Lightsaber Bow – Droo’s Notes

Okay, so Droo saw my post on the Lightsaber Bow and decided that it was so very technically incorrect that he needed to write his own to correct my completely inaccurate depictions of his skill and craft. I believe the phrase used was, “Some kind of lightbulb? Some kind of lightbulb?! I’ll have you know that I had very specific lightbulbs in mind!” So, without further ado, Droo’s notes:

I am fascinated with the manipulation of light for the purposes of display and quite often forget that what I see as normal physics is usually never known or seen by most people that do not need to understand the inner workings of the universe. I envy them, because mostly, I have found the only reason to know the inner workings of the universe is because you need to oil the gears turning the crystal spheres.

The design has gone through several iterations, even before I pulled out my notebook to work out which ones would require a Mr Fusion to be strapped to a violin. The “laser bow” is currently in the grey area of engineering, between prospecting for parts and calculating the various requirements to decide which of the two current contenders is less likely to result in personal injury. I have at all times tried to use a continuous light source. Although I love LEDs, I think that this project requires more than a string of dots. The person who is going to enjoy the bow the most is James, so if it breaks the illusion of a light sabre, then the project is a failure.

Castor and his cane.  But mostly Castor.

Castor and his cane. But mostly Castor.

The original idea was similar to the Castor’s light cane from Tron Legacy, made from Perspex. This was doomed to failure from the start, as mentioned by Becky, due to the requirement that it has to be able to play a violin.

The second iteration (and currently under development system) is a regular violin bow, bound with Electroluminescent tape. This is a thin sheet of plastic with a layer of phosphorescent material that is excited to the point of illumination by an alternating electric current. Since it is essentially a long, small capacitor, it can be paired with an inductor to make a tuned resonator, oscillating at the operating frequency of the electroluminescent tape. The major problem is the size of the inductor is in the ball park of 2-16mH, which needs about 500 metres of copper.

A new idea, suggested by Becky, is a fibre optic bundle, finely sanded to emit light. This goes back to the problem of flexing the bow, as there are few adhesives that would last under such circumstances and still hold glass. I have modified the idea and I am now looking for a hollow braid rope, made out of fibre optic plastic. This will allow me to slip a cover over the bow and not need me to worry about individual fibres peeling off. The ideal braid would be similar to the very cheap hobby rope, such as:

Twisty rope stuff

Cheap Nylon Braid

This will allow me to go back to the Mk1 version, but allow the bow to flex. It would also allow the colours to change (just in case J pulls a Samuel L Jackson and demands a purple light bow[1]). Currently this version is in the parts prospecting stage, as I am looking for a hollow braid rope, about one and a half metres long, of fibre optic plastic. I may have to make a rope braiding loom and weave one myself[2], but that just means that I can start selling them.

The next challenge will be the electronics on the bow. If I can power the lights, then I can move on and start to do very small scale electronics to control the light source (although the thought of soldering components that are 0.2mm to a side scares me. I can only do down to 0.8mm at the moment)

Becky’s Addendums:
[1] J does want a purple bow ala Mace Windu. Purple is his favourite colour.
[2] Y’know, I can weave. I own a loom. Just saying.


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