rjs

On 2/9/2016 at 5:22 PM, Mikey98118 said:

Timgunn, I like that idea; very practical way to vary secondary air intake.

Thanks Mikey,  I pm'ed him with more or less the same comment.  I was reluctant to say it in the forum since the heavy hitters were already taking their cuts.  I hope he tries it and reports the results.

First of all best wishes concerning your daughter.

Concerning your burner:

There shouldn't be any flame at the rear of the  burner.  I suspect you have some propane leakage issues back there. 

And Frosty is gonna want to know some additional info on what you are using for a jet and what size it is?

Also how are you adjusting/controlling your propane pressure and what do you have it set to?

Regards,

Bob

6 hours ago, uncrash said:

The only thing besides adjustment that seems to need work is to seal the sliding choke.  Any recommendations?  

Yeah fire it up and play with the choke.  You will find that there is no reason to completely choke the burner.  The point of the choke is to be able to adjust the flame across the range  of reducing to neutral to oxidizing at a variety of pressure settings.   Oh yeah watch this video https://www.youtube.com/watch?v=VxzdqcPzXj8ob

Bob

2 hours ago, swedefiddle said:

Happy New Year,

Have you hooked it up to your Forge yet? You paid for a Chevrolet and you expect a Cadillac?

The gap at the end is not a problem, there is a set screw holding the end brass bushing in place. This center bushing can probably slide in and out to Tune it, this may as well be causing the mig tip to not be exactly in center. I think it is close enough to not affect the operation of the Burner. The Slide does need to be sealed, it is a restrictor, so you can adjust the quantity of air to give you a good burn. This is an Atmospheric Burner, The mig tip locates the propane discharge, the gas pressure coming out of the jet creates a low pressure just behind the Tip, atmospheric pressure is then higher than behind the Tip. Air is then pushed by Atmospheric Pressure to fill the low pressure area, which will mix the propane and Air together. The location of the Mig Tip is adjustable, The quantity of Air is adjustable, The propane pressure is adjustable. You are adjustable. Try it before you fuss!!

Neil

Agree on every point.  This is essentially the same burner that dave hammer describes in his you tube video and the design seems to work well (at least for me.)  Hose, regulator, and stainless steel construction all for under a hundred bucks seems like a great value.

Bob

3 hours ago, Mikey98118 said:

rjs,

They claim it can be used for brazing; by this we assume they mean hard brazing. What the American Welding Society terms braze welding and the Brits call spelter brazing. We assume this meaning because silver brazing uses much lower temperatures that can alredy be achieved by any air-propane torch. Since their claimed temperature of 4172 F is within hard brazing range, technically speaking it should be able to do so. But here's the catch: just because we can do a thing doesn't mean we can do it well. An oxy-propane flame is about 4800 degrees and it doesn't do braze welding well. You want at least an oxy-propylene flame (5200 F), and oxyacetylene is better (5800 F). We have all experienced the frustration of trying to overreach with a poor tool. If you want to braze weld and don't have an oxyacetylene torch set, I would recommend using a twin carbon arc instead.

after a number of years without access to my oxyacetyline rig I have recently aquired another one so my interest in the propane/air rig was largely theoretical however the portability of thie unt still makes it interesting on some level.

Interesting you should mention the twin carbon arc approch.  those things seem to have faded into oblivion as the years have gone by.  Back in the fifties (yeah i was around back then) there were ad's for them in all the how to magazines.   I always suspected  (i have never used one) it was because while they might work for some things they could not come close to the finess/control you can get with an oxyacetyline rig.

44 minutes ago, Frosty said:

The Sandia forge is an effective "recuperative" design. "Recuperative" refers to recouping or "recovering" waste, heat in this case.

As Mike points out propane has a relatively low flash temperature and it took the rocket scientists at Sandia (no fooling rocket scientists) some time developing the heat exchanger in their forge so it wouldn't get too hot pre-ignite in the mixing chambers.

Another more effective recuperative burner is preheating the propane. There isn't the same limit to temperature there is preheating the air. Fuel preheat systems are the norm on hot air balloons. It's been quite some time since I really messed with improving my burners and a quick search isn't turning up any of the references I'm recalling though IIRC the ones I found most informative were by a British outfit.

The ones I recall were preheating the fuel electrically to temps in the 1,000c range. The numbers they were charting were showing better improvement in combustion efficiency that using preheated air.

When I say as I recall this was from before the accident so I'm working with sort of fragmentary memories. Still, I can't stop thinking about ways to wrap the copper supply line in the forge and this leads me to think I'm remembering rather than imagining.

Frosty The Lucky.

Hi Frosty,

another reason those guys preheat their propane is that they take it out of the tank and up to the preheater as a liquid.  If they tried doing it the way we do it they would quickly cool their fuel tanks to the 0 psi level.  the one I was just reading about had two burners each rated at 15,000,000 btu's and no more fuel tank capicity than a lot of us have running our forges.  "twin JetStream Series II burners, produce a heat output of 15,000,000 Btu's per burner or approximately 4,390 kW"   and no I do not think I want one of those in my shop.   Years ago one of those things landed in a field across from my place, they hit the burners a few times on the way down and it sounded kinda like a carrier was doing cat shots out on the sound.

rjs

1 hour ago, Mikey98118 said:

I'm simply not that trusting of foreign made tools. An American manufactured tool exposes the manufacturer to devastating law suit losses, if the tool is defective and proves dangerous. But, try suing a French manufacturer in a French court "Yankee"! So, when I see normal safety concerns ignored by a manufacturer, who is beyond retaliation, I "just don't go there."

I hear that and I do not disagree. 

I took anofher look af the users manual and they do not rely on the hot air for ignition, instead they show some yoyo liighting it with a cigarette lighter. lol   Certainly this is not a tool you could ever turn your back on and no one is suggesting using it as part of a forge.  They do claim brazing heat with propane/air which I found interesting.

1 hour ago, Mikey98118 said:

The ignition temperature of propane is 470 C; well below even the heated air figures, so I would not trust the safety of this tool.

I think they are counting on it igniting the propane, the manual called for waiting for full electrical heat before turning on the propane.

13 minutes ago, Charlotte said:

The famous Sandia forge that was created in the Sandia labs used two stainless steel tubes that heated the air pulled by the burners  in the forge.   The plans may still be available from  ABANA.  The tubes were placed so that they crossed the dragons breath at the year of the forge.     I haved use a similar set up to preheat the air going to my burners.   It works well and can raise you forge heat without additional fuel.   Adding heat with a heat gun etc. is a waste of energy and fairly futile.    Redesign the forge so the exhaust blows over pipes that lead to the burners.   Doing this naturally aspirated is difficult.  With a blown system careful thought about where you introduce the propane will be required. 
 

No I will not tell you more about my design.  The wrong way of doing it could blow yourself up.

Btw a propane air torch supplied with compressed air amount to the same thing as the illustration. 

Thanks Charlotte,

I have looked at the sandia forge info and while impressive it all seemed a bit much. 

If horrible freight were selliing a chinese knockoff of these for a reasonable price I would just get one and to play with but they are not.  Oh well.

rjs

 I came accross what appears to be a heat gun combined with a propane burner at this web site:

http://www.onlygaz.com/pages/gas_torch.html

  Anyone know anything about these gizmo's? 

 Articles posted on the site appear to be in french and all points of sale appear to be in France.

They have an english users manual (pdf) it says that the unit preheats the air to 650 C and also preheats the propane some.  The operating gas pressures are down around bbq levels  ie very low.

RJS

1 hour ago, Kyle Cox said:

6" without the collar extension 

I am thinking that is a bit short for good mixing.  How about some other opinions here?

how long is the 3/4 inch pipe?  It looks a bit on the short side in your photos. 
Flame retention in the open air is a problem that goes away when the burner is in a hot forge.

15 minutes ago, Kyle Cox said:

.030

have you tried one size larger?  ( .035 if you are using mig tips)

jet size?

If that remark was intended for me,  The hard bricks I was refering to came from a local tile shop.  I am sure they were never intended for forge tempratures.  I later found a local source for soft fire brick for a brick pile forge.  after watching flux eat holes right through those  I  Moved on to a carved up five gallon propane tank with rock wool insulation and a  floor of poured castolite 3000. 

bob

the ones I have melt after a while.   I'm pretty sure they were intended for a fireplace floor.

He can have my old hard firebricks also (worthless for a forge.)  Do all of us have a pile of those laying around dating back to when we were clueless?

Bob

If you can replace the 120 tooth gear with a 127 tooth gear you can cut accurate metric threads.  

Regards,,

Bob

with the propane turned off find out if your valve has a mehanical stop or if it falls out at full open.  assuming it has a stop try your forge at the WFO setting.  

earlier frosty mentioned altitude,  a good point.  How high are you?

I looked at these forges at the diamondback web site and it appears the pressure guage is at the regulator and that there is also a control valve  (needle/ball?) very near the burners true?  Do you have this valve all of the way open?  If not try that.

As long as your guage pressure at the regulator output  remains constant (where you want it to be) then tank freeze up is not the issue. 

I have seen crud clog up needle valves and jets requiring maintenance.

Bob

w

bob

get a 0-50 psi pressure guage, stick it on the end of the manafold where you have a pipe cap now then report back with some numbers.  oh yeah, and lose the attitude.

pressure is approx 4/10 of a psi from a bbq regulator,  for a forge something on the order of 25 psi (adjustable) would be more in order. 
Then you will probably find that your jets are way to large.  rule of thumb seems to be .023 mig tips for 1/2 inch tube, .030-.035 mig tip for 3/4 inch tube,  .045 mig tip for 1 inch tube (inch measurements refer to nominal pipe sizes.) when things are working right these things are noisy.  What you want is for it to run perhaps a bit lean when unchoked then choke it down to neutral to slightly reducing (rich) for work. 

Good insulation is important!   once metal starts to glow it is radiating btu's at an incredible rate.  iirc radiant emissions go up with the 4th  power of the temperature (absolute.)  much of this radiated energy can be returned to the work piece by surrounding it with good insulation which catches and re radiates the energy leaving the work.

Velocity of the burning mixture is also important.  hot gas loses heat in a hurry in contact with cold metal. it is important to have a good blast going to replace the cooled gas with more high temp gas.   looking at your photos the flames appear very rich and way too low in  velocity. use a smaller jet with more pressure to get more air in the mix and increase velocity.

Have fun and  be safe.

Bob

1/8" pipe thread in the united states is 27 threads per inch.  the taps come in tapered ( 1/8" NPT) which is what you need for 1/8" pipe fittings and  streight (1/8" NPS) which are hard to find and only used for electric lamp fittings as far as I know.   Also avliable are 1/8" NPTF fittings and taps (hard to find and more expensive than 1/8"NPT.)

The threads on mig tips do not seem to be standardized so measure carefully and buy accordingly.  ebay is you friend for odd size taps

next step, carefully take it apart and see what is inside.

How does air get into your shop?  If it leaks Like a sieve then no problem.  If on the other hand it is virtually air tight then try it with a window or a door open.  All that hot air you want to go up the chimney  has got to come from some where.

 

Bob

I just noticed the bit about the door being open.   sorry about that.