Let there be light!

It has been a while since my last posting, but I have been busy researching lighting sources for my next Zero-G flight. You will recall that my concern was that I could not get sufficient light inside the cabin to get good video except when next to a window, and I was looking to either buy or build something to deal with that problem.

As luck would have it, a posting on Gizmodo lead me to a new product, the Digi-Slave Flex Ring 6400 LED Macrophotography Light. After some consultation with the manufacturer, I purchased one for testing.

To my great surprise and pleasure, this little beast pumps out enough light to permit videography not just at 300 fps, but also 600 and 1200 as well! Check out the video below, the shots were taken in a totally dark room, lit only by the Digi-Slave.

The trick to getting the maximum light out of this device is to use rechargeable Nickle-Metal-Hydride (NiMH) AA batteries. While these do not provide as much voltage as regular AA cells (1.2 vs. 1.5v), they have lower internal resistance and can provide higher current flows than even "high-discharge" Lithium batteries. Enjoy!

Back to Basics

After the abysmal failure of my carbonated soda tests, I went back to the drawing board and rethought the whole concept. I finally realized that I'd been a bit too ambitious, and needed to get back to basics.

Since plain old bottled water is already deployed in the cabin during ZeroG flights, I decided to build an experimental platform that would permit me to get good video (both regular and high-speed) of water spheres. I needed something that would let me get good images of fairly large blobs of water that were floating freely in the cabin, and also let me collect the water at the end of the free-fall segment. Here's what I came up with...

The vertical frame mounts the camera and operator handles, and will also contain a set of high-intensity LuxStrip LED light bars to provide the light needed for the high-speed camera. The horizontal frame is the liquid-collection device, which is constructed out of plastic sheeting, the remains of 5 disposable diapers, and, of course, duct tape.

Everything is constructed out of T-slot extrusions and connectors from Amazing Robotics plus a few bits that I hacked together in my workshop.

The nice big red handles are perfect for controlling the device, pointing the camera, and wicking up the water afterwards.

The diaper+plastic sheet can be removed and replaced in flight; it attaches to a UHMW base plate via some velcro tabs.

Finally, the whole thing folds flat; locking and unlocking is controlled by two wing-nuts; no tools required!

Needless to say, if I can come up with an acronym for this device that matches a major diaper brand, the sponsorship opportunities are literally out of this world ("4 out of 5 incontinent free-falling mad scientists prefer Depends").

PS: Some things I learned while abuilding...

T-slot extrusion is great for these kind of prototyping projects; here are a few things I learned along the way.

• Most of the supplied nuts and bolts are 10-32. I happen to love 10-32 cap screws so I replaced them with some nice buttonheads.
  

• The big red handles use 1/4 bolts; the problem is that 1/4 nuts won't fit in the extrusion. The solution is to use flat automotive speed nuts and a little hackery. Speed nuts are weird spring-steel flat plate devices, and the 1/4 ones almost but not quite fit in the slots. To get them to fit, you do the following: thread a junk 1/4 bolt onto it (the bolt may get a little mangled), clamp one end in a vice, and use a tightened-up adjustable wrench to take the bow out of the nut, so it's pretty much flat. Once you've got it to where it will slide easily in the slot, remove the bolt and test out another one to make sure that the little fingers that grasp the bolt are not too loose, and not too tight. You may have to adjust them with the vise or pliers.
  

• A length of piano hinge with holes that are the right size for 10-32 bolts (any hardware store will have some, you can cut it to the length you need) will fold so that the sides are close to parallel if you secure it by alternating 10-32 buttonheads + a small washer (so that each buttonhead touches an empty hole on the other half of the hinge).  The buttonheads act as spacers.

• The plastic corner connectors have fingers that have starter holes for small set-screws (you will understand what I mean if you get some). However, the cube-corner connectors (not actually used in my device) have one set of fingers that don't have the starter holes, probably because of a limitation in their manufacturing process. Just stuff the no-hole fingers into a bit of the t-slot extrusion and drill your own in using a #41 or so drill bit. Update: I've been told that you can also screw the set-screws into the ends of the fingers without drilling.

• One of the big pains with T-slot extrusion is when you realize that you need an extra square nut in a section to mount something, because this means you have to take things apart -- unless you know about a trick. It turns out that the 10-32 square nuts have enough variability in their size that some of them can be inserted directly into a slot. To find nuts with this property, slide a bunch of them into a slot, turn the extrusion so that slot is on the bottom, and shake the nuts back and forth; the special secret nuts will drop out. Repeat the process with the remaining nuts rotation 90-degrees, as usually only one axis is short. Set these nuts aside for emergencies. To insert a nut, put it into the slot, put your finger on it, turn so the slot is on the bottom, and slide the nut back and forth; it'll seat itself quite easily (assuming you've got the orientation correct, a 50-50 shot).
  

High-speed video LED lighting tests

One of the important supporting projects I have been working on is developing a better light source for the Exilim EX-F1 camera.  As you may recall, on our first flight, we depended on getting light from a cabin window, but this placed a lot of restrictions on freedom of movement, which is important because if you are strapped down, your apparatus isn't always in microgravity; it depends on how good the pilot is at flying the parabola.  If you are freely floating, on the other hand, any variations just cause everything to wobble together, so other than some minor effects due to friction with the air, everything will be very close to zero-g as long as you don't hit a wall, and nobody hits you!

Therefore my plan is to build a portable light source for the camera.  Typical video camera lighting systems start at over $100 for a 10watt halogen system, so I figured it would be more fun to build my own using multiple 3watt luxeon white LEDs from SparkFun (they also have some nice heatsinks for these nasty little critters).

Here's some video of the first test runs, which are very encouraging.  I soldered up 8 3watt LEDs to heatsinks, put them on a styrofoam ring, and wired them up in parallel to 3 1.2v NiMH cells (so I'm actually undervolting them a bit).  You have to use NiMH or NiCd for this kind of application because non-rechargable cells just can't source the current needed - probably 5 or 6 amps total.

Epic Fail!

The initial tests of my 2D Menticulator device failed in so many ways, it's just not funny!

To start with, the pneumatic cola dispensing system doesn't work -- because the bladder used to force the cola out of the bottle acts as a massive nexus of nucleation sites. As soon as you try and put the bladder into the coke bottle, all the CO2 comes out of solution! Foom! So unless I can come up with a system that either avoids the problem or can repressurize the bottle with C02 to put it back into solution, all the lovely pneumatic gear I cobbled together is useless, at least for the purposes I originally intended.

And to make matters worse, even careful attempts to decant the soda into the 2-D menticulator failed miserably. Despite being made with panels of carefully cleaned acrylic, it is rough enough that most of the CO2 comes out of solution and sticks to the walls, both reducing the amount of CO2 available for menticulation and obscuring the view of the convection process. Again, I'd have to repressurize the apparatus to force the gas back into solution.

I think the video I shot of the final test says it all. What happens at the end is just icing on the fail cake, so to speak.

I therefore find myself compelled to choke out the hateful lines, "Curses! Foiled again!"

On the bright side, I have yet to have to utter the deathless lines that doom an Overlord to eternal ignominy -- "I would've have gotten away with it if it wasn't for those meddling kids!"

In other news, work on a LED-based lighting apparatus for the Exilim camera is proceeding fairly well; I'll be posting on that soon.

A Pneumatic Cola Dispensing Manifold

It has been a while since my last post, for which I apologize. I've been busy dialogue-editing an interesting Japanese film about the Special Attack Forces (aka the Kamikaze). But during spare moments I've been working on an improved method of dispensing cola from a 16oz bottle.

Here you see the cola dispensing manifold before assembly. One side of the T-joint is the gas input, which feeds the gas down into the bottle through the cap and into a balloon using some tubing. The displaced liquid goes back up through the joint and out the other side of the T, flowing around the gas input tube.

As I had to get the hole in the cap right in the middle to avoid having the nut on the inside catch on the neck of the bottle, I used my Sherline mini-lathe to get it as close as possible. The cap deformed a little bit when clamped into the lathe but the hole was centered to within a millimeter or two...

The components were bolted together, and I used teflon pipe-wrap tape to ensure that they were gas and liquid-tight. I also put some silicone sealer under the big washer to make sure the cap hole would not leak.

Here is the device completely assembled. As with my previous experiments I used a punch-balloon as the bladder.  Both the bypass tube and the tube inside the bladder had some notches clipped into them to ensure that there were multiple outlets, eliminating the chance of an outlet getting blocked.

As you can see, it inflates very nicely...

My current thinking is to have multiple cola bottles (with manifolds on each) as well as multiple gas bottles, with a piping and valving system that provides redundancy.  Everything will be assembled onto some perf-board that is sized to fit in a rolling carryon bag.

Oh, and I've built a 2D Menticulation test chamber as well, which I'll probably test out this weekend.

Pneumatic Soda Deployment Device Improvements (Part II)

A quick trip to the party store this weekend provided me with a variety of balloon styles to play with.  The best candidate so far is a "punch-ball" balloon, which is both much thicker than a normal balloon and is also pleated.  The fill tube extends into the neck of the balloon right down to the tip, which makes it easier to insert the whole assembly. Also, before inserting the balloon, I pop in a short length of polyethylene tubing that serves as a bypass and allows soda trapped under the balloon to escape.

The system permits quite precise deployment of the soda, although I am still considering implementing a flow restrictor. In the second image, I've deployed soda most of the way up the tube but halted it at that point. By fully expanding the balloon I can expel almost all the soda, although in practice I'll only need to display a few fluid ounces.

One possible improvement might be to use a smaller bottle and a tube sized so  that when the bottle is completely empty, I have a soda globe of exactly the right size.

Cola Deployment Improvements

Finally managed to make time to do more testing of the Mark II Cola Deployment Device. Following up on a suggestion that I consider using a small bike pump as the pressure source, I started playing around and came up with this test apparatus.

The basic idea is that the pump is used to pressurize an empty 1-liter PET bottle that contains a couple of balloons that serve as a quick-n-dirty pressure indicator. These bottles can take quite a bit of pressure before they go bang, certainly much more than you can get into them with a hand-pump.

Then a valve is cracked to blow up the balloon inside the cola bottle and expel the cola.  It's pretty controllable but I'm probably going to put in some sort of flow restrictor to make it more controllable.

All of the tubing and fittings are available at Lowes or Home Depot. The tubing is (iirc) translucent semi-rigid polyethylene -- the other option, clear vinyl, doesn't work as well with the fittings.

The fittings themselves are simple $2-4 plastic push-on, quick-release fittings. Amazingly, these are almost totally gas tight!  I pumped the reservoir bottle up to 4 or 5 bar and left it overnight and the leakage was negligible. These things are like legos for low-pressure pneumatics! On the other hand, the brass compression fittings you'll find in the same aisle at the store are a pain to work with -- very hard to get gas-tight.

Tip: some of the fittings have threads on them, which can be very handy (I added such a fitting to the cap of the 1-liter bottle, for example). However, these are pipe fittings, so they have NPT threads on them, which are different from regular UNC/UNF threads used on common nuts and bolts in the US. Even my usual black-market nut connections couldn't fix me up.  However, I eventually found my way to the illegal nut dealers at Steven's Hardware here in Wilmington, where I learned the magic word. The magic word is "lamp nuts" -- for some reason, they use NPT threads!

The major remaining design issue is the balloon inside the cola bottle.  Sometimes it gets caught on the sides of the bottle and this results in another part of the balloon getting stretched until it breaks. I am currently using double-balloons but I'm thinking that finger-shaped balloons will work better.

I've also been working on a 2-D Cola Convection Display Device, I'll post on that soon.