Jack Evers

When I've made things of spring steel that had to flex, any cooling beyond air cooling seemed to result in breakage.

Different forges and people difference make anything a guesstimate but a pound per hour of burn per nozzle and a dollar per pound cost would be ballpark. Go out to the shop for a couple hours with a two burner going half the time approximately $2.

Different boards, someone just suggested a hood for the gas forge with a squirrel cage blower and dryer vent hose to carry the warm air to your tanks. Sounds like a pretty good solution.

OK back to the freezing propane problem. It has more unknowns than a 25 cent hamburger so you need to fill in your own situation. First to address Woody's concerns about propane/butane ratio. A few facts: air to cleanly burn Methane, the primary component of natural gas, equals 10 times the volume of methane air to cleanly burn propane equals 25 times the volume of vaporized propane air to cleanly burn butane equals 32.5 times the volume of vaporized butane We all know that we can't connect a natural gas appliance to LPG (propane), but to a lessor extent the same holds true for for a propane rich LPG vs a Butane rich LPG. Although LPG is a broad term, it's application in the US and Canada is somewhat narrow. As appliances become more refined the fuel mix is narrowed and the LPG you buy is more defined. Here are some comments from a former LPG certified technician in West Texas and an LPG dispatcher in the Northern Mid west. "The majority of propane appliances (including vehicles) these days require a high percentage propane fuel to optimize efficiency. I have been out of the business for a few years, but I would allow that there few suppliers of propane selling a fuel less than 90%." "yep, you're right for our neck of the woods. we use the HD 5. i just talked to CHS propane division. that's cenex harvest states. there is a commercial grade of propane used in southern Minnesota that is to only go for corn dryers (which is burned in a liquid form-unlike a vapor for houses and cylinders) and if you were to accidentally get it in your tank for your house, it would not be nearly as efficient and make your appliances all burn yellow. so our HD-5 up here cannot be less than 90% propane, it's 5% propylene and the max it can have in it for butane is 2.5% and the mixture does not change during the year. in fact, the guy i talked to,*********, says the mixture hasn't changed in many years. the butane is added to propane because it adds to the BTU content, making it more efficient. " The HD 5 spec mentioned is a fuel spec for the US and Canada which requires the propane to be > 90%. If your supplier may be supplying vehicle fuel, the mix is mostly propane. If you're buying from some off brand such as the corn dryer guys or you're in some other country you need to do your own research, Europe along the Mediterranean allows some extremely high Butane mixes. Seems that driving North to South over there with an LPG fueled vehicle could be a problem. That said, if you can keep the liquid that I'll call propane to suggest it is mostly propane, at zero F or above, you should be all right for delivery pressure. As we draw off vapor the propane comes first and some computer simulations by a Chemical engineering friend suggest that as we use up a bottle that started at 90% propane we may be down to 70% or less propane 30% or more butane when the bottle is a quarter full. The boiling point is closer to -15 degrees than the -44 for pure propane. Heat transport theory suggests that most of the heat transfer into the bottle will be into the liquid so a bottle a quarter full will only receive about a quarter of the outside heat that a full bottle will. A nearly empty bottle costs in three ways, limited heat transfer, a limited latent heat reservoir in the liquid, and an enriched propane fraction meaning lower pressure.or higher required temps. Since transfer is related to wetted wall and our 20, 30, 40 lb bottles are all the same diameter 1/2 full refers to 10 pounds of liquid. 1/4 full in a 40 lb bottle would be the same. Some quick and dirty experiments that I've run suggest that the overall heat transfer coefficient U for a full bottle is around 5 BTU/hr-degree for free convection (sitting in still air) and perhaps 20 with a fan (I used a 20 incher about 4 feet away) Now there are a number of possibilities for the tank: 1) For safety reasons it stays outside and vapor is piped into the shop. You really can't work much on sub zero nights. 2) It's in the back of a pickup, same problems as case 1 3) It's inside a heated shop. Generally no problem until liquid levels are very low and demand is high. 4) It's in an unheated shop that will warm up as you work In cases 1 and 2 with air temps in the 20's or above, the tank at least half full and for case 4, a good fan blowing on the tank will probably keep you in business. One pound of propane vaporized and burned per hr will require a BTU input of 185 BTU/hr, at a heat transfer coefficient of 10 (half full tank and a fan) the required temperature differential will be 18.5 degrees. 20 degree air and zero degree liquid works. At a quarter full, you'd need air at 35 - 40 degrees. For folks looking at electric heating pads and such. 185 BTU/hr is about 60 watts. or a 5 amp heater. A brew belt is only 25 watts. It would help though.That assumes all of the heat goes into the tank. Guess after all the number crunching and asking questions, the only new idea I have is use of a fan (forced convection) It was a fun project though. So keep your tanks fairly full (or use larger tanks) and remember that while a 20 degree wind may be unpleasant to you your propane will love it.

A quick preliminary estimate (hopefully a SWAG -scientific wild xxx guess - rather than a WAG)suggests a heat transfer under a strong fan of about 10 BTU/ft 2/degree F. i.e. if you have a sq ft of surface in contact with the liquid (20 pound bottle about half full) are using about a pound of propane per hour and need zero degrees on the liquid, the air temp is 20 degrees, you can transfer about 200 BTU per hour which would be just about right. I'll do some experimentation.

You might look at this article. http://www.spaco.org/hrvscr.htm Don't know if you started with hot rolled (probably A36) or cold rolled (probably 1018), but the specs on A36 allow almost twice the carbon and some of that stuff can get really hard. It can be annealed but needs more care. As a farrier, I've bought some boxes of horseshoes that had to be worked hot (easy enough) or carefully annealed before working cold. A while back I was making a forged door pull, just grabbed a likely cross section from the scrap bin and, made it, quenched it and trashed a drill bit trying to drill it. Wood ash cooling was all it needed.

It's been a long time since I took my graduate level heat transport course, but I think that I can still figure out an estimate if I can locate my book. Now you're putting the pressure on.

This has gotten me thinking, if the air around the tanks is say 20 degrees or higher, just a plain old fan aimed at the tank would help. I may try to run the numbers this week.

To put it simply, problems start when the liquid (not ambient) temps drop a ways below zero F. When that happens is complicated. How hard are you drawing vapor, how much liquid is in the tank, how long do you work at a time?, I gave an example on Maddog's thread. For the hobby blacksmith (working in an unheated garage probably qualifies) running an hour or so with tanks at least 50% full shouldn't be too much problem at reasonable temps - say 20 degrees or more.

Here's a link to maddog's thread

Last I heard, there were no federal transportation laws on smaller quantities, but state laws could be put in place. Again, the last I read 90# was the break point for small quantities so 100# could be a federal law. I did take the shutoff handle off my truck forge, forcing me to turn it off at the bottle. I was pretty bad about turning it off at the forge while working, then forgetting to turn the bottle off for transport under a cover.

Railroad workers (and I'm sure other places) used a similar hammer to drive spikes while reaching over a rail. http://www.google.co...iw=1265&bih=568

The reason is that if the safety pops in an upright position, you will vent vapor. If it's on it's side with the safety covered by liquid and you vent liquid, it's a good deal more hazardous.

To reply to the statements about insulation, propane can supply about 20 psi of delivery pressure at zero degrees F (liquid temperature, not air temp) and probably 12 psi or so at minus 10*F. In other words unless the ambient temp around the tank is below zero, it would be counterproductive to insulate. The complication is that almost 185 BTUs is required to vaporize a pound a propane. This either comes from outside the tank and is conducted through the walls or it comes from cooling the liquid. 0.6 BTUs will change the temperature of one pound of liquid 1 degree F. This means the energy required to vaporize one pound would cool a pound of liquid by about 300 degrees (185/0.6). If you are running at a level of about 2 pounds/hr (a 20 pound bottle lasting 10 hours),you must supply 185 times 2 = 370 btu/hour to vaporize the liquid. Assuming there is 10 pounds of liquid in the tank and all of the heat came from the liquid, the liquid temp would drop by 62 degrees (370/.6/10). That's OK if the liquid temp was 60 or 70 when you started and you only wanted to run an hour. It's not OK if the liquid was at something like 20 degrees when you started. It's also not OK if there's only 2 or 3 pounds of liquid. In a practical case, then the heat of vaporization comes from both sources, but if the air temps are low and a limited amount of propane starts out already chilled, there won't be much heat conducted through the walls and the propane temp will drop quickly into an unuseable range. Water, a heat lamp, hairdryer, etc can help, but a larger tank kept relatively full is probably the best answer. As a farrier, I do travel with 20 pound tanks and on cold days my forge welds often get brazed instead of welded.

I disagree that the capacity in pounds is pounds of water. Water weighs 8.33 pounds per gallon hence 20 pounds of water is is only 2.4 gallons. Propane is 4.2 ppg and 4.7 gallons would be close to 20#.

I'm more of a farrier than a blacksmith, just lurk around here a bit. They're all good arguments subject to constraints. I remember some time back at a big horse show I was watching the show farrier make shoes. He was telling someone that he got better shoes cheaper by making them. At that time, I felt I could make a pair of shoes about a dollar cheaper than buying them and I could do 4 or 5 pairs/hr. Now it's been nearly 50 years since I was willing to work for $5 an hour, but he had to be there anyhow, making shoes attracted attention so he might as well make some shoes. Today the cheapest bar stock that I can buy is already made into a horse shoe. It still might make sense to make shoes and attract an audience but it's still cheaper to buy them.

Curiosity question, the extra molten metal on the outside is milled off, what about the inside? Or does centrifugal force take care of it and force everything outward?

I have a Vulcon marked at 250 lb, but weighs 280 on the bathroom scale. I can't see that casting was real accurate, and guess that most anvils are at least as much as the marked weight, often more.

Made my first spring hold down many years ago. I knew nothing, quenched in oil, broke immediately. Made the second, heated to non magnetic and air cooled, worked fine, made a couple more, still have all three.

I use Firefox rather than explorer. It has a translate button on the toolbar. First time I ever tried to use the button but it did a fine job of translation. Yuor stand looks fine. Click on the anvil subject area. There was a thread on Anvil stands a couple weeks ago.

Here's a link to a thread showing new face welded over an old one. Beyond my welding skills, but may give you some ideas.

A somewhat different use of truck spring, but still a heat treating question so I'll leave it here. Some years ago I used truck spring to make a barstock shear, 1/4, 5/16, 3/8 thick and up to 1-1/4 width. I merely heated above magnetic and let it air cool. It lasted for years, but what would others have done?

LPG is a gas that can be liquified by pressure at normal temperatures. Basically propane and butane or some sort of mix. Butane requires lower pressure at a given temperature so is safer in hot areas but will start to fail you at temps near normal room temp (assuming you'd like 10 psi or so supply). Propane is good to temps well below zero, but has very high tank pressures as temps go into the triple digits. Your gas company may vary the mix with the season, but use mostly propane..

I have made a forge welded bar shoe on a 9000 foot pass in Clorado. That said, my blower powered Mankle would not weld (I couldn't get the adjustment right) until I replaced the blower with an atmospheric conversion. It is a horseshoer's special plus four from the middle 70's, still in use.

$!69.50 - less than $150/pound - pretty good deal IMO.