Ballast chamber volume

[paul von braun]

Dear all,
I am planning on using a rigid diving chamber for static diving (non aspirated, so that the air inside will become compressed as the water is pumped in). What sort of volume will I need to make this? Am definately going to use the OTW type VII kit, which is 1/32 scale.

Thanks in advance,



Paul Brown.

[JWLaRue]

Hi Paul,

I have the OTW

Hi Paul,

I have the OTW Type VII and (also) use the OTW dive module. The ballast tank size is approximately 11 inches long and 4 inches (ID) in diameter.

This size provides the 'right' working ballast volume for static diving from a full surfaced condition to on-the-bottom.

-hope this helps,

Jeff

[anonymous]

Just a reminder that you

Just a reminder that you will need to allow for the compressed air space in your design.

You will typically only fill the tank half to 2/3 full using the usual gear pump producing 1 to 2 times atmospheric pressure.

This bigger tank size is a slight disadvantage in an otherwise excellent system commonly used here in the UK.

[JWLaRue]

Good point about needing to

Good point about needing to volume allow for the compressed air. The OTW module has a dry space that is twice the size of the ballast tank.

one other note.....the OTW dive module fills the ballast tank to 85+% of actual volume......

-Jeff

[paul von braun]

Thanks for your advice peeps.

Thanks for your advice peeps. As luck would have it the the inside dia. of my wtc is also 4"!!!! so guess what I'm going to do!

[Guest]

Please remember that the OTW

Please remember that the OTW WTC/module uses a special electronic probe controller to switch the pump off when the water level reaches 85%.

Without this gadget you run the risk of flooding the forward chamber if you copy the OTW design- that would be bad.

OTW will probably be able to supply you with the controller, failing that you can fashion a float shut-off assembly to avoid the above, which is simple and cheap, if a little crude.

Or you can copy the eden/sheerline system which pumps into a sealed tank as Davy described.

If you go with the latter, you will need to make the tank a bit larger than the OTW system to allow for the increased air pressure in a smaller volume.

Don't forget to baffle your tank regardless of the system used, it's quite long, and as it has an exposed water surface, sloshing is real risk if you don't divide the tank. I'd recommend a minimum of three baffles for the tank.

Andy