courtiron

You can use fibreglass woven sleeving. I use this: http://www.mcmaster.com/#sleeving-insulation/=scinyf Once you cover the coil, it needs to be stretched tight, and then coated with sodium silicate (water glass). This hardens the wrap to a rock like surface, it's less than a buck per foot, and holds up well. The silicone fibreglass that I use, sized for 1/4" tube, also works well, but is affected by the radiant heat... after 7 years my original coil is pretty tattered, but still functions. This is quicker, but does not stand up as well as the coated fibreglass sleeving, buts its a lot quicker... kind of fits with the idea of induction heating... I have no patience :>) paul

@ Tommy ... I haven't seen the plans for the DIY heater, but if it is modular it may be possible to fit some of the parts to your heater. Your power supply is functioning. It may be that all yours needs is to replace the control circuits. I'll have to promote this thread to a start page... :>) paul

I started casting again about 6 years ago. As I cast rather sporadically, I opted for petrobond. It has gone up a little in price since I started using it, and is currently about $60 for 50 pounds. Open the bucket and go to work, no tempering and very little venting required. Not ventilation venting, but mechanical venting of the mold to allow gas to escape type venting. The detail will be very good with petro, but it is a pain in xxxx to mull with blade/roller mullers. The petro will pack under the rollers and stall small machines, and since it won't mix well in these it tends to pulverize the stuff that remains on the plate under the rolls. Petrobond is way fine enough out of the bucket. Id like to try this mixer style this summer: http://www.indiamart.com/emkay/inovating-blenders.html seems like it would blend well. If you are re-oiling petrobond, try a VERY small quantity of low ash two stoke oil or synthetic ATF. Start with a teaspoon for ten pounds or so. Once you add too much, its a mess to recover it. paul

Hey Tod I am afraid you are not missing anything... I started to build the site and got distracted. It's a good thing lots of other things got done... I have been meaning to update the coil info as well. The two right hand coils were an attempt to build a coil that can be used to heat a flat sheet of metal in the center (not just an edge). They did not work well. I have since wound a coil that is fairly effective at heating sheet metal. I have built a flex hose that is about 24" long, and functions fairly well. I understood that Grant had a hose extention available as well. They are a compromise, and while they work they can have problems. I wind my coils to fit my machine, and while the might work on someone elses' system, I cannot guarantee it. I will tell you the safest method of matching a coil to the heater though. I use a digital volt ohm meter that has a frequency counter function built in. Wind the coil and connect it. If the frequency the machine selects to resonate the coil falls in the range of the manufactures specified range you're done. If it is to low, remove a turn or increase the spacing of the turns, and if it is too high add some turns or space the coils more closely. The siliconized sleeving is applied over the coils after they are formed and before they are brazed in the connectors that I use. I prefer flared connections instead of compression fittings... much better electrical connection. This makes a difference at the kind of currents that occur in induction heater coils (possibly as high as 1000 amps). My machine looks different due to the removeable side covers to allow easy cleaning of the interior, you can just see the lock and key near the top on the left hand side.... need better pics... the cleaning should be done on a regular basis. I also DO NOT recomnend anything other than soft water and anitfreeze with a anti-foaming agent (pick it up at AutoZone) be used in my machines. Never use DEIONIZED OR R-O WATER. If this is used without antifreeze you will digest every piece of metal in the machine, antifreeze helps forstall this, but I still do not recomend it. paul

Induction heaters I have been selling 18 KW single phase 220v induction heaters for about 5 years. Out of repect for Grant I didn't really make that well known here. I understand that some folks have been seeking a supplier for units of this size. Please visist www.courtiron.com to see what I have to offer. I have demonstrated the unit I sell at the Quadstate Round up for the last couple of years and have been at the last two UMRBC conferences as well. paul sperbeck Courtright Iron Works LLC forge@courtiron.com

I realize this is rather after the fact, but I thought that I would tell you about my first exposure to bidding. I began work for a small ($750,000 a year) plumbing contractor a number of years ago as a field supervisor. My responsibilities were mostly administrative in nature. I made sure that the jobs had enough manpower, attended job meetings, ordered material and machinery, took out permits and attended to the daily needs of the foremen and the crews. As I progressed my boss had me start bidding small jobs. In plumbing, unlike blacksmithing, the ratio between labor and materials runs around 50-50. The first jobs you bid are scary. You will wonder what you forgot, You will forget somethings... gauranteed. Our bid sheets had some spaces that never varied. You need to factor in overhead, while out custom was not to charge up front for doing an estimate which resulted in a FIRM price, we did include the time that it took in the final price. It is part of overhead. Include applicable taxes, fees disposal charge and shop materials. Floor sweeping compound, shop rags, hand cleaner, brooms and anything else that you can figure out that will need to be replaced from wear. For example: 2 brooms per year? Take price of brooms divided by 2000 to equal hourly dollar figure to add to hourly overhead. That doesn't seem like much, but some one has to by it... it shouldn't be you. Then add everything else... It is likely that the previous owner spent time working with customers and ordering material. You will likely do the same. All the time that you spend not working on a customers' project is overhead. When I worked as a plumbing job foreman I found that the time that i had available for 'working with the tools' varied from 35 hours out of 40 to as little as 10 hours or less out of 40. There are other responsibilities that you have when you 'run' things that do not generate income for the business but still must be done. Try to break down any project into little pieces that you can visualize or time study and use them to extrapolate how much time the whole project takes. Things that you will not likely think of at first but must be included: Material handling Receiving and shipping ordering material Tracking orders and backorders (we never accepted backorders, we found they consumed way more time to track. Better to reorder somewhere else or later if possible) DO A TIME STUDY OF EACH OPERATION YOU ESTIMATED. Did I shout that loud enough? Merely taking the time to estimate an operation is a waste of time if you do not use that as a time study tool. If you did not figure enough time you need to increase that time for the next estimate. If you figured to much cut those to a more accurate number to improve you ability to get more work in the future. I use the word estimate in the sense that it is a tool that you use to arrive at a FIRM SELLING PRICE. Nothing will aggravate a customer more than being given one price, and then later being asked to pay more. Would you by a car if the salesman quoted you one price then when you came to pick it up he asked for 40% more? If you are quoting directly to the customer, you and the owner need to decide how much profit you need to make to stay open and use that to establish your markup. The estimating and costing is also overhead, but if in the years ahead you decide to strike out on your own, the figures that you create daily will always be with you. We had jobs that either the boss or I lost money on. We ate those losses and used them to improve our bidding skills. We did not want a reputation in our industry of some one whose word was worthless. paul

Last summer I was casting bronze at the local Thresheree. We used an alloy of about 88% copper and 12% tin by weight, a classical bronze alloy. Small A-1 graphite crucibles were used and we melted approximately 1-1/2 lb. batches. I had used a small amount of aluminum melting flux 'cause thats what we had. It cast well and all the castings were poured in petrabond sand. We also discovered that the initial melt, ie chunks of tin and chunks of copper melted in about 80% of the time that it took to melt chunks of bronze of an equal total weight. We figgered that the tin melting first provided a hot pool of metal to conduct the heat into the copper faster. We did not do brass last year as I did not have a pyrometer at the time. Overheat brass and nasty zinc oxide is formed... galvanizing poisoning... to be avoided. The bronze did not seem to be as susceptible as copper to oxidation, but that is only an impression... no science content. Another source of tin is 95-5 tin lead solder. paul

Couple of observations on my 18kw heater. I had a request from a fellow smith that I met at Quad State this year regarding heating some 1/2" x 4" flat stock. When I got back to my shop I wound a coil and gave it a try. I was able to raise 3/4" of an inch length of the 1/2" x 4" stock to forging temp in about 40 seconds, and heated over 2" of that same stock in about 2 minutes. With a different coil you can heat 3/4" of 5/8" round to yellow in about 5 or 6 seconds. Coils can be wound and tried in about 15 minutes, and you will find that you will have quite a few coils in a month or so of working with your heater. 18 kw input requires 75 amps at 240 volts. Thats pretty much the max for 220/240 supplies. Higher power inputs will use higher voltages to keep the current down to a reasonable level. If you doubled the voltage of my 18 kw system and kept the current the same, (which is way easier in electronic devices) you would then have a 35-36 kw input machine. Not saying that you can do that... more of an illustration... Most all of the inverter induction heaters use a phase lock loop oscillator to adjust the machines frequency to match the coil that you have installed. Most of my coil designs operate at no more than 50 kilocycles or so. Someone had mentioned surface heating and was wondering how effective these machines were at heating materials for forging. Using induction heaters to surface harden camshafts and the like requires higher frequencies and MUCH higher power levels to quickly heat heat the surface only then and self quench, and even there I would suspect that additional quench might need to be harden the surface. At lower power levels, like the 18kw maximum system that I have, even the surface heating that my system creates will heat the stock though to the center in short order. I had commented before on engineers trying to talk me out of induction heating in the past... "It won't work unless the coil is matched to the stock" What they were saying was it won't work at a level of efficient and speed that matches the production requirements that they expect, but I have found them to be very useful in spite of the engineers predictions.

I was initially discouraged from trying induction heating when I first thought of using it for small shop metal heating years ago. I built and initially tested a converted automobile alternator to use it's 3 phase output without rectification, and while the AC output was a great frequency for through heating, max about 10 kilocycles per second, the transformers and coils required made the experiment unpractical. Fast forward to the solid state modern electronic inverters... the initial units looked great and the phase locked loop frequency adjustment made them more practical, but the cost was HIGH. Now they are much more affordable. The other knocks on them, which also kept me from trying them, was the engineering communities comments about efficiency and localized heating. While the mismatch of coil shape to the end product may be very important in an industrial application, it is much less so for small shop practice. A properly matched coil may heat a shape to useful temperatures in 3.155 seconds.... if mine takes 10 or 12 I don't mind. If the transfer efficiency is 89% for a properly matched coil and mine is 25% but still gets to the same temperature I'm down with that also. Building a coil can be done mathematically and my first efforts were calculated using some freeware I found to match the inductance of the factory coil. I have since become more empirical. I measure the coil that I make with the frequency meter in my Digital VOM, and if it falls within the range of the operating frequency of my heater I leave well enough alone. It is certainly true that a coil may only heat a 3/4" length of a piece of 5/8" round to forging temperature, but it is equally true that by moving the piece back and forth through the coil that I could heat a 6" length as well, sort of like what would happen if you were heating a rod with a rosebud torch. And while less efficient, you can heat a piece of stock by placing it next to the coil in stead of thru it. To get a mental image of what I'm saying remove your ring from your finger and balance it on it's side on your finger. This is not as quick to heat as placing the stock through the coil but it does heat it. Yes they are expensive to purchase, but in operation they draw very little power unless the unit is actually heating. I'd have to ask my wife about the power bills, but if we are billed at about 10 cents per Kilowatt hour, my 18KW heater uses about $2 running for an hour without turning off... my duty cycle isn't that high. Paul

I had one instance years ago where I had to 'fill' a huge gap. At the time I was an apprentice, and as any of you that have been apprentices know, if your journeyman tells you to do something, it is simpler to do it and fix it later if he was wrong. I had two 10" s40 pipes at about 28' above the floor, parallel and separated by about 40'. What I wanted to do was weld one of the 90's on the 39' odd length of pipe and then haul the whole thing into the air and fit the last 90 in and weld it up. The boss laughed and asked if I wasn't capable of welding the other 90 on and keeping it plumb and square? I told him that I certainly could but the odds were that the two runs of 10" that we were connecting to were most likely neither parallel or running on the same plane. I was directed to weld both 90's on. They were perfectly aligned... to bad the pipes weren't. Since I was on one end of the piece and the boss was at the other end when I asked him how the fit up was at his side he said it was fine... he lied... I welded my joint then went to the other end... I had a 3/4" gap at the bottom of the joint and about 3/8" gap up one side. Torched out some of the pipe, and some of the fitting, and even after that I had an ugly gap. Most pipe welding at the time was done with 1/8" 6010 (Lincoln 5P). I still like it a lot. I use 7018 in all positions, but as my eyes age, it gets harder and harder to see the puddle-slag interface of 7018... I used a defluxed piece of 5/32" weld rod as a filler rod and filled the gap. And while the huge gap will certainly shrink a lot more than a properly fitted joint, the filler pass and the cover pass that is the norm in pipe welding (3 passes are common, root, filler and cover pass) also anneals each prior pass... hopefully that reduced the stress somewhat. The last time that I had a opportunity to check the job, some thirty years later, that joint hadn't failed. I asked a journeyman that was getting ready to retire some years ago how he knew when it was time to retire... he just looked at me and said "you'll know". Took another 15 years but last year I "knew" too. After 41 years in the pipe industry I pulled the pin and retired also. When you get to demo a building that you helped to build the hand writing's is on the wall. Hopefully I never became that crotchety old duffer that I had to put up with on that pipe job. I was still having a good time, but it was time... Paul

Just for safety sake measure the voltage between the blower frame and ground. You will likely have to disconnect the ground to do this. This blower should be grounded when in operation even if there was no provision for it as it was manufactured. I repaired one of these some time ago, and coal dust had collected on the armature around the commutator which resulted is a leakage voltage of some thing in the neighbor hood of 65 volts. NOT GOOD. At least ground the frame, but if you have leakage you should either repair the commutator yourself or have it checked out at a good motor shop. This is only a problem with universal motors (those with brushes) but if you have a rheostat speed control that is most certainly the type of motor that you have. Paul

Just for safety sake measure the voltage between the blower frame and ground. You will likely have to disconnect the ground to do this. This blower should be grounded when in operation even if there was no provision for it as it was manufactured. I repaired one of these some time ago, and coal dust had collected on the armature around the commutator which resulted is a leakage voltage of some thing in the neighbor hood of 65 volts. NOT GOOD. At least ground the frame, but if you have leakage you should either repair the commutator yourself or have it checked out at a good motor shop. This is only a problem with universal motors (those with brushes) but if you have a rheostat speed control that is most certainly the type of motor that you have. Paul

Tried this a few years ago and wrote it up for the UMBA newsletter. I took a 12" chunk of 1018 cr and heated one end and forged to about 3/16" flat and quenched it. Then I forged the other end to 3/16" and fluxed with borax and coated it with cast iron turnings from a brake drum lathe. Heat it just below a welding heat and quench it. One end clamped in a vise bent to a 90 and the end with the castiron turnings fractured when I tried to bend it. Don't know how high the carbon was but it was hard. It's not case hardening but it did get hard.

Don't know about forge welding it, but it tig welds just fine.

If you have trouble locating dc blower motors, check here Burden Sales Surplus Center pretty cheap, and they have been around for years.