Diving the Chinese TF12 Helmet

New Zealand helmet diving pioneers, Keith Gordon and Harry Guy, introduce Mike Ward to his first helmet dive

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Here Mike is being dressed for his first helmet dive. He is very familiar with the gear as he has a growing collection of standard diving helmets, suits, weigh belts and boots. He is an experienced SCUBA diver and a member of the Historical Diving Society. Mike looks like he really wants to get going and actually dive gear like his own.

Why the laughter? I guess I must have a piece of rope ready for the next step..

My rope is now in place as a jock strap that keeps the brass corselet firmly on his shoulders, come what may. He has a perfectly aligned corselet and Santa Barbara rigging of his weight belt andbelly valve. He looks great pre-dive and it subsequently went very well. Note the twin tank SCUBA air supply he will use, via the figure 8 coil of hose taped up with an intercom cable. This is called an umbilical. Keith is very attentive as Mike will need help all the way to the water. He is the divemaster. I am the assistant dresser and will act as safety diver and photographer.

Mike in the traditional "hero pose", He is just about ready to dive.

This is one small step for a man...

I have jumped in. We are standing on a 5 foot shelf. Mike is stoked as you can see.

Mike heads off down to the bottom. He is controlling his descent with his left hand on the down line. Everything is by the book.

Mike is on the bottom. "Diver on the bottom" is a good call as the divemaster should know that all is well and will generally slacken the hose to allow more freedom of movement. When you dive in the ocean the divemaster generally keeps a fairly tight rein on the hose during descent, to prevent what is called a "fall". See the bubble of air that extends about a foot down from the exhaust valve. This is called the "suit bubble" and acts as a buoyancy compensator that adjusts as you turn the exhaust valve wheel that adjusts the loading of a spring. It also acts as a counter-lung. If it was not there you would be unable to breathe in.

MIke explores the ancient art of walking on the bottom.

Note how his arms are elevated which causes the sleeves to fill with air and increase buoyancy. It feels good in this position as the arms are comfortably supported. It is a bit like a "walker" that allows old people to keep their balance. Raising the arms allows you to float off the bottom, and lowering them allows you to sink. It is a bit like being Peter Pan.

If Mike lowered his arms there would be a surge of bubbles and he would become less buoyant. Note here that the flow of bubbles is a bit low. Carbon Dioxide is probably building up. I will debrief Mike after the dive. Experienced skindivers tend to do what Mike is doing here.

Mike is very relaxed and virtually weightless. It is very comfortable, and SCUBA divers usually feel quite at home straight away.

Mike has really raised his arms. Raise your arms and you fly. There is a dream like quality to this maneuver, and it is almost automatic. SCUBA divers need to learn that they should push their arms down to descent. This is not so intuitive, and a better idea than hanging more lead on the belt or ankles.

Note then continuing low air flow, even as Mike exercises. He found climbing the ladder made him puff. So my debrief was short, and he understood the needed corrective action immediately. He needs to open the air metering valve a little more, and a lot more during exercise. Half the fun with this gear, is watching others use it from the water, thinking about safety and comfort, and talking about it later.

Next was my dive. This allowed Keith to introduce Mike to dressing and managing standard divers. What helps is that I am hard to manage. Here Mike takes my picture when dressing it is almost complete. I am adjusting the shoulder ropes on my weight belt. They are set up with trucker's hitches which makes it easy. I am using a much older helmet. It was made by Siebe Gorman in London in about 1915, and is still as good as new. Imagine using 95 year old SCUBA gear that has never been fully serviced. This stuff is very durable.

Mike snaps Keith screwing on the front light, also called the face plate. At this point I have turned on the metering valve to start ventilating the helmet. The exhaust valve pops off at 0.5 psi so the whole suit blows up at this point. This is comfortable and normal, but can make screwing in the faceplate a little difficult. In the water the suit will only be inflated down 1 foot from the exhaust valve because of the hydrostatic gradient.

I am tucking the cuffs under to reduce air leakage as the suit becomes pressurized.

Mike took this shot as I entered the water. You can see that hydrostatic pressure collapses the suit that is deeper than the exhaust valve. It remains inflated higher up. This causes the helmet to lift off the shoulders, and this is controlled by the jock strap which is well shown here, and also by the weights which are pulling down on the shoulder straps. It is all very comfortable, even if it looks pretty tough.

Here I am sitting on the bottom and raising my legs. I am testing my limits here in the safety of the pool. This is how you can start a blow-up, and an uncontrollable ascent to the surface. Mike is waiting for that to happen I think.

See the air accumulating around my legs. I have time to lower my legs and avoid trouble. As I said, you learn a lot from watching divers from the water. I would only do this sort of thing in a shallow pool, but blowups and near blowups are quite an important area to explore there.

See how my jockstrap should have been tighter, The helmet is riding a little high. There will be hilarity all around, as I ask for a more vigorous "jocking" on my next dive. I tend to go through cycles, as far as this is concerned.

Heading for the surface, with a generous suit bubble as I have adjusted my exhaust valve so it cracks at a bit more pressure than the standard 0.5 psi. This is like blowing up your BC in SCUBA diving.

Breaking surface, Mike's family has arrived!

Thats all folks. A good day. Mike is stoked. We need more people who want to dive this way, as it always has to be a team effort.