Even though based on a US made diving helmet, this modification deserves a place in the German chapter. Rainer Lange from the northern German town Lübeck built himself a shallow water diving equipment based on the American ‘Aquabell’ (see also the Aquabell chapter on this website) Rainer decided not to use the plastic collar the Aquabell is standard supplied with, a collar the diver is supposed to fill with ‘something heavy’ to keep the helmet from floating (see first picture below) instead he uses 2 steel weights which are directly bolted to the clear plastic dome of the helmet. His explanation is the following:
‘Der Gedanke des Entwicklers , den Kragen vor Ort mit Sand oder Beton zu füllen ist nicht praktisch. Jedes Material hat neben Gewicht auch Auftrieb der im Wasser vom Gewicht abgezogen werden muß. Wasser hat eine Dichte von ca. 1 , Sand ca.1,5 , Beton 2 , Steine ca. 2,5 , Stahl 7,8 , Blei 11,3
Um für den Helm die benötigten 15 kg Abtrieb im Wasser zu habe braucht es:
1,45 Liter Blei = 16,45 kg
2,2 Liter Stahl =17,20 kg
10 Liter Steine = 25,00 kg
15 Liter Beton = 30,00kg
30 Liter Sand = 45,00kg
Sand und Beton scheiden wegen Gewicht an Land und den Volumen praktisch aus . Soviel passt garnicht in den Kragen. Wenn man den Kragen verwendet , sollte man ihn zB. mit Eisenschrott füllen.’
For those who have a problem reading German: Rainer concludes that due to the volume of both the helmet itself and the collar it won’t be sufficient to fill the collar with sand, stones or concrete because it won’t provide enough weight; only scrap iron or lead are heavy enough. In order to dive the helmet with as little weight as possible he bolted 2 steel weights directly to the clear plastic dome rather then to fill the collar with it, this because when using the collar he would need much more weight to compensate for the water displacement of the collar itself as well.
For the helmets’ air supply he replaced the small electric Aquabell compressor with a reducer and air hose from Dräger. Rainer mainly uses his diving apparatus in swimming pools but when weather and visibility are good he also dives it in open water.
