Retractable LED Blade V1

This is a device I designed for a school project, so it is not fully complete and there are likely to be changes in the near future. I'll add updates as I complete more!

This is the base mechanism for a sci-fi prop blade. It takes heavy inspiration from the Assassin's Creed blade mechanism, but I've modeled everything myself in CAD to best fit my own design. I've also incorporated LEDs that activate when the blade is extended. The spring motion can pull the blade both in and out with a turn of the wheel.

• 3D printer
• PLA filament
• battery contacts
• nickel plated strips
• m2 screws (8mm, 12mm)
• m2 nuts
• rubber bands
• tension springs (diameter no more than 5mm)
• LED light strip
• 20 AWG stranded wire
• wire cutter/stripper
• heat shrink tubing
• soldering iron and solder ("Helping Hands" suggested but not required)
• file set
• craft foam
• super glue
• hot glue

stl files for this project can be found here: https://www.thingiverse.com/thing:5369255

Be conscious of the orientation of the parts when printing! Try to keep the striation from the layers horizontal for the moving parts to reduce friction.

Some pieces may need to have the surfaces filed down in order to move smoothly. The paddles especially are likely to need a bit taken off the top and bottom. File as you need to reduce friction.

To start we'll need to solder some parts to create our LED circuit. We'll begin with the blade. Start by determining how long a length of LED strip will fit on the blade. Make sure to cut the strand where directed. Leave about half an inch of room in the back of the groove for the wires.

Cut two short lengths of wire and solder them at a 90 degree angle sideways to two flat battery contacts. The positive contact wire should be pointing left as the picture shows, and the negative one should be pointing right.

Place some heat shrink on the wire before soldering any more. Then solder the positive contact to the positive terminal on the LED strip (it should be marked with a + sign), and the negative contact to the terminal for the color you want your strip to light up as (Red, Blue, or Green).

Once both contacts have been connected to the LED strip, place the contacts through the holes in the blade and make sure they can sit flush with the cubes on the bottom. Depending on the accuracy of your #D printer, you may have to add a tab of craft foam between the blade and the contact to raise it off the surface. Use a small amount of hot glue to do this so it can be easily removed in case adjustments are needed.

Once you have the contacts situated, if your LED strip has adhesive, peel the backing off and secure it in the groove on top of the blade. Otherwise you can glue it.

Now you have the blade finished!

Take two battery contacts with springs and solder them each to a length of wire long enough to feed through the hollow divider in the middle and leave an inch or so on the other side (and don't forget the heat shrink!)

Bend the small metal tab on the end of the battery contact close to a 90 degree angle, then feed the wire through the hollow divider, starting from the front of the base.

Use super glue to glue the back of the spring contacts to the inner front wall of the base. Try to get them centered in each groove and don't let them stick out of the top or the blade will be scraping against them!!

Now the tough part... grab the wires coming out the back of the base, then make sure you know which wire is which. Using two colored strands is useful here. The wire on the left side is going to be your positive wire. The one on the right will be the negative wire. To the negative (right) wire, solder another battery contact with a spring. Cut a nickel strip to about 1 inch. To be sure of the measurement, ensure that when placed into the small slot leading to the larger chamber in the battery box, that the strip can touch the far lip but not stick out past the back of the box. Solder the positive (left) wire to the end of this strip.

Now, squeeze the spring battery contact into the small battery box chamber through the hole in the back. Center it so the spring sticks out the round hole in the divider and super glue it to the wall. Then slide the nickel strip into the hole on the other side, and glue it so it's flush with the wall as well.

There you go! Second half of the circuit is done!

Now that all of the electronics are in order, it's time to put all the pieces together!

Start with the paddles. Wrap a rubber band around the hook on the bottom. Make sure it isn't too tight or too loose. You may have to double wrap depending on the size of the rubber band.

Now take one of the paddles and align the hole with the holes in the floor and ceiling of the chamber on the right side of the base. Place a pin in the holes to hold the paddle in place (for a pin I used a very small nail that I cut down to size). Do the same thing with the other paddle, ensuring the rubber band is free in the groove and not wedged under one of the paddles. Check to see if the paddles are moving smoothly, and file them down as needed.

Next, place the blade in the track and push it backwards into the retracted position. When the blade passes the back paddle, it should swing out and lock it into place.

Connect the middle plate and the two L-shaped bars with two springs and set the bars in place so the foot of the L is pointing towards the interior. The springs should have a small amount of tension in this position. Be careful, because the bars will fly off if bumped out of position!

Gently place the middle plate on top of the blade, making sure the bars are to the left of the blade, and the back bar is hooked onto the notch on the left side of the blade. You will probably have to push the front paddle in before the plate will sit flush.

For the top plate, take the bottom disk with the peg and fit it through the hole in the plate from the bottom. It should sit flush with the rest of the plate aside from the peg. Then take the top disk and place it on top, sandwiching the plate between the two disks. You will have to make sure the inside of the two disks are lined up before pressing them together.

Take a 12mm M2 screw and insert it through the hole in the top of the disk. Use a nut on the bottom to tighten. Make sure the disk spins freely without too much resistance. Do a bit of filing if it doesn't.

Align the screw holes on the back of the top plate, the base, and the battery box. Use a screw of appropriate length and a nut to tighten them into place.

Place 4 coin cell batteries into the battery box with the positive terminal touching the nickel strip and the negative terminal touching the spring contact.

Use a screw to fasten the lid onto the battery box.

Congratulations! You're done! Turn the wheel on top clockwise and see the results!