Wednesday, June 17, 2009

Give’em some credit

Knives come in all shapes and sizes, but this recipe is for an unusual one – a knife concealed as a credit card. In the movie Glimmer Man, noted martial artist Steven Segal used one to surprise-attack a group of mobsters. Such a knife is not really hard to do, just be careful about carrying it in your wallet. If it gets picked up by the airport scanners, you could get in trouble.

1) Get 3 cards – 1 normal credit card (preferably expired), one card that is not a credit card (because they are not flat), but has a magnetic stripe on the back, and a 3rd card that is of the same size, but does not have to have any markings (could be an old drivers license or company keycard, for example)

2) Get a snap-knife blade of the slim type (also known as a “Japanese Knife” blade).

3) Cut the 3rd card to shape as is illustrated in the image. The idea is that the hole in the blade will be secured using an axle and when rotated, will protrude down about ½ of an inch.

4) Cut the bottom card (no. 2) as is illustrated in the image. This hole will be used to extend the knife, and hold it in place.

5) Cut a hole in the 1st and 3rd cards, about 1/16” wide. Try to make the holes exactly above each other. This will be used to hold the axle that holds the blade in place.

6) Using simple contact glue, glue the bottom card (no. 3) to the middle shape (card no.2). Try to make the gluing as clean as possible, with no glue traces on the contour lines.

7) Place the blade in the cavity that’s in the 2nd card.

8) Glue the top card (no.2) to the middle one, and again – try to make it clean.

9) Use a piece of soft plastic as the axle, and insert it through the top hole, the blade’s hole, and the bottom hole.

10) Cut the axle so that it protrudes only about 1/16” to each side.

11) Using something hot, push on the axle’s ends, and flatten them. This can be done with a soldering iron, but works just as well with a large nail’s head, heated over the stove-top. Ideally, the outcome will be an H shaped axle, as flat as possible on the credit card.

12) Now, use your finger to push out the blade and hold it in place. Practice extending it quickly and holding it steady. Keep in mind that the blade is really sharp, and if you keep the knife in your pocket or wallet, it has no safety and can extend and cut the wallet or wound you.

Sunday, June 7, 2009

Hold my hand

I’ve already discussed 3D photography on my last entry here, but this time I want to talk a little more about making things easier. The trick to 3D photography is taking two pictures, with the camera a certain distance apart in each one. If your hands are stable, you can just snap one and move the camera, but a better option is to use some sort of camera mount to help you along. Using some simple items from the Lowe’s, you can build a special camera slide for 3D shooting for less than $20. Here’s how.

The main component is a ball-bearing drawer slides. By attaching a pair of cameras to a slide, you can easily move the cameras in parallel. My slide mount was built using a D806 16” slides, which sell for around 12$ in hardware stores. You will also need some 3/8” thick wood, some tee-nuts and “key” screws, a flat metal attachment plate, as well as some other smaller screws.

1) Attach the thin part of the 1st slide to the 2nd using small nuts and bolts. The nuts and bolts should be small, so as to not interfere with the closing of the slides. This essentially creates a single slider that can be extended from 16” to 47.5”.

1) Saw the 3/8” thick wood into 3 pieces – 2 of them about 4” long each, and a 3rd about 2.5”. The ideal width of the board is about 2.5”, but that does not have to be exact. The longer pieces will hold to cameras to the slide, and the 3rd will hold the slide to a regular tripod.
2) Attach one of the two long wood pieces (Approx 4” long) to the slide, using small wood-screws.

3) Bend the metal attachment plate to a U-shape, roughly 1.5” wide. This piece will attach the 2nd camera to the bottom part of the slider.
4) Using small nuts and bolts, attach the plate to the bottom slider, at about the 5”-6” of its length.
5) Attach the 2nd long wood pieces to the U-shaped attachment plate. Ideally, the wood pieces should be touching each other when the slide is in a closed position.

6) Drill a ¼” hold in each wood plate, through which you will insert the key-screws and attach the cameras to the slides. You can use basically any ¼” screw for this, but key-type screws will allow you to attach and remove the cameras at will without using tools. You will also have to use a thicker drill-bit, about 6/16”, and widen the bottom-part of the hole, to allow the key-screw to get in a little more; otherwise it will not be able to reach the camera. It needs to protrude above the upper surface of the wood piece for about 2/16”-3/16”. The location of the hole would be in accordance with your cameras, in order to place them in the middle of the board. This does not have to be exact. In my setup, the screw hole is at the back-side of the wood, so the entry point is at the back, allowing me easy access to remove the cameras.

7) Drill a similar hole in the smaller wooden piece, exactly in the middle, and hammer-in a “tee nut”. If you have chosen too-soft wood, it might buckle under the pressure, as the slides can be quite heavy. Turn the wood up-side-down, and attach it to the bottom of the slide. Make sure the tee-nut is hammered in at the TOP of the piece of wood, as it is supposed to be supported by the wood against the pressure from the tripod screw. The screws that attach it to the slide need to be strong, so as to not get pulled out by the weight of it all. In fact, when the slide is fully extended, it will be much heavier on one side, so support it with your hand, or another tripod to make sure it doesn’t fall apart. In fact, make sure your tripod is sturdy and heavy in the 1st place.

To use this, an ideal setup would include two identical cameras, and you would pull them apart on the slide to a distance that’s 1/30 of the distance from the camera to the closest object seen in the photo. Pressing both shutters simultaneously is key to getting a good picture for moving things like people, animals or traffic.