Posts by timgunn1962

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    That "flare" looks pretty nice. I assume it's a flame retention cup, as per the Amal injector sheet?…al/amal_gas_injectors.pdf

    There's lots of stuff on the interweb about "flares" in conjunction with homebuilt burners. I get the impression most of it is largely BS. The Amal injector has that nice coppery expansion section already built in and doesn't need, or benefit from, a flare.

    The retention cup is very good at retaining the flame on the burner when it is used outside a forge. I also tend to use retention cups in dedicated Heat-Treating forges because the forge temperature is so low (around 800 degC) that the cup helps. For more "normal" forges (forging-to-welding temperatures), the forge works like a big flame retention cup and keeps the flame attached to the nozzle.

    I mention this only because the retention cup is not an easy-to-find off-the-shelf part, AFAIK, and I'd hate anyone to be put off using an Amal injector as a result.

    It may be they've got it right.

    It sounds like you might not be familiar with pipe threads?

    At risk of seeming patronising (if you know all this already), pipe threads are sized on the Nominal Bore of the pipe.

    This means that the OD of the pipe will be the Nominal Bore plus two nominal wall thicknesses. A 3/8 BSP thread will therefore have an OD of around 17mm and a 3/4" BSP thread will have an OD of around 27mm.

    In fact, the OD of the pipe is now fixed and the bore gets bigger or smaller for different pipe schedules. Schedule 5 is very thin-wall pipe, schedule 80 is thick-walled and schedules 10, 20 and 40 are somewhere in between.

    It'll give you a headache if you are used to the threads used for fasteners, which are sensibly sized on major diameter, but it does all make sense really.

    The 1" and 3/4" Amal injectors both use the same casting, so make sure it's their cockup before sending it back.

    Copper has a higher thermal conductivity. It is much denser, but has a much lower Specific Heat Capacity than Aluminium. Surprisingly, the heat capacity of a given volume of Copper is only 41% greater than that of the same volume of Aluminium. Because Aluminium is so much cheaper than Copper, particularly when talking in terms of volume, it is MUCH cheaper to go to a thicker Aluminium plate, rather than a Copper plate of the same thickness.

    Using quench plates, the limiting factor on the cooling rate will usually be the heat transfer at the interface between the workpiece and the plates.

    Plate quenching is only normally applied to Air-hardening steels. They don't really *need* the increased quench speed provided by plates in order to harden. The plates mostly help to keep things straight.

    If higher quench speeds ARE needed, the logical step is to oil-quench. The contact between the workpiece and quench medium (oil) is MUCH better than between the workpiece and metal quench plates and this gives greatly increased heat transfer.

    If you have the choice between 1" Copper plates and 1" Aluminium plates with no other difference, by all means go for the Copper. If you have a choice between 1" Copper plates and 2" Aluminium plates, go for the Aluminium. Otherwise, use whatever is affordable and available.

    Inverterdrive are indeed pretty good for providing information and are usually pretty good on pricing too.

    I quite like the TEC Aluminium-frame motors. I feel they are a budget "real industrial" motor. We've used quite a few at work and they've acquitted themselves well.

    They have all the "proper" industrial flexibility with the feet movable, the terminal box rotatable and either face- or flange-mount drive end covers easily fitted.

    Using that motor with a 230V VFD, you'd connect the 3 phases out of the drive onto U1, V1 and W1, with the links configured as in the right-hand photo on the page.

    I'd strongly recommend using one of the Invertek IP66 drives with the controls on the front. Probably a…vertek-ODE-3-120070-1F1Y/

    It seems hideously expensive compared to the cheap one off ebay, but it does include all the stuff you'll have to source if you go with the cheapie. If you want to do it anything like right and don't have contacts in the trade or extremely finely-honed scavenging skills, it is quite likely that the apparently-cheapest VFD will prove to be the more expensive option.

    The IP66 drive is fully sealed against dust and is also sealed against water, though it is for indoor use only. The cheap Ebay drive is probably IP20 protected against objects 10mm or larger (effectively fingerproof) and unprotected against liquids.

    Using an IP20 drive indoors can certainly be done, and for many applications it is no problem at all. Grinders are not among those applications, unfortunately.

    A VFD needs cooling air. It switches large currents very fast and generates magnetic fields at the switching components. An unsealed drive will therefore effectively take all the iron-dust-laden air from its surroundings and pass it over a magnetic field generator that will die spectacularly as soon as it comes into contact with conductive dust. No names, no packdrill, but there are folk on here who have killed new drives within minutes.

    I have mounted several IP20 drives in IP66 enclosures, added start/stop, fwd/rev and speed controls, and built something that works almost as well as a factory IP66 drive. Cost saving has been considerable when I've been able to scrounge the stuff, but is negligible when I have to pay for it all.

    Safe is a relative term........

    The chamber is big and the openings are small. If you fill the chamber with a gas/air mixture and THEN ignite it, you can expect exciting things to happen....

    The ends of Mark's are just ceramic fibre board cut to fit the shell and pushed in. Although it looks like a rough job done by a careless hairyarse who didn't give a damn. In fact, it was done by a moderately careful hairyarse who did. There is a cross-member that will probably stop the back blowing out, but the push-in front end is intended to blow out relatively easily if there is an internal explosion. It's not in any way scientific and it'll still not be safe, but it "should" limit the severity of any explosion somewhat.

    At about 1:10 in the video, you can see that the burner is retained by a Terry clip. This is an important safety feature. The burner can be held and lit outside the forge, then once it is burning, located in the burner port and pressed into the Terry clip. Lighting it outside the forge and then inserting it dramatically reduces the likelihood of an explosion.

    I am guessing your burner is a Black Dragon unit from Neels Van Den Berg? If so, it looks like a very good burner. The only concerns I'd have with it in this application would be the sensitivity of the sliding choke and the gas jet sizing. It seems to be good for welding temperature, which needs quite a lot of air relative to fuel. This means a strong "draw" at the air inlet and this in turn means that the air gap needs to be pretty small for HT temperatures with a rich burn. It also means that very small movements of the choke are needed for precise temperature control.

    At about 2.22 in the video, mark adjusts the choke by something that seems to be considerably less than 1/10th of a turn. It's a 1/2" BSP thread at 14 TPI, so 1/10th of a turn is 1/140th of an inch of axial choke movement: about 7 thousandths of an inch. That degree of control seems likely to be difficult to achieve with a sliding choke.

    I have a feeling Mark has a 30 jet in his. For HT, I now tend to use a 60 jet in the 1/2" burners. This gives a bit less less "draw" and the temperature is slightly less sensitive to small changes than with the 30. If the Dragon burner has changeable gas jets, a bigger jet might make things easier for HT.

    Most standard 3-phase motors below about 2.2 kW, 3 HP are wound for 230V in Delta and 400V in star. These will work from a 230V input VFD when connected in Delta.

    In My Humble Opinion (rough translation: others might disagree but they will be wrong), the best motor to use is a 2 or 3 HP, 1.5 or 2.2 kW, 4-pole. This will be rated at "about" 1500 RPM on 50 Hz UK/European mains frequency or "about" 1800 RPM on North American 60 Hz mains frequency.

    The VFD will certainly be able to run the 4-pole motor from about 10 to 100 Hz for about 300- 3000 RPM. It is likely (but not absolutely certain) that it will run happily up to 120 Hz and "about" 3600 RPM.

    If you get a 2-pole motor, rated for "about" 3000 RPM at 50 Hz, minimum speed (10 Hz) will be about 600 RPM and maximum speed (60 Hz) will be about 3600 RPM, so the 4-pole gives a significantly wider speed range.

    Further explanation will need to wait until I'm sober, along with VFD advice.

    As have I, so you are covered for availability Josh.

    I don't think the PM facility is available without a paid subscription. If some mutual acquaintance would be good enough to either send me Luddite-friendly contact details for Josh, or can send Josh my mobile number, we can sort something out.

    Best bet is probably for me to send two of the 1" burners for you to have a play with and find what works for you. Once you are happy, you can sort out replacements and/or send them back.

    The difference between the Butane, Propane and Natural Gas burners is "just" the jetting.

    "We" have relatively unusual needs in terms of combustion equipment. Most industrial/commercial combustion processes are trying to get the maximum usable heat from the gas. This generally means a fuel-lean burn with an excess of air.

    Most combustion equipment uses both primary air (drawn in before the nozzle: in this case at the Venturi) and secondary air (air that comes in after the nozzle). Most forges only use primary air. Any secondary combustion usually takes place outside the forge as the Dragons Breath and does not contribute to the conditions in the forge itself.

    We don't want excess (primary) air, because excess air means that there is free Oxygen in the forge and this will react with our steel causing scaling. We therefore want a fuel-rich burn, giving a reducing forge atmosphere and much less scaling. The extra fuel used is an acceptable tradeoff for the reduced scaling.

    Combustion chemistry is not quite as simple as the stuff most of us did in school, where most of the reactions were effectively irreversible. At high temperatures, the reactions are reversible and reach an equilibrium point that depends on the reactant concentrations and the temperature. This means that there is not a definite point at which the mixture changes from scaling to not-scaling.

    There is more of a very wide grey band, going from very-scaling-indeed to hardly-scaling-at -all.

    Very-scaling-indeed tends to be quite close to the stoichiometric mixture: the mixture at which all the fuel gas combines with all the Oxygen in the air, leaving neither fuel nor Oxygen after the flame. This is also the mixture at which the flame temperature is hottest.

    As the mixture becomes more fuel-rich, the forge atmosphere becomes more reducing (less tendency to scaling) and the flame temperature reduces.

    At the rich extreme of the range, the flame temperature is down to about 800 degC and the burn is so rich that unburned Carbon soot is deposited on surfaces. It seems that this "should" give minimal scaling and reduced decarburization, but I have not done any scientific testing to confirm/deny this.

    Going a little richer is just about possible, but not far below 800 degC, things are not hot enough to sustain combustion and the forge will stop burning.

    The jet size determines the mixture with the choke fully open: smaller jet, leaner mixture and, as long as it does not go beyond the stoichiometric point, higher flame temperature.

    The choke allows the user to reduce the proportion of air, so it is no problem to run the burner richer than the choke-fully-open mixture.

    Adjusting the choke gives control of both the flame temperature and the "reducing-ness" of the flame (together). Adjusting the gas pressure gives control of the amount of flame.

    The physics of the Venturi means that, once the choke position is set, the mixture ratio (air:fuel) will remain pretty much constant over quite a wide pressure range.

    For our purposes, the optimum jetting is that which will give us a high enough flame temperature for our hottest intended use with the choke fully open.

    I did quite a bit of fiddling with jet sizes, starting from scratch with a lashed-up forge and some expensive temperature-measuring equipment, to try to establish my idea of optimum jetting. I came up with 30, 60 and 120 jets for the 1/2", 3/4" and 1" LV injectors respectively. I was trying for rich-but-near-stoichiometric with the choke fully open.

    When I was fiddling about with Heat-Treat forges a little later on, I was having a little difficulty reaching temperature on a longer-than-previously-tried forge and tried the 60 jet from "my" 3/4" burner in the 1/2" burner. It gave the higher temperature because it flowed twice as much gas as the 30 jet, but also gave "better" control at low temperatures: less temperature change for a given rotation of the choke.

    When I tried it in a more conventional (but small) forge, it would still exceed the 1300 degC I think of as welding temperature, so I consider it good.

    A bit more experimenting convinced me that the 60, 90, 150 progression for the 1/2", 3/4" and 1" would do anything most smiths will realistically need.

    Archiving sounds far too organised John. Between BB and Photobucket, it's gone.

    For most of the stuff most normal smiths (oxymoron?) will want to do, the standard Burlen/Amal jetting for Butane seems pretty much ideal.…ors/butane-injectors.html

    It's the Long-Venturi versions that "we" want.

    I've tried the 1/2", 3/4" and 1" Butane-jetted injectors running on Propane and they seem to give an adequate working range: from Austenitizing temperatures with the choke nearly closed (around 800 degC, 1472 degF) to nice hot welding temperatures (well in excess of 1300 degC, 2372 degF) with the choke fully open.

    The highest forge temperature I've measured on the Butane jetting is 1545 degC, 2813 degF and the lowest I've been able to sustain has been 760 degC, 1400 degF.

    I have a vague feeling that Will's welding forge might be running on a slightly smaller jet than the 150 that is normally fitted to the Butane injector, but Owen doesn't seem to find the 150 a problem in his welding forge.

    I'd need to check my jet sizing numbers for going hotter: they are somewhat smaller than the sizes for "general" forging stuff and will get into the properly steel-melty range. Probably unnecessary unless anyone is making Wootz or similar.

    I don't see a need for normal folk to go any bigger than the 1" injector. I had a 2" back at Jack's last hammerin and it was complete overkill. Will had a brief play with a 1 1/2" and decided it was too much, sticking with the 1". That said, if any of the usual suspects feel they need to build something properly big, drop me a PM or phone call.

    Looking at the picture, the thermocouple colour is less bright than the hottest part of the blade. The thermocouple temperature is presumably in the 840-880 degC range you quoted and the hottest part of the blade therefore seems to be significantly hotter than this.

    Back in the days before high-temperature Infra-Red pyrometers, there used to be an optical high-temperature pyrometer design that used an electrically-heated Platinum wire. The operator held the instrument with the wire between their eye and the object being measured, adjusting the heating current until the wire appeared to merge into the background because the wire and the object were at the same temperature/colour. The temperature of the wire could then be read from the instrument.

    We can use the same principle with a thermocouple: Since we can read the thermocouple temperature accurately, we know the temperature of anything in the forge that is the same colour as the thermocouple.

    You will need to run the forge outside, preferably somewhere sheltered from breezes. The plan is to run the forge VERY rich. It WILL produce a lot of Carbon Monoxide (we actually want this, as it reduces scaling and seems to go some way to reducing decarb) and this is very poisonous. Death tends not to improve ones knifemaking skills and seems best avoided. It is certainly worth arming yourself with an understanding of the risks associated with Carbon Monoxide so that you can take sensible precautions. A few minutes Googling should cover it.

    If they are Insulating Fire Bricks, using them front and back should work fine. Narrow slot at the front for the workpiece should be OK. If they are dense bricks, I'd imagine they won't help the temperature distribution as much.

    The way I see things in my head is to take several strips of blanket, about 1" wide, placing them in the mouth of the (cold) forge to form a 1" thick wall and reduce the size of the opening until it is just big enough to accept the workpiece. The opening actually needs to be big enough to allow the hot gases out and the usual advice seems to be for the total opening to be about 7 times the area of the burner tube. In fact, the expansion of the gases depends on temperature and the factor of 7 is ample for welding temperatures. A factor of about 4 or 5 "should" be adequate for HT temperatures. In reality though, the limiting factor is likely to be the size needed to admit the workpiece: a 2" diameter opening would have 7 times the area of the 3/4" ID burner tube and is probably about as small as you'd want to go to pass a blade.

    The back opening can be completely walled off if your workpiece is short enough to fit.

    The forge can then be lit. It will need to be lit carefully, with a flame source already in place as the gas feed starts. I usually use a propane torch inserted through the opening and playing on the mouth of the burner. If you don't get it lit as the gas starts to flow, the small explosion as the gas/air mixture in the forge ignites will blow out the blanket wall.

    Get the burner running at whatever choke opening is needed to get the forge hot. If you try to light it with the choke at the setting needed to hold HT temperature, it just won't light.

    Set the pressure to a realistic forging pressure. You'll be adjusting the choke but not the pressure from here on in. I'd guess around 5-10 PSI, but it's only a wild guess and will depend on the forge/burner. I used 15 PSI in my video, but that was for a 1/2" Amal burner.

    Put in the thermocouple and start measuring the forge temperature. Once it is above about 900 degC, you can start to reduce the choke opening. Take it down in small steps and watch the temperature, leaving a decent interval between adjustments. Try to keep the thermocouple out of the direct flame.

    You want to get the temperature into the HT range from above. If you overshoot the adjustment when closing the choke, there is a fairly high probability the flame will go out and you'll need to restart, I would not try to go below 800 degC on the first 2 or 3 runs.

    Once the forge temperature is where you want it, watch it for a few minutes and make sure it is stable to within a few degrees.

    Once you are happy with the temperature, put the blade in. Try to keep it out of the direct flame. The thermocouple reading will usually drop as the cold blade goes in and then recover. Once it has recovered, look in at the blade and the thermocouple, checking the colour is not markedly different, and wait for the soak time. Then pull it out and quench it.

    If you are HT-ing multiple blades, you'll need to do them one after another. It's not a setup that's conducive to production work.

    Once you've gone through the process the first time, any thoughts of a double-burner setup for HT will go right out of the window as you start to understand the challenge of setting 2 burners to the same temperature.

    Mark's setup was built to cope with a 15" workpiece (a competition cutter) and only uses a single 1/2" burner. Owen (Blademaster) has a very effective purpose-built single-burner HT setup that has treated many, many swords. I really don't see any need to go to multiple burners for HT.

    Luke: How do you get the temp low in the forge? Less air or more pressure?

    Luke's 3rd pic in the OP shows a pronounced variation in colour, and therefore in temperature, across the workpiece. It's not easy to estimate how great the difference was though. I think there may have been more consistency to come by reducing the air further.

    Folk have been Heat-Treating blades for a long time, mostly using very basic equipment, much of it running solid fuel, and employing a high level of skill to overcome the limitations of that equipment.

    With gas-fired equipment, there are two basic adjustments: the amount of gas being burned (nigh-on everyone understands this) and the temperature at which it burns, determined primarily by the air:fuel ratio (remarkably few people seem to understand this).

    A Naturally-Aspirated burner with a choke is usually tuned with the choke fully open and the jet size selected to give a flame temperature at, or slightly above, the maximum temperature required. Closing the choke will then richen the mixture by reducing the air supply relative to the fuel. This reduces the flame temperature and makes the flame (and therefore the forge atmosphere) more reducing (chemical term: effectively the opposite of Oxidising).

    It is possible, with a well-designed/built burner, to richen the mixture enough to get the flame temperature down to around 800 degC, 1472 degF. This allows for "good" Heat-Treating temperature maintenance without a high level of operator skill. My personal experience has been that temperatures down to about 750 degC, 1382 degF are possible with care, but that it is difficult to maintain a flame at such temperatures. At temperatures this low, the flame in the forge is so rich that Carbon tends to be deposited on the workpiece. There is often a lot of Dragons Breath and it tends to be yellow.

    If you can get the flame temperature down to the top end of the HT temperature range for the steel in use, you can run a fairly high gas pressure/flow rate and get a small enough temperature gradient that the entire workpiece is within the HT temperature range.

    I'm really not good at explaining stuff, so I videoed a small forge/burner setup, a while back,to try to show the effect of adjusting the mixture. The burner was Naturally-Aspirated and based on an Amal atmospheric injector. I apologise for the quality of the video.

    Mark Jacob posted a shorter, better quality, video of a purpose-built HT forge in operation. Again the burner is NA and based on the Amal injector.

    Although I still don't think there's anything else quite as good as the Amal, the Devil Forge DF-series burners do have a very good choke setup. It actually looks to be a lot better than the one on their DF_Prof series, which are more expensive.

    The choke should allow you to restrict the airflow and reach a cool, (very) rich flame at the sort of temperature you want for HT. It'll be smoky, probably very yellow, and will look nothing like any flame you'll ever see in a forging, or welding, forge before.

    I think it'll probably be quite difficult to run the small Devil Forge with such a rich flame because the openings are so big that air can get in at the bottom and mess with the mixture: it's primarily for this reason that the forge in Mark's video has such a small exhaust/workpiece port.

    I'd be inclined to try temporarily closing down the Devil Forge openings with Ceramic Fibre blanket when using it for HT, but I don't have one to try. I'll happily provide a couple of square feet of 1" CF blanket and a thermocouple, FOC, to the first person (UK mainland only) who'll undertake to post a writeup of their attempt.

    Alternatively, as Blademaster says, a muffle can be very effective at reducing temperature variation throughout the workpiece.

    As Mike says, using a reasonable-sized enclosure generally deals with the cooling. Steel enclosures shed heat much better than GRP.

    There are formulae for calculating how much heat dissipation enclosures will provide. In many cases, the enclosure manufacturer will have the information on their website. Often only the vertical surfaces are considered.

    The drive specs will give the maximum heat produced by the drive and the maximum permissible ambient operating temperature inside the enclosure.

    I am a sad geek and did a lot of calculation a while back. I am also fat, lazy and do not shed heat well. My calculations boiled down to a 400H x 300W x 200D steel enclosure being sufficient to run any single-phase-input drive up to 2.2 kW (3HP) continuously at any ambient shop temperature I would realistically be working in.

    I actually fitted some 2.2 kW drives in 300 x 300 x 200 enclosures with glass in the doors, which were otherwise destined for the skip. The glass does not shed heat nearly as well as steel and the enclosures are smaller, but these have been pretty much trouble free to the best of my knowledge.

    I find the 400H enclosures are easier to wire up as I tend to fit blue 3P + E IEC 60309 IP67 sockets in the bottom to allow different machines to be plugged in. The glass doors are nice because you can see the display.

    I fit a remote control box on a flying lead that can be located at the machine being used. I use a green flush start button (needs to be pressed with a finger), a red projecting stop button (can be pressed with an open palm or similar), a keyed Fwd/Rev switch with the key removable only in the FWD position (some machines cannot safely be reversed, so taking the key out ensures they are not reversed) and a speed control pot. The switches and buttons are 22mm industrial types.

    22mm industrial pots have been hard to come by and most of mine have used 10-turn Bourns or Vishay pots bought off ebay for around £10 with a 0-100 indicating knob. When I've had the budget, I've used industrial single-turn pots from Lamonde at around £40.

    The last drive I put together used a EMAS single-turn 22mm potentiometer, which seems fine and is half the cost of the Lamonde one.…ttons/emas-potentiometer/

    Enclose it to at least IP55.

    Grinding dust WILL kill it INSTANTLY.

    You are not dealing with a "normal" dust situation.

    Most inverters have cooling fans which will massively increase the airflow past the power electronics in order to keep them cool. The power electronics components switch large currents, which means that they produce quite strong magnetic fields which will attract any steel dust. They also deal with high voltages which means that any conductive material contacting them will short things out very easily.

    The drive will concentrate all the dust from a large volume of the workspace in the place where it will do the most damage. I know at least one person who has killed 2 drives, the second within 10 minutes of starting it, through not sealing them.

    Hamilton only seem to list high-pressure Propane regulators with a 0.5 bar minimum pressure. These are horrible.

    It's a shame because I've absolutely no problem with Hamilton otherwise. Everything I've had from them has been exactly as described and the service has been excellent.

    I've tried many and have had enough of really cheap regulators. I now tend to buy plugged (no gauges) Propane regulators from a proper welding supplier (about £30). They are much more rugged than the cheap ones and seem much easier to adjust finely.

    I'm not 100% certain, but I think the clip-on regulators are all low-pressure: 37 mbar for Propane and 28 mbar for Butane. They are intended for barbeques, gas heaters and the like.

    While it is possible to get a forge burner to work at the low pressure, it's not easy. It'll generally take either a much-larger-than-usual Venturi burner or a blown burner.

    We usually use cylinders with a female thread intended for use with screw-on adjustable-pressure regulators. 0-2 bar (0-30 PSI) is probably the most common range, with 0-4 bar (0-60 PSI) also being quite common on forge burners. Note that the 0.5-2 bar and 0.5-4 bar regulators in the link are not at all nice to use with forges because the 0.5 bar minimum pressure means you can't slowly increase pressure when lighting and also limits the turndown for heat-treating.

    With the big suppliers (Calor and FloGas) once it's empty, you can usually exchange a cylinder for another type: you'll have paid the deposit initially and it's the same deposit for most sizes of cylinder, Butane or Propane. I'm not sure about the GasLite cylinders though. Are they the pretty designer ones?

    If you can chop it in for a different one, you could run your BBQ from a screw-in cylinder if you also get a screw-in fixed-pressure 37 mbar regulator. A 1.5 kg/hr should be enough for most BBQs (it's the same throughput as the 27mm Patio Gas regulator). Trying to get a 0-2 bar high-pressure regulator to control pressure down at 37 mbar for a BBQ is not really a practicable proposition.

    That's a strange cylinder fitting to me. As far as I can tell, the Calor UK 34 kg cylinder size is only available in Northern Ireland, so I presume it's an Irish standard size.

    The thread on the cylinder is male, rather than the UK-standard female cylinder thread.

    It looks like it needs a regulator with a connection like this one


    The UK standard looks like this one


    CAVEAT: I do not recommend either of these regulators. You really want 0-4 bar or 0-2 bar, depending on the forge suppliers recommendations. The "Zero to" bit makes a big difference to usability for us. The 0.5 bar minimum setting on the linked regulators is a PITA. It obviously limits the low-end adjustment, but it can also make lighting a bit more exciting than is strictly necessary. My main problem with it though is that it means that you can't shut off the forge with the knob you usually use to adjust it and therefore reach for automatically. When the midden hits the windmill, I don't want to have to start thinking clearly.