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About Latticino

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    Senior Member

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    Upstate NY
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    Blacksmithing, bladesmithing, glassblowing, restoring and playing antique flutes. HLG and boomerangs, recumbent bicycles, sea kayaking, white water canoeing, reading SF/Fantasy

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  1. Got that trick from Matt Parkinson. Not sure where he learned it. Great for low tech heat treatment.
  2. That's right. No castable in between layers of blanket. You can rigidize with colloidal silica, if you want, but even that is not required. The castable refractory belongs on the inside.
  3. I've recently done some calcs that indicate that you don't get appreciably more thermal efficiency from more than 2.5" of 8# density high temperature ceramic blanket insulation. The relatively low density of the blanket prevents it from being a significant heat sink, though any mass will retain some heat. The castable insulation refractory (Kastolite or equal) is more dense than the blanket. As such is a poorer insulator, and more of a thermal mass, making it a bit of a heat sink. Not as much of one as a hard brick, or heavy castable refractory like Mizzou, but still what I like to call a thermal battery. That is why it should be on the inside of your forge where it can both protect the blanket and provide some "smoothing" of the internal temperature profile when you make changes like opening the forge door or putting in large masses of cold stock (if one cares about such things ), not in between layers of blanket. This is clearly evident in a forge with a castable floor when you put in cold stock. It sucks the heat right out of the floor, which you can see if you move it before the stock heats up to general internal forge temperature.
  4. The issue I think you are going to run into is that the clogger's stock knife is a very specialized tool that doesn't seem to be all that common over here in the states. I expect there are some critical subtleties regarding balance, hardness, springiness, weight, blade curvature, edge bevel, and proportion that work together to make a more or less successful copy. You might get it right on first try, but I would doubt it. On first view it should be able to be produced by anyone who makes swords, or perhaps pole arm weapons with long tangs, but if you go to someone who has never made one you will need to pay for them to climb the learning curve for a new form. As a custom order I can't imagine it costing less than twice what you could get one for from a smith who makes them regularly (like the pictured one you linked from the Stark Raven folks). Of course If I needed one myself I'd try to knock one up from an old leaf spring using the dimensions from their site and making a stab at the various geometries from source photos and drawings: From Stark Raven: "The blade of the light stock knife is about 5/16" thick at the spine and 1-3/4" wide. The shaft to which the maple handle is mounted is of 1/2" x 1" cross section, tapering to 1/2" square where it meets the hardwood handle; the overall length of this knife is 33", with about a 16" cutting edge." Also this blog which has a bunch of nice photos and a description of forging one:
  5. That is an excellent suggestion. Pretty easy to get a small pancake compressor to use to atomize the fuel source then tie in a small "squirrel cage" blower to bring in the required combustion air. And running electric 25' is easy as well. You can even keep your oil storage tank remote if you elevate it and gravity feed the feed line. How are you measuring that accurately? Did you do a multipoint traverse of a fixed size chamber with a hot wire anemometer or pitot-static probe and manometer gauge?
  6. OK, I used a different sizing tool, for air at higher pressure in pipe rather than very small diameter duct (25 PSI instead of standard temperature and pressure). Air is compressible, so it makes a big difference. Using this calculator, and air at 25 psig, I get a loss for a 10' section of 3/4" pipe of only 14 psi. Like I said, I don't do much with compressed air design. Might be feasible with a compressor, though I also would be concerned about the strength of the hose, and stand by my statement that it is a extremely inefficient option.
  7. Lets assume you are discharging into "free air" at the end of a 10' long standard 3/4" garden hose. If you are attempting to move 250 CFM of standard temperature and pressure air (for density and viscosity) through said hose, the friction loss will be on the order of 2,620 inches of water gauge (or around 95 PSI). That is not including entry and exit losses, which will certainly be present, or any residual pressure you might need at the termination (for blasting through a coal grate or pile of fuel and clinker). I believe the term you are looking for is an air compressor, not a pump, but finding one with those unusual flow characteristics may be problematic (a typical 5 HP dual stage compressor will move around 15 CFM at 95 PSI, you are talking about a bank of large compressors). High pressure blowers exist that will move 250 CFM, but will struggle greatly with the over 260" of loss. Unfortunately I don't deal with compressed air design all that much, so can't advise you further, but my instincts say that it will be a remarkably inefficient and costly method of transporting air for a forge, not to mention issues with water vapor. Why are you considering this method of air transport?
  8. Another classic method is to determine the volume of the anvil (roughly from measurements if you must, or using the old water displacement trick if you can) then multiply by the average density of steel (The theoretical density of mild steel (low-carbon steel) is about 7.87 g/cm3 (0.284 lb/in3).
  9. How about the Aspery books? I know they lean a little towards artist hand smithing, but they still do cover the basics well, and the projects teach applicable skills that crossover to production work and planning. The illustrations are good and the author is available as a visiting instructor. Nothing for power hammer or presses to speak of as far as I know, but my basic thermo class didn't exactly prepare me for HVAC design either, it just gave me the framework to understand what was important.
  10. It puts the mass in the correct place to resist the load forces from that configuration of elbow. By changing the moment of inertia to a higher value you better utilize the available mass of the section to handle the probable load vectors (think I-beams). The primary bending load for a well set log tong is in the plane of the taller part of the section. BTW here is a thread that might be worth review:
  11. I would consider making a "Haberman" bend at the teeth. That will add considerably to the assembly strength in use. Might have been what you are calling the upset. Definitely recommend heat treating and at least medium carbon steel for this effort as well as a really beefy rivet and welded ring.
  12. Thomas, Agreed. There is also a rather profound difference between "natural" (unpowered) ventilation, like you use, and mechanical ventilation (fan powered), like I use. The chimney effect can also come into play. In my shop, in addition to the 30" diameter sidewall exhaust fan (ideal for high airflow/low static pressure applications, think barn peak exhaust fans) I have a 10" turbine vent in the roof peak to take advantage of the buoyancy of the hot exhaust gasses. When it comes to proper ventilation I'm a belt and suspenders guy.
  13. I'm afraid you missed my point. 38 CFM is insufficient. A small toilet room fan will give you that much exhaust. You should strive to get 8 to 10 times that much, at least, if not much more. As for the opening for the fresh air, the size there depends on how strong an exhaust fan you have (external static pressure it can exert), what noise level from the system you can tolerate, and whether you have an issue with entrained weather (rain or snow). A good rule of thumb would be for entry velocities to be kept below 500 feet per minute. I'm not sure what you mean by 3 x 5 holes. 3" x 5" square? How many? It is best to err on the side of caution. In my shop I use a medium size sidewall exhaust fan that probably moves over 15,000 CFM and keep a full size door open when forging. I also have a CO monitor.
  14. It all depends on the size of the unit. You need to look at the airflow the greenhouse system induces when in operation (CFM) and compare that to the room volume and forge burner size you have. Unfortunately ventilation codes have not kept up with the recent upswing in interest in blacksmithing, and provisions regarding venting the appliance (forge) are typically deferred to the manufacturer's requirements (which don't exist in any commercial or DIY builds I've seen). The closest thing in the 2015 International Mechanical Code is for Educational Metal Shops, which require at least 10 CFM per person and 0.18 CFM per SF of floor area. For your 10 x 10 shop that would be a minimum of 38 CFM of ventilation air. In my opinion that is grossly insufficient for safe operation of a smithing shop with a gas forge. I feel that you need to exhaust (and makeup) at least the products of combustion in addition to the occupant ventilation requirement. At minimum I would target mechanical exhaust at 10 air exchanges per hour for your forge. If your roof is at 15' for the 10 x 10 structure that would require at least 250 CFM of exhaust. Personally I don't think sophisticated controls of the exhaust fan are required. Turn it on when you start your forge and shut it off approximately 10 minutes after the forge is turned off. Any other controls are just a potential point of system failure. My personal system has a manual switch for the exhaust fan with an override to turn it on if the room temperature gets to a certain point (set currently at 85 deg. F.).