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I need to to put together a DIY rotary ball mill, ideally the drum would spin at about 60 rpm. If I buy a second hand, relatively low power AC motor with around 1000 rpm written on the side my understanding is I can get a dimmer circuit and wire it in to slow the spin speed. Does this sound about right? Is there a better way of going about this on the cheap?
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Dec 11, 2019 04:33
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Rozzbot posted:I need to to put together a DIY rotary ball mill, ideally the drum would spin at about 60 rpm. A dimmer isn’t what you want. Modern dimmers for lighting work by rapidly switching on and off and effectively chopping off portions of the AC sinusoid and sending less power to the load. This works fine for resistive loads like lights. It doesn’t work well for reactive loads like AC motors. Also, the kind of motor matters. If this is a single-phase induction motor, which is probably is, then the motor speed is determined by frequency, not line voltage, so simply varying the supply voltage won’t change the speed. If you load the motor and reduce the supply voltage, you will see a reduction in rpm and in torque but the motor will still be attempting to synchronize with the input frequency and you can damage the motor that way. Torque is a factor of voltage:frequency ratio, and varies by the square of the applied voltage. So you load your motor and reduce the voltage to lower the torque to lower the rpm. Reduce the voltage by 50%, the motor’s now only producing 25% of the rated torque, and it’s slipping madly and drawing more current to try to stay synchronized but it can’t and that current’s just turning into more heat and burning out the windings.That’s not how you want to do speed control. Single-phase induction motors aren’t really well-suited to this, but depending on the specific kind of motor a variable-frequency drive could work, because it can vary both voltage and frequency to keep that ratio constant. NB: am exception would be shaded-pole motors, like those in ceiling fans. They have low torque output anyway, so you only see them in applications that don’t require a lot of torque, like the said aforementioned ceiling fans. And that’s how those can get away with using dimmers or triac-based fan controllers. But even then, 60 rpm is a really low speed, I don’t think you’d have much luck slowing one down that much. Phanatic fucked around with this message at 05:53 on Dec 11, 2019 |
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Dec 11, 2019 05:08
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Rozzbot posted:I need to to put together a DIY rotary ball mill, ideally the drum would spin at about 60 rpm. I am going to guess that someone will reply with a picture of a dimmer circuit burnt to a crisp that had been running a ceiling fan. I would imagine a fan controller would do a better job than a dimmer. E: Based on the above, I am probably wrong. I mean, it is probably true that a fan controller would do a better job than a dimmer, but also probably not right. carticket fucked around with this message at 05:12 on Dec 11, 2019 |
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Dec 11, 2019 05:08
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Rozzbot posted:I need to to put together a DIY rotary ball mill, ideally the drum would spin at about 60 rpm. Were you going to direct drive it or use a belt? With a belt you can just make the wheels sized correctly for a 1000 to 60 reduction. You'd end up with a ridiculously energy inefficient and high torque ball mill though 
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Dec 11, 2019 13:17
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Rozzbot posted:I need to to put together a DIY rotary ball mill, ideally the drum would spin at about 60 rpm. Even if you have the right "dimmer" (motor controller) a 1000 RPM single phase AC motor is going to have basically no torque dialed down to 60.
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Dec 11, 2019 17:48
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I could probably run it like 120 rpm but I doubt that's going to make the situation much better. There's a few 60 rpm motors on eBay but they are 24V so I'm not sure they will give enough torque. However, they are so cheap I'm just going to try one of these out first. Thanks!
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Dec 11, 2019 22:12
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Rozzbot posted:they are 24V Aren't those DC motors? You'd need a power supply to run it too.
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Dec 11, 2019 22:14
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Yeah, we've got a bench supply we can trial it on till we figure out something permanent.
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Dec 12, 2019 00:57
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So I'm replacing the outlets in my basement because they don't match the paint (parents repainted the walls but left in the ugly black outlets) and aside from realizing all these outlets are 15a on a 20a circuit which I learned isn't per code I think, I don't think caulking an outlet is either? If it is code then it's still a pain in the rear end to remove
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Dec 14, 2019 04:04
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Rozzbot posted:I could probably run it like 120 rpm but I doubt that's going to make the situation much better. Most 60RPM motors are just 3600RPM motors with a gearbox. A multiple-pulley setup to run your motor at 1000 RPM and have it spin the drum at 60RPM is best here. That's roughly 16:1, which means a 1.5" pulley on your motor spins a 24" pulley on your drum; this doesn't seem great. A pair of 6" pulleys and 24" pulleys gets you a 16:1 reduction without too much trouble.
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Dec 14, 2019 04:20
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Endymion FRS MK1 posted:So I'm replacing the outlets in my basement because they don't match the paint (parents repainted the walls but left in the ugly black outlets) and aside from realizing all these outlets are 15a on a 20a circuit which I learned isn't per code I think, I don't think caulking an outlet is either? It is pretty common and allowed... And then I stumbled onto this on the internets which seems to help confirm it. There is an exception in Code which permits the common 15A receptacle on 20A circuits if there are two or more sockets on the circuit. (NEC 210.21B3). The common double receptacle is two sockets. Mirroring that, there is a UL requirement that all 15A receptacles must have an internal capacity of 20A - only the socket itself is 15A.
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Dec 14, 2019 05:38
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Table 210.21 (B)(3) Circuit Rating - 20 Receptacle Rating - 15 or 20 It's completely allowed. Now, this does all depend on what you're drawing down there.
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Dec 14, 2019 15:51
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I'm noticing that nearly every plug in my house is so loose the plug falls out. I looked online and see people changing out the middle plug piece and it looks doable, but is this something that can reasonably be done, or is this one of those things you should hire an electrician for?
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Dec 16, 2019 17:29
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Just replace the whole outlet. They're cheap.
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Dec 16, 2019 17:57
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Yeah they’re like a dollar each just replace them. And it’s definitely DIYable.
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Dec 16, 2019 18:38
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I just realized the "middle plug" is actually the whole outlet, so I guess I'll give it a try and not kill myself. My uncle lost half a hand due to electricity, so has been a low key phobia of mine.
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Dec 16, 2019 18:43
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LorneReams posted:I'm noticing that nearly every plug in my house is so loose the plug falls out. I looked online and see people changing out the middle plug piece and it looks doable, but is this something that can reasonably be done, or is this one of those things you should hire an electrician for? I assume you mean the whole receptacle, there are no user serviceable parts inside. You're going to find generally 4 parts here: The cover/faceplate, the receptacle itself, the wires, and the box it all lives in. Generally this should be easy, assuming your wiring isn't degraded or super old. If you want a hot-take on if the wiring is going to be a problem for you and own 0 specialized tools for electrical work go plug a lamp into one of the oldest looking outlets, turn it on, and go kill the breaker. Go back, verify the lamp is switched on but not illuminated. For extra overkill, go verify the lamp is still on & functional in another outlet. Grab a small flathead screwdriver and undo the 1-2 screws on the faceplate and remove the faceplate. Be careful not to jam anything behind it, if it's stuck to paint then a razorblade just along the edge should help you. Take a well lit, in focus picture or 2 of the inside of the box and post it here. Put the cover back on, re-energize the outlet at the breaker. From there the supplies are generally this, with the caveats of if it's in the bathroom or kitchen you need at least 1 GFCI outlet, and it's probably supposed to be 20 amps. These are $20/ea. They will save your life. Match the shape: https://www.homedepot.com/p/Leviton-15-Amp-Tamper-Resistant-Duplex-Outlet-White-10-Pack-M22-T5320-WMP/100684043 (Or singles if you're only doing a few, or want to try your hand first. Note the "TR".) https://www.homedepot.com/p/Leviton-Decora-15-Amp-Tamper-Resistant-Duplex-Outlet-White-10-Pack-M22-T5325-WMP/100684055 Buy these: https://www.homedepot.com/p/Klein-Tools-Non-Contact-Voltage-Tester-NCVT-1SEN/100661787 https://www.homedepot.com/p/Commercial-Electric-Outlet-Tester-with-GFCI-OTG-102R/206029151 A small flathead screw driver, and a philips screwdriver because gently caress flathead. (And philips.) First go around and test your outlets with the outlet tester. If you find anything wrong write down exactly what it was so you can potentially fix it later. The most common is going to be missing ground and "hot/neutral" reversed. Practice with your non-contact voltage detector - figure out a known-on and known-off indication. If you can't get both of those stop work and come post about it. Now on to replacement. Generally you kill power at the breaker, verify it with the non-contact tester, remove cover, verify it again, look around inside with the a flashlight and make sure it looks like the sample picture above, remove the outlet from the box, note where the wires are going (brass, silver, or green screw, wire color) - label them with some masking tape if you need to. Unscrew the wires carefully. Toss outlet. Screw wires to new outlet making sure everything is how it was before assuming it was correct (black/brass, white/silver, bare/green), reinsert it, screw it down, replace the cover, re-energize, test with your outlet tester. Torque on those screws is "hand-snug", if you crank it down you're going to strip the screws, crack your faceplate, etc. For a professional like, orient your faceplate screws vertically, backing it off half a turn if you need to while still maintaining it snug to the wall. It shouldn't flex assuming everything is done correctly. Now sit back and laugh because lord knows you're going to find some hosed up stuff in there and this all assumes ideal best case scenario. If you find cloth insulated wire, knob and tube, or a general clusterfuck I wouldn't pull the outlet from the box. You're quickly going to get into electrician territory if you don't want to crawl around in your attic/crawlspace or cut the walls. Note: I did not read the words, but this site has good pictures of said ideal best case: https://www.thespruce.com/install-an-electrical-outlet-or-receptacle-1824695
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Dec 16, 2019 18:45
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LorneReams posted:I just realized the "middle plug" is actually the whole outlet, so I guess I'll give it a try and not kill myself. My uncle lost half a hand due to electricity, so has been a low key phobia of mine.
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Dec 16, 2019 18:46
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Bad Munki posted:Get an outlet tester if you don't have one, use that to make sure you've found the right breaker. A non-contact tester is also good, but really only rely on that to confirm there IS power, rather than a lack of it. That is, only count on those to say "YES POWER" only, they don't have a "NO POWER". Silence is not a response! I do give myself a high confidence reading on "likely no power" by keeping an energized extension cord near me and going "off (outlet), on (cord), off (outlet)" - takes 2 seconds and doubles as a light source for working.
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Dec 16, 2019 18:50
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Use tamper resistant (TR) outlets as has been mentioned. They come in 10 packs to save you some money. An outlet tester is nice to have too, but you can use a lamp or anything else that plugs in to verify that the circuit is off. A radio is nice for this as you can verify circuits by yourself at the panel if you turn it up loud enough to hear. When the music stops, you found the circuit. Since you'll be working on so many circuits, now would be a great time to label your circuits if they aren't labeled already. Take a face plate to the store to match the color. There are 2 shades of beige.
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Dec 16, 2019 19:26
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kid sinister posted:There are 2 shades of beige.
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Dec 16, 2019 21:25
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Also face plates are cheap if you buy them in a box of ten at a time, so if any of yours are cracked, chipped, scorched, painted over, mismatched, or otherwise imperfect you can replace them all along with the outlets. Plus you can be sure the colors match and if you prefer the look of 'decora' style rectangular shaped outlets you can get those instead.
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Dec 16, 2019 22:44
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Nevets posted:Also face plates are cheap if you buy them in a box of ten at a time, so if any of yours are cracked, chipped, scorched, painted over, mismatched, or otherwise imperfect you can replace them all along with the outlets. Plus you can be sure the colors match and if you prefer the look of 'decora' style rectangular shaped outlets you can get those instead. BTW these boxes are "down" if you look at the supplies in any store. Aim for the literal bottom shelf and look for a tag that says "contractor pack". The stuff at eye level will be $1+/plate fancy bullshit. It's literally $2 in materials, outlet included, to replace an outlet and cover.
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Dec 16, 2019 23:02
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kid sinister posted:There are 2 shades of beige. Ivory and Almond.
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Dec 16, 2019 23:21
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not sure if this is where this goes, but i might as well ask. i'm trying to run power to my outdoor shed - probably in the 50 amp range - and while I have an electrician to do all of the actual wiring, I'm gonna do the trenching and conduit work myself. my big problem? my deck spans the entire width of my lot, which means there's about 50-60 feet or so that i can't vibratory plow, trench, or even directly access the ground below my deck. does anyone have any recommendations short of renting a small directional drill? is there any conduit I can run along the surface of my deck within code?
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Dec 17, 2019 02:53
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Pull up some boards and dig between the joists? No, you can't lay conduit along the ground. The shortest depth allowed is rigid conduit at 6 inches deep. However, rigid is the hardest conduit to work with because, well, it's rigid. There's no digging a vaguely straight trench that the conduit can bend to follow with rigid. It has to be straight, dirt and tree roots be damned. Keep in mind the 360 rule for conduit. You're allowed a maximum of 360 degrees of conduit turns between pull points. That's 4 right angles max. Where do you live that the ground isn't frozen right now? In St. Louis, we had a snowstorm so big, my kid got today off school and they already called off tomorrow. Oh, the other 2 choices for buried cable are UF cable with no conduit at 24 inches deep and THHN inside PVC conduit at 18 inches deep. Even with UF, you'll need to protect it in PVC from where it exits your house down to depth. Same goes for the shed. kid sinister fucked around with this message at 03:13 on Dec 17, 2019 |
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Dec 17, 2019 03:11
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Open up the deck, dig your trench, then close it up again. I was asking similar questions a few years back when I just wanted to go under a 4' section of concrete sidewalk, and got the same answer.
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Dec 17, 2019 03:27
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the big problem is that my deck is a; framed by an insane amount of hardscaping and b; the boards run perpendicular to what my trench would need to run, so the joists are right but I would need to tear up like half my deck, two hardscaped walls, and a paver staircase just to run twenty feet of conduit. i dig a lot of irrigation, I'm not worried about trenching a straight line, it's just accessibility that's an issue. i'm in New Jersey, it's been staying kinda mild and insanely wet so i could dig if i had to, but this is probably not happening until the spring. I'm just trying to figure out the best way to approach it.
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Dec 17, 2019 03:29
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A 50S RAYGUN posted:the boards run perpendicular to what my trench would need to run That's how decks are built, with the deck boards perpendicular to the joists. Either direction, you'll have to deal with wood.
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Dec 17, 2019 05:42
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i know, it would just be way easier to pull up three boards and dig under six joists than to pull up like thirty two boards. any other options? I couldn't run it along the top of my fence or something?
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Dec 17, 2019 06:18
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A 50S RAYGUN posted:i know, it would just be way easier to pull up three boards and dig under six joists than to pull up like thirty two boards. Where are the power poles? Separate service is an option.
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Dec 17, 2019 07:43
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trench -> box -> conduit along the face of the deck -> box -> trench -> win. You can absolutely have exposed conduit. SCH 80 PVC is probably going to be a minimum for anything within 6" of the ground or exposed to damage, but IMC may also be an option. Depending on your jurisdiction, you might be able to get away with EMT, depending on the cable you're putting in it.
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Dec 17, 2019 12:28
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Yeah, what the above said. Trench as far as you can, come up right next to the deck and mount a weather-proof outdoor junction box. Run exposed conduit along the deck and into the house the rest of the way. You can use EMT but be sure to use compression fittings and not set-screw fittings. edit: EMT exposed, not buried. Don't bury EMT.
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Dec 17, 2019 14:00
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Hi everyone! I have (what I hope) is a simple electrical question: My wife and are under contract for a house and our inspection showed that, to our surprise, the house has knob and tube wiring. We were surprised because all of the outlets are modern, three prong, grounded outlets -- it turns out they're connected to knob and tube and thus ungrounded (which is Not Good!). In my stupid municipality, during an inspection you can only ask for things fixed that are 'material defects' - not simply an old, outdated system which is no longer up to code but functions properly. For example, we could ask for the outlets to be grounded, but could not ask for knob and tube to be removed simply because there's knob and tube in the house. We just paid for two electricians to come out and look at the house and according to them the knob and tube system has been tampered with - both because they've attached 3 prong outlets to it, and because they've spliced romex at some point to have romex run to the panel box. They also found that the outlet in the upstairs bathroom while 'grounded' (it's not GFCI) is actually ungrounded because the ground wiring isn't connected to anything. My question is this: I assume this is a Bad Thing and an obviously defective electrical system. And how much would it cost to rewire an older house? It was built in the 1930s out of plaster and lathe, and I assume you'd have to open up all the rooms as well as the ceiling (there's modern ceiling fans in every room which of course likely connected to knob and tube). I can't imagine this a cheap repair! They also would need to find where splices were made between the romex/knob and tube and remove and replace those. We've also learned that the house is uninsurable due to the knob and tube system.
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Dec 17, 2019 19:31
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A 50S RAYGUN posted:i know, it would just be way easier to pull up three boards and dig under six joists than to pull up like thirty two boards. Maybe post a picture if you can.
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Dec 17, 2019 19:38
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Seven Hundred Bee posted:electrical nightmare The only way this could be worse is if the house also has a Federal Pacific StabLok breaker box.
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Dec 17, 2019 19:45
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Seven Hundred Bee posted:Hi everyone! How much earnest money you got on it? I mean this all sounds like you have every reason to tell the sellers to gently caress off without penalty, but even if someone tried to claim you didn't, I'm willing to bet the cost of fixing this nightmare is vastly higher than the earnest money, so worst case scenario, you're only out that if you walk. I would also bet that your offer is contingent upon actually securing a loan, and I *guarantee* whatever loan you've applied for is contingent on the house being insured. Uninsurable => unfundable => no sale
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Dec 17, 2019 19:53
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Oh I am definitely in my rights to ask for the wiring to be replaced now
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Dec 17, 2019 19:55
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Seven Hundred Bee posted:Hi everyone!
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Dec 17, 2019 19:57
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Bad Munki posted:How much earnest money you got on it? I mean this all sounds like you have every reason to tell the sellers to gently caress off without penalty, but even if someone tried to claim you didn't, I'm willing to bet the cost of fixing this nightmare is vastly higher than the earnest money, so worst case scenario, you're only out that if you walk. Note, this is the same place he's been posting about in other threads. 20 of the windows don't open, which he rates as a safety concern (I rate it as "that's an old house and kinda typical" - perhaps it's the entire second floor though, I don' know - I do know ladders take out non-opening windows just fine) with some painted closed, probably with lead paint as well as some with broken counterweights. So there's $15-25k in work right off the bat. This same poster is getting insurance quote saying the 90 year old slate roof is uninsurable as well. Poster states they "are not handy." There are numerous reasons for someone to walk from this house without serious concessions and there are many, many more for this particular poster to run away screaming. This is not the house for you Seven Hundred Bee.
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Dec 17, 2019 19:59
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