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  1. This is all very helpful. The slab roller is still just an idea, since I have several more time critical projects to tackle. However, if I do decide to build one, I will probably not be worried about using chain drive.
  2. I have had some success lately building an extruder and some custom dies for my daughter, so now I want to move on to the more ambitious project of a slab roller. I want to build something better than the do it yourself cable driven single roller type. Those are quite clever in design, but also seem to have many drawbacks. My daughter does mostly hand built work from slabs, so if I build one, I really want something with a wide two roller design similar to the North Star. I plan on using surplus thick wall aluminum irrigation pipe for the rollers. Knurling the rollers will take some effort, but I think I am up to it, and the tensionizing adjustment does not seem too difficult. But driving the rollers will be the real challenge. I do not have the ability to machine custom gears, and purchasing them can really run up the cost. Also, gears are much more fussy about precision alignment and engagement. But bicycle chains and gears are readily available and produced at an economy of scale such that they are very affordable. They also do not require as much precision, and by selecting the correct gears I think I can get a 4 to 1 reduction ratio similar to the high end machines.. But are they strong enough, and are there any unseen issues? I have seen some moving table style slab rollers that use cables or chains. Other than the known disadvantages of the moving table design over a dual roller design, how do they hold up? Do the chains wear quickly or break under heavy use? Has anyone ever tried driving a dual roller setup with chains, and discovered it is a dead end? Does anyone know how much force is needed to drive a roller on a system like this? And, am I crazy to consider trying this approach? The chain path will need a bit of thought to get the rollers to both move in the correct direction, and to also maintain proper tension as roller spacing changes. But am I missing something else that will be very important? Eventually I may just give up on the idea and just help her buy what she really wants. But like I said. I know that I can build the rollers and the tensionizer. It would really just be a matter of designing and fabricating the correct drive mechanism. What types of issues are seen on these dual roller units?
  3. I believe that the entire gas supply for both the pilot and the main burner is controlled by an electrically activated valve controlled by a thermocouple. That's really about all there is to the system. If the temperature sensor at the pilot is not hot enough to show that the pilot light is really on, no gas will flow to either the main burner or the pilot. The only other part of the system is the red button, which is just a simple momentary bypass valve to provides an easy way to light the pilot. It only supplies gas to the pilot though, not the main burner. With most of these valves there is even a mechanical lockout that only allows you to depress the red button and light the pilot with the manual control valve for the burner in the off or pilot only position, so that the appliance does not suddenly start up while you are still lighting the pilot. As always, exercise extreme caution around any gas appliance, and contact a knowledgeable professional if there are any issues. Also be aware that parts on most of these systems are not interchangeable. So, even if there are user replaceable parts, you will need to insure that you have the exact right replacement parts. So, if the pilot light lights when you press the red button, but then goes off when you release it, there are usually only four common reasons. 1. You did not hold the button long enough, so the thermocouple did not get hot enough. 2. The pilot light is not heating the thermocouple well enough to work due to alignment or flame issues. 3. The thermocouple is bad. or 4. the main switch is bad. Given your tests so far, (heating the thermocouple with an external source), 1, and 2, are probably not the issue. Cleaning the contacts was also a good move. It is still possible that you have a bad thermocouple. That is the most common failure point since it sticks directly into the flame and deteriorates over time. But a stuck or corroded valve is also a possibility. That is something that just should not be second guessed. If you have not tried replacing the thermocouple, you might try that. Otherwise it is time to replace the whole thing.
  4. Wow. Thanks for all the great advice. Particularly the videos. I will definitely forward that to my daughter. She is new to doing her own firing and kiln maintenance, so the advice should go a long way to getting her on the right track. BTW. I did end up calling Skutt. It took quite a while to get through to a technician. But once I did, they were quite helpful. Here is a summary of what they told me. If you are having trouble with the kiln not reaching temperature, or having long firing times, there is nothing better than reading the resistance directly with an ohm meter to better understand what is happening. However, for typical operation of a kiln with built in diagnostics, you should not need you to do that. Just using the diagnostics screen to read the current is probably all you need to do. For this kiln they said the current should read about 18 amps for the top and bottom elements when they are new, and 15 amps for the center elements, also if new. Once they drop to 16 amps or lower for the top and bottom elements, or 13 amps or lower for the center elements, they probably need to be replaced. I asked if reading the current was less reliable than reading the resistance. But they said that directly reading the resistance has no advantage as long as you have a good reading. If the current reads good, that is a reliable indication that everything is working properly. If the current is low there might be more reasons for it other than worn elements, such as low line voltage, a loose connection, or a failing relay. That is when you need to do more testing. But if the current reads good, that is the best indicator that you should get a good firing. They also said that if you are ever worried that a firing is taking a bit longer than expected, or something just does not seem right on an SK series kiln, you can reassure yourself by just hitting the 7 key on the front panel at any point during a firing. Hitting the 7 key while the kiln is firing will cause it to report the current in amps that each element set is pulling. You can compare that to the rated current for your kiln, and verify that the kiln is still operating properly. If one of the elements reads a really low or zero current, an element or relay is probably worn or damaged, and you will probably need to abort the firing. But otherwise it just helps to reassure you that everything is OK, and the firing is proceeding properly. I also asked if you had a bit more leeway in when you replace the elements, since my daughter is only firing to cone 6 rather than cone 10. But he said not really. Cone 6 does give you a little extra margin, but not a lot. If she was doing low fire work to say cone 06, you might be able to wait longer to replace the elements. But cone 6 is close enough to the temperature of cone 10 that you probably would not get a lot of extra life out of an element that had dropped below the rated current. At least that is what they said. Thanks again.
  5. Hi, I am not an artist, but am helping my daughter set up a new studio in her garage. Or a garagio as I believe it is sometimes called here. She has worked in a community studio for some time, and now wants more control over her work. The plan is to slowly add to the studio and eventually transition to it over the next year or two. She recently bought a used Skutt KM 1027 kiln which we wired up while I was visiting. This kiln has built in diagnostics, so I was wondering if regularly testing the element resistance is really needed most of the time. From the diagnostics screen you can have the kiln measure full load amps, voltage under load and unloaded, and the current through each set of element pairs individually. It does not seem to have an automatic resistance measurement, but these built in readings seem adequate for most day to day monitoring. I checked the service manual, and it states that an increase in resistance of more than 1.5 ohms indicated elements that need to be replaced. For the elements in this kiln, that is about a 5 or 6 percent increase. Using ohms law, this would mean that a decrease in current of 5 or 6 percent would also indicate worn elements. If you have a kiln with built in diagnostics, shouldn't it be fine to just monitor any drop in current until you see a significant change? My daughter certainly has a good quality multi-meter, and regularly checks the elements in her smaller Paragon kiln using it. But the wiring on the small kiln is less complicated and easier to access. Unplugging the larger kiln and opening up the access panel to individually check the element resistance seems like overkill unless there is an indication of issue. Particularly given the built in diagnostics. What do you folks do? Now I know that if a problem occurs, nothing beats directly reading the element resistance, because you might have other problems. A relay might be going bad, or there could be a poor connection somewhere. There might also have been a drop in line voltage under load, although the kiln does measure that as well. But on a regular basis, it would seem fine to trust the current readings, and not break out the multi-meter until there was more of an indication that something was going wrong. How often do you folks break out the ohm meter and test elements at the source? And do you open up the access panel and test the resistance at the connectors as Skutt shows in their manual, or just probe the elements inside the kiln? Also, would it depend on weather the kiln has any built in diagnostics? I will probably call Skutt to get the official story, but sometimes the folks using the equipment on a day to day basis have more practical advice. By the way, the kiln is supposed to be capable of reaching cone 10, but she only plans to fire to cone 6. Does that have any effect of how carefully she needs to adhere to the recommended replacement resistance? The elements right now are showing less than 1 ohm of resistance change,and are not warped or sagging. But I was wondering in the future what advice to give her.
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