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jackssmirkingrevenge wrote: Sometimes you need an arsehole to say the things everyone else is too polite or tactful or afraid to say, it's a necessary evil.

Agreed!

Gippeto wrote:

jackssmirkingrevenge wrote: Sometimes you need an arsehole to say the things everyone else is too polite or tactful or afraid to say, it's a necessary evil.

Agreed!

I love being that guy!!!!

So I have been doing lots of freediving recently and I really want a depth gauge but a cannot afford one So I have been thinking how to make one...

This is what I got: Buy a cheap pressure gauge, epoxy a small bit of tube onto the threads and then epoxy a tire valve into the tube. Then fill through the tire valve until 2 bar is in it.

When going underwater when at 33ft it should reduce the gauge to 1bar and 66ft to 0 bar. Im not diving deeper than that at the moment... The only thing is... is will the gauge work underwater? Or will it just cave in?

if it's sealed (the gauge) then I guess it should work underwater with no modifications

I don't get the physics here.

If you have 2 bar in an incompressible tube, why should this pressure reduce as you go deeper?

I was left wondering the same thing all day. Can't you just use a precise gauge that is open to the water? My thinking is that it's similar to gauges used in potable water supplies; 10m deep = 1 bar of water pressure.

MrCrowley wrote:I was left wondering the same thing all day. Can't you just use a precise gauge that is open to the water?

That would corrode beyond repair on its first use.

Here's another thought, why not connect the gauge to the nozzle end of a syringe, and cut down the plunger so that just enough is left to keep the seal steady? That way as you go down the pressure increase will compress the plunger, increasing the reading on the gauge. You could leave out the gauge altogether and just mark pressure increments on the syringe body.

why not connect the gauge to the nozzle end of a syringe, and cut down the plunger so that just enough is left to keep the seal steady? That way as you go down the pressure increase will compress the plunger, increasing the reading on the gauge.

unless that gauge was sealed, and the hardware store type aren't, the needle wouldn't move at all because the water pressure would be pressing on the <strike>little piston</strike> bourdon tube inside of the gauge and on the syringe essentially canceling each other out. I actually like the original Idea though you might want to drill some ports in the steel casing of the gauge so the pressure doesn't crush the glass because it couldn't equalize fast enough.

pneumaticcannons wrote:unless that gauge was sealed, and the hardware store type aren't, the needle wouldn't move at all because the water pressure would be pressing on the little piston inside of the gauge and on the syringe essentially canceling each other out.

That doesn't sound right because they have different areas...

Also, what "little piston"? This is what most air gauges look like inside:

That doesn't sound right because they have different areas...

Forgot about that little tidbit, lol
But yea you were right. Though the needle movement would be minimal because water pressure still is pressing against the bourdon tube... unless you used a really wide syringe.

Also, what "little piston"?

I had no idea that it is actually called a "bourdon tube". I learned something today

pneumaticcannons wrote:Though the needle movement would be minimal because water pressure still is pressing against the bourdon tube... unless you used a really wide syringe.

My suggestion assumed the gauge was sealed... I would just encase the gauge in a block of epoxy et voila

tie 20 meters of rope to a float put a not in the rope ever meter or so and bam you got a depth gauge!

jackssmirkingrevenge wrote:I don't get the physics here.

If you have 2 bar in an incompressible tube, why should this pressure reduce as you go deeper?

Thinking about it your quite right... I think i would have to have a piston.

EDIT: Boom http://www.instructables.com/id/Diving-Depth-Gauge/

Read your full post and you already mentioned it :V Nice one

boom!!!! hehe exactly what I was thinking of!

[youtube][/youtube]omg they are awesome