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R Fraser

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Everything posted by R Fraser

  1. I thought is was like toilets flushing and tropical storm rotation, it depends on your location relative to the equator? Richard
  2. I too found finches book helpfull. The price on Amazon has got to be an error because that is where I bought mine and it was well less that 700 USD! Amazon was kind enough to offer to buy my used copy for 2.03 USD though! Talk about depreciation. Richard
  3. The Sandia Forge reported up to 30% improved efficiency if I remember corectly. Nils Lou suggested significantly increased efficiency with his recuperating power burner set up but I do not remember if he made any specific claims. I would be concerned that depending on the location of the recuperators and the temp of the exhaust gases a closed loop system relying on natural draft flow to feed the burners primary air the CFM flow of primary air may be low, possibly too low to offer any meaningfull cooling of the recuperators and thus the burner. This would also limit your ability to control the
  4. This sounds like a recuperating (spelling?) type furnace I first read about when making my first blacksmith forge, I found the plans on the Sandia website (many years ago). It called for oval stainless steel pipe(s) running through the exhaust vent that was then collected and used to supply combustion air to the burner(s). These were atmospheric burners, and it was a small furnace < 2 cubic feet. In Nils Lou's book "The Art of Firing" he talks about a similar design for a ceramic kiln, but it is using a power burner with the blower first running through a pipe matrix in the exit flue to pic
  5. I just built a kiln of this size and to fire to cone 10 in 8 hours (roughly) it needs 320,000 BTU/Hr input, and I have 2 burners that are fueled by high pressure propane that will put out 150,000 BTU/Hr on 3.5 PSI. I have fired several times now and have to throttle back to make it to 8 hours. The design is mostly a modified Oregon Flat top design as discussed in Nils Lou book the art of firing. The Burner you have pictured looks like a MR 750 or MR 100 style burner, but as pointed out type of fuel and how supplied, your elevation, orifice size, size of supply pipe, regulator capcity all influ
  6. My Laguna Pacifica wheel actually came with the advice to spray the belt with a silcone based spray on lube periodically to keep it quiet. Seemed like it would make it more prone to slippage, but I never did have that problem. When the belt got noisy, like neoprene rubbing unhappily together a quick squirt made it retunr to silent running status. Richard
  7. I bought a ball mill from an EBay vendor that is very servicable for about 150.00. I have milled several rounds of glaze for Raku and cone 10 reduction using the "jars" made from schedule 40 PVC plumbing fixtures (6" pipe, closed end cap, reducer and rubber cap secured with a SS band clamp. I bought ceramic ball media from a ceramic supply vendor in 1 inch, .75 inch and 0.5 inch sizes. It seems to work great, and I have made my own jars since for far less than the EBay vendor was charging. I imagine over time some of the PVC winds up abrading off the inner walls, but I have assumed any present
  8. I read a tip somewhere that you can use the same diffuser to mass produce bits of wadding from your favorite wadding formula, just roll it into the diffuser, let it dry a bit and invert. Presto! Never occured to me to make little itty bitty tiles. Could make a very cool mosaic with these! Richard
  9. I have a safety tip. Much of what is sold as "consumer grade" disposable gloves are not latex free, and you may have to read the fine print to know it. All health care facilities are now "Latex Free Zones" due to the risk of serious allergy developing over time to latex both in staff and patients. Significant allergy can occur often only after sustained chronic exposure. The non-latex gloves do not have the same degree of elasticity and in some cases the same feel as the latex based gloves. Make sure you look for latex free on the box, particularly if you know or suspect you have a latex sensi
  10. I have a strong affinity for a Shinto style belief system when it comes to my kilns, and generally offer premium Sake or good quality single malt Scotch to my little kiln Kami cups. I also feel strongly that my kiln Kami do not like to drink alone, so after loading and before lighting the pilot burners I have a toast or 2 to the happiness of the kiln and its ware, and another wee dram to wish for a safe & happy firing. It is surprising that the Greeks felt they needed more antagonistic dieties than charitable ones when it came to their pottery. Richard
  11. I love mine, and the free wheel feature is actually pretty cool. I have not noted bogging when throwing larger bits of clay though I must admit I do not often ask the wheel to spin more than 30 pounds. It is very quiet. I like it much more than the Pacifica 400 I was using. I threw on Brents in a studio and prefer my Shimpo. Richard
  12. Thanks for this. I was pretty sure that the math was done for this. This info is very helpfull. Richard
  13. After enough electrical disasters (sawzall vs. 220 line on the far side of the joist, small electrical fire after 220 wire of new dryer- fire department not involved) to make most sensible people actually pay a qualified person to do the work you would think I would know better, and yet… I bought a new 10 CF electric kiln and put in an 80 amp breaker for the 220V service, and bought some copper cable the size of a baby’s arm to hard wire the kiln to the junction box. Now I know the conventions for electrical wiring i.e. green = ground, and the large green cable in the guts of the
  14. Wow, that is a very cool set up. I think instead of re-building this kiln this summer perhaps I will build some power burners. I do have a couple of questions: are you running natural gas or propane, if propane are you on 11in WC or high pressure. How did you determine the CuFt/minute for the blower to orifice match? Do you have an orifice chart? To do this my current build the high pressure pilots and Baso's were by far the most expensive part, but safety first. So I would need to base any power burner on the high pressure propane source if I want to include the pilots and Basos. I do have
  15. I asked Marc Ward about this when I was planning my Raku kiln and he felt positioning the burner in the middle aimed straight in was fine, as the high pressure burner generates alot of turbulance on its own. I was going to try to point it along a tangent to the kiln interior to swirl and mix it up inside but it would have been difficult to get it aimed that way, and the flame tends to hug the wall it is aimed along anyway. Straight in has worked great for me and if there are any "cool spots" in my kiln I have not been able to find them. My octagonal shelf sits on three 8 inch posts which puts
  16. Thanks to all that replied to my post. I found the suggestions most helpful. I found the round foam pads I purchased a couple of years ago specifically for the purpose of trimming large platters and started to use them again as well as using a thin plastic recycling bag with the center cut out to the size of one of my 12inch bats to keep the rims from drying. I threw another 8 platters from 9 to 10 pounds resulting in around a 16 inch platter and not one has cracked. I really think that in addition to keeping the drying even, trimming the foot ring with the center of the platter well supp
  17. I love your burners! I was going to build power burners as I have a blower from by forge that I am not using but was not sure about the orifice size and pressure, to air flow rate ratios for optimal performance. New power burners are big $$, but as you demonstrate very easy on the wallet in cost of firing. I think I am burning at least 14 gallons of propane in a firing for this kiln. Did you make the burners yourself? You are probably using low pressure propane too? Richard Here is a picture with a list of parts of my forced air burner. If you have any questions let me know. Aloha,
  18. R Fraser, now that's a kiln! Very nice. I think enlarging my inlet and possibly the outlet is probably the answer for my problem. Why would you want to create back pressure? If I want to alter the kiln atmosphere during the firing, ie to fire the glaze to maturity in a reducing atmosphere can alter the glaze appearance, in which case I often let the glaze cool more before placing it in the reduction container. It mainly allows me more options to manipulate the final glaze appearance. Restricting the exit flue alters the flow of secondary air which changes the effeciency of the combu
  19. My first firing was about 10 years ago, no fiber, one forced air burner, cone 10 in 4 hours. It was too fast, unlike the Olympic Torchbearer the top was 2 cones cooler. Over the years I added fiber, another burner and two collars. I added fiber to slow the cooling for better glaze colors. Adding the second burner at the top evens out the firing. The forced air burner are very efficient. I now fire in about 7 hours to cone 10 with about 9 gallons of propane. Aloha, Ken I love your burners! I was going to build power burners as I have a blower from by forge that I am not using but wa
  20. It is true that if the secondary air is restricted by having the burner too close to the inlet port, and or the burner port diameter is too small relative to the burner diameter the temp rise will quickly stall. On my current raku kiln I run my MR 750 around 2 inches out, and the inlet diameter is an inch to an inch and a half greater than the burner diameter. I usually leave the burner damper open fully. The exit flue is 8 inches and when I want to reduce the glaze during firing I can adjust the exit flue with an IFB to create a little back pressure. My kiln is 24 inch diameter cylinder by 26
  21. My first raku kiln was a brand new garbage can with 1 inch of 2300 degree cerawool liner held in place with porcelain buttons. I used a 300K BTU high pressure propane weed burner for the first few firings then a MR 750. Like Marcia says about an hour for the first load and 30 to 45 minutes for following loads. It still amazes me that even though I routinely hit 1900 degrees on my pyrometer the paper lable on the can never burned off, only just slightly browning over time. The temp probably could have come up faster but I always try to go gently through 950 to 1100 degrees so I slow down the pr
  22. I should have added that I use a large cut off bow I made to free the platter immediately after throwing. The cracks pretty much cut down the middle, more or less tracing the diameter of the platter. With previous platters I had used 2 inch high density foam bats to support the span of the platter. This time however I threw a large clay chuck to trim the platter and the middle was un-supported. Several - probably all of them that cracked - 6 now, were soft enough I am sure there was some sag, and the dryer ones probably developed the cracks while trimming since the chuck really only supported
  23. I need some advice about platter related matters. I recently threw 10 platters that started with 3kg to 4 kg of stoneware (Continetal Clay Buff Stone Ware with Ochre), and 2 havecracked in the middle during drying after trimming the foot rings. I had trimmedthem a little wetter than I typically like but had time constraints as usualand felt they were sufficiently firm for trimming. After trimming I put theplatters on ware boards and covered them with plastic sheeting (formerlykitchen garbage bags). For certain the rims were a bit dryer than the center sothere was some moisture disequilibrium,
  24. I converted a 10 CuFt Olympic Torchbearer in a similar fashion and I used 2 MR 750 burners on high pressure propane and never had to exceed 5 PSI to fire to cone 10. I could easily have run most firings in 6 hours or even less if I wanted to as the the MR 750 has more than ample capacity on HP propane (BTU/Hr) to fire a 10 CuFt kiln even with just 3 inches of IFB. I never added any insulation except at the base as it was hard brick (a terrible heat sink-probably eating 20K BTU/Hr per firing). My intent was more to explore the possibility of converting to down draft and really wanted to even ou
  25. I read about plans for the same thing on an Roger Grahm's web site from Australia. All you need is a 2 lead type oxygen sensor and an Ohm/Voltmeter. Apparently you can buy used oxygen sensors fairly cheap from junk yards if you remove them yourself, but I priced new Bosch sensors with an extended probe at around 100.00USD. There is a thread about this on clayart but the original (as far as I know) discussion and link to the PDF with the how to set up and "calibrate" is found here: http://members.optusnet.com.au/~rogergraham/the_kiln_exhaust_sniffer.pdf The Main page that is filled wit
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