4mm doesn't seem to be small enough. Then there are jets available for 3D printers which look promising, but I doubt they'd be small enough, either. The ceramic burners, in conventional fireboxes being discussed, seem not to be able to supply heat in the flues and that was another part of my reasoning for the 'gas specific' (or 'in flue' burners) design. The Finnish gentleman suggests as few flue tubes as possible, as does Kozo Hiraoka in his Pennsy switchers, both of which are coal fired. What I'd like to find is a design for 'in flue' burners. I'm weary of the empirical methods. I have more than few failed experiments! There are a few designs for poker burners on the 'net. Ron Reil's come to mind.
I live in Australia and even given our abundant supplies of coal, it's difficult to source good steaming coal. Some clubs do actually import Welsh coal. We once had a supplier of 'char' who has since ceased trading, therein lies yet another part of my reasoning for gas specific boilers. These boilers are very much simpler, particularly in flanging and staying. I use the Australian Miniature Boiler Safety Committee's methods for calculations and I find the AMBSC specs. to be indispensable.


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## Steamchick

Hi Wazrus. My experience. In the UK there are model suppers (e&@y) that will sell jets 0.15mm and 0.2 mm and above for £2.50 inc. P n p. But I buy cheap Chinese drills for 0.25 mm and above and drill my own jets.  Not perfect, but I buy 10 drills for the price of 1 jet, so I' m on a winner at 2 or more jets per set of drills.
But I wonder at the power you need for that decent sized boiler at 180mm diameter. Jets basically limit the gas that you can have. So look-up some tables for the BTU per jet size, convert to kW, and assume you need over 30 kW of burning gas to power a loco big enough for your boiler, and I guess you'll need 2 or 3 burners at 0.4mm jet! So why do you want smaller jets?
I also think for you dia 35mm fire tubes you need blowlamp type burners, with cones of radiant material. What may work for you is a few coils of nichrome wire. Say that you have 0.5mm wire. Make coils at 10mm, 14mm, 18mm, 22mm and 26mm, and with some wire spacers fit them inside each other, and use a propane blowlamp into the flue tube with the coils, and see if you get a good glow for a long length. The dire is the have visible red heat for 2/3rd of the flue tube length, but use the coils full length as even the black heat from wires will pump lots of radiant heat from the gas exhaust into the flue metal walls. Check exhaust temp of the exhaust from the flues, then you can compare wire heat exchanger configurations. Remember. Gas below 350deg.C. will stop burning, so if the gas temperature is over 350 just after the last flicker of flame, then you have burnt all the gas. Otherwise you'll be creating a Carbon Monoxide exhaust. That is dangerous, so please experiment outdoors, or have a CO detector (and believe it!) If indoors.
For those that don't know. CO in any amount causes permanent brain damage. In your life, the more CO you inhale the quicker you'll bring on dementia, so avoid breathing it wherever possible. End of safety message.
The alternate way to have a gas burner is to have a very large surface area of radiant: e.g. a large flat ceramic or wire mesh radiant burner the whole length of the underside of a long horizontal boiler, with all the gases directed to one end and through longitudinal flue tubes. My stationary boiler is this configuration, but most locos would not suit this (conventional designs that is!).
Cheers.
K2


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## Cogsy

Steamchick said:


> For those that don't know. CO in any amount causes permanent brain damage. In your life, the more CO you inhale the quicker you'll bring on dementia, so avoid breathing it wherever possible. End of safety message.



This is overstating the risk and being alarmist in my opinion. Obviously too high a concentration is very dangerous but there is a threshold where damage starts to occur and we are all routinely exposed to at least some CO as a product of almost all combustion processes (including the humble log fire). To suggest that minute amounts of CO exposure contribute to dementia is completely unfounded in literature. Even brain injury organisations do not make such claims : LINK.


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## Steamchick

Sorry Cogsy,
Seems I have the wrong answer again..., I just remember what my school chemistry teacher told us about smoking. The CO combines with haemoglobin to form Carboxy-haemoglobin, which in turn blocks oxygen transmission to the brain - causing headaches, permanent brain damage, and potentially death... But I have no idea what concentrations we normally live with - having grown-up with coal fires, dirty vehicle exhausts, paraffin heaters in the front room, smokers everywhere until less than 20 years ago, and the teachers (most of whom smoked) said there was enough CO in a cigarette to cause "some" damage...
When I have a major blow-lamp job that sets-off the CO alarm in my garage, (Rarely!) I do the sensible thing and get out and ventilate the garage. - Because I don't know any better... But my model boilers (burners) don't set-off the CO alarm.
And I was told that my Mother's dementure in Old age was caused in part by a lack of oxygen to the brain, that occurs as the body ages. But I haven't studied dementure, just know it isn't good.
I'll have a beer and crawl back into my corner... - or does the alcohol affect the brain?
Cheers mate!
K2


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## fcheslop

No need to drill 0.2mm holes for jets ,Simply drill to 0.4 and swage the hole down around a correct sized bit of wire. My lathe wont go fast enough to drill .2mm . The loco guys have used the idea for years
I tend to make 10 blanks drilled at 0.4 then swage them to the size I need
On my simple marine boilers I find the burner csa should be no more than 1/3 of the flue area. They must be only fed by primary air or at least the ones I make?
The nichrome mesh is available on ebay and is sold for something to do with those ecig thingy ma bobs.
I do use steam tables and start any boat build with a scale speed in mind and start with the prop this gives rpm this gives steam consumption and so on
with a good bit added for losses
A wee video of an experimental Cracker

And a wee plant for a 10 inch Puffer


Just built for the fun of it
A pic of the simple marine boiler
keep well
cheers


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## HMEL

Steamchick said:


> Tell us more... I use "Model boilers and boilermaking" for a basis of my calculations, along with some theoretical gas consumption tables per jet size, and a huge fudge factor (<70% of expectations become reality). The biggest difficulty I find is in estimating heat losses... so I really go to town with complex insulation on my boilers. (Just a sheet of "bought insulation" is laughable to me!). I feel boiler and pipework losses are the most neglected areas of model engineering.
> Any advice is welcome!
> I am also a believer (as an ex-design-engineer) in calculations predicting optimistic results in the hands of the inexperienced. I spent some of my life being inexperienced  in most things! (Now I reckon I'm inexperienced  at everything).
> Ta, K2


Will start with the burner size.  Boilers design is part art and part science.  So to start off with will go with a small boiler that needs to have its fuel input evaluated so we can estimate the burner size.  We want to know in calories or btus how many are needed. At this point it does not matter what the losses are we want the theoretical heat input.  Forgive me but I will use the btu system.  Its the same method for the metric system.

Lets say this model boiler has a steam output of one lb per hour and its operating pressure is 5 psig or about 20 psia (absolute).  From the steam tables found in textbooks or now on line we determine that this lb of steam has 1157 btus per lb of energy.  Now technically I should give credit of the energy of the incoming water and it will range between  18 and 150 btu per lb depending on the water temperature. but to make my life easier for this simple example I will ignore it.  Now we know from various calculations of combustion that the water of combustion will comprise a major heat loss up the stack.
A good coal will be about 85% whereas gas might be in the range of 78%.  So because I know nothing is perfect I choose a number of 75%.  I take my 1157 and divide by .75
That means I have to deliver 1542 btus in fuel whether I burn coal, gas , or oil. For grins I want coal and it has a heat value of 10000 btu per lb. And for one hour of operation I will need about .15 lb of coal for my steam engine to operate for one hour.  A gas burner would be a little trickier because we have to consider burner size operating pressure, but it can be done.  Ceramic heaters would also have to put out 1542 Btus in an hour.

But this is an area I do not know very well.  I would think that a ceramic heater would not be capable of as much thermal radiation heat transfer.  A furnace is designed to absorb this heat with the rest being absorbed in the back passes of the boiler.  The flue tubes absorb heat by convection heat transfer.  You want these to be as clean as possible with an acceptable pressure drop.

So I hope I haven't taken the fun out of making a model steam boiler.  But I will tell you even the big boilers face issues in the design and start up.  And we only just covered the numbers for fuel input.


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## Steamchick

doubletop said:


> I got a PM from Tups (Cris) for more details on the replacement ceramic burner I have made. This one works and if I dont forget to open the blower before I stop running it doesnt go out.
> 
> Some of this is a repeat from the Rob Roy thread but for completeness Ill do it again here and hopefully by the end it will all make a bit of sense;
> 
> The problem I had been having with running my loco successfully on gas was although I could get the engine up to pressure relatively easily maintaining it was a problem so I ended up going round the track in short runs followed by a recovery of pressure then on again. On the assumption that the more heat you can get into the engine the more steam you make and keep up the pressure. I have been experimenting with burners and learned something from the exercise. Some of it is blindingly obvious but it has helped me understand what is going on, or not as the case may be.
> 
> The basics being.
> ·    To get more heat you need to burn more gas (I said it was blindingly obvious stuff)
> ·    The amount of gas you burn is a factor of jet size and jet inlet pressure.
> ·    You need the right balance of primary and secondary air to ensure complete combustion (its about a ratio 1:24 gas:air for propane (4%:96%)
> I made myself a test rig so I could see what was going on. Regulator on the gas bottle, Input pressure gauge and output pressure gauge after the gas tap
> 
> Gas Control Rig
> 
> 
> 
> 
> 
> 
> 
> 
> 
> The assumed problem with the ceramic burner was that it couldnt get enough secondary air. If it is running on the electric blower its fine, on the steam blower its fine. But add more gas and the engine whistles like kettle as it tries to draw air through the holes on the firebox door. If the pressure is too high, and the blower is off, it flashes back with a huge pop or just goes out. If it goes out there's no indication as you can still hear the gas flowing. Not good
> 
> My starting pint was the local guys who had given me a lot of advice based on the success they had with gas firing their locos.
> 
> First was to put a baffle on the front of the burner to keep the flames in the firebox for a while rather than shoot straight down the fire tubes. This keeps the heat where you need it and stops you melting the paint on the smokebox. Believe me it works, I ran the loco once with it out and the smokebox paint job looks a bit sad now.
> 
> Stainless Baffle on original burner
> 
> 
> 
> 
> 
> 
> 
> Baffle in the firebox, note its at the fire tube end not the fire door end.
> 
> 
> 
> 
> 
> 
> 
> (_I am convinced this is a major contributor to success)_
> 
> 
> The next was make a new burner I started with making a new burner based on some old magazine articles, the intention being that the gaps between the tubes would allow enough secondary air.
> 
> 
> 
> 
> 
> 
> This didnt work too well and made a couple of versions but they just didnt give the heat and there was lots of un-burnt gas.
> 
> *New Burner*
> 
> I then turned to resolving the secondary air issue with the ceramic burner I had seen a version of a burner with tubes running through it. I wasn't about to hack my burner about in case I was wrong so set about making a copy
> 
> All the parts alongside the original
> 
> 
> 
> 
> 
> 
> 
> New and old
> 
> 
> 
> 
> 
> 
> 
> 
> New burner with the lid off
> 
> 
> 
> 
> 
> 
> Installed in the loco you can see the baffle in the front
> 
> 
> 
> 
> 
> 
> 
> 
> Make sure that the burner is as high up in the firebox as the jet holder will allow e.g hard against the foundation ring.
> 
> The dimensions for mine is 26mm high, 42mm wide 85mm long. This just fits in the firebox allowing for the ends of the stays and a little bit of room for the baffle
> 
> Through the middle are 2 x 12mm tubes for the necessary secondary air . To hold up the ceramic there are 2 x 15mm sleeves around the air tubes and strips of copper soldered on the inside edges of the body.
> 
> The jet holder is 38mm long 12mm dia brass drilled 8mm for the jet assembly, It is cross drilled with 6 x 5.6mm holes set at about 60degrees. The jet is a #15 held in with 6BA screw. The jet holder is mounted as low as it can be in the burner body. I'm sure it can be longer, as your installation would require.
> 
> My original was stainless steel, this one is copper, as thats what I had. Im sure brass would be just fine. (either way16-20swg)
> 
> I got my ceramic from Bruce Engineering (Polymodel) in the UK
> 
> Polly Model Engineering: Bruce Engineering, Model Engineer's Supplies
> 
> It cuts really easily; I did the holes for secondary air pipes by using an offcut and twisting it slowly as it worked through the material.
> 
> See these drawings from Sandy C his burner gives a good view of a similar sort of burner albeit smaller and no secondary air holes. However it give you a good idea on sizes. Most of my burners have had some basis on this burner from Sandy and there does seem to be some commonality with parts.
> 
> Home Model Engine Machinist Forum
> 
> *Running with it*
> 
> As with any loco a blower is needed to get the burner running otherwise youll get lots of flame out of the firebox door. I start at about 5-7psi gas pressure with the blower going, it doesnt need much of a blower, I use a computer fan in a cut down plastic funnel on a long coper tube so the whole lot doesn't melt. That said with the baffle it not like there's flames shooting out of the loco flue.
> 
> 
> 
> 
> 
> 
> 
> Once a bit of steam pressure is available (5-10psi) the steam blower can be opened and the external fan removed. As steam pressure comes up more gas can be applied. I find that 20psi max is good for my burner on this loco. It takes only about 10 mins from cold to full steam pressure (80psi), my boiler takes about 500ml of water.
> 
> OK I understand theres a but of reluctance to go to gas burners, but when they work they work pretty well, and clean up at the end of the day is just about zero in the firebox area. And if you have a problem with water, as I have been having on my small loco, no grappling for the dump pin. Just shut down, sort the water, if you've got steam pressure and bit of steam blower and re-light.
> 
> Hope that is of use to somebody
> 
> Pete
> 
> PS
> 
> For those of you who missed it, here it is running
> 
> [ame]
> 
> Dodgy track at the end caused it to slow and stop



Unfortunately, since 2011 Sandy C Appears to have dissapeared...?
So the link to his burner design does not work for me.
One point I note is that the air supply through the burner is too small for the jet. Using  a #15mm jet (~0.34mm dia. ??) you should have at least a 12mm hole up the mixer tube (for Butane at 15psi: Propane at 20psi) otherwise you can't  get enough air into the burner body for the flames to burn properly on the ceramic. - You may be able to get away with a 10mm dia properly designed venturi, as gas n' air flow is super-complex.... (literally "Aircraft" and "rocket" science!!). Hence all the secondary air and forced draught needed with this burner with only 8mm dia mixer tube - which should be at least 7 x the diameter for max draught (air ingestion) from air hole to end (actually only half as long as needed).... But the secondary air from the 2 tubes through the middle of the burner does not make a compact, intense flame - needed in a small firebox.
So although you manage some success, a properly sized and design venturi air intake is needed to get the best from the burner. I would even suggest there is un-burnt gas (lots of CO) in the exhaust, as flames will not propagate very far up the flues before cooling below combustion temp for the CO and residual air in the exhaust gases. You really need the burner to be "roaring" with flame noise so all the gas is burned in the fire-box without touching the firebox walls. If the ceramic is a mid-orange, it should not "melt or crack" and will give the max radiant heat possible - which will all be absorbed by the walls of the fire-box - before the hot exhaust gases do their heat transfer in the flue tubes. Actually, the best efficiency is when the flue gases at the chimney are nearly the same temperature as the steam (at pressure). You can't get below the steam temperature in flue tubes without sucking heat from the steam! For max power, you'll waste a lot of heat out of the chimney, but need to pump-in a lot more heat.
Poorly designed burners give gas firing "bad press".
C'est la guerre.
K2


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## wazrus

Just noticed the re-appearance of this thread. I'm not entirely 'au fait' with the computer processes. However, I've had my 'gas specific' boilers on hold since 2017 due to health issues: nothing to do with Co! I'm sort of in the process of getting under way again, but there's a lot of back-tracking to do. I do note the remarks re venturis and I've made more than a few of those, too. Further, the 'pipe burner' types I've seen on the 'net seem to get away with pretty much any old venturi. Some even use pipe reducers. I had though it'd be vastly more scientific than that! I'll try to work out how to attach pikkies to my next, but one gas burner type I have used is known in culinary circles as a 'Mongolian' burner and this uses a circular 'manifold', around which are spaced as many burners/jets as you'd like. I did sort of copy the idea, using a steel body instead of the cast iron manifold, on which i mounted about eight burners. This setup was, I thought, very successful in open air, pumping out a very hot, blue flame, in fact the flame was almost invisible: but it was plenty hot! A nice, big bushy flame, just right for a vertical boiler I was fiddling with at the time. As Steamchick says, the gas-to-air ratio is the critical part of the business and the reason I concluded burner design to be something of a black art. Making jets was another exercise, but not in futility: in fact, i though mine were quite successful. Lathe speeds just aren't enough, so I used a small pneumatic die grinder, spinning up to 30,000 rpm and this, together with mounting the jet in the grinder chuck, did the needful. Like, you, I buy those cheap Chinese drills and mount 'em in a chucking arrangement which I feed to the rapidly spinning work by hand. It worked quite well, but the jet design itself is lacking, in that I used an installation screw slot across the jet face. However, I've sourced some #mm A/F brass hex, which should allow easier access.


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## Steamchick

Maybe it will help if I say a ceramic or other burner is like the all too familiar car engine (for some). An engine has been design and tuned for a certain power output. A burner likewise. The car engine has intake ports designed to be big enough for the power required - but not a lot more!  And tuning for extra power shortens the life-time of the engine. Likewise the ceramic burner. If you use a bigger fuel jet than the air intake is designed to take, then the rich mixture will not produce extra power, rather it will burn less efficiently and use more fuel to make less power with dirty exhaust. Likewise a ceramic burner. Too big a jet, or too much gas (pressure) creates a rich mixture by filling the mixture tube with gas and not being able to suck-in enough air, so the fuel-air mix does not burn completely. Therefore the need for secondary air. The correct mixture gives a "High powered" twin blue cone flame. In the light blue core cone, the hydrogen burns with some oxygen from the air, and the carbon burns to carbon monoxide with some oxygen from the primary air. In the outer dark- blue flame, the carbon monoxide (poisonous!) burns with more oxygen from the air, hopefully all from the primary air-hole. If this burn is compact and a good conical shape it will be the hottest, as used by blow-torches to heat metals for silver soldering, welding, etc. But if there is too much  gas, = not enough primary air, the carbon monoxide flame has indistinct edges where it mixes with secondary air, often not completely, so sending un-burnt CO up the flue, where it poisons the atmosphere. On cars, CO emissions have been virtually banned as a toxic and environmentally harmful exhaust gas. 
So the ceramic burner - and other radiant burners - when properly designed and certified by industrial manufacturers - are made to be clean and efficient burners. Many "amateur" burners are neither clean nor efficient. (Been there, done that, made better burners!).
So my message is simple. Don't use a jet or gas pressure higher than recommended by the manufacturer. Do check the combustion is completed in the blue cones, and not reaching any metal of the firebox.
You can buy a CO meter for 30 quid (less maybe?) that will tell you if the exhaust is clean (= good combustion). Use a Rooney CO alarm in you garage, or workshop, when firing any gas appliance inside. Turn OFF gas and GET OUTSIDE. When the alarm sounds.
Enjoy!
K2


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## Steamchick

fcheslop said:


> ............ Using different burner ideas the flue exhaust has dropped about 140c and the gas consumption has also gone down. The engines rpms have gone up to near what I need for this wee boat. May have to take it to *Roker *for a test run when she is finished...........
> cheers


Hi FC Heslop: When you mention Roker.... in Sunderland? - why not come along tomorrow (19-Sept.) for our Open Day at the Model Engineers' club? - I'll be in't gazeebo next t' small sunken garden track - probably steaming (gives me something to do when there's no-one around)...?
From my experiments (with a 2" diameter flue on a 4" diam. Cornish Boiler) I found a blow-torch type burner was limited to a 0.3mm (no.12?) jet.... due to back-pressure from 6 x 1/2" dia. flues in the second half of the fire-tube after the 2" dia. fire-box end? When I made a tube of wire wool about 1 1/4" ID x 1.3/4" OD, with an end about 1/4" thick, I found I could increase the burner to a 0.35mm (no 16?) jet. About 1/3rd. MORE gas being burnt. I reckon this was the effect of the much increased radiant heat in the Fire-tube, also giving cooler gas in the flue tubes (cooler exhaust has less volume than hotter exhaust - hence lower back pressure). I haven't done the calcs, but the jet size does tell a useful story. The visible orange and red radiant zone is all around the wire tube for about the middle 3" of the 5" total length of wire wool tube. But the infra-red "black heat" from the rest of the wire wool tube will also be transferring heat by radiant means to the fire-tube, so cannot be ignored.
Enjoy!
K2


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## Steamchick

Perhaps I should add... I have studied a few coal and gas fired boilers, and compared the "advantages" of radiant + "conducted" heat in the fire-boxes versus the "conducted" heat from hot gas in flue tubes, and considered how a flame burner (very little radiant heat) versus a ceramic radiant perform. The limiting factor is a "pressure-volume" factor of the restriction of flue tubes. A coal-fired designed boiler will have relatively long and small CSA flues, but manages to fire the coal and generate huge amounts of exhaust because it is forced - by blower or blast from engine exhaust. But comparing non-forced gas systems (the only pressure gradient being from gas jet and combustion pressure above atmospheric, pushing gases through the flues to an "atmospheric" pressure in smoke-box) I found that for boilers with long and small ID flues, a flame burner is nearly as effective as a radiant burner... due to both being restricted by the amount of gas that can pass up the flues. In fact, considering the exhaust gas temperature of "roaring flames" versus radiant burners, the boilers with long a small flues can absorb the heat from this gas, but are simply innefficient for the exhaust from typical radiant ceramic burners. In one case, the calculations indicated that the "maximum" burner (camping stove roaring type) could give the same "boiler output" because the flues could absorb lots of heat, whereas the ceramic was hardly better, because the "radiant" was half-lost shining straight up the flues to the top of the smoke-box dome! - and there was much less heat in the exhaust gas for the flues to take-up. But for many boilers, even a 10% improvement by using a radiant burner in the fire-box will be better than just a flame burner in the firebox, at the gas jet and pressure to reach the limit of "flue-gas-flow".
My studies are suggesting that the best radiants are as per the woven wire wool industrial radiant burners now being manufactered by various industrial burner makers in sizes small enough for the model boilers. e.g. Beakart... Furinit®. a 100mm x 45mm burner can produce18kW  - according to the brochure!





Enjoy! (safely!)
K2


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## Steamchick

As Steamchick says, the gas-to-air ratio is the critical part of the business and the reason I concluded burner design to be something of a black art. Making jets was another exercise, but not in futility: in fact, i though mine were quite successful. Lathe speeds just aren't enough, so I used a small pneumatic die grinder, spinning up to 30,000 rpm and this, together with mounting the jet in the grinder chuck, did the needful. Like, you, I buy those cheap Chinese drills and mount 'em in a chucking arrangement which I feed to the rapidly spinning work by hand. It worked quite well, but the jet design itself is lacking, in that I used an installation screw slot across the jet face. However, I've sourced some #mm A/F brass hex, which should allow easier access.
[/QUOTE]
K
Hi Wazrus. I was interested in your post. The "Mongolian" burner arrangement you mention has been mastered by a few - Marty burners have been quoted in some posts, and another guy (J. E.  Nystrom? Someone will correct me as my memory isn't perfect!) Has published his Christmas tree design in a magazine. I know a guy with a 4in vertical boiler for his Clayton wagon who has used 3 Xmas Tree burners successfully. He rates the whole burner at 27 kW max on Propane, and has now mothballed the coal fire grate and shovel. I am trying to advise someone in the club on how to gas fire his 3 1/2" 0-6-0 loco, with a grate 45mm x 85mm... I really have no experience except some reading of others' successes, so would be glad to know of your firebox size, and your "best" burners? - jet sizes and number of jets?
On making jets... I have gone a different route. I found my 1000rpm hand grinder was too fast for 0.30mm drills and below, as the end just flew off over 8000rpm! Imperfect centre in the collet I guess... and centrifugal forces flung the drill to parts unknown.... but I have success with a very accurate chuck in the lathe tailstock.... and at a relatively slow speed 
(below 1000rpm) carefully and delicately feed the tailstock mounted drill into the jet, held in the chuck. Lots of practice, and a couple of dozen drill bits later I can fairly accurately make 0.25mm drilling in brass.. I pre-drill so the jet hole is between 2 and 3 mm deep into a 1mm feed hole.
But the key to success is a centre hole, that is barely a pin-pick dot made by a very sharp conical dremel bit with a sharp centre. This too has been mounted in the tailstock, 1 operation before drilling. The accurate centre ensures the sub-mm drill doesn't wander and go over-size.
I also use hex brass rod to make jets now, but for many years simply used 3/16" round bar, and filed 2 flats - to suit a primus proprietary jet tool.
Hope this helps,
K2


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## Steamchick

Correction, my hand grinder does 16,000 rpm. - just a tad more than 1000 rpm... the 6 makes a big difference!
K2


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