Question for Pete or Tromic

[Rafter]

Hey Guys,

Even though I named Pete and Tromic please if you can answer my questions your help is appreciated. I am sorry for my newbie questions but i need to clarify a few things. I have being reading many of your threads regarding mods etc. On the Tomba kit you guys talk about "Hydrolock". I assume, what you mean is that the small amount of water inside the muzzle does not allow the ring/seal/slider to be pushed into position. That is why the shaft needs to be modified or loaded out of the water. Is this assumption correct? Also, what is what you guys call "Hydrobrake" is it the same thing? Thanks a lot.

 

[popgun pete]

A hydraulic lock or "hydrolock" occurs when water is trapped in a volume which is being progressively reduced in size (e.g. by parts telescoping or one part moving into another) at the point where the seals take up and remove any escape path for the water. As water is incompressible the now trapped water volume can no longer reduce in capacity and any relative movement between the engaging parts will cease. Hydrobraking is a similar situation where there is a small escape path for the water, so the water volume still reduces, but at a much reduced rate as the water is pushed through the small gaps. As long as water can escape there will be no locking condition.

If you have reached a hydraulic lock condition, but can exert enough force to cause some other part to subsequently move, then a part being pushed in can advance or penetrate further, but the "rear wall" has to move back to accommodate this movement as the trapped water volume remains a constant. The "rear wall" being the piston in a pneumatic speargun, the advancing part being the spear tail and a sealed slider, or plug, as in a vacuum barrel system. If the seals on a plug just start to engage and then no movement is possible without a big effort, then a way around this is to tip water out from the part while held above the surface. Another solution is to have a one-way valve that opens to let water out, but not in, somewhere else in the system, such as an expanding rubber ring valve around the body of the muzzle.

Removing metal from a spear, say adding a short flat section to its cylindrical surface, is a way to provide an escape path for the water which postpones the hydraulic lock occurring right up until the actual moment that the seals take up, with them being sufficiently well inserted by that time that they will stay engaged and not fall out of where they are intended to sit. Then when the "rear wall", i.e. the piston, moves backwards, a developing vacuum as a new volume opens up in the inner barrel behind the now stationary plug causes its seals to be pulled in even tighter causing a slight compression of these seals. Basically spear modifications, if required, are about improving synchronization of these events.