For SCUBA divers, safety and deco stops are an important part of the activity and should be performed properly and fully to maintain as broad a safety margin as possible to prevent DCS and other issues.  Most recreational dive clubs and operators also maintain a requirement that divers end up back on the surface with 500psi in order to maintain a reserve in case of emergencies.  This catches a large number of the infrequent incidents that can occur due to inattention, equipment failure or other causes.  As an additional step, many groups also employ some kind of extra gas supply available at the designated safety stop to allow divers yet another option in the event of an incident allowing them to complete their safety stop fully even during a full out-of-gas scenario.  One option is to run long hoses ending in second stage regs all the way from the boat to the anchor line to supply divers with air/oxygen.

The “Hang-Tank” is also known as a “stage” or “deco” “tank”, “cylinder” or “bottle” and is a self-contained cylinder and regulator configuration that is placed on the anchor line, or below the boat in some way at a depth that allows divers to complete their safety stop.  This piece of equipment has been around for a long time and so is nothing new.

Technical divers have and use their own and are self-sufficient, where many recreational clubs, boats or groups have a more communal approach since in the recreational realm this is meant as a contingency instead of part of the regular dive.  However when I’ve seen it in use, it’s often ad-hoc using someone’s 2nd cylinder and spare set of regs as opposed to a specialized set of equipment. This isn’t in itself wrong, but I think there are opportunities for improvement over that system.

What follows is a collection of my own suggestions and thoughts surrounding this important piece of gear.  It’s not meant to be the end-all and be-all, but may provide a sound foundation for anyone looking to set up a hang-tank for their group or personal use.  I would further like to suggest that no-one follow this guide blindly, but think through what I’ve laid out, and use what makes sense for you and your situation.  Also, I’d like to encourage everyone to think about improvements (which I would love to hear about).

Configuration

1. A 72/80 cu. ft aluminum cylinder should be designated and clearly marked for the purpose.
2. The tank should be designated and treated for nitrox use and filled with 36% (or similar) to maximize safety and off-gassing at 15’ without having to resort to special oxygen compatible regulators.  Divers using the tank would regard it as air, and use it as such.  No marking on the tank would denote it’s actual oxygen content except perhaps a maximum operating depth (MOD) of 100’  (arguments for or against the green/yellow marking for nitrox can be made, but that is ultimately up to the individual/group that owns the tank).
3. The hang tank kit should include a special set of regulators that are designated for the hang tank only and that travel with the divemaster kit.  The regulators should be assembled using a first stage and two second stages on 40” (octo-length) hoses with an easily readable pressure gauge on a short (6” High-pressure Hose) to minimize entanglement hazards and risk of damage.  Ideally, no LP hose should be attached, but if an LP hose is included it may be bundled as outlined below.  One might also consider having the regs detuned as well to help prevent free-flows due to current.
4. There should be a means of stowing the 2nd stage hoses on the tank when they’re not in use to keep them from dangling, but allow quick and easy access.  Bungee, rubber or elastic wraps around the tank would suffice.
5. A set of open-water & altitude tables should be affixed in to the tank for diver reference.
6. A re-usable slate and pencil should be affixed to the tank in a fashion that allows it to be removed easily and passed via the safety diver/swimmer to surface support & the dive master.
7. The hang tank should be affixed to the anchor line or on the regular route to the surface at 15’.  At a bare minimum, a line should lead divers to the hang tank without their having to go above 10’ in depth (ideally staying at or near 15’).   A length of bungee cord can be used in suspending the tank to absorb some shock resulting from rough surface conditions and minimize bouncing of the tank and divers.
8. The tank should have two to three 2 lb clip-on weights attached to it for the use of divers having difficulty maintaining their stops.  The weights might be marked brightly and clearly (pink/orange) and be used by any divers who are using the hang-tank to aid in identifying the fact that the tank is in use or there is something going on.
9. A strobe or glow-stick may also be attached to the tank to assist in its location.

Procedures

Preparation

Before diving begins, the tank is assembled using the usual procedures to check for odours in the gas, o-ring quality, oxygen concentration if nitrox is used, etc.  The valve is turned on and a couple breaths are drawn from each of the attached regulators.  The pressure of the contents is verified as adequate for the dive.  The valve is then closed leaving the regulator hoses pressurized.  Hoses are stowed using the elastic/bungee wraps on the tank and any tables/slates/weights attached either with clips or in pockets (preferred for light-weight items).

Deployment on the Anchor Line

The hang tank is swum to the anchor/bow line and attached securely to the line at a depth of 15’.  At this point, the valve is opened and closed to ensure the hoses are pressurized, but that in the event of a free-flowing reg due to current or other causes, the contents of the tank are not emptied.  A strong recommendation is made to have a dive team work together to deploy the tank.

Alternate Deployment

Ensuring the valve is closed and the hoses are pressurized, the tank can be dropped over the side of the boat on a hang line along with a guide-line attached to the bow/anchor line.

Use

Divers should not make a practice of using the hang tank except in circumstances where no-decompression limits have been exceeded, or a diver running low enough on air that they cannot reach the surface with 500psi in their own tank after completing a safety stop.  Upon an incident requiring use of the hang tank, divers make their way to the hang tank utilizing air-sharing techniques if necessary.

If the incident triggering use of the hang-tank is exceeding the no-decompression limits, then both buddies should make use of the tank while perfoming their stop to increase the safety margin.  Otherwise divers with sufficient gas in their own tanks should continue to use their own supply.

The regs are deployed to each diver as required and the valve opened.  The divers can then make the switch to the hang tank regs and stow their own regs.  The tables stowed on the tank can then be un-stowed and consulted.  Regardless if the divers have been diving air or nitrox up to this point, the tables are consulted as if the whole dive were performed on air, and the divers complete whatever safety/deco stops are indicated by the tables.  The only exception of this is if the divers suspect hypothermia onset (note: not simply discomfort due to cold).  Divers should attempt to maintain their depth such that their chest is at 15 ft.  Upon completion of the proscribed stop, the divers switch back to their own regulators or air sharing as required and ascend in a controlled manner to the surface ending their dive.  Preferably, the valve on the hang-tank will be closed when the divers finish with it, but this is reduced to a suggestion to lower task loading on final ascent.  The incident must be reported to the divemaster along with pertinent details of the incident including the length of the actual safety stop performed.

Retrieval

All divers must be accounted for before the diver assigned to the task retrieves the hang-tank.  This may require the diver assigned to surface from their dive (having performed their safety stops) to check with the divemaster before submerging again to retrieve the tank.  A strong recommendation is made to have a dive team work together to retrieve the tank.

Training

The use of the hang tank should be included in a course (most likely at the advanced level) including actual in-pool practice where possible.  An orientation covering the features, placement and use of the hang tank should be held regularly with divers (ie. at the beginning of a dive day).

John Pultorak spent close to $3000 and ten hours a week over four years to make ~15,000 connections between ~500 chips to build his AGC clone.  Then he documented it all in this exquisite 9 volume set of documents.  Even better, he’s released his information into the public domain to save others from having to do all the research and development themselves.

Like many of these niche interests, there’s a group of enthusiasts who can help you with your version.

John has documented his project in 9 separate pdf files:

Disclaimer

I am not a professional underwater videographer/photographer, nor am I a mechanical engineer or have any other official credentials.  I’m not responsible if you choose to try this yourself and end up with a waterlogged hunk of plastic and metal, but it’s really not that hard either if you choose to try this, I’d encourage you to do so.  Just make sure you test things in small steps first before risking your expensive goodies.  Also don’t let the fact that you’re using a camera distract you from your responsibilities under water.  Keep checking your gauges, and watch your buddies… even the ones not in front of the camera!  A camera is a lot to think about beneath the waves (you’ll be surprised), so if you’re not ready for it, don’t take it!

During the summer of 2004 I’ve finally got around to gearing up and getting involved with a local SCUBA club.  This is not an inexpensive proposition,
but this summer should see the end of the major budget hits for a while.  I went on my first dive trip with the EUC (Etobicoke Underwater Club) to Tobermory for the August long weekend.  A couple divers brought their digital cameras with waterproof housings and were able to get some great shots while sitting on the bottom.  I’d brought my video cam and got lots of video on the surface of activities on the boats, but that wasn’t really why I was there…  I want submerged video.  Ikelite makes a housing for my Canon ZR-70, but the cheapest I could find it for was $640 US.  I paid $440 US for the camera itself!  Now I understand these nice cases give you pretty much full control of your camera using zoom and start/stop recording as well as full use of the digital still camera capabilities of this particular model, but I reasoned about this, and I don’t feel the need for any control over the camera besides pointing it at interesting things.  My reasons are as follows.

1)  The digital still quality of this camera is poor by my standards, and wasn’t really on my list of requirements when I bought it.  – Don’t need it.

2)  I can’t remember where I heard this, but it made too much sense to ignore.  Most underwater photography (including videography) is in relatively close quarters  5-15ft, so you want to use a wide angle lens if you’re able.  One of the reasons I selected the ZR-70 was that it came with a wide angle lens, however the zoom function is extremely limited with the wide angle lens in place.  – Scratch this too.

3)  Now what about that all important start/stop recording button? Well obviously this would be the first control I’d want implemented, but a few thoughts on that.  I’m not going to have use of the viewfinder, so I have no feedback about the camera’s state of recording.  I’ve had cases where I get myself messed up, and end up recording when I don’t want, and then as soon as I want to capture a moment, I bring the camera up, press the record button, and end up pausing the camera instead…  that’s when I DO have use of the viewfinder.  So why increase the risk of that happening?  Finally, any additional controls on a SCUBA rig increase the workload of the diver no matter if they plan to use them or not.  Any device you bring with you on a dive is part of your rig.  A camera may not be life-support equipment, but it can be a definite distraction.  Why make something any more complicated than point and shoot?  Anyone with a current PC has the capability of editing video now anyways.  – It’s settled…  No start/stop recording button.

My Plan

In researching the problem and available solutions, I came across this fellow’s site.  The simplicity of his Mark III design appealed to me.  It’s truly elegant in its simplicity, and his thinking seems to be along the same lines as mine.  He now sells a production version of his housing here. If you’re at all nervous about building your own housing, then you should contact Paul and see if the housing will fit your camera.  From what I can see, he’s a craftsman and I don’t think you’ll be disappointed.

The design I’m using is based on Paul’s, though I plan to add a few refinements (which you’re free to incorporate if you read this Paul).  The housing body is built from clear acrylic plastic tube and sheet.  The body is made up of a 5″dia. disk 1/2″ thick,  5″OD tube with a 1/4″ thick wall approximately 7″ long that are welded together. The open end of the body is closed off by another 5″diameter disk that 3/4″ thick.  This plug has a step machined in it for an o-ring. The whole thing will be held together with a couple draw-latches.

I have
selected 1864A13 from McMaster-Carr for $9.23ea.  I picked these guys for three reasons.

1)  304 stainless steel construction

2)  Ability to adjust their length (flexibility is nice when you’re dealing with hand construction)

3)  I really like their low-profile smooth lines.  Too many of the latches I looked at had upturned ends and such that could snag on lines and either open if the latch isn’t pinned, or just cause nuisance hang-ups with any lines that might be in the water.  Why not streamline wherever possible? One drawback is that the cleat that comes with this draw latch mounts in the same orientation as the latch (Unlike Paul’s Mark III who’s cleats mount on the flat surface of the plug).  This means that in order to mount it to the plug, I have to cross-drill the holes and then have shear force on the bolts.  I’m afraid of the acrylic cracking if I do that, so I’ll have to work on another solution.

Any means of fastening should be good.  One could even use thumb screws.  Anything that puts a bit of axial pressure on the o-ring.

As I mentioned, the construction will be acrylic.  I obtained some 1/2″ sheet, 3/4″ sheet and 24″ of 5″dia tube.  This is enough material for three housings by this design, and it only cost me $160 CAN.  I called in a couple favors at a local machine shop and they fabricated the three pieces I needed.  Thinking about it now, I believe I can make the disks on my 7×12 lathe, but I still can’t easily true up the ends of the tube.

All three pieces are made of clear acrylic, though the two ends have protective paper/plastic still on them.

For this design, there are two points of failure.  The obvious leaking that most likely will occur in the first few feet of descent, and crushing of the housing.  Leaking obviously endangers the camera, but is relatively minor compared to a catastrophic implosion that would destroy the camera with hundreds of bits of acrylic.  Obviously both these scenarios must be tested before the camera will be placed inside.

A Bit On The Seal

The trick is to maintain a seal at the surface.  In theory anyways.  Any mechanism that holds the end cap (plug) on at the surface and seals the housing will become redundant as soon as you start to submerge past about 15 feet.  At this point, you’ll have roughly one-half atmosphere of pressure on the housing.  Both ends of the canister will have about 7.5PSI pressing them together.  For my 5″ diameter cylinder, this works out to over 300lbs of force!  That means for most diving (25+ feet) you’d be hard-pressed to remove the plug.  Further, not only could you undo the latches at this point without actually risking your camera (no I won’t prove it to you with a camera in the case…just trust me), but also the seal will only get tighter and tighter as you go to greater depths.

With this simple design there are two styles of seal that I’m going to try.  First is the basic o-ring that Paul used for his Mark III, is a quad o-ring which is approximately 4x the price, but gives you some redundancy by doubling the number of seals.  From Able O-Rings in Toronto, the regular O-ring is $1.10, and the quad is $6.39.  I haven’t decided on the frequency of o-ring replacement yet, but regardless of which I end up using, I think the cost of replacing a quad o-ring before each trip is well justified.

The o-rings of course will be smeared with silicone grease to make the job of the o-rings a little easier.

Testing

After further research into camera control glands (I don’t plan to use them on this housing, but we’ll see…  plans change), I found Tom’s site which is not only encouraging for home-brewed dive accessories, but had a couple interesting tidbits for someone like myself.  At this point, the important thing is that he turned me on to an inexpensive pressure testing apparatus that I had not previously heard of.  The device is called a “pressure paint pot” and is a large canister that is meant to be pressurized to dispense paint to a spray gun.  He pointed me to one at Harbor Freight for about $80 US.  Unfortunately we don’t have Harbor Freight in Canada, though I’ve visited a number of their outlets on my travels (even buying my air compressor from them in Memphis).  Up here the next best thing is Princess Auto.  They have a virtually identical model for about $160 CAN. A little more than I wanted to spend, but still doable (and I’m still well under the price of any other housing out there).  I have yet to pick it up, but rated at 80PSI as Tom pointed out, this will allow me to test to roughly 160fws.  This will come in handy when I decide to try to improvise control glands and want to make several controlled tests.

Construction

I have the three main pieces of the body shown above, but never having done any serious work with acrylic before, I need to work on my technique before I try to cement the fixed end onto the cylinder.

Other parts that have to be fabricated are:

1)  Latch Mounts – I don’t want to drill and tap holes into the tube itself so I have to fabricate a couple of blocks to mount the latches to.

2)  Retaining Bar – The cleats that came with the draw latches mount so that the bolts will have a shear force on them that makes me nervous of cracking
the acrylic.  To deal with this, I’m going to fabricate an aluminum bar that will span across the back of the plug, but won’t be fixed to it.

3)  Camera Tray – The camera will mount to the tray using its 1/4″-20 tripod mounting hole and then slide into the housing.  The tray will be guided into the housing so the camera lens will be aligned properly.  The tray also serves to open a space below the camera where lead can be placed to adjust the boyancy.

4)  Lanyard tie – You really need to tie equipment to something, and I prefer not to tie a lanyard to the latches.

4)  Protection Ring – A ring of acrylic tube that will be cemented on the front of the housing concentric with the lens of the camera.  It simply protects the acrylic surface in front of the camera lens.  The plastic is easily scratched, so the ring will try to protect it.  In the future it may even receive a colour correcting filter.

5)  Handles – I don’t have a plan in place for these yet. It’s still percolating.  The whole package might end up looking something like this…

Latch Mounts

Using a bandsaw I took a scrap chunk of smoked (brownish tinted) 1/4″ sheet and ripped it into a 1″ wide strip.

Using a flat surface, I sanded one edge of each of the 1/4″ strips smooth.  first with 120 grit waterproof sandpaper (you need to use water when sanding acrylic), then moving up to 220, 360, 600, 1000 and finally 1500 grit.  These steps are probably overkill, but it meant that I needed fewer strokes at each step before I was able to move on.  I can’t argue with the results, after the 1500, the surface feels as smooth as the polished surfaces.  A quick touch with a buffing wheel, and it’d come up beautifully.

Note: Waterproof sandpaper is available from any automotive store that has body paint and other detailing supplies.  The waterproof sandpaper is quite resilient if you keep it wet. You can even rinse it under a tap to get the waste shavings out when cleaning up and reuse the paper.

Sanding the Edges

The strip then had its end trimmed off square and a length 3″ long was cut off to work with.

I wrapped 120 grit paper around a piece of left-over 5″ tube and clamped a straight guide (can be wood, metal or plastic) parallel to the axis and on the outside of the tube.  This setup was used it to shape the profile so that the mounts would sit firmly against the side of the housing without too much gap.  The shaping of that inside curve took the most time out of any other step in this project.

Once shaped, the strip was cut into two 1 1/2″ blocks and the mounting hole locations for the draw latches were marked, center-punched, drilled and tapped.  Take it easy with the tapping as the plastic can tent to grab.  Back the tap out regularly to clear chips, and  use water as a cutting fluid.

The Latch Mount

The Latch Mount – End View

<Construction Details to be Completed>

Testing

I’m sorry, I moved kinda quickly on the final assembly.  It really did go to fast to keep up with, and I’ve been lazy about documenting it, but I promise I’ll finish that soon.

To test the housing, the harshest test for this design (without control glands) is also the easiest to perform.  Leaking is most likely to occur at the surface or within the first few feet of decent.  So I drew a cold bath, set a couple weights from my belt (6lbs) into the housing so it would sink.  Then a regular o-ring was selected and greased lightly with silicone.  The housing was clamped shut with the draw latches and lowered into the bath.  I left it sit for an hour and returned to find a completely dry interior.  I then repeated the experiment with the quad o-ring which should only improve the safety margin.  Again the results were perfect.

On to proper weighting.  To get things moving quickly for the maiden voyage, I went and bought a two-pound belt weight and used an old luggage strap to tie it onto the housing.  Then with the camera installed and sealed inside the housing, I put everything into the bath to see if it would sink or float (I expected it to sink).  Then through repeated trials I gradually drilled into the lead weight using a drill press until the whole thing just barely floated.

You’ll have to decide for yourself what your preference is when it comes to positive or negative buoyancy.  The trade offs are pretty straight forward.  Negative and the camera will sink, and stay put on the bottom where you dropped it.  Positive and it’ll float to the surface, but be subject to currents and winds making it harder to find later.

Maiden Voyage

Well the day finally came to test the camera and its housing beneath the waves.

The site of this auspicious event was the Innerkip Quarry in Ontario.  There happened to be a bunch of people from the club going and it’s closer to my place than most destinations.  Some would think this is a terrible place to test a video camera, but it actually turned out to be perfect as it highlighted a few points I’d failed to consider (I’ll get to those later).

For those who don’t know Innerkip it’s just an old quarry with the usual assortment of hardware sunk on the bottom for divers to find…  and find they must… visibility ranges from nil, all the way to 12 feet or so depending on the amount of student traffic.  We figured on our first dive we passed within 10 feet of two airplanes not having seen a thing.

I was feeling brave after the bathtub test and was eager to get on with things, so I nixed the thought of diving with an empty canister. So the camera was loaded in.  The housing was prepared as during the final testing with one minor change.  I had forgotten to grab a bit of foam to wedge behind the camera to keep it pressed forward in the housing.  I looked around, but the best I could find in the car was one of my just removed socks.  So in it went.  I powered on the camera, started recording and closed up the housing careful to keep lint and dog-hairs out of the seal.

We got in the water and set out on our first dive of the day. As we went it quickly became apparent to me that something had changed and for a bit I couldn’t figure it out.  The housing now was sinking slowly instead of rising when I let it go.  I scratched my head for much longer than I should have on that, then remembered the (clearly visible) sock.  It was enough to throw out the balance.

The dive was made with a couple minor stops on the surface while we tried to sort out interesting destinations.  We finally found one of the school busses after about 35min of bottom time, and then moved on after everyone (besides me) had swum the length inside the bus.  I guess I started the camera too soon on shore, ‘cuz after about 45min I ran out of tape.  Of course this was just as we came across the second interesting thing, an upside-down car.  When we returned to shore and had relaxed a bit, I reviewed the tape.  Very quickly I could see something was wrong. Almost none of the shots were in focus.  Right there I realized that I was going to have to use a separate check list for the camera configuration. I’d left the camera zoomed about half-way through it’s optical range, and with the wide-angle attachment on the camera, it won’t focus on anything if you zoom any further.  Darn. I had to scrap that tape.  Besides that, the housing kept the camera perfectly dry and proved to be not too bad for diver comfort.

Dive Two

Correcting the zoom setting, I again prepared the camera for another dive (recharged and rewound).  On the second attempt, we saw a lot more and I got a few interesting moments on tape.  At first I was pleased with the set up of the weight exactly as it was because the housing leveled itself nicely and all I had to do when not swimming was nudge it around in the water.  From the outside this felt great!  But when I reviewed the film I could see that the housing was pitching and rolling around a fair amount. Moving the center of gravity up some would improve this as would turning on the image stabilization (doh!) on the camera.  Also having real handles out away from the body would dampen the operators movements somewhat as well.
Other observations that came out of filming in this muck was that the auto-focus tended to be counter-productive as in the murk, the camera tended to hunt around trying to find solid edges.  This made some otherwise fine scenes with divers at the limits of visibility useless.  That’s fine though, all in all, the housing proved itself though I never exceeded 25 feet, I’m confident that it’ll do well in the future.  On the second dive I turned on the camera immediately before getting in the water, and the tape lasted beyond the duration of the dive this time.

The biggest surprise to me was the shear amount of work a video camera is under water.  I’m not referring to physically carrying the camera, that’s not bad at all, and it actually kept me from using my arms too much, so I’m sure my buoyancy control will improve faster.  No, I found that the task loading for the operator went waaaay up.  It was no longer “fun” diving, it became real work just trying to find interesting things to point the camera at, keep yourself relatively steady (without using your hands), keep your range right, etc., on top of the usual monitoring of your life support, buoyancy and buddies.  No wonder people often feel that diving with a photographer is diving alone.  This doesn’t discourage me from my project, but I’ll be forced to be more selective about the dives I take it on, perhaps even leaving the camera behind on most new dive sites.  Time will tell.

Some Notes: Things to Think About

- Turn off Auto-focus + manually set for ~10ft

- Image stabilization on/off ? judgment-call based on weight placement and other requirements

- ballast weight placement – low-mid body…  low CG makes camera self-level, but camera can oscillate if allowed to float freely… mid-body cam won’t self-level as quickly, but also won’t oscillate

- Tape loading door…  mine is obstructed by any tripod/platform that screws into the available mounting hole…  camera must be unscrewed before tapes can be changed

- battery life

- ballast adjustments should be carried out using complete kit…  any changes will affect buoyancy.  (remember the sock?)

]]> http://madpenguin.ca/blog/2009/03/17/diy-underwater-video-camera-housing/feed/ 0 http://madpenguin.ca/blog/2009/03/11/pin-pushers/ http://madpenguin.ca/blog/2009/03/11/pin-pushers/#comments Thu, 12 Mar 2009 04:42:28 +0000 madpenguin http://madpenguin.ca/blog/?p=143 Here’s one of my early projects done while the Canadian Women’s Hockey Team were winning the gold medal in 2002 with the use of my 7×12 minilathe from Grizzly.

These are nesting pin pushers for a couple types of electrical connectors I was using commonly at the time. They combine together into a nondescript brass rod to carry in a pocket.

Well I’ve finally started to fulfill a small dream of mine… I’ve begun putting together a proper machine shop. Now that I have a small collection of wonderful tools, I thought it’s time to start on a real project. I don’t have a mill yet to convert to CNC so I thought I’d grab some of the parts and scrap I have laying around and build my first CNC machine. The end result should have a work envelope measuring about 8×8x2″. Yes it’s small, but one has to start somewhere, and as I’m now back at my parent’s place while I save for a house, I’m tight on space.

At work, I’m fortunate enough that over the past couple years we’ve gone through a series of upgrades and I’m generally right in the middle of it all. Out of this comes all kinds of bits and pieces that I’m always hoping might be useful “someday”.

In going through my assortment of aluminum parts, I found I had a couple assemblies of linear rails with bearing glides just begging to be used. Also, during a recent trip to Vancouver I stumbled across a linear stage with ball screw and coupler that had about 2.25″ of travel and a NEMA 23 mount that would make an excellent Z axis. I also have a number of NEMA 23 4 pole steppers, E-stop buttons, limit sensors and a bunch of heavy aluminum bars. I went out and purchased some cheap “hardware store” grade 5/16-18 all-thread and some single-sided copper-clad board for making the stepper motor drivers, but that was about all I needed to buy.

To control my machine, I’m using EMC from NIST, which I’m extremely happy to see available. I’ve been using Linux for some time and was thrilled to find EMC in an obscure link on a long-neglected page. The software performs better than expected. I installed it on a couple of my machines to play with way back in October. Now it’s found a home on a real (toy) machine.

Items completed

Start small… Make a 3/8″ OD – 1/4″ ID collar to adapt the Z axis linear stage for use with the stepper motor. (This happened to be my first real part made on the lathe, made from a slide rail removed from a dead flatbed scanner by my girl friend) Completed 12/05/2001
Build a Stepper Motor Driver. I found a very inexpensive and simple design at John Kleinbauer’s web site. From what I’ve seen and heard, John has great plans but I already have materials that I wanted to use so I took advantage of the simple schematics he had posted.  I simplified the design a bit (took out the pull-up resistors on the 7474 and tied the inputs directly to +5V) and designed a PCB around it. I also elected to use 74HC86s and 74HC74s as the CMOS has better noise immunity than TTL. I was pleased, though my etching skills leave something to be desired, the boards worked as designed. I also had some 15ohm 50W resistors already mounted that are ideal for this application. Digging around I also found a 24V 360W DC switching power supply that’s compact, light and more than I’ll need to power this project. With the stepper motor set on the table, and the driver board, resistors, motor, power supplies and a function generator acting as a “step” clock, I powered it all up and was thrilled to see the motor twitching, but not quite rotating. Swapping pairs of stepper wires eventually found a combination that allowed the motor to rotate. Completed 12/08/2001
Assemble the Z axis linear stage, stepper and driver into a working component. This went as expected with no hiccups. The stage would run to one end of its travel, and then sit and grind as the stepper skipped steps, and then run back when I changed the direction input. A small but significant mile stone! Completed 12/09/2001
Connect the Stepper Motor Driver to my industrial PC running EMC. This was probably the fastest and simplest of all the steps as I found a 12 conductor cable with one end terminated in a male DB-25 and the other end with wires already stripped in one of my bins, and I just wired the three (CLK, DIR and GND) appropriate wires for the Z axis to the stepper driver, and booted up the EMC computer. The EMC.ini file already had axis_2 (Z) configured properly for a 200SPR and 5TPI screw, so I started up EMC, and tried manually moving the axis… I work on controls and process equipment daily, but there’s Still something amazing about this stuff…I let out a “Yip” that would not be described as quiet when that bugger moved for the first time. Then refusing to wait to see something go to town, I loaded up the 3dtest.ngc program that comes with the EMC BDI, and let the thing crank away. The stage isn’t quite long enough for that program as the stage hits the mechanical stops at both ends, but hey… it runs! (not to mention making a really kewl jet-engine like sound as the axis moves through an arc.) Completed 12/10/2001
Convert one of the bearing slide assemblies to a stepper driven axis. This was a couple evenings work, but a lot of that was holding bits of aluminum and plastic and such together trying to envision what combination of my scrap-pile refugees would work best. I ended up making a nut from some sort of acrylic block, an aluminum bracket to hold the free end of the lead screw (bushing to be added yet), a NEMA23 motor mount, and a motor-lead screw coupler made from the same bit of precision rod as the linear stage collar. Completed 12/12/2001
Build a second Stepper Motor Driver. This came together pretty quickly… I’d really like to build a proper etching tank so it takes less than 45 min to etch a board, but one of the main points of this exercise is to get away from chemical etching, so unless this whole project is a major flop, I’ll live with what I have. Completed 12/13/2001
Assemble the Motor, Axis and driver and connect to the EMC PC. Set axis parameters appropriately (input_scale = 3600SPI), load EMC and run 3dtest.ngc… Yeah baby, just like downtown! It sure sounds busy when the motors start grinding Completed 12/15/2001
Make a third Stepper Motor Driver. Due to impatience, my PCB quality is suffering. This one has fly-wires attached to fix broken traces. Completed 12/16/2001
Finish the 3rd axis with a few changes from the first design due to available materials. Completed 12/16/2001
Assemble the 3rd Motor, axis and driver and connect them to the EMC PC, make changes to the .ini file to suit, and try it out. Hmmm… The motor seems like it’s trying to step in one direction, but only twitches once in the other direction. Hmmm… well it’s late, and time to move on…I’ll tackle that one another day. Completed 12/16/2001
Assemble the X and Y axis into a single unit. Well this took a bit, but After drilling holes in a few wrong places, and generally messing around, I managed to put together what I think will be a workable design using some pre-machined stock. I didn’t even have to cut it to length! My luck so far has been incredible… This is almost too easy. I don’t know what’s wrong with this picture, but something’s gotta give. The table top is just lexan, but I’ll be replacing this with something a little more rigid at some point. I’d like to make a vacuum table instead of a plain flat table. Completed 12/17/2001
Test the X-Y table with a pen (fixed Z). After I figured out the problems with my 3rd motor driver (swapped fly-wires and still another broken trace), I experimented with a marker, pencil and pen mounted on a stiff ruler (this experimentation shows in the first drawing). Just to get the machine going, I ran an old .ngc file I had for an early revision of my stepper motor driver board. Due to my playing with pens, it’s kinda messed up, but overall not bad for my first try. I also see evidence of missed steps, but at this point I’m just happy to have something moving! Completed 12/17/2001	The Setup
Grab unused BOSCH structural aluminum extrusions from work to mount my Z axis. Still have to bolt the “H” (seen in pictures) to the base, but with this extrusion I can adjust the height of the cross-beam to meet my tooling requirements. Completed 12/20/2001
Mount Z axis. I don’t know what I was thinking… I was going to drill and bolt the Z to the aluminum…but this stuff is so great… T-nuts!!! This way I’m able to loosen and move the Z side-to-side to suit the application. Make additional tooling for devices other than spindle. ie. digitizing probe, pen holder, scribe holder, etc…. Ok well… I’ve got a pen holder… more to come. Completed 12/21/2001
Assemble a Controls Cabinet for the drivers, power supplies and perhaps the PC. This went incredibly well. After juggling things in my hands trying to figure out a layout, I decided to “just start drilling” and ended up with the cabinet you see. I tried a test run, but it stopped working about 15 minutes in. I knew those ballast resistors got hot (I’ve boiled water on ‘em in operation)… but they managed to melt the solder on the 24V line. I guess I’ll have to put in an aggressive fan and perhaps some ducting… I hope I don’t have to go to water cooling just for this. Completed 12/23/2001
Decide on a spindle motor. Well this was almost done for me. Canadian Tire had a great sale on DeWalt tools including their cut-out tool which I ended up with for $79.99can. It’s a nice beefy 5A motor that operates at 30,000RPM but has no speed control, so I may have to work on that. I’d heard online that the Dremel tool has some sort of bushing rather than ball-bearings, but mine states on the label that it indeed has ball-bearings, so I’ll make up tooling to mount it as well. (12/28/01)
Make tooling for mounting the spindle motor. This was pretty quick to do stealing a few minutes here or there to drill and tap holes, and bore large holes in 3.5×3.5×0.675″ aluminum plate. I’ve completed mounting brackets for both the DeWalt (12/30/01) and the Dremel (12/31/01), and am happy with the fit and finish given that I’m working with a small lathe, drill-press and a hacksaw. (Mental note: band saw..band saw…BANDSAW!)
Make some actual cuts. I just modified the cds.ngc program that comes with EMC and hot-glued a 5×5″ chunk of pink foam to the table and let fly… this is where the poop really gets cooool. The DeWalt’s a little loud (I have to sit in my room wearing ear plugs), so I’m looking forward to doing more with the Dremel tool(12/30/01). The Dremel is much lighter-weight, so one has to watch the feed rates (especially if there’s extra hot-glue in its path), but it seems to do an admirable job with the foam(01/01/02). Here’s some pics of cutting a pattern using Gcode output by DesKAM’s DeskART using a picture of my face taken by my girl friend. I’m not really happy with the way DeskART makes the cuts, though I can see it’s the easy way to compute things. It has the cutter “scan” across the image line by line. I’d like to try a “waterline” approach where each colour gradient is outlined by the cutter. I may have to try my hand at writing some software for this.(01/03/02).
Change Lead screws. I was unhappy with the performance of the 5/16-18 lead screws that I’ve been using, so I purchased some 7/16-14 stock and made up new lead screws and modified the nuts to match. Once done this, I lowered the maximum acceleration to 2 instead of 20 and more than doubled the slew rate of the X and Y axis to 15IPS. I’m ecstatic with the results thus far given the minimal amount of time I’ve been able to devote to this project(01/02/02). I tried doing a larger image, but the x-axis wandered to the left as the run was completed, so I again lowered the acceleration to 0.5 and now not only does it not do that, it makes a really cool “I’m a busy machine with a purpose but I belong in a sci-fi movie” sound. (01/05/02)

Items still to be done

• Perform further tests varying feed rate and travel using a ball point pen.
• Check for and measure backlash on all axis.
• Add spindle-power control relay.
• Mount limit switches.
• Add E-Stop button
• Build vacuum table, wire and plumb vacuum.

A Few More Views

Pausing at a safety stop on the Niagara II
– Photo Gillian Ord

I was excited. My first real dive trip was just beginning and with great conditions promised by our weather friends, I piled all the camp and dive gear I own into my RAV4 and headed out of town.

It was with visions of timbers, ballast and boilers dancing in my head that I made my way up Highway 10 from Brampton, through Orangeville, Shelburne and Owen Sound.

Finally as dusk was falling I arrived at Tobermory. Happy Hearts Campground was a welcome sight. I hadn’t made reservations for the weekend, and had only given a verbal (and foolhardy) “I’ll go!” to the club, so it was with just a touch of trepidation that I went to register, half expecting to be turned away. Well I was pointed to the overflow field across from Art and Mary and all was well.

By 9:30 I had my tent pitched and home away from home was established. Shortly after, Mike our “Cruise Director” swung by and insisted that I get ready for a night dive.

“But I don’t have a light!” I protested, not wanting to expose my lack of training in nocturnal aquatics.

“No problem, I’ll find one for you.”

With that he tore off to his camp expecting me to follow in the RAV, and so I did dutifully. A light was scrounged, and Mike, Sue, Lori, Art, Fred and I caravanned in a variety of vehicles to the Tugs just off Tobermory harbor. We tooled around the periphery of Tobermory for 7 or 8 minutes until we arrived at a parking lot that shows by the single row of spaces is very near a shoreline. Most of us were loaned filled bottles from a stash that Art kept in his van so we weren’t eating into tomorrow’s provisions.

We geared up and following Art, we scrambled down a slippery dirt path and out onto the boulders lining the shore. By this time it was as dark as it gets, and the flashlights were already coming in handy.

Art gave a briefing detailing the path we would be following, down the shore to the right, to the point roughly halfway between the waterline and the markers, then out into open water, and back to the left continuing along the rock face and eventually up to the shore in front of the fishing dock.

Glow-sticks were handed out and secured to tanks, everyone’s gear was double checked, and with that we stumbled and waddled over the rocks on the shore, and eventually sagged into the water. I felt that familiar sense of confining freedom releasing me from the weight of all the gear, but stuck bobbing on the surface while I struggled to strap on my fins.

Once we were all in the water, gear in place, the “Ok” was passed around. We were on our way.

I was paired with Art at the lead of the excursion and can think of no place I’d rather have been. He has a curious and fun, play-filled style about him that encourages exploration and sets a newer diver at ease immediately. We headed for the first tug, and he found some mechanism left over from the engine and swung the steel contraption to show that it still moved freely (no doubt helped by Art on previous expeditions). He then swam around to an opening in some timbers, and swam through. Upon his exit, Art motioned for me to follow the same path he’d taken. I had conditioned myself to avoid ANY overhead obstacles until I’d gained a reasonable amount of experience, so the prospect of even a couple of two by fours blocking my direct ascent was a small, but not insignificant challenge to my ego.

Sensing Art’s desire to encourage exploration but not endanger his charges, I sucked up my courage (and a lungful of air), and followed suit. I can honestly say that after the apprehension I’d felt, it was a small rush, and a sense of accomplishment that greeted me on the other side. This was a theme to be repeated later on the Niagara II but on a grander scale.

Art also demonstrated the angle of a rusted pipe laying on the bottom that had several perforations formed along the upper surface. Before I realized what he was doing, he’d removed his secondary and placed it in the mouth of this 14″ pipe and pressed the purge… lo and behold bubbles trickled out along the length of the pipe. Basic physics, but one of a diver’s equivalent to playing with a campfire.

The most memorable moment of the dive came about 10 minutes later as the six of us hovered in a group along a rock wall face. Art had us extinguish all our dive lights… and we sat bathed in weak light from a moon that was nearly full, in about 25′ of water… Magical.

The rest of the weekend was an incredible experience totaling 7 dives for me (doubling my log book in the process). With W.A. Spears and the Teak Bay chartered, there was ample room for all (we were a little short of divers actually). We dove on The King, The Caroline Rose, and at the Grotto on Saturday, then made the long trek to The City of Cleveland and finally The Minch on Sunday. The weather throughout was outstanding, allowing ample opportunities for sunning on the ships decks, games while the boats relocated, reading and for me unfortunately, responding to pager messages from the office (by the way for all wondering, GSM coverage works very well for the Tobermory area… including up to The City of Cleveland).

One of the biggest positives about the weekend is the people involved with the EUC. While (as of this writing) I still have to convince them to accept my membership fees, I was accepted from my arrival as one of the group, and was being continually checked on to find out if I was in fact enjoying myself. While sucking bottled air was the reason for being there, the group definitely made my weekend.

My last dive of the weekend was on The Niagara II, which you all know was sunk by the club on May 15th, 1999. That happened to be my 26th birthday, and a full year almost to the day before I was certified. This was a birthday present worth waiting for.

Craig, Gillian and myself departed from the beach at Little Cove carried by Art in his zodiac. We managed to quickly navigate our way PAST the Niagara, and on to the Caroline Rose. Oops! We backtracked and found that the markers had been obscured by… uuuhh another dive boat. Perhaps fueled by too many James Bond and military movies I’ve decided that the zodiac is my personal favorite mode of diver transportation on the surface.

Once tied off, briefed and assisted by Art into our gear we made a slow descent along the bow line. I had to take the descent slower than usual as my left ear wasn’t clearing easily. We landed on the bow of the ship where Craig immediately found a winch control panel with buttons and levers still in place and movable. We proceeded aft along the starboard side pausing at a sticker commemorating the day of the sinking proclaiming it to be “A Titanic Event!” We crossed over to port just before the wheelhouse and explored a bit until Craig maneuvered up to the wheelhouse and finned his way in. I followed and there with Craig at the wheel and myself standing at the window we mugged for Gill’s camera, playing Exxon Valdez with a glass beer stein that appeared to have been left there for just that purpose.

It was then that the bane of photographers everywhere struck made all the more frustrating in 80′ of water with limited bottom time… the film ran out. I had taken Gillian’s shiny new digital camera and she was posing… and no matter how hard I pushed the button… no clicky… no flashy. What a downer. Shrugging, we moved on though I felt terrible that I had failed at this simple mission. Through the rest of the dive Gill managed to salvage a few more keepsake photos by deleting a couple of the less desirable shots from previous dives, but that moment was lost.

What followed was what I had alluded to earlier during our night dive with Art. While briefing us for this dive, Art let us know about a penetration route that gave me a moment or two of anxiety at the outset, but I quickly found that by not rushing myself faster than I was comfortable, I was able to move on with reasonable comfort and a level of mental clarity that allowed me to thoroughly enjoy the experience.

We ascended to the top of the smoke stack and then in order of Craig, Gill and finally me, we descended down feet first. I had some difficulty seeing where I was going due to the two other’s bubbles, but eventually made it down, and we bottomed out our dive in the engine room at 85′. Following the other two out into the larger engine space, I hovered and watched as they playfully finned up a staircase and out a side corridor to the starboard of the ship. We paused there and collected ourselves again, flashing a big “Ok” to each other as well as a grin or two.

On the stern of the ship we spotted the blue-grey form of the Canadian Flag as it only appears at 75′, hanging in soggy, half-hearted gravity. We checked our gauges and almost sadly but with that familiar thrill of discovery we started the slow ascent along the stern line from the 42o depths. The last submerged memory of that dive was that of Gillian waving me off the line a few feet so she could snap my picture on this my deepest and coldest dive to date.

So after a weekend of worship at watery altars, and 7 baptisms emerging renewed very time, I called an end to the weekend with some sadness. I loaded up everything that I’d brought, and headed back home with the RAV up to the gunwales with gear.

Text – Scott Holmes
Photos – Gillian Ord