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Junk_Enginerd
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[*] posted on 29-8-2020 at 01:54
DIY burners and torches


Is anyone here making high performance burners and torches? It's a subject that I think is really interesting. It'd be cool to discuss this with others a bit.

I've made quite a few experimental burners for different purposes.

I made a 100 kW liquid fuel burner for metal casting that's been of great use to me. It's based on a pressurized air driven degreasing sprayer. That tool probably has a better name in english, but I can't recall it at the moment lol.
I run it on gasoline, E85(ethanol fuel mix) or diesel depending on the needs. E85 is the "easiest" fuel, it works most reliably and isn't too picky about fuel/air mix, so it's what I use the most.
Diesel is better for reaching the highest temperatures, and is better when I want to melt brass/copper/cast iron and is significantly cheaper since it's a LOT more energy dense. It's more finnicky though. The range of fuel/air ratios that work well is narrower, and it's difficult to ignite it properly if it's not being sprayed into an already hot furnace.
Gasoline is my last choice, it's a lot like diesel except more volatile of course. It tends to get "explodey" if you're not igniting it properly or you're in the wrong fuel/air ratio. It likes to launch my furnace lid. Mostly a nuisance rather than anything dangerous though.

I also made a forging burner from scratch, that I typically run on E85. It's a little smaller at ~20 kW. It's built on the same principle as the degreaser; a center nozzle that accelerates air and draws in and atomizes fuel from its circumference which is a larger diameter tube surrounding it. An adjustable cowl around the nozzle can be adjusted via threads to provide a larger or smaller gap around the circumference to adjust the fuel/air ratio. Also implented a fuel valve adjustment as well as an air pressure regulator to be able to control as many aspects of it as possible.

I'm currently trying to make a good surface mix oxygen/propane burner for glass work, and it's proving to be quite a challenge. Drilling and generally working with <1 mm holes and tubes is seriously difficult. Add to that all the aerodynamic phenomenons that don't tolerate any surface finish variations or burrs...

Has anyone DIY'd a glass working torch? They're so ridiculously expensive. I'm not really serious enough about my glassworking hobby that I could justify spending hundreds or even thousands of € for one...
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macckone
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[*] posted on 29-8-2020 at 08:05


Glass working torches are more precision devices than a metal melter.
You can make one from copper parts but you still need hoses and regulators for the propane/oxygen or hydrogen/oxygen mix depending on the type of glass. Borosilicate is usually hydrogen/oxygen mix from what I can tell. There are videos online about making HHO torches. But for real glass working you need compressed gas.
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wg48temp9
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[*] posted on 29-8-2020 at 11:25


Quote: Originally posted by Junk_Enginerd  
Is anyone here making high performance burners and torches? It's a subject that I think is really interesting. It'd be cool to discuss this with others a bit.
I've made quite a few experimental burners for different purposes.
snip

I'm currently trying to make a good surface mix oxygen/propane burner for glass work, and it's proving to be quite a challenge. Drilling and generally working with <1 mm holes and tubes is seriously difficult. Add to that all the aerodynamic phenomenons that don't tolerate any surface finish variations or burrs...

Has anyone DIY'd a glass working torch? They're so ridiculously expensive. I'm not really serious enough about my glassworking hobby that I could justify spending hundreds or even thousands of € for one...


I have made Bunsen burners and a Meker burner for higher temperatures. I experimented with them to understand the flame stability.

My last experiment was with DIY classic glass blowing torch (inner air jet with an outer coaxial gas supply) with preheat on the air supply. The idea was to make a propane air torch hot enough to use on borosilicate glass.

What do you want to discuss?




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

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[*] posted on 29-8-2020 at 13:39



Quote: Originally posted by macckone  
Glass working torches are more precision devices than a metal melter.
You can make one from copper parts but you still need hoses and regulators for the propane/oxygen or hydrogen/oxygen mix depending on the type of glass. Borosilicate is usually hydrogen/oxygen mix from what I can tell. There are videos online about making HHO torches. But for real glass working you need compressed gas.


They sure are.

Yes, I've recently learned that fuel type and fuel/oxygen mixtures are of utmost importance. I got myself a small pressure swing adsorption oxygen concentrator for endless O2, so that's sorted out at least. I'm currently using a mini gas welding torch with O2 and propane, but it's difficult to get a flame that's sufficiently oxidising.

I have made a ~2 kW HHO torch. I'm actually considering making it a part of a burner. The concentrator isn't quite supplying enough oxygen to achieve an oxidising flame and also get enough heat. Maybe a hybrid with a center HHO burner and a surface mix oxy/propane burner on the periphery would work well.

Quote: Originally posted by wg48temp9  


I have made Bunsen burners and a Meker burner for higher temperatures. I experimented with them to understand the flame stability.

My last experiment was with DIY classic glass blowing torch (inner air jet with an outer coaxial gas supply) with preheat on the air supply. The idea was to make a propane air torch hot enough to use on borosilicate glass.

What do you want to discuss?


And how did the preheating work out? I've wondered whether it's best to heat the air or the fuel, or if it even matters much. I really should explore preheating more. See, one issue that I keep being bugged by when using propane is that the slow flame speed cuts you off right when it starts to seem like you're nearing a satisfactory heat output. If one could preheat the air past propane's auto ignition point, that might make the flame speed less of a problem.

I'm sort of short on ideas right now and I'm hoping to find some inspiration when it comes to figuring out a design that's both effective and feasible to build. I have to admit though, I haven't tried the most basic single tube-in-a-tube design.

I tried making a tiny little monster, first making <0.5 mm glass tubes and trying to use them for a surface mix torch. Everything got so tiny I couldn't really build it properly lol.

I also tried what I suppose could be considered a kind of Meker burner. I gave up on drilling extremely small and very deep holes in things, so I thought of something else that's got long and straight cavities: cables! I tried making a premix torch out of a 100 mm2(!) cable, but it swallowed too much heat. It didn't take long until the most of the cable was >150°C and eventually the copper at the tip started catching fire. This was with oxygen gas rather than air.
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[*] posted on 29-8-2020 at 15:26


Quote: Originally posted by Junk_Enginerd  


And how did the preheating work out? I've wondered whether it's best to heat the air or the fuel, or if it even matters much. I really should explore preheating more. See, one issue that I keep being bugged by when using propane is that the slow flame speed cuts you off right when it starts to seem like you're nearing a satisfactory heat output. If one could preheat the air past propane's auto ignition point, that might make the flame speed less of a problem.

I'm sort of short on ideas right now and I'm hoping to find some inspiration when it comes to figuring out a design that's both effective and feasible to build. I have to admit though, I haven't tried the most basic single tube-in-a-tube design.

I tried making a tiny little monster, first making <0.5 mm glass tubes and trying to use them for a surface mix torch. Everything got so tiny I couldn't really build it properly lol.

I also tried what I suppose could be considered a kind of Meker burner. I gave up on drilling extremely small and very deep holes in things, so I thought of something else that's got long and straight cavities: cables! I tried making a premix torch out of a 100 mm2(!) cable, but it swallowed too much heat. It didn't take long until the most of the cable was >150°C and eventually the copper at the tip started catching fire. This was with oxygen gas rather than air.


I used a hot air gun in a crude set up. Central jet hot air with an outer coaxial propane flow. But the central jet was too large to suck in the propane correctly. I think what was need was a a quartz or ceramic tube containing a kW electric element and a nozzle/jet at the output end.

I don't think preheating the fuel will work because there is not much of it compared to the air so it would have to be heated to > 1000C to add significant temperature/heat to the flame and that temperature would crack the fuel and then probably deposit carbon in the heating tube.

The simplest construction for a Meker burner is wire gauze. You can press gauze in to a dome with short skirt by pushing the flat gauze in to a tube with a slightly domed rod a but smaller in diameter the internal diameter of the pipe.

The problem with premix flames is stability. The exit velocity must be greater than the flame velocity or the flame will travel back in to the exit tube but if the exit velocity is greater than the flame velocity the flame will lift off the exit and may blow out or burn several inches from the exit were the gas velocity has slowed to less than the flame velocity.

In a Bunsen burner two effect that improve the flame stability. One effect is the gas velocity is slower near the exit pipe walls and the flame is operated fuel rich which means the edge of the flame mixes with air and burns faster keeping the fast central flow ignited. The is achieved in some burner by a outer ring of holes.

Can you explain what you mean by "slow flame speed cuts you off". Do you mean the flame lifts off the burner and what type of burner where you using ?

Below is one burner I constructed. It worked very well with high flow rates with no flame lift off because the flame above the small holes with slower flow did not left off and kept the central high velocity flow ignited.

mekerdiy.JPG - 40kB

[Edited on 8/30/2020 by wg48temp9]




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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[*] posted on 30-8-2020 at 00:44


Ah, did you use the hot air gun directly? So that the pressure from it was insufficient and forced you to use a too large nozzle?

The way I've thought about doing it is to provide air from a compressor, and en route to the torch pipe it through a copper tube or such, which can then easily be heated to any desired temperature either with a torch or electrically.

Oh yeah good point. In propane/air it's just something like 7% propane for stoichiometric if I recall correctly.

Yes, I mean the flame speed cuts you off because the flame lifts away from the nozzle and eventually blows itself out.

I've made dozens of different experimental burners with varying results. Don't know the terminology for what type they might have been, but most were based on either using two tubes for a coaxial flow and mix, or a perpendicular venturi like a carburetor. Mostly liquid fueled as well, either by atomization or boiling. LPG is around 4x the cost of other fuels here in sweden, so at least for the powerful burners for metal work it's a little impractically expensive.

Another solution for handling the instability of the premix flame that I've succesfully used is to use an expansion cone. If the stream is led into an expanding cone, then the speed of the flow is guaranteed to have slowed down enough for sustained combustion at some point in that cone. But that's not a perfect solution for glasswork since one would typically want access to all of the flame.

I've also thought about using an electrical solution to bypass the flame speed problem. I'm not sure if it would be too difficult to sustain an electrical arc in such a "windy" environment, but perhaps a simple glowing filament of some sort would work well too, provided it can withstand the environment without being roasted to hell.

I think I should experiment more with splitting the flow a bit. Slowing the mix down on the edges to sustain a central flame sounds pretty good, and also simple enough to implement.
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[*] posted on 30-8-2020 at 03:51


Junk_Enginerd@

Yes, I was forced to use a large pipe for the hot air.

Yes a heated pipe would be much better and if electrically heated with say Nichrome or Kanthal wire wrapped round the tube the pitch of the wire could be increased at the hot end of the pipe to reduce power loading at the hot end. Of cause such systems the heating power must be reduced before the air flow is reduced assuming you trying to get the air to say +600C.

Ideally the heating element would be controlled by monitoring its temperature and adjusting the current to keep the temperature constant and mostly independent of the air flow.

Yes slowing the edge flow is simple to implement with baffles or a short flare so the central area is flowing faster but don't forget you need something to stop flash back such as small holes as in the pic I posted in my previous post.











i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

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[*] posted on 31-8-2020 at 02:14


If you don't use it very often, there are oxypropane burner brazing / welding kits for $100, with disposable O2 and propane tanks. A spare O2 tank (1 liter, 90 bar) costs about $22.
Another option might be a zeolite based oxygen concentrator, New they are rather expensive (in the order of $600) but maybe you can get a rejected (i.e. not suitable anymore for medical use) from a hospital.
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[*] posted on 31-8-2020 at 07:17


Quote: Originally posted by metalresearcher  
If you don't use it very often, there are oxypropane burner brazing / welding kits for $100, with disposable O2 and propane tanks. A spare O2 tank (1 liter, 90 bar) costs about $22.
Another option might be a zeolite based oxygen concentrator, New they are rather expensive (in the order of $600) but maybe you can get a rejected (i.e. not suitable anymore for medical use) from a hospital.


I have an oxy/propane mini welder kit that uses disposable bottles but fuuuuck that shit. The oxygen bottle is 900 mL at 110 bar and costs $35. That oxygen lasts for literally 15 minutes. Just using it gives me anxiety lol.

I also have a zeolite oxygen concentrator. Bought it 2 weeks ago and I've so far used it for 20 hours. Got it for $200 though. Thanks, China.

I was gonna build my own concentrator because they're really quite simple, but unfortunately I couldn't find a source for buying the right zeolite. :/
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[*] posted on 31-8-2020 at 22:10


Quote: Originally posted by wg48temp9  
Junk_Enginerd@

Yes, I was forced to use a large pipe for the hot air.

Yes a heated pipe would be much better and if electrically heated with say Nichrome or Kanthal wire wrapped round the tube the pitch of the wire could be increased at the hot end of the pipe to reduce power loading at the hot end. Of cause such systems the heating power must be reduced before the air flow is reduced assuming you trying to get the air to say +600C.

Ideally the heating element would be controlled by monitoring its temperature and adjusting the current to keep the temperature constant and mostly independent of the air flow.

Yes slowing the edge flow is simple to implement with baffles or a short flare so the central area is flowing faster but don't forget you need something to stop flash back such as small holes as in the pic I posted in my previous post.


What about using a heat gun ? Those are available in the local hardware store, normally used for paint stripping, for a few tens of dollars. The air it releases is several hundred degrees C.
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[*] posted on 1-9-2020 at 01:30


Heh, he did say that's exactly what he used. The problem is they provide too low air pressure, so you can't get enough gas velocity to get a good mix. It works, but not ideally. That's why a heated pipe supplied fed with compressed air is better.
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[*] posted on 2-9-2020 at 04:33


Quote: Originally posted by Junk_Enginerd  


I have an oxy/propane mini welder kit that uses disposable bottles but fuuuuck that shit. The oxygen bottle is 900 mL at 110 bar and costs $35. That oxygen lasts for literally 15 minutes. Just using it gives me anxiety lol.



That oxygen consumption is useful. That about 0.5l/s. I will round that up to 1l/s which is equivalent to 5l/s of air. Air (typical room conditions) has a specific heat of 1.21J/l.K. So to increase the temperature of 5l/s by 800C will require approximately (specific heat varies by temperature) 5kW. I have about 4kW available in my workshop because of the limitations of the cable connects to the distribution box and the 20A breaker.

I have three 1.5kW heating elements (tungsten quartz) available. My air compressor is 9.6CFM which is about 5l/s but I don't know what pressure that is specified at, so I may need an old propane tank for additional storage.

From what I remember those welding sets with disposable bottles have small torches with small flames and I don't know if heated air at say 500C air will increase the flame temperature sufficiently to enable borosilicate working.




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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[*] posted on 4-9-2020 at 00:11


Quote: Originally posted by wg48temp9  
Quote: Originally posted by Junk_Enginerd  


I have an oxy/propane mini welder kit that uses disposable bottles but fuuuuck that shit. The oxygen bottle is 900 mL at 110 bar and costs $35. That oxygen lasts for literally 15 minutes. Just using it gives me anxiety lol.



That oxygen consumption is useful. That about 0.5l/s. I will round that up to 1l/s which is equivalent to 5l/s of air. Air (typical room conditions) has a specific heat of 1.21J/l.K. So to increase the temperature of 5l/s by 800C will require approximately (specific heat varies by temperature) 5kW. I have about 4kW available in my workshop because of the limitations of the cable connects to the distribution box and the 20A breaker.

I have three 1.5kW heating elements (tungsten quartz) available. My air compressor is 9.6CFM which is about 5l/s but I don't know what pressure that is specified at, so I may need an old propane tank for additional storage.

From what I remember those welding sets with disposable bottles have small torches with small flames and I don't know if heated air at say 500C air will increase the flame temperature sufficiently to enable borosilicate working.


Don't make too many bets on the accuracy of that information. I did the math on it as well, and nothing matched up. Either I'm way off on the 15 minutes or the volume/pressure on the bottle is wrong is some way.

I'd say with the oxygen bottle I used at most maybe 4-5 times as much as my concentrator provides, so 4-5 L/min. 1 L/minute of 93% oxygen, which my concentrator provides, is definitely enough for small borosilicate working. As long as the pieces aren't too large, it'll happily heat it to a syrup consistency, almost liquid. I've only had issues with heat after I messed up a little in a T-joint between two boro test tubes(16 mm dia) where the glass started to get up to 4 mm thick in places.

The difference in heat using oxygen instead of air really cannot be overstated. You don't just get a much higher flame temperature, but also a much higher flame propagation speed, so you can have a much "denser" flame and that combined with the temperature means a way higher heat output. For example, quickly swiping a finger through the flame of a standard bunsen burner is no big deal at all. You can't do that even with a candle sized flame when using oxygen. You'll get burnt in the few milliseconds you are near the flame.

If you're unsure about what temperature you can reach by heating the air, there are convenient ways to calculate this. I've attached a handy spreadsheet calculator that I think you'll find useful.


9.6 CFM is quite a high rating, so unless it's a >2 kW compressor it's probably not rated for that volume at pressure. I have a 2.2 kW compressor and if I recall correctly it's rated to 8.5 pressurised CFM.

Yes, it's a small premixed oxy/acetylene welding style torch. Flame is -volume wise- roughly the size of an ordinary cigarette lighter flame, but of course much, much hotter. Again, it handles boro silicate just fine, up to maybe keeping 15 square cm of normal thickness glass workable at any time.


Attachment: AFT-Calc1.xlsx (193kB)
This file has been downloaded 45 times

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[*] posted on 4-9-2020 at 12:29


Quote: Originally posted by Junk_Enginerd  

snip

Don't make too many bets on the accuracy of that information. I did the math on it as well, and nothing matched up. Either I'm way off on the 15 minutes or the volume/pressure on the bottle is wrong is some way.

I'd say with the oxygen bottle I used at most maybe 4-5 times as much as my concentrator provides, so 4-5 L/min. 1 L/minute of 93% oxygen, which my concentrator provides, is definitely enough for small borosilicate working. As long as the pieces aren't too large, it'll happily heat it to a syrup consistency, almost liquid. I've only had issues with heat after I messed up a little in a T-joint between two boro test tubes(16 mm dia) where the glass started to get up to 4 mm thick in places.

The difference in heat using oxygen instead of air really cannot be overstated. You don't just get a much higher flame temperature, but also a much higher flame propagation speed, so you can have a much "denser" flame and that combined with the temperature means a way higher heat output. For example, quickly swiping a finger through the flame of a standard bunsen burner is no big deal at all. You can't do that even with a candle sized flame when using oxygen. You'll get burnt in the few milliseconds you are near the flame.

If you're unsure about what temperature you can reach by heating the air, there are convenient ways to calculate this. I've attached a handy spreadsheet calculator that I think you'll find useful.


9.6 CFM is quite a high rating, so unless it's a >2 kW compressor it's probably not rated for that volume at pressure. I have a 2.2 kW compressor and if I recall correctly it's rated to 8.5 pressurised CFM.

Yes, it's a small premixed oxy/acetylene welding style torch. Flame is -volume wise- roughly the size of an ordinary cigarette lighter flame, but of course much, much hotter. Again, it handles boro silicate just fine, up to maybe keeping 15 square cm of normal thickness glass workable at any time.


I took your oxygen consumption of your torch as a guesstimate.

I take the specs of diy equipment as potentially exaggerated. My compressor spec says 2.5HP which is only 1.9kW.

Thanks for the spread sheet. I think it does not give the correct AFT for propane/oxygen though its about correct if the AFT graph is in Fahrenheit not as marked Centigrade ??? Its probably something I am doing wrong.




i am wg48 but not on my usual pc hence the temp handle.

Thank goodness for Fleming and the fungi.

Old codger' lives matters, wear a mask and help save them.
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[*] posted on 8-9-2020 at 06:01



I once attempted to make a oxy fuel torch for working fused quartz. You need WHITE heat and you need a large flame because you must work the glass when it is in the flame. It immediately goes stiff when taken out of the flame. There are mainly two types of oxy fuel torch. One type mixes the oxy fuel before it appears into the open to be burned (premix) the the other has the fuel and oxy pipes coming to together at the burning point and they mix in the flame (sort of).
I decided to attempt the premix. It had mixing chamber (a pipe) with two pipes going into it (o and fuel) and a grid of holes for to light the mixed gas coming out. Sometimes it worked OK. It was terribly noizy. Sometime the fuel/oxy would detonate inside the chamber and it would do this at about 4 Hertz! A great crow scarer, not a good fuzed quartz glass torch. There is nothing more disconcerting that looking at a piece of white hot glass suspended in the oxy/fuel flame of a crow scarer going at four Hertz. The noise when it was doing this would put you out of the parish.
If you are going to attempt to make a oxy/fuel torch I suggest you start with the postmix (not the premix type).

Perhaps they are called laminar flow (as opposed to premix)?
https://www.youtube.com/watch?v=FqMaLCVf794&app=desktop

Glass blowing torches as stated are very expensive. They are complicated giving different temperatures for different areas of the flame. They are like three torches in one housing giving one flame. And precision made too.
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[*] posted on 8-9-2020 at 16:07


Quote: Originally posted by Junk_Enginerd  
Is anyone here making high performance burners and torches? It's a subject that I think is really interesting. It'd be cool to discuss this with others a bit.

I've made quite a few experimental burners for different purposes.

I made a 100 kW liquid fuel burner for metal casting that's been of great use to me. It's based on a pressurized air driven degreasing sprayer. That tool probably has a better name in english, but I can't recall it at the moment lol.
I run it on gasoline, E85(ethanol fuel mix) or diesel depending on the needs. E85 is the "easiest" fuel, it works most reliably and isn't too picky about fuel/air mix, so it's what I use the most.
Diesel is better for reaching the highest temperatures, and is better when I want to melt brass/copper/cast iron and is significantly cheaper since it's a LOT more energy dense. It's more finnicky though. The range of fuel/air ratios that work well is narrower, and it's difficult to ignite it properly if it's not being sprayed into an already hot furnace.
Gasoline is my last choice, it's a lot like diesel except more volatile of course. It tends to get "explodey" if you're not igniting it properly or you're in the wrong fuel/air ratio. It likes to launch my furnace lid. Mostly a nuisance rather than anything dangerous though.

I also made a forging burner from scratch, that I typically run on E85. It's a little smaller at ~20 kW. It's built on the same principle as the degreaser; a center nozzle that accelerates air and draws in and atomizes fuel from its circumference which is a larger diameter tube surrounding it. An adjustable cowl around the nozzle can be adjusted via threads to provide a larger or smaller gap around the circumference to adjust the fuel/air ratio. Also implented a fuel valve adjustment as well as an air pressure regulator to be able to control as many aspects of it as possible.

I'm currently trying to make a good surface mix oxygen/propane burner for glass work, and it's proving to be quite a challenge. Drilling and generally working with <1 mm holes and tubes is seriously difficult. Add to that all the aerodynamic phenomenons that don't tolerate any surface finish variations or burrs...

Has anyone DIY'd a glass working torch? They're so ridiculously expensive. I'm not really serious enough about my glassworking hobby that I could justify spending hundreds or even thousands of € for one...


I'd be interested to see what your pressurized air driven degreasing sprayer looks like along with your torch you made. I've been trying to figure out what you might be talking about as far as the tool, but I'm stumped when it comes to the air driven part.

Have you measured the temps you get with the torch you made? I was thinking about making an O2 concentrator and run it from an arduino or eventually a PLC. I think you will be able to get the temps you want if you used O2 mixed with the gas.
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[*] posted on 10-9-2020 at 14:04



An example of a torch that does not premix the gasses. This type I believe is the easiest to make.

Yob
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[*] posted on 10-9-2020 at 19:00


Quote: Originally posted by yobbo II  

An example of a torch that does not premix the gasses. This type I believe is the easiest to make.

Yob


I really don't understand what you are referring to. Are you saying a torch that doesn't have more than one gas and just uses atmospheric O2 to burn? Are you referring to the OP in your post?
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[*] posted on 10-9-2020 at 20:42
Post mix torches



I'll show you a selection of what we call post mix torches, where the oxy and fuel mix at the face of the torch. On the left is a fairly simple 9 hole torch. It might seem crude but it does pack a punch. If you notice the valve assembly there is a separate control for the centre oxygen port. What this does is control the centre of the flame to give a more direct jet like flame by giving the centre more velocity.

It gives a slightly more varied flame than the other two torches that give a hot flame or a softer bushy flame, with a bit more or a bit less power.

The small hole spacing burns more fuel for a given area and essentially gives you heating power. But it is also more efficient burning so there is less glare from the unburnt fuel, the 9 hole can get quite glarey to work with and I tend to prefer using sunglasses just to start the thing.
Torches (3) (768x1024).jpg - 209kB Torches (1) (768x1024).jpg - 244kB
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yobbo II
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[*] posted on 11-9-2020 at 05:21


Quote: Originally posted by RogueRose  
Quote: Originally posted by yobbo II  

An example of a torch that does not premix the gasses. This type I believe is the easiest to make.

Yob


I really don't understand what you are referring to. Are you saying a torch that doesn't have more than one gas and just uses atmospheric O2 to burn? Are you referring to the OP in your post?


Sorry I did not post the link.
https://www.precisionglassblowing.com/product/shimadzu-quart...

Picture from site below.
It is easy to see/understand the constuction because the torch is made from glass (quartz). They are very pricey.
This is a post mix torch (as opposed to a premix) although there is a small amount of glass tube for the mixed gases to flow through before coming to the 'outside' of the torch. Perhaps you could refer to this torch a slight hybrid between premix and postmix? Others here will know alot more about this.

All I am saying is that (I believe) the post mix torch will be easiter to construct that an premix torch. You can have an array of tubes in a grid. The tubes carringg the O2 and the spaces between the tubes carring the fuel.

I hope to attempt to make one of them some day. Also I have a large welding oxygen bottle for O supply. As stated above I attempted to make a premix torch which did not work.

Also with working glass in general I believe it is important to have a crossfire of two or more torches for the beginner. The crossfire makes the needed skill less demanding untill you develope some ability

Yob

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[Edited on 11-9-2020 by yobbo II]
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Chemetix
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[*] posted on 11-9-2020 at 11:24



Quote:

Picture from site below.It is easy to see/understand the constuction because the torch is made from glass (quartz). They are very pricey.This is a post mix torch (as opposed to a premix) although there is a small amount of glass tube for the mixed gases to flow through before coming to the 'outside' of the torch. Perhaps you could refer to this torch a slight hybrid between premix and postmix? Others here will know alot more about this.


That's a picture of a plasma torch used in an instrument. ICP or inductively coupled plasma uses radio frequency to heat a stream of argon to plasma. A sample of aerosol is injected to be analysed using it's emission spectra.

Burner torches look like this http://www.blueflametech.com/
http://www.asahiglassplant.com/products/quartz-burner-en/


Quote:

Also with working glass in general I believe it is important to have a crossfire of two or more torches for the beginner. The crossfire makes the needed skill less demanding untill you develope some ability


Not really, no one has taught glass blowing with a cross fire since the 50's. The added awkwardness of working with another flame negates any benefit from the even heating.

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[*] posted on 11-9-2020 at 22:54


Quote: Originally posted by Chemetix  

I'll show you a selection of what we call post mix torches, where the oxy and fuel mix at the face of the torch. On the left is a fairly simple 9 hole torch. It might seem crude but it does pack a punch. If you notice the valve assembly there is a separate control for the centre oxygen port. What this does is control the centre of the flame to give a more direct jet like flame by giving the centre more velocity.

It gives a slightly more varied flame than the other two torches that give a hot flame or a softer bushy flame, with a bit more or a bit less power.

The small hole spacing burns more fuel for a given area and essentially gives you heating power. But it is also more efficient burning so there is less glare from the unburnt fuel, the 9 hole can get quite glarey to work with and I tend to prefer using sunglasses just to start the thing.


So with the 9 hole torch, it looks like there is the main fuel line that is on the bottom with a lever valve, and then I guess an O2 line running above it that looks like it has a smaller tube coming off of it to feed the torch in a different place than the larger O2 tube.
I guess I could be mixing up fuel & O2, they could be switched, IDK.

So does O2 come from around the 9 holes and the fuel comes through the 9 holes? I'm trying to figure out how the O2 connection at the top of the torch differs from the connection on the side of it.

Either way, thanks for posting, I love seeing this stuff and figuring out how it works!
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[*] posted on 18-9-2020 at 07:01


Quote: Originally posted by yobbo II  

I once attempted to make a oxy fuel torch for working fused quartz. You need WHITE heat and you need a large flame because you must work the glass when it is in the flame. It immediately goes stiff when taken out of the flame. There are mainly two types of oxy fuel torch. One type mixes the oxy fuel before it appears into the open to be burned (premix) the the other has the fuel and oxy pipes coming to together at the burning point and they mix in the flame (sort of).
I decided to attempt the premix. It had mixing chamber (a pipe) with two pipes going into it (o and fuel) and a grid of holes for to light the mixed gas coming out. Sometimes it worked OK. It was terribly noizy. Sometime the fuel/oxy would detonate inside the chamber and it would do this at about 4 Hertz! A great crow scarer, not a good fuzed quartz glass torch. There is nothing more disconcerting that looking at a piece of white hot glass suspended in the oxy/fuel flame of a crow scarer going at four Hertz. The noise when it was doing this would put you out of the parish.
If you are going to attempt to make a oxy/fuel torch I suggest you start with the postmix (not the premix type).

Perhaps they are called laminar flow (as opposed to premix)?
https://www.youtube.com/watch?v=FqMaLCVf794&app=desktop

Glass blowing torches as stated are very expensive. They are complicated giving different temperatures for different areas of the flame. They are like three torches in one housing giving one flame. And precision made too.
Yob


I've made a few premix oxy/fuel torches. It ends up working poorly due to the small volume of O2 I'm currently getting from my oxygen concentrator. This means it's a small flame, which means I need to make absolutely ridiculously tiny holes to keep the flow speed up. I'm talking about <0.05 mm holes. If it's a single hole, maybe 0.2-0.3 mm dia is optimal, which is quite close to not mechanically drillable in a good workshop, not to mention how hopeless it is at home.

My hydrogen/oxygen torch was premix, since the gasses mixed already in the electrolysis cell. I seem to recall that hydrogen/oxygen burns even faster than acetylene. It's absolutely nuts, something like 10 m/s, so the nozzle needs to be extremely small, especially because there was no compressor involved so the pressures were <1 bar.. I made the nozzle small enough by starting with a 1 mm drilled hole in brass and forging it smaller. Hammering around a hole with a ball hammer will push the metal toward the middle, effectively shrinking the hole. Hard to make the hole nice and cylindrical though, so it's a bit hit and miss.

Though I recently realized a way to make extremely fine nozzles, that also end up having an exceedingly directional and laminar flow. Surprisingly simple too. I ended up taking a 5 mm glass tube and just gently heating it. As it starts to flow, it will start to draw itself into a more spherical shape, and the hole ends up getting smaller and smaller. If it's not small enough, just heat it up again. Theorerically there's really no limit to how small you can shrink the hole this way, though if overdone the hole will close up entirely.

I took a photo of the flame I got with a glass nozzle and it's insane how smooth it is. Running it with no oxygen, a small flame would happily burn at a stable 10 cm away from the nozzle. And I mean there was no flame between the nozzle and the flame, just a freaky floating flame in mid air. I'll see if I can find the pic and upload it later...
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