• Molding a long, flat object?

    I want to cast a long, thin part in hard urethane (80D) for prototyping. The part will be about 33" long, about 5" wide and about 1/2" thick and is a long radius arc of a circle, as though you have cut a sector from a disc. It is intended that the upper and lower surfaces of the part will be rolling surfaces. The lower surface is... show more
    I want to cast a long, thin part in hard urethane (80D) for prototyping. The part will be about 33" long, about 5" wide and about 1/2" thick and is a long radius arc of a circle, as though you have cut a sector from a disc. It is intended that the upper and lower surfaces of the part will be rolling surfaces. The lower surface is supported atop some transfer ball casters and a second piece can be rolled along the upper surface. Therefore, I want the upper and lower surfaces to pretty flat and straight. 1) Is molding an appropriate method for what I want or should I be looking at a different process? 2) Would a silicone mold, with a support structure to maintain rigidity, be sufficient as a mold? How do you suggest maintaining straightness and flatness? 3) How do I fill the mold? Do I create a two part mold, tilt it a bit and fill by injecting from the lowest point? Is there a way to fill the open mold and lay the second portion in place without making a giant mess? How would you actually make this part? I do have vacuum equipment suitable for de-airing. Any tips relating to mold release, etc. would be appreciated Thanks
    1 answer · Engineering · 3 weeks ago
  • What is an iPhone Activation Lock and why would one appear on my phone?

    I had been using my phone earlier in the day. Battery was getting low (but not seriously low) so I plugged it in. A few hours later, I picked up my phone to text a friend and there is an Activation Lock on my phone, and it wants me to enter my iCloud login credentials. To me this looks like a classic Trojan. But could it just be a glitch in the... show more
    I had been using my phone earlier in the day. Battery was getting low (but not seriously low) so I plugged it in. A few hours later, I picked up my phone to text a friend and there is an Activation Lock on my phone, and it wants me to enter my iCloud login credentials. To me this looks like a classic Trojan. But could it just be a glitch in the system? Or could it be legitimate? What triggers an Activation Lock? I think the first message I read might have said something about an attempt to use Find My iPhone
    1 answer · Cell Phones & Plans · 3 months ago
  • Mac terminal command syntax?

    I need to go to Mac Terminal to get something done. The command refers to an application file name that includes both a space and a decimal. The app file name is FireCapture v2.6.app My Unix experience has a lot of dust on it. I can make the command succeed if I simply rename the app to FireCapture, but I would prefer to keep the version... show more
    I need to go to Mac Terminal to get something done. The command refers to an application file name that includes both a space and a decimal. The app file name is FireCapture v2.6.app My Unix experience has a lot of dust on it. I can make the command succeed if I simply rename the app to FireCapture, but I would prefer to keep the version information. Will wrapping the app name in quotes work like this? command "FireCapture v2.6.app" Is there a better way to do this?
    2 answers · Software · 3 months ago
  • Need help with Mac terminal commands?

    My Unix days are long, long ago. The goal here is to get Gatekeeper to allow an app to run. Please refer to the photo. Background: At Step 1, I ask for a listing of Desktop to verify that the app that I want to allow, FireCapture v2.6, is present. At Step 2, I issue a command to Gatekeeper to add the exception. It fails. At Step 3, I issue the... show more
    My Unix days are long, long ago. The goal here is to get Gatekeeper to allow an app to run. Please refer to the photo. Background: At Step 1, I ask for a listing of Desktop to verify that the app that I want to allow, FireCapture v2.6, is present. At Step 2, I issue a command to Gatekeeper to add the exception. It fails. At Step 3, I issue the same command as a superuser. The command fails. After Step 3, but before Step 4, I rename FireCapture v2.6.app to FireCapture.app. You can see the Finder is showing the name of the app as FireCapture.app At Step 4 I issue the same command as Step 3 and it works. Subsequent testing of the app verifies that Gatekeeper now allows the app to launch. Question 1: Why did the commands fail when the app name was FireCapture v2.6.app, but succeeded when the name was changed to FireCapture.app? Question 2: Was it necessary to issue the command as superuser once I had the name fixed or would the command have worked without the sudo?
    2 answers · Software · 3 months ago
  • Numerical values in TIFF files?

    Why are numerical values in monochrome TIFF files different from those in RGB TIFF files?
    Why are numerical values in monochrome TIFF files different from those in RGB TIFF files?
    1 answer · Software · 7 months ago
  • What fact check site do conservatives trust?

    I'm not trolling here. I know that they don't like Snopes because, well the Mikkelsons are from California, so they'er obviously liberals. So, if Snopes is unacceptable and I want to let one of my conservative friends know that no one is putting HIV infected needles in gas pump handles, that it's an old scare going back to when... show more
    I'm not trolling here. I know that they don't like Snopes because, well the Mikkelsons are from California, so they'er obviously liberals. So, if Snopes is unacceptable and I want to let one of my conservative friends know that no one is putting HIV infected needles in gas pump handles, that it's an old scare going back to when there were pay phones and people supposedly put HIV infected needles in the coin returns, who can I send them to that they will actually trust the source.
    20 answers · Politics · 8 months ago
  • What famous (possibly infamous) Chicogoan?

    died in the summer of 1957 - 59 or maybe 1960. The person died someplace else and was returned to Chicago for services. Whoever it was, had enough significance that it warranted a police escort, and people lined the road taking pictures of the hearse as it left the airport
    died in the summer of 1957 - 59 or maybe 1960. The person died someplace else and was returned to Chicago for services. Whoever it was, had enough significance that it warranted a police escort, and people lined the road taking pictures of the hearse as it left the airport
    3 answers · History · 9 months ago
  • Hydrogen alpha imaging with a high megapixel color sensor vs a dedicated monochrome camera?

    I have a Sony Alpha7R Mk2 DSLR which produces 42 Mpix images. Given that only one in 4 pixels is going to see anything in a Ha image, that cuts my resolution by a factor of 4 resulting in effectively a 10 Mpix image. The highest resolution I see on the monochrome cameras is about 5 Mpix. Am I better off using 1/4 of the pixels of a Bayer filtered... show more
    I have a Sony Alpha7R Mk2 DSLR which produces 42 Mpix images. Given that only one in 4 pixels is going to see anything in a Ha image, that cuts my resolution by a factor of 4 resulting in effectively a 10 Mpix image. The highest resolution I see on the monochrome cameras is about 5 Mpix. Am I better off using 1/4 of the pixels of a Bayer filtered sensor that has 42 Mpix or does a lower pixel count monochrome camera still have other advantages?
    Astronomy & Space · 1 year ago
  • Comments on this telescope please?

    I am interested in getting an entry level telescope with the primary goals of lunar and planetary viewing (as opposed to deep space objects). I have a good bit of experience with photography and microscopy. The Celestron Advanced VX 8" EdgeHD appears to be about the level that I am looking for with a decent, but not huge aperture, Go To system,... show more
    I am interested in getting an entry level telescope with the primary goals of lunar and planetary viewing (as opposed to deep space objects). I have a good bit of experience with photography and microscopy. The Celestron Advanced VX 8" EdgeHD appears to be about the level that I am looking for with a decent, but not huge aperture, Go To system, and reasonable portability. I have both Nikon and Sony full frame cameras for image capture. Would you recommend a different scope (somewhere near this price point)? What accessories do you consider indispensible? I plan to use the scope to observe the eclipse. Aside from the necessary neutral density filter and suitable eye protection for myself, is there anything else I would need?
    4 answers · Astronomy & Space · 1 year ago
  • Telescope for general viewing plus solar?

    For many years I have been interested in astronomy, but made a decision a good while back to go the direction of microscopy rather than getting a telescope. With the upcoming total eclipse, I have a new impetus to my astronomy urges. But I don't want to buy a dedicated solar scope, at least I don't think so. After the eclipse, I would like... show more
    For many years I have been interested in astronomy, but made a decision a good while back to go the direction of microscopy rather than getting a telescope. With the upcoming total eclipse, I have a new impetus to my astronomy urges. But I don't want to buy a dedicated solar scope, at least I don't think so. After the eclipse, I would like to use the scope for more traditional stuff - moon, planets, nebulae... I am at the point in life where I can afford some decent optics. A four figure price tag isn't too much, though I need to question how much I'll really be using it if we start talking 5 figures. What sort of system should I be looking at? Am I seriously hobbling my eclipse viewing by relying on add-on filters for a traditional scope? Is an internal doppler etalon essential for a good hydrogen alpha image (this feature seems to be emphasized in the dedicated solar scopes)? What add-on filters would be most useful for the eclipse? It's probably another discussion altogether, but do you have any recommendations for automated trackers to accommodate for Earth rotation?
    2 answers · Astronomy & Space · 1 year ago
  • Firing a howitzer?

    I have an old picture of my father's artillery unit. One shows a soldier about to fire the weapon and it's obvious that he is yelling something. OK, so maybe it's "Fire!" But is that what someone in the military would actually say? What is the name of the cord that is pulled to fire a howitzer? What would a soldier yell just... show more
    I have an old picture of my father's artillery unit. One shows a soldier about to fire the weapon and it's obvious that he is yelling something. OK, so maybe it's "Fire!" But is that what someone in the military would actually say? What is the name of the cord that is pulled to fire a howitzer? What would a soldier yell just before pulling it?
    2 answers · Military · 2 years ago
  • When do I need a Windows partition on a Mac?

    If I get a Mac computer, under what circumstances do I need a Windows partition on my disk to support Windows programs? I have some third party programs that are not supported for a Mac. When does Windows emulation work and when doesn't it? One program in particular that I'm concerned about uses TCP/IP and Jumbo Frames to communicate on... show more
    If I get a Mac computer, under what circumstances do I need a Windows partition on my disk to support Windows programs? I have some third party programs that are not supported for a Mac. When does Windows emulation work and when doesn't it? One program in particular that I'm concerned about uses TCP/IP and Jumbo Frames to communicate on Ethernet. I'm not sure what sort of device drivers it might be using. How can I tell if program will work under Windows emulation?
    2 answers · Software · 2 years ago
  • Is there a minimum time between lives?

    After a person dies, is there a minimum amount of time that the spirit resides in the other realm (I don't know what else to call it) before taking on a new form, or can it be essentially immediate?
    After a person dies, is there a minimum amount of time that the spirit resides in the other realm (I don't know what else to call it) before taking on a new form, or can it be essentially immediate?
    10 answers · Religion & Spirituality · 3 years ago
  • Microsoft Windows updates?

    Last night I wanted to do a major data copy - nearly a Tbyte. I knew it would take a long time so I set it to run overnight. I didn't want some random Windows update to terminate my copy process, so I unplugged the Ethernet cable that is my computer's connection to the internet. Much to my great disappointment this morning when I woke up... show more
    Last night I wanted to do a major data copy - nearly a Tbyte. I knew it would take a long time so I set it to run overnight. I didn't want some random Windows update to terminate my copy process, so I unplugged the Ethernet cable that is my computer's connection to the internet. Much to my great disappointment this morning when I woke up the computer, I saw a login screen. Microsoft had managed to reboot my computer (and of course, trash my copy) without my computer even being connected to the internet. So what happens then? Does Microsoft download updates that contain a time bomb set to run at some particular time?
    3 answers · Software · 6 years ago
  • How to measure magnetic field intensity?

    I want to measure H, not B The magnets in question are permanent magnets (large Neo or SmCo magnets), not coils =====================....Steel ____........................____ |..N..|........................|..S..| |..S..|........................|..N..| -------------------------------| |...............very.................| |......high... show more
    I want to measure H, not B The magnets in question are permanent magnets (large Neo or SmCo magnets), not coils =====================....Steel ____........................____ |..N..|........................|..S..| |..S..|........................|..N..| -------------------------------| |...............very.................| |......high permeability......| |............material..............| -------------------------------- ^^^^^ Magnetic circuit ^^^^^ How can I determine the magnetic field intensity or the mmf of the magnets? The measurement needs to be something I can actually do, not some giant set of Helmholz coils in outer space
    1 answer · Physics · 6 years ago
  • Can steel be made magnetically soft?

    Can steel be heat treated or otherwise changed from magnetically hard to magnetically soft? I want to use steel wool bits to visualize magnetic fields. The iron filings that you can buy for the purpose are junk - very irregular in shape and size. I have not found any source for high quality filings. I want long, thin particles, where... show more
    Can steel be heat treated or otherwise changed from magnetically hard to magnetically soft? I want to use steel wool bits to visualize magnetic fields. The iron filings that you can buy for the purpose are junk - very irregular in shape and size. I have not found any source for high quality filings. I want long, thin particles, where "long" may be 1-2 mm and "thin" is 20% or so of the length. High aspect ratio is another way to put it. Particle length can certainly have a good degree of variability; I'm more interested in the high aspect ratio. If you imagine small bits of 0000 steel wool, that's what I'm looking for. But steel will retain a field once it has been exposed to a magnet. I want the particles to be magnetically soft so they don't retain the field. Is there any way to treat bits of steel wool to make it magnetically soft, or is there a source for high aspect ratio iron (not steel) bits?
    1 answer · Engineering · 6 years ago