author

Bradscopegems

1
Inbox View Profile
24Comments

Tell us about yourself!

  • Travel Toy - Miniature Magnetic Breakfast

    If swallowed, button magnets are dangerous to kids. Two of them may stick together so tightly that they pinch the wall of the gut and become tightly attached. Can you be sure that the clay or adhesive will never break, releasing objects that a child might swallow, perhaps years after your kids have grown up? They are not as dangerous as a single button battery, which, even if flat, releases alkali strong enough to burn through a child's oesophagus in less than 2 hours. This can cause death.

    View Instructable »
  • Bradscopegems followed Tools, Tools, Assistive Tech, Hiding Places and 12 others channel
  • Adjustable Dado Jig From Scrap Wood

    Am I right in thinking that you can use only one diameter of bit with this jig? Also, does the accuracy depend on the circular router base being exactly concentric with the bit? I am making a similar jig but have made a rectangular aluminium base plate screwed to the original circular base with one longer edge slightly further from the bit than the other. I always use this edge against the fence ( i.e. turn the router around when I am using the second fence. I am using a 1/4 diameter bit to start with, but your design is so good that I would be happy to make a series of jigs to suit a range of bits and make it easy to cut dados of all sizes with minimum number of passes.

    View Instructable »
  • Bradscopegems commented on Loblaw's forum topic Dado vs Router?

    In Europe, table saws for amateur use are made with shafts too short to accommodate a dado blade and the blades are not easy to purchase. This is apparently to prevent the use of dado blades on machines without fast braking of the blade. A router table is undoubtedly safer. I have made two router tables, broadly following designs that are on the web. One is for comb-jointing, the other for edging and dado-cutting. I can post the designs if people are interested, but there are already a lot of ideas published on router table design.

    View Topic »
  • Hybrid Workbench Roubo/Nicholson

    Thank you for these explanations from pro woodworkers. I was once given a traditional woodworkers' bench. It was as beautiful as a traditional clinker-built rowboat. My problem was that I was always working with quite small pieces of timber and could not clamp them to the top, except in the vice. Should we conclude that the traditional bench always needs to be enhanced by adding the dog holes and very expensive dogs? I look forward to advice on this. My aim is to discover the best design for someone short of both space and money (my shed is so small that the bench has to serve as assembly table, desk and mount for bench-mounted router tables etc.

    Thank you! This does help. I look forward to your post on making DIY dogs.

    View Instructable »
  • Hybrid Workbench Roubo/Nicholson

    As an amateur carpenter, I have never understood why the traditional woodworking bench has such a thick top and, quite often, a deep apron along the front (though this seems to be absent in this case). I have made a bench using a welded steel frame with a top made of inch-thick ply, which is much easier to clamp to: it is really just a simple table top which works fine for me. (See photo).

    View Instructable »
  • Hot Glue Gun Holder

    An advantage of a very similar design, published in the UK in the January 2019 issue 276 of 'Model Engineers' Workshop' is that the wooden parts are screwed to a small but heavy steel cooking tray. This prevents the whole caboodle from falling over when the power cord is moved, which can send drops of scalding glue flying. A further improvement to both designs would be to install a bent metal bracket with a flat surface that makes contact with the glue gun nozzle. If there is no such blockage the gun drips glue on the base all the time when it is hot.

    View Instructable »
  • In Vino Veritas - a Wineglass Oscillator

    Dear WilkoL, I am delighted that you got it to work! I will now try to explain circularly polarized light, though this message may be too long for the Instructables format. Light is exactly the same as radio, except the wavelength is a million times smaller. If you think of a WWII jeep, it has a whip antenna which is vertical. The transmitter also has a vertical antenna, which emits radio waves, consisting of a spreading electric field which oscillates from upwards to zero to downwards: i.e. the force is a vector quantity which varies sinusoidally in strength but always has a vertical direction. An electron in the jeep antenna gets driven upwards and downwards by the field, because it is charged and the field exerts a force on it. If the antenna is horizontal the electron cannot move …

    see more »

    Dear WilkoL, I am delighted that you got it to work! I will now try to explain circularly polarized light, though this message may be too long for the Instructables format. Light is exactly the same as radio, except the wavelength is a million times smaller. If you think of a WWII jeep, it has a whip antenna which is vertical. The transmitter also has a vertical antenna, which emits radio waves, consisting of a spreading electric field which oscillates from upwards to zero to downwards: i.e. the force is a vector quantity which varies sinusoidally in strength but always has a vertical direction. An electron in the jeep antenna gets driven upwards and downwards by the field, because it is charged and the field exerts a force on it. If the antenna is horizontal the electron cannot move along it and so no current flows and the receiver does not pick up the signal. The radio wave is said to be linearly polarized in the vertical direction. Natural light, e.g. from the sun, contains a mixture of waves polarized in all different directions. Linear polarizers allow electrons to travel in only one direction and convert their energy into heat, so the only light waves that get through are the ones with the field vector at right angles to that direction : it just goes through as if the electrons were not there. In the nineteenth century it was discovered that an array of very fine gold wires placed in parallel acts as a polarizer, and some fancy linear polarizers act in that way, being made of conductive nanoneedles running in parallel in glass.Their output is polarized at right angles to the direction of the needles. So much for linearly polarised light. The most important thing is that in the path of linearly polarized lightan electron experiences a force which oscillates in strength from positive to zero to negative, to zero, to positive again but always up and down along the same direction, called the direction of polarization. Many materials such as liquids, unstrained glasses and even some crystals let light waves travel through at one velocity, which is always less than the speed of light in a vacuum. However, most of the classes of mineral crystals and many strained materials have a direction to them, rather like the grain in wood. If the e field of a light wave is parallel to the 'grain' the light is slowed down relative to the speed of a wave with the electric field at right angles to the grain. Such a material has two velocities for light and is called birefringent. This is where everything gets complicated. Imagine you are an electron sitting at the exit face of a birefringent sheet, with the 'grain' at 45 degrees to the direction of polarization of the input light. Suppose the polarization is originally North-South. You will experience one wave oscillating NE to SW and another one SE to NW. If these waves arrive in phase with each other the result will be a comfortable force on the electron just like the force exerted by the original wave, and it will be always NS. But if one wave is slowed down relative to the other, by 1/4 cycle because of the effect of the 'grain', the hapless electron will suffer a force which does not vary in strength at all, but rotates continuously. You have to draw the vector arrows on paper to see why this is so. This is called 'circularly polarized light' and comes in two types, with the field vector rotating either clockwise or anticlockwise when you look along the wave in the direction of travel. If the thickness of the sheet of birefringent material is varied, you get other results, where the electronic field strength varies in such a way that the head of the vector arrow describing the electric field travels in an ellipse. A circular polarizer consists of a sheet of linear polarizing material cemented to a birefringent plastic sheet of just the right type to induce the quarter-wave phase difference described above. As you know, ordinary polarizers are useful for photography since if the polarizer is oriented appropriately is can cut out the reflection from a wet road or a window. An ordinary linear polarizer might improve the photo, but it would transmit linearly polarized light into the camera which might not be reflected properly in an SLR or might affect metering. Circularly polarizing filters are preferred because the light they send into the camera has no trace of the direction of polarization of the light that came through the linear polarizing layer. I suspect that all the circular polarizing filters that are now sold have the same handedness, but if you can get some 3D spectacles of the type that have circular pol lenses they will be left- and right- handed, with the amazing property of being crossed whatever the rotational position, provided you have the birefringent layers facing each other. Also, with these, your wineglass will bright up whatever the direction of the strain and this is used in commercial inspection equipment for detecting strain. Try to get hold of a little book by Shurcliffe and Ballard if you are getting interested in this branch of optics.Brad

    View Instructable »
  • In Vino Veritas - a Wineglass Oscillator

    Dear WilcoL, I am not sure why it is not working, but it may be that squeezing the glass does not produce enough strain. As you know, acoustic stress can make a glass vibrate so much that it breaks and I am sure you were not squeezing hard enough to shatter the glass. You might try the polarized light experiment again, but making the glass sing by the moist fingertip trick. There is a YouTube video called 'Wineglass resonance in slow motion' which shows strong sound from a speaker being delivered at the resonance frequency. The width of the wineglass oscillates by several percent without the glass breaking, so the glass waggles visibly like it is made of soft rubber, but you can only see this if you have a fast camera and view the scene in slow motion. A tube of b…

    see more »

    Dear WilcoL, I am not sure why it is not working, but it may be that squeezing the glass does not produce enough strain. As you know, acoustic stress can make a glass vibrate so much that it breaks and I am sure you were not squeezing hard enough to shatter the glass. You might try the polarized light experiment again, but making the glass sing by the moist fingertip trick. There is a YouTube video called 'Wineglass resonance in slow motion' which shows strong sound from a speaker being delivered at the resonance frequency. The width of the wineglass oscillates by several percent without the glass breaking, so the glass waggles visibly like it is made of soft rubber, but you can only see this if you have a fast camera and view the scene in slow motion. A tube of black paper and turning the room lights off may help to see faint signals with your apparatus . Were you able to get a good 'extinction' ( i.e. total darkness) at two rotational positions of the analyzer? Your polarizers look like the correct linear polarizers that you need, but I should mention, in case you don't know, that there are circular polarizers that will not give an extinction unless you orient both of them with the polarizing sides facing each other. [Circular polarizers are often sold for photography. They consist of a polarizer with a birefringent plate cemented to one side ( i.e. they are not symmetrical like ordinary linear polarizers).] But I think you were probably using the correct kind. I have to go away for a week now, so I will not be able to try anything in my home lab, but I will do so when I get back.

    View Instructable »
  • In Vino Veritas - a Wineglass Oscillator

    Dear WilcoL, My advice would be not to put any colour filter over the sensor: as the strain increases the glass will go from totally dark between crossed polarizers to grey and then to white before reaching the colours, starting with red. For maximum sensitivity you want your sensor to pick up all the wavelengths in the grey and white light.Concerning the instructions in the book, I would not recommend that anyone who is not a pro glass cutter should attempt to cut such a long strip. Special tools and protective clothing would be needed. The sequence of components historically was light source, linear polarizer, glass specimen, second linear polarizer in the 'crossed' orientation so no light gets through, then the eye of the observer. 'Analyzer' was used to mean t…

    see more »

    Dear WilcoL, My advice would be not to put any colour filter over the sensor: as the strain increases the glass will go from totally dark between crossed polarizers to grey and then to white before reaching the colours, starting with red. For maximum sensitivity you want your sensor to pick up all the wavelengths in the grey and white light.Concerning the instructions in the book, I would not recommend that anyone who is not a pro glass cutter should attempt to cut such a long strip. Special tools and protective clothing would be needed. The sequence of components historically was light source, linear polarizer, glass specimen, second linear polarizer in the 'crossed' orientation so no light gets through, then the eye of the observer. 'Analyzer' was used to mean the second polarizer, because it could be used to analyze the light coming through the specimen. For example, if you saw colour, you could test whether it was due to strain birefringence by turning the analyzer through 90 degrees, which would cause the colour to change to the complimentary colour ( red to green, blue to yellow etc). I suggest that you do not try to repeat the hazardous experiments of 1892. The simplest experiment would be to add a bright light source of large area to your existing kit, with crossed polarizers on either side of the wineglass and just look visually to see if the wineglass gets bright when you make it vibrate with the speaker. You might even be able to use your laptop screen as the light source: the LCD emits linearly polarized light with the direction of polarization at 45 degrees to the vertical. Then you need find only one of your polarizing sunglass lenses.... By the way: a scientist is defined by doing experiments to satisfy his or her curiosity, not by whether he is paid to do this professionally, So you are one, and a highly ingenious one too! Your apparatus could lead to a useful device for testing glass under acoustic stresses.

    View Instructable »
  • In Vino Veritas - a Wineglass Oscillator

    This may perhaps give you an idea. I design microscopes and teach optics, and I am always looking for nice demonstrations. One useful source is a book by Lewis Wright published by Macmillan in 1892 and titled 'Light: a course in experimental optics, chiefly with the lantern.' The lantern in question was often equipped with a polarizer and an analyzer to reveal birefringence. One of the demonstrations ( on page 285) is a demonstration of 'Effects of Sonorous Vibration' on a strip of glass. It uses the fact that glass shows strain birefringence when it is vibrated. I have not tried it yet, but I summarize it as follows: 1. Cut a strip of glass 5 to 6 feet long, two inches wide and about 1/4 inch thick. 2. Render the edges safe by means of a stone ( modern diamond sharpening plate woul…

    see more »

    This may perhaps give you an idea. I design microscopes and teach optics, and I am always looking for nice demonstrations. One useful source is a book by Lewis Wright published by Macmillan in 1892 and titled 'Light: a course in experimental optics, chiefly with the lantern.' The lantern in question was often equipped with a polarizer and an analyzer to reveal birefringence. One of the demonstrations ( on page 285) is a demonstration of 'Effects of Sonorous Vibration' on a strip of glass. It uses the fact that glass shows strain birefringence when it is vibrated. I have not tried it yet, but I summarize it as follows: 1. Cut a strip of glass 5 to 6 feet long, two inches wide and about 1/4 inch thick. 2. Render the edges safe by means of a stone ( modern diamond sharpening plate would work well).3. Grip the glass at the exact centre in wooden jaws in a vice. I am guessing that the jaws should not be more than an inch wide.4. Shine a powerful light through the glass, near to the vice, projecting an image of the strip on a screen and place a polarizer and analyzer in the beam on either side of the strip in the crossed orientation, with the directions of polarization at 45 degrees to the long axis of the strip.5. Draw a 'wet flannel cloth' down the strip from the free end above the light beam to produce a 'shrill but wonderfully clear musical note'. Other kinds of cloth 'have too much bite, and tend to drag the vice about'. 6. During this musical note the glass becomes bright between the crossed polarizers, showing the strain induced by the vibration. The brightness varied sinusoidally at a high frequency, as could be demonstrated by projecting the beam on a rotating mirror and observing the dotted line of light. If you can send light through your wineglass from a source of polarized light and cover your photodiode with an analyzer, rotating the analyzer to block the signal when the loudspeaker is off, you may be able to pick up the vibrations in the wineglass without needing exact alignment. Hope this works! I tried to make a version once with a piezo transducer to vibrate the glass, but could not get the right frequency.Brad Amos

    View Instructable »
  • Thank you for this detailed reply. The slicing action seems li ke a good improvement on the basic designs.

    View Instructable »
  • A lovely project! But I am puzzled by the photo next to Step 3. Why has the board suddenly become tipped up at an angle instead of lying parallel with the bench surface? And why is the nylon runner for the plane also at an angle to the board surface? I understand the previous photos but not this one.

    View Instructable »
  • Thank you, seamster and Matlek. I have happily renewed my subscription, since I love Instructables and learn a lot from others. I will take Matlek's advice and try to submit something myself. My expertise is mainly in microscopes, so a bit specialized for most members.

    View Topic »
  • Inexpensive Garage Lights From LED Strips

    This is the image with the LEDs at the top and the vertical stripes are the reflections.

    View Instructable »
  • Inexpensive Garage Lights From LED Strips

    Second attempt to post an image, this time with a smaller file size.

    View Instructable »
  • Thank you ! Your article inspired me to make a long-needed ceiling light over a kitchen worktop. I stuck 5 LED strips, each 2 meters long, and connected them in parallel to a 12v 10A DC laptop power supply. Because I did not want the light to glare over the dining table, I mounted the strips on an L-section extruded aluminium strip, so that the LED strip was mounted parallel to the ceiling and the vertical part of the L acted as a shade/ reflector. Unexpectedly, the aluminium's fine marks along the direction of extrusion diffract the LED light, creating a very pleasing appearance of 3D in the reflections, which I have tried to show in the photo attached.

    View Instructable »
  • Bradscopegems commented on tguck32's instructable How to Temper Steel

    This is a great demonstration. Presumably you have to start with a low-carbon mild steel, or the rods will not bend easily. You could extend the demo by smearing the central part of the rod with case-hardening compound to introduce extra carbon before heating, then clean up and check the strength and hardening before and after annealing. As jtobako says, the interference colours are also instructive: yellow is a good tempering colour, blue is a nice decorative one which apparently gives a little corrosion protection. With such a thin rod the interference colours may run along very quickly, so heat carefully when tempering!

    View Instructable »
  • Scotchbrite General Purpose scouring pads, such as are sold in hardware stores, contain mineral particles ( probably aluminium oxide, which is the same as emery). They are capable of scratching both steel and glass. If you want to avoid this you have to find grades specially made for cleaning non-stick pans.

    View Instructable »
  • This is very helpful. I have been looking for a suitable circuit on Google but did not find this simple use of a 555 IC. Thank you!

    View Instructable »