Trygons designed and made a free-diving no-limits "sled" ,and safety system.It was used by Herbert Nitsch to brake his own world record.

picture 1: A brief stop at 30 meters to fill up the eqex on the way to the 214m World Record

2 years ago, in a conversation about no limits free diving with Herbert Nitsch, we asked him how fast he can equalize with depth. He answered with the question: “how fast can a sled descend?!”
So a new project, in collaboration with Herbert himself, for making the fastest sleds for no-limits began. After spending a lot of time analyzing most of the previous attempts, we decided to work a lot on hydrodynamics and safety.
The three main problems from the previous no limits dives were:

Speed: they were so slow that the dive was taking too long
DCS/embolism: Incorrect speed at different stages and mechanical defects caused serious dcs/embolism accidents.
Narcosis: This, on many occasions, was the initial problem that caused the rest. The free diver made wrong or delayed decisions due to deep waters narcosis.
So the main objectives were:

Increasing the speed by improving the hydrodynamics of the whole diver/sled shape. Increasing the weight was proven not to improve the speed a lot. Also, an increase in weight increased the possibility of mechanical failure. So the diver had to ride without fins and a “CH” (cone head) was attached to his shoulder and head picture 2: Minutes before the dive. The cone head attached to Hebert’s shoulders.

 The CH was there to improve Herbert’s hydrodynamic shape in both the downwards and upwards direction. This hydrodynamic improvement doubled the speed of the sled! Also, as it was made of hard foam it served as the lift bag too. Accidents from airbag failure were therefore avoided.
During the last few meters before arriving at the surface the sled had to come to a stop by any means necessary. If the free diver surfaced with more than 1 meter per sec speed (not to mention 4m/sec), it would almost certainly cause an embolism. To avoid this happening, there was a weight of 50kgr attached to the main line and suspended at 20meters depth. When the sled would hit it, it would make a slow “crash” stop. The diver could then slowly swim to the surface by himself.
A high power electric counterbalast was designed and constructed.

picture 3: Testing the equipment months prior to the attempt. The electric counterbalast was the first machine made, because it was the main safety apparatus.
This could lift everything up at high speed. So, the surface crew could also make decisions about the dive without any input from the diver. By watching the sonar, they could see if there was a problem. The machine was made with 2X24volt 4.5ps electric car starters. Each motor had a totally separate electric circuit and batteries, and was capable of making the lift by itself. Also, a quick “total power cut” was nearby to avoid any chance of a motor remaining on after the 20meter ascent stop. If this was to occur it would lift the diver by force to the surface and cause an embolism.

At touchdown an auto release system would release the sled weight automatically in case the diver was in narcosis. In this way, no time would be lost at the most dangerous point of the dive. The 30kgr buoyancy of the cone head was the uplift force. But just in case, the counterbalast was simultaneously started.
Special video housings were made so as to have the minimum resistance at high speed to record the attempt without failure. Without video there would be no validity of the record.
After the first test runs of the sled, an unexpected problem occurred: due to the extreme speeds involved, the mask, suit and other equipment of the diver were ripped off or damaged. So a special suit was designed and constructed at “Mantaray suits”, along with a hydrodynamic fluid goggle mask. This mask was CAD/CAM designed and constructed based on a laser scan of the face, so as to have the best possible lens position and overall hydrodynamic shape.
After proving and measuring the new abilities, Herbert was able to make a new World Record dive program:

By using his “equalization extension” (eqex), which was strapped to him, he would put his hands stretched down. This had another impact to the shape, giving another burst of speed.
During the ascent he would start slowing down at the 60meter mark by slowly getting out of the sled and preparing for the last 20meter swim.

picture 4: Getting out of the sled for the last 20meters of the ascent. The eqex, designed by Herbert himself, is the Coca-Cola bottle hanging underneath. Herbert was filling it with air from his lungs at 30meters depth. Afterwards, below 100 meters, he was using this air to equalize!

Using his gained time, Herbert would make a decompression stop at about 10meters depth before surfacing, until the diaphragm contractions would start.

picture 6: the last few meters on the way to the surface were done very slowly by hand to allow air to expand in the lungs without injury. The first ever decompression stop in the history of free diving

A good free diver would escort him after the 40meter point on his ascent. If that appointment was later than 4 minutes, the diver would give him an o2 tank to commence decompression and, of course, abort the dive.

As known the dive was a success and a new free diving World Record was set at 214 meters. The cone head, hard foam lift bag, electric counterbalast, automatic bottom weights release and face molded fluid goggles were all systems that were used in this attempt for the first time ever. Also, the ascent (4,2m/sec max) and descent (3.5m/sec max) speeds, as well as the depth (214m), were the highest ever by far.
From Trygons side, the success was mainly that the dive was carried out with an unprecedented level of safety. All previous no limits methods were highly improved or totally changed.
However, there are things that could still be improved in the future. These are listed below, for anyone who is working in the same field. It is very important that information on what is probably the most dangerous sport should be available freely. Unfortunately, there have already been many serious and fatal accidents that could not have happened if this knowledge was available.
Of course these are only ideas, and we don’t accept any responsibility at all regarding the use of any of them. Also we don’t sell or make any parts for no limit sleds any more (except video and fluid goggles), because the responsibility is too high.
So:

picture 7: The following day the cone head cracked open

The uplift force of the CH was dropping because water was forced into the high density polyurethane.
Also, because there was a steady 30kg buoyant force, the sled weights were increased by another 30kgs.

picture 8: The 3D igs file of the CH can be downloaded here. Also, there are a lot of pictures of the rest of the sled (brakes, roller bearings etc).

These additional weights were lowering the level of safety of the dive. So a good idea for improvement is to use compressed air again but with a hollow CH. The CH would be full with water in the downwards direction and filled with air in the upwards direction. So the sled weights could be 30kg instead of 60kg.

There was a big problem caused by the bottom camera record validation rule. The rule states that the bottom camera must show at least the sled reaching the bottom mark on the rope. But the filming distance at these depths is limited, so the sled had to stop at a very narrow target. Above that target the sled would not be in the picture, and below it the sled would hit the camera. Stopping a 4m/sec running sled within a half meter was like a crash.

Picture 9:Picture 9: The bottom stop made of water bottles with drilled tennis balls was the best possible stop used. Of course the bottles exploded and can be heard on the bottom camera audio!

This crash was hurtful for the diver and also for the sled. The next sled must have the bottom camera mounted onboard filming the rope. So there could be a longer braking distance below the bottom mark.

The counterbalast length was limited to the available boats length, 10meters. This was too short and must be much longer. One of the biggest dangers is the sled hitting the counterbalast weight, or the counter weights hitting a safety diver.
Even with these improvements, the danger for a achieving a new world record is very high. Also a minimum budged would be around 50 thou Euro and with a minimum of 6 person crew of experts, and another 10 persons for secondary work.