# fred_

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• fred_ commented on hombremagnetico's instructable Pocket Size Spinthariscope4 months ago

Cool be looking for that post. tl:drthe nrc considered a teacher using the source in the classroom. In the case of misuse, the following scenarios are considered: (1) exposure to a teacher whoremoves an 241Am source from a smoke detector for use in classroom demonstrations aboutradioactivity, and (2) exposure to a person who removes an 241Am source from a smokedetector and subsequently swallows it by accident. To estimate the potential radiation dose tothe teacher, it is assumed that the teacher stores the 241Am source in a convenient location in aclassroom and is exposed at an average distance of about 1 meter from the source for1000 h/yr. The EDE rate at 1 meter from a 37-kBq (1-Ci) source of 241Am without regard forshielding by other materials is about 0.09 nSv/h (9 nrem/h) (see...

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Cool be looking for that post. tl:drthe nrc considered a teacher using the source in the classroom. In the case of misuse, the following scenarios are considered: (1) exposure to a teacher whoremoves an 241Am source from a smoke detector for use in classroom demonstrations aboutradioactivity, and (2) exposure to a person who removes an 241Am source from a smokedetector and subsequently swallows it by accident. To estimate the potential radiation dose tothe teacher, it is assumed that the teacher stores the 241Am source in a convenient location in aclassroom and is exposed at an average distance of about 1 meter from the source for1000 h/yr. The EDE rate at 1 meter from a 37-kBq (1-Ci) source of 241Am without regard forshielding by other materials is about 0.09 nSv/h (9 nrem/h) (see Section 2.15.3) and the annualEDE to the teacher could be 9×105 mSv (0.009 mrem). Also, the teacher handles the 241Amsource for 10 h/yr during classroom demonstrations at a nominal 1 cm distance (due to the sizeof the disk upon which the source is mounted) then the dose equivalent to a small area of skin2–223on the hand is about 0.3 mSv (30 mrem), based on a calculation using photon fluence andtissue (skin) energy absorption. Assuming a 10 cm2 exposed skin area out of a total skin areaof 1.8×104 cm2 (ICRP 26) and a skin weighting factor of 0.01 (ICRP 60), the calculated EDEwould be less than 1×105 mSv (< 0.001 mrem).

• Any plans to add some pan and tilt steppers/servos and scan a region for imaging?

• 1 year ago

Nice work. If you mix the epoxy carefully to not introduce air bubbles than pour it in a 2nd container and mix again rather than going nuts scraping that container sides then a light tough of a hair dryer after pouring, you might find you can use less over pour and not get bubbles and maybe have less clean up. Again nice work.

• fred_ commented on novelchip's instructable Easy Rubber Machining With a Needle1 year ago

Great work. It looks like you've sorta made a single flute end mill. Some other ideas might be a zero helix router burr or negative helix end mill. Have you ever tried liquid CO2 or Nitrogen to stiffen if up before cutting? Maybe try preping the part and spoil board with some dry ice to see if needle cuts even cleaner. Maybe some pc board tools that tend to be cheaper than buying from a machining supplier. Just spit balling some ideas. Again great work.

• fred_ commented on Paige Russell's instructable 10 Unusual Uses for Pencils2 years ago

Have you ever tried molybdenum disulfide paste (not moly grease)? It's messy stuff but you'd only need a little. It should be a little more slippery than graphite.

• fred_ commented on Paige Russell's instructable 10 Unusual Uses for Pencils2 years ago

(preferably white) pencil erasers are commonly used to clean contact pads on printed circuit boards.

I *think pressurized pens are either required or preferred in space. The urban legend that NASA spent millions developing a pen that would write in space while the USSR used pencils is false. NASA after buying stupid expensive mechanical pencils, bought pressurized pens for around \$2.50 in bulk. The USSR bought the same pens about a year later. The conductive dust and broken pencil points floating around was thought to be a hazard. Don't know if that is still the case. For uber geek points read the book "The Pencil" Henry Petroski :)

• fred_ commented on bennelson's instructable Build Your Own Electric Car!2 years ago

That in essence is the perpetual motion, over unity, free energy, scam. All you can accomplish with that is decreased efficiency. If there was a 100% efficient alternator (there isn't) and charging a battery was 100% efficient (it's not) the best you could do is 0% gain. The energy you diverted to turn the alternator could have been used to move the car.

He tested it at 12 volts but 72 volts is pretty common for a forklift motor. You'd smoke a 12 volt motor at 72 volts in short order. You can over volt say a stepper motor but you have to control the current. 24,36,48,72,80 volts are typically used for fork lifts. There would be a name plate rating on the motor. The battery box that held the fork lift cells (they're individual so you can swap them out as the pack ages) would also have a name plate xx-yy-zz on it. xx*2 is the voltage.(zz-1)/2*yy would be rated amp hours. (rated at 16% amps * 6 hours)

There's only so much you can do with a given battery capacity. To make a battery last longer your only option is to lower your current draw. For lead acid google peukert's law. Your options are drive slower, improve Cd, reduce frontal area, chop weight, use more efficient drive train, reclaim a little with regen braking etc. Complicated costly and not a great fit for a diy project with a typical car. It's a ground up exercise. No battery comes close to gasoline's energy density, so it's all about efficiency.For a given volume lithium ion has a higher capacity and less weight then lead acid but are comparatively more expensive and finicky to operate. A prius battery is about \$3000 i don't know it's capacity but I think the system runs at over 300 volts so you can't just plug it into a ...

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There's only so much you can do with a given battery capacity. To make a battery last longer your only option is to lower your current draw. For lead acid google peukert's law. Your options are drive slower, improve Cd, reduce frontal area, chop weight, use more efficient drive train, reclaim a little with regen braking etc. Complicated costly and not a great fit for a diy project with a typical car. It's a ground up exercise. No battery comes close to gasoline's energy density, so it's all about efficiency.For a given volume lithium ion has a higher capacity and less weight then lead acid but are comparatively more expensive and finicky to operate. A prius battery is about \$3000 i don't know it's capacity but I think the system runs at over 300 volts so you can't just plug it into a 72 volt forklift motor. As a hybrid it's approach is to have limited capacity matched to a smaller gasoline engine to keep it loaded pushing it higher in it's efficiency curve. The gas engine doesn't have to idle and gets a boost from the battery so it can be smaller and work harder or not at all. 2 commercial solar panels if you could fit them might be ball park 1hp. at high noon. Flee power compared to what you need.

• fred_ commented on mikeasaurus's instructable Unusual Uses for Zip Ties2 years ago

Mostly agree, but the "good stuff" comes from thomas&betts. :)

• fred_ commented on mikeasaurus's instructable Unusual Uses for Zip Ties2 years ago

Just adding to the people that used them to keep the stupid shower caddie in place. The unusual part is, this is from a guy that has imported shower caddies and manufactured ty-raps :) Small world LOL. The most obvious might be using one to keep a bunch of other ones tidy in storage.The most unusual might be fasciotomy wound procedures to save limbs or radiation hardened ones used in satellites.

You can get flush cutters. It helps if you maintain tension on the tail a little when you cut it flush. The cut end will suck back into the head a little. There are also cheapo devices that tension and cut the end off all in one motion. Maybe google ty-rap or cable tie gun? The pro ones and automatic installation tools are pretty spendy.

• fred_ commented on danielrp's instructable Superb Lab Power Supply2 years ago

Nice 'ible and comprehensive. Does the transistor pad specify thermal paste? You might get a little better transfer without it. Niggle replace "wheatstone" with "diode" in step 2. Sharp looking front panel.

• fred_ commented on b89kev's instructable How to Pan Fry the Perfect Steak2 years ago

A dry steak has been over cooked or had poor marbling. The salt on the outside will draw moisture then brine the meat. You have to give it time. This will help slightly with moisture and flavor retention. If you salt and don't give it time you have a wet surface which doesn't help browning and liquid didn't get distributed into the meat. Salt it, wait, dry it, sear it.A wet brine will result in more moisture absorption and also more moisture loss when cooking. The end result being more moist product with more lost meat flavor. You may prefer a dry brine on a chicken. Give it a shot.

• fred_ commented on b89kev's instructable How to Pan Fry the Perfect Steak2 years ago
• fred_ enrolled in Table Saw Class2 years ago
• Most domestic hardwoods are ok. Oak wouldn't be the best choice because it has an open grain. Some of the exotics like rosewood can be an allergy issue and some need special care to glue up. Hard maple walnut cherry are probably the most common for cutting boards. The end grain boards are also easier on your knife edge.

• fred_ commented on KJMagnetics's instructable World's Simplest Electric Train2 years ago

Flip both magnets and it will run in the other direction.

Check Jan16 American Journal of Physics.It's a pushmepull you. Pulling on the north pole at one end and pushing on the north pole at the other end of the battery.The copper tube won't work. But drop a magnet down a copper pipe and see how slow it falls :) Strong magnet and less clearance in the pipe the better the effect.The magnets complete an electrical circuit with the battery and portion of the coil it contacts. This movement energizes a new portion of the coil and round it goes.No electrical contact no current in the coil so no electromagnet and no movement. The plastic tube or close to electrical contact won't work.

• fred_ commented on keokg2's instructable Wifi Extender2 years ago

instructables messed up my poor ascii art. The probe should all be vertically aligned with the bottom tick mark. :)

• fred_ commented on osgeld's instructable Master a perfect inline wire splice everytime3 years ago

It's possible to pull company data off the hard drive even if it's been formatted or even over written. There are free programs to wipe a drive and over write it enough times to prevent hardware methods of extracting data. Or just crush the drive platters. Why scrap a puter that still has worth to somebody?

• fred_ commented on vina1991's instructable ULTRA CHEEP HOME AUTOMATION UNDER \$53 years ago

It's probably not the best circuit for a few reasons. You'd probably get corrosion where the copper wire attaches to the bolt. A DC current is likely to corrode the ss bolts and would make a small amount of chlorine. Chlorine and copper are two things you'd want to keep away from a marine tank. You could probably use a cheap pressure sensor and a pic/duino etc to analyze rational level measurements and other logic tests to trap system failures. That way you'd only have a plastic tube exposed to the water with the electronics away from the moisture/salt. Might be \$10+ range though.

• fred_ commented on bekathwia's instructable Hard Cook Eggs with Steam3 years ago

It's not as likely to be as reproducable for a few reasons. Every oven is different, pretty much nobody calibrates their oven (or even knows that your can). Every spot in the oven is different and the temperature swings as it cycles might be 50 degrees. Steam or boiling gets everyone to get similar results. A little more goof proof.If you're getting 90% or better clean peeling eggs don't change :)Steam or already boiling water gets you a few things. The size of your burner is mostly out of the equation. The faster start then the cold water start method gives slightly less time for the egg white to bind to the shell membrane. Mostly the change in ph as the egg ages makes them easier to peel. I go with the boil cover and let sit for 10 minutes with the lid on method. Then crash cooling i...

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It's not as likely to be as reproducable for a few reasons. Every oven is different, pretty much nobody calibrates their oven (or even knows that your can). Every spot in the oven is different and the temperature swings as it cycles might be 50 degrees. Steam or boiling gets everyone to get similar results. A little more goof proof.If you're getting 90% or better clean peeling eggs don't change :)Steam or already boiling water gets you a few things. The size of your burner is mostly out of the equation. The faster start then the cold water start method gives slightly less time for the egg white to bind to the shell membrane. Mostly the change in ph as the egg ages makes them easier to peel. I go with the boil cover and let sit for 10 minutes with the lid on method. Then crash cooling in an ice bath prevents over cooked green tinged smelly yolks and rubbery whites and helps older easy peeling eggs make a nicer egg shape when their larger air pocket in the shell rapidly shrinks (for deviled eggs).02 if you're lucky enough to have right out of the chicken eggs don't waste em by hard boiling hard to peel eggs. BTW don't wash them if anything dry wipe them. Leave the protective film on the egg intact.