timgunn1962

It looks reasonably usable. It's nice and small (any idea on weight?), so should be reasonably portable. Price seems pretty reasonable too.

Have you bought it yet?

If you're not interested in buying it, send me the details and I'll have it in a flash.

425 lb

3 Hundredweight of 112 lb each               336 Lb

3 Quarterhundredweight of 28 lb each       84 Lb

5 pounds of 1 lb each                                   5 Lb

Total                                                          425 Lb

Chuffing is often (usually?) caused by too low a mixture speed. For a Venturi burner, this is effectively the same as too low a gas pressure.

The flame-front starts to move down the burner tube, through the gas/air mixture, faster than the mixture is moving the other way. Somewhere near the Venturi, it goes out because it has run out of mixed gas and air. There's a delay while fresh mixture makes its way along the burner tube to the chamber, where it ignites and the process repeats.

Turning up the gas pressure usually solves the problem. Obviously adjusting the regulator won't work if the low pressure is due to a frozen cylinder.

Once the mixture speed towards the chamber is higher than the flame speed, the flame will stay in the chamber

The OPs question was whether there have been any studies comparing Venturi and blown forges.

But the question was about the difference in gas consumption. 11 pound cylinder of gas at the burner ejctor enough for me 8-9 hours. The burner air blower for 11-12 hours.

In this case, you simply seem to be saying that your atmospheric burner uses more gas to achieve the same result as your blown burner.

This may be helpful information. I can't tell though, because you've not given any other information at all; a study would be expected to eliminate, or at least take account of, all the other possible variables.

One thing worth pointing out is that both Banan and Tom Oldsmith are apparently running on Natural Gas, presumably at a very low pressure. The low pressure is somewhat challenging for a Venturi design and is perhaps the only constraint under which I would tend to build a blown design in preference to a Venturi.

If it rises fast and maxes out, it's possible that the input type is set incorrectly. In the settings menu, "inty" should be set to "K"

I'm not sure what it'll do if it sees sensor break, but I'd expect it to drive high. You can probably test this by unplugging the thermocouple from the readout with it powered. Check your wiring to make sure nothing could be coming loose when it heats up.

Other than that, I'd advise speaking to the tech support line; I guess they keep normal office hours?

What is the problem you are seeing?

No display? Display, but no reading? Reading, but one that you cannot believe?

It looks like the instrument comes preset to the thermocouple it is supplied with.

The polarity of each of the connections in the temperature sensing circuit is critical. The red-marked thermocouple wire needs to connect to the red cable core, which needs to go to the negative terminal on the readout (if you've cut it down to fit, you'll have lost the ink mark on the end, so you'll need to check everything else is correct and try the thermocouple both ways to check it; the right way is when the reading goes up when you heat up the thermocouple).

Then it's plug everything in and power it up via the DC power supply.

There doesn't look to be too much else to get wrong, just looking at the manual. http://auberins.com/images/Manual/AT100KLN%201.pdf

Just checking: If you have cut the thermocouple down, you are using the bit with the welded junction, not the 2 cut-off ends?

Just thinking out loud, I'd expect it would be possible to use "Incoloy straight rod heating elements". They are basically the same as water heater elements, but can be specified for use in air instead. Watt density would need to be much lower than for water heating, but the incoloy elemets are supposedly good to 1600 degF surface temperature. You'd need to find suitable elements for the size of furnace and carefully work through the manufacturers' design calculations; best is to work out a ballpark design and use this to fill in their design spec sheet, letting them do the final calculations.

Control would almost certainly need to be with a thermocouple and PID controller; these are cheap (probably a lot cheaper than a thermostat able to cope with the temperatures involved) and give much more precise control.

Personally, I'd use the controller to switch the power via an SSR, rather than a contactor, for shorter output cycle time, but the element manufacturer can provide advice on this.

What size of workpiece are you intending to deal with in the forge? I assume you'll be forging sections and joining them together afterwards?

I've built half a dozen electric HT ovens broadly similar to Andy Gascoigne's plans on the British Blades site, including a sword-length one. I'd expect going electric to be heavy on power.

I suspect that the temperature could possibly be achieved with Propane, given a bit of thought and a good burner design, though I've not tried to get down that low myself. The lowest I have aimed for on my forge was a steady 750 degC (1382 degF) and that was relatively easy (it was a general-purpose forge intended to go from HT to welding temperatures and also reached 1413 degC (2575 degF). If it's not possible to get the flame temperature down low enough simply through good mixture control, I'd expect a radiant heating system, where the burners heat the roof of the forge and the radiated heat from the roof heats the workpiece, to be possible.

It seems like an interesting project. Some more details on the forge dimensions needed would be good.

Not wishing to come aross as pedantic, but I think the flame sensing used for gas flames is normally UV, rather than IR.

As I understand things (and I could be wrong), the reason for using U/V is that it senses the UV radiation from the actual flame and doesn't "see" the IR from the chamber lining.

Purely on loss of air supply, I'm not sure either would necessarily work to cut the gas feed to a blown forge fast enough to be a useful safety feature. With IR, the lining is likely to remain hot enough to trigger the sensor for a while, and with U/V, there is likely to still be some combustion going on, albeit very rich, after the air supply fails in most designs. I suspect a simple air pressure switch would get the job done cheaper, quicker and more reliably.

My feeling is that if you are building a blown burner because it is easier to build than a Venturi, adding in all the safety features will actually make it harder to build than a good Venturi system.

If you are building a blown system because you have insufficient gas pressure for a good Venturi (perhaps you are using mains NG), then go ahead and build the best/safest blown system you can. Please research it properly first though.

One of the difficulties when burners, forges, etc are under discussion is terminology. "Heat" and "Temperature" seem to be used interchangeably by many people and they are not the same thing at all.

There are really two things that affect the temperature achieved by a given gas forge/burner combination.

The first, and the one that most people "get", is the amount of gas being fed.

The second, and the one that some people seem to get but others don't, is the amount of air being fed along with the gas.

The most important thing is really the ratio of gas to air. This ratio is what governs the flame temperature.

Whatever burner is in use, the maximum flame temperature occurs at the "stoichiometric" mixture. This is where all of the Oxygen in the air, burns with all of the fuel gas, resulting in no remaining unburnt gas and no unburnt Oxygen. For Propane burning with air, the temperature of a stoichiometric flame is 1980 degC (3596 degF), assuming the gas and air are at 20 degC (68 degF) before they are burnt. This temperature is also called the "adiabatic" flame temperature.

Air contains about 79% Nitrogen. Although the Nitrogen doesn't play any appreciable part in the combustion, it is along for the ride. Because it is mixed in with the other stuff, it ends up at the same temperature as the Carbon Dioxide and Water vapour produced by the combustion process. The heat absorbed in raising the Nitrogen to 1980 degC (3596 degF) is quite significant. If there was no Nitrogen, that energy would be available to raise the temperature of the Carbon Dioxide and Water vapour instead. The adiabatic flame temperature for Propane burning with pure Oxygen (i.e no Nitrogen present) is considerably higher at 2820 degC (5108 degF).

Going back to burning with air, if we adjust the fuel/air mixture so that it is either side of the stoichiometric ratio, the flame temperature will reduce.

If we add extra air (a lean burn), there's no extra gas for the extra Oxygen to burn with, but the extra Oxygen and Nitrogen will absorb some of the energy produced, reducing the flame temperature

If we add extra gas (a rich burn) instead, there's no extra Oxygen to burn it with. The unburnt gas will absorb some of the energy produced and this will reduce the flame temperature.

If reaching a specific temperature is the only concern, it's best to go lean; gas is expensive and air is free.

Unfortunately, "we" usually need to use a rich flame as the free Oxygen in a lean flame causes scaling and Carbon reduction problems in "our" application.

The big difficulty for many is likely to be judging the mixture. If you can measure the temperature, increasing the amount of air slightly will show which side of stoichiometric you are on; the temperature will rise if the mixture is rich, fall if it's lean. Most folk don't have the kit to measure temperatures in the range needed for forging. Very few indeed will have the kit to measure welding temperatures. Almost none will have the kit to measure stoichiometric flame temperature.

In my, admittedly limited, experience, many (perhaps even most) Naturally-Aspirated gas forges will actually get hotter with a smaller gas jet, against the expectations of their builders.

I suspect you'll struggle to find a smaller jet that will directly swap with the .023 MIG tip, which is as small as MIG wire usually gets, but to get the 1/2" burner working well, it's what you need to do.
 

Well, I decided not to go with 1 1/4'' pipe and went to 1'' with good results I think. Even with the smaller pipe I had to kick the orifice up to .050 and it still seems a little lean. I used a cast iron bell fitting (1''/1.25'')on the end and it helps to prevent flame out although mounting it will be a little more challinging. The blue flame cone gets up to 6'' long at 20 psi......

Fit a choke to it and you'll be able to control the mixture/flame temperature all the way between whatever you've got and reducing/Heat-Treating.

Keep the gas jet diameter in proportion to the pipe diameter and you should be OK.

If necessary, I use a drill in a pinvice to open up MIG tips to the desired size; it keeps the conical lead-in and maintains the discharge coefficient. A plain drilled hole without the lead-in will flow about 20% less gas than a mig tip.

Heat (BTU) output goes up with the area, not the diameter.

Adding a choke is a really good idea. The mixture adjustment gives control of the flame temperature. The gas pressure controls how much gas. The combination of the two controlls how hot your forge gets. Depending on the forge design, it can also control how much of the forge gets that hot.

The center number is not in stones it's in quarter hundredweights which is 2 stones, the final number is then the remainder of the quarter hundredweight so [0-9] [0-3] [0-27]

It's unlikely you'd find one heavy enough to find out, but I'd imagine the first number (Hundredweights) could go up to 19, as a ton in this system is the long ton, of 2240 lb or 20 cwt.

At that age, it may not be easy to get a direct replacement motor. It may well predate the IEC standards that most European motors are built to now and might not fit the base and the pulley. The base is generally pretty easy to adapt, but you may need to think in terms of a motor and motor pulley combination, rather than just the motor.

Based on Hans' figures, the nearest current standard IEC motor would be an 11 kW/15 HP 8-pole motor (which would give 750 RPM running synchronous to UK 50 Hz mains and a bit slower under load). This would be on a 180L frame and have a 48mm shaft.

It's worth shopping around, but the following should give the general idea:

http://www.motorcontrolwarehouse.co.uk/ac-motors/three-phase/ie1-standard-efficiency/tecc-cast-iron-0-55kw-to-315kw-2-/-4-/-6-and-8-pole-models-available/tecc-three-phase-cast-iron-frame-8-pole-models-available-choice-of-mountings-ac-motor-11kw/prod_62.html

Hi Andrew.

I think I can remember your setup: static phase converter into a 3-phase 415V Siemens minimaster 420  VFD. The VFD seemed pretty meaty so I assume it was at least 3 HP. The VFD was running a grinder when I was there.

It's a bit more faffing about, but I'd expect you could run the power pack from the Siemens VFD. I think (though I'm not 100% certain) that the VFD will deal OK with the phase imbalance, even at full load. The VFD should be able to display current, so setting the relief valve wouldn't need a separate ammeter.

I think you'd need a separate power feed to run the solenoid valves, but that shouldn't be too big an issue.

Regards

Tim

Gedore stuff is generally good. It's not a brand I seek out because it tends to be fairly pricy in the UK, but the quality is pretty high. I've only really used their spanners/wrenches and sockets though.

Cromwell in the UK sell a range of "Kennedy" machinists hammers from 0.5 kg up to 2 kg, at reasonable prices and fairly decent quality. They appear to be German-pattern (DIN 1041) and are well worth checking out. Nearest branch to you is probably Rochester, but they also sell online.

I'd recommend something similar to these from Omega:

http://www.omega.com/pptst/KHXL_NHXL.html

I'd go for type K, 6mm diameter (or 1/4" depending on what is available wherever you buy). I'd go for 600mm or 24" of probe below the handle. This is long enough and rigid enough to put the tip where you want to measure without having your hand too close.

Personally, I prefer a grounded junction for fast response when I'm checking the temperature is constant throughout the forge, but the insulated junction is probably a little more rugged and it's what I'd recommend to most people.

Omega are about the biggest name in thermocouples worldwide, and the Super Omegaclad XL sheath is rated for 1335 degC, which is higher than most. Shipping costs hurt though.

Thermocouples are widely used in industry and there will be local(ish) suppliers. The biggest problem is usually knowing what to ask for. A type 310 stainless steel sheath will be good enough; it's rated to 1100 degC, but this is for long-term use. It will last a while above that and is even good for checking up to forge-welding temperature (around 1300 degC) for the hobby knifemaker.

It will need a miniature type K plug to suit the readout.

For a readout, get a TM902C from ebay. There are lots of sellers. Price is 5 or 6 bucks/euros delivered (et 2 for when you melt or stand on one). They seem too cheap to work, but they do work very well indeed.

They read to 1365 degC, but only degC; no degF option, and only with type K thermocouples.

Bottles, where in the world are you?

From what I can make out, most US phase converters are 240V output, whereas most European ones have an autotransformer to give 415V output.  In both cases, the third phase is shifted using a capacitor (or several) and this doesn't usually give perfect 120 degree phase angles, causing an imbalance between the voltages on the motor phases. The voltage imbalance means the current is also imbalanced and when the hardest-working winding is at rated current, the other 2 will be doing a bit less, hence the derate. It's the motor that needs to be derated, not the converter, so your 3 HP motor might effectively become a 2-and-a-little-bit HP motor.

I've not played with hydraulics in decades, so I'm rusty, but I think I understand what you've got there.

Almost all hydraulic pumps are fixed-positive-displacement pumps, which means the flow through the pump is directly related to the pump speed. On a fixed-speed motor, it's effectively fixed.

The amount of work done per pump revolution depends on the pressure. More pressure, more work, more current drawn by the motor. The pressure is set using the relief valve. Once the pressure is high enough to crack the relief valve, the pressure will be maintained at the relief valve setting as the relief valve dumps the oil back to the tank.

Once there's clean oil in the system, I'd proceed as follows:

Back off the relief valve fully. Start the pump and measure the current in each of the 3 phases. Find the one with the highest current and leave the ammeter on it.

Wind in the relief valve and watch the current come up. When you are approaching the rated current for the motor, check all 3 phases again and pick the one with the highest reading. Adjust the relief valve until it is reading rated current and lock the relief valve. check all 3 phases again to make sure none is drawing higher than rated current.

At this point, take a look at your pressure gauge, if it's working. Whatever it reads is the maximum you can get without overloading the motor. It might not be what you want, but you are stuck with it. From your original post, it seems it might only be around 1000 PSI.

Next step is to sort out the valving, connect your cylinder and see if you can live with what it is giving you.

The flow control is best left wide open unless you find you need to reduce the ram speed. It's just a restrictor and basically causes the relief to open earlier than it would otherwise.

On a simple hydraulic setup like yours, you don't have the facility to adjust the relationship between flow and pressure.

Nice anvil.

Work wouldn't be Whitechapel Bell Foundry by any chance?

When you get the problem, can you increase the gas pressure at all, or are you at the limit of your regulator?

The thing I'd suspect is that you are seeing the flame run back down the tube until it runs out of mixture. There will then be a brief pause as fresh mixture reaches the hot forge and relights. It will then happen again.

In your bottom pic, gas enters on the left, draws in air through the tee and mixes the gas with the air from there to the end of the tube.

To get a stable flame, the speed at which the flame-front moves left-to-right through the gas/air mixture needs to match the speed that the gas/air mixture moves right-to-left.

The flame speed varies with air:fuel ratio and with temperature: it moves faster if it is hotter. As a fairly general rule, you need to start most gas forges on low pressure and build up the pressure as the forge heats up. Starting too high will cause the flame to detach from the burner. Running too low when hot will cause the flame to burn back down the tube.

When the flame burns back, it radiates heat in front of it and generates a pressure wave, both of which increase the rate at which the flame moves. It will therefore accelerate down the tube until it runs out of mixture somewhere near the tee and goes out. Once unburnt mixture reaches the hot chamber, the cycle can start again.

Often, the frequency of the cycle starts quite low and increases, as the temperature of the burner tube increases due to having the flame run down it.

One of the things a flare does is give a variable area so the mixture slows as the area increases. This gives a fairly wide range of gas feed pressures over which the flamefront and mixture speeds can be equal somewhere within the flare and maintain a stable flame.

The flare does other "stuff" as well, but it gets a bit more difficult to explain.

My feeling would be that, whether they work or not, they are not likely to be a particularly good use of resources; They'll tell you if you've exceeded a certain temperature. If you use two, they can tell you if you are within a given range.

To use them, you need to have pretty good access to the workpiece. This may limit the techniques available to you: it seems to me it would be difficult to use a steel-tube muffle with Tempilstiks for Austenitizing, for example.

They are 70-plus-year-old technology, according to their website, which means they predate the transistor, let alone the Integrated Circuit. They are certainly proven, but may have been overtaken by developments in the last 7 decades.

A modern electronic handheld temperature readout and a suitable type K thermocouple can be bought for less than 4 Tempilstiks can (I'm in the UK, so YMMV, but it looks like the ratio is pretty similar in the USA). The thermocouple/readout is far more useful.

Just for future reference, a few blobs of barbeque paint or VHT in flat black will solve the emmissivity issue and let you get good IR temperature readings from the different surfaces. At work, I usually use a piece of black duct tape on the surface for temperatures up to maybe 100 degC/200 degF.

Ambient temperature changes "should" directly affect the forge temperature by the same amount. Ambient drops X degrees, forge temp drops X degrees. Ambient rises Y degrees, forge temp rises Y degrees.

Breezes can affect the temperature, especially on Naturally Aspirated burners, by affecting the mixture. It's really a case of try it and see.

Biggest problem outside is likely to be the cylinder temperature dropping in cold weather and not supplying enough pressure. Big cylinders, a gentle heat source, or placing the cylinder in a tub of water can help. If you go for the tub of water, don't let it freeze with the cylinder still in.

Maybe McMaster Carr?

http://www.mcmaster.com/#oil-cups/=lw1xxe

I drill soft firebrick with a holesaw, no problem.

Depth of cut is usually limited to about 1 1/2" with a standard holesaw, so it tends to be a case of drill as deep as you can, then break out the core and repeat if you are doing a full brick at 3" thickness. 

I often use a smaller holesaw once I've started a big hole, and take out 3 or 4 smaller cores with perhaps a 20mm holesaw, knock off any remaning  nibs and take another bite with the big one. It's only really needed for the bigger holes (3" hole for a 2" burner, which uses 2 1/2" NB pipe for the retention cup). Once you've got the hole started, it will guide on the OD.

If you can get to both sides, it's easier to run a pilot hole through with a longish drilbitl and use a holesaw from both sides.

Depending on the soft brick, it can ruin the holesaw. JM23 or K23 is nice and soft. Some of the others are harder and will quickly render the holesaw useless for anything else, LW23GRD are the toughest on tools that I've found in the UK.

I have pinned soft bricks together with stainless steel TIG rod. It's the easiest way I have found to bridge the roof of a quick-and-dirty softbrick forge.

If you grind the end of the rod down to a D-bit; take off half the the rod for the first half inch or so, you can drill a hole almost the full length of the rod through several bricks and either snip off the protruding ends once it's through, or withdraw the "drill" and fit another rod. I tend to use 2.4mm rod (3/32") because it's what I have. 

I started by using hardened drill-rod for the D-bits, then got lazy and used unhardened drill-rod, then got bone idle and just used the welding rod itself. Hardened drillrod lasts longer, but the welding rod is easy and cheap. It helps to start the hole with a normal drill bit, or I sometimes drill a hole through a scrap of wood and hold it against the brick to give me a straight start.