Opening and closing beam katana (Tsubaki from No More Heroes)

I recently decided I'm going to go as Travis Touchdown for Halloween, and a friend and I decided we were going to attempt to make the Tsubaki Beam Katana. (the one in the middle)
We've thought about making one that is always closed, (not able to extend out to open position) so I can wear it on my belt. But where's the fun in that. So we thought of course about making one that will always be extended out, (not able to collapse into closed position) but it would be cumbersome at times that I would need both my hands wherever I was, and I don't like putting things down, just so I can come back to it to see that it's been handled by someone else and broken, (I plan on it being sturdy, but still, someone will find a way) or even worse... missing. So I guess the only option would be to make a fully functioning one (being able to extend and collapse through the use of buttons, and when extended out, pressing a switch to turn on a light for the "beam")

So basically this
except without the hitting of people part. lol

There is multiple ways I've thought on how to approach this, the simplest, but non awesome way, would be to just use gravity, like the old school toy lightsabers. If there's no other way, I guess that will be what I have to end up doing. But, lets not give up so soon shall we? I've thought of using a long spring, but the only place I thought of where to put that would be in the tube that would light up for the 'beam', but once lit up you would be able to see the shadow of the spring projected onto the tube, and I don't really want that. Another idea was to use air pressure somehow, I really don't know how though, this kind of stuff isn't exactly my forte. And my last idea was some gears that could possibly be used on the stick piece that extends on the outside of the beam, to hold the top of the whole beam katana, but that might be hard to pull off since that piece is going to be sectioned like an antenna that extends out.

So what I'm asking for is different ideas that I could possibly use to get this thing to shoot open on command. I would like for it to shoot open and snap closed, but being able to get it to only shoot open seems more plausible in this situation. (and just manually close it by hand) But if you have ideas for it to open AND close on command, then please share, for I just may try it.
Thank you for your time in reading this, and any help you have to offer.

Picture of Opening and closing beam katana (Tsubaki from No More Heroes)
well i am a 17 yo inventor who build a working blood berry and i had with the same problem when i was surfing on the internets i found the solution is actually easy there are some self defense tactical batosn that are strong and retractable and can be found on e-bay...i know is late but its a good answer hope it works for this hallowen LOL
REALIZER7 years ago
How about this?
Instead of the good, ol' gravity-based swingin' open that you mentioned, you can connect the top part of the sectioned, hollow plastic 'laser' blade with a strong piece of PE line, or better, wire, that is connected to a pull-back gear, ones you often see at children's toy car. When a switch is pushed, or flipped, the tension accumulated in the motor will pull up the string, connected with a small wheel inside the blade's upper part (which shaped like an umbrella) until it hits the top, and for the 'steathing', just put a piece of tab at the higest section of the 'laser blade' to pull it down.