Double PCP Regulators?

[oldskoolzzz]

Thanks for taking the time with that reply Rob

Very interesting

[MartynB]

Interesting thread

[Rich]

Is it true that some regs let by? I believe it is.

If you have a two-reg set up and the second reg isn't designed to take the same high inlet pressure, what happens to the second reg when the first reg lets by? Surely both need to be designed for the maximum?

[derekm]

No they’re two stage because of the volume and rate needed for your lungs at 1 bar is totally different to the volume and rate of an airgun at around 80 times that.

The second stage uses water pressure to change in the pressure to balance your needs as you change depth and the pressure changes and it does it on demand.

A single stage couldn’t do that. A single stage doesn’t work on demand, it works to fill a fixed volume at a fixed pressure. Hence the second stage on a dive set because lung capacity and water pressure vary.

The second stage on a dive cylinder is about 1/10th of that of an airgun before it gets lowered for your lungs. If there was some flaw with regs your logic would be there would be 3 regs.

Its not some new invention they’ve been working that way for decades just like well designed single stage regulators have been. There isn’t a problem that need solving with single stage regs on airguns.

I appreciate the differences in flow for the two different applications Rob, but I can assure you that a single stage SCUBA regulator most certainly does work on demand. There were many on the market,with at least one by Siebe Gorman, who were the creme de la creme for diving equipment.

[RobF]

I appreciate the differences in flow for the two different applications Rob, but I can assure you that a single stage SCUBA regulator most certainly does work on demand. There were many on the market,with at least one by Siebe Gorman, who were the creme de la creme for diving equipment.

Ok, I've done what everyone does and mix on demand with regulation. Ok, they all work 'on demand', that's how they work, one side demands thus lowering the pressure and the valve opens.

Single stage regulators aren't the go-to bit of kit in diving because they can't normalise the breathing effort required across a fill (and the balance of that against depth). They require more effort to breath later on than earlier in a fill where they are easier. They also don't normalise the breathing effort of the change in depth, as you go deeper you need more pressure to fill the lungs with normal ambient air pressure. That's why holding your breath when you rise is dangerous because your lungs expand. You can still use a single stage though. It's just been a lot more common for decades to use a two stage because it makes life easier.

They used single stage in the 50s until the 70s. I've never used one but then I've not been diving for 20 years in any form unless you count mucking around with full face in the shallows.

Diving is different in that it is a dynamic situation on both sides of the valve. The pressure changes by 100% in the first 10 meters of water for instance.

With an airgun it isn't, the volume and pressure is fixed on the outlet side (ignoring tiny deviations of atmospheric air pressure).

Demand or not, I can't see the reason for a second stage, but I'm open to reasons why they might be if someone knows why, but I can't see why as creep and response and consistency have been solved.

[xbow]

Could it be something to do with the size and materials used. Smaller, lighter components can move quicker but can’t handle high pressures? Just a thought.

When I first bought my P700 from a shop in Germany I tested it for consistency and at first I thought my chrono was broken, or I hadn’t reset it. Pellet after pellet showed the same FPS at 6ft lbs. After some more shots it did start to show some variation but so small as to make no difference. When I made a new reg for the gun I retested it and the variation had gone up a bit at just under 12ft lbs but still so small to make no difference.

They’re still all dependent on the nut behind the trigger.

[derekm]

Rob, serious question now and not being agumentative. If single stage regulation is so precise, why do PCPs frequently/always(?) have a sweet spot of reservoir pressure for best consistency of muzzle velocity?

I can see a logic for two stage, even if in practice there is no need.

[xbow]

Rob, serious question now and not being agumentative. If single stage regulation is so precise, why do PCPs frequently/always(?) have a sweet spot of reservoir pressure for best consistency of muzzle velocity?

I can see a logic for two stage, even if in practice there is no need.

I know this is a problem for unregulated air rifles but didn’t know this was a problem with those with regs? Are there any specific models that suffer with this? Just wondering.

[Spray1Mark]

As alluded to already FX aren't the first to do it, Daystate did it a long time back, secondly FX are stepping upto 300 bar in the future so it makes total sense.

[xbow]

As alluded to already FX aren't the first to do it, Daystate did it a long time back, secondly FX are stepping upto 300 bar in the future so it makes total sense.

Walther used to have 300 bar cylinders, do they still have them? As diving cylinders only go up to 300 bar though I don’t understand (no surprise there ) the point. I thought most rifle cylinders were 200 bar or has that changed since I stopped FT a few years back. It’s of no consequence to me now, I just find the topic interesting.

[RobF]

Rob, serious question now and not being agumentative. If single stage regulation is so precise, why do PCPs frequently/always(?) have a sweet spot of reservoir pressure for best consistency of muzzle velocity?

I can see a logic for two stage, even if in practice there is no need.

No worries.

Sometimes they don't is the simple answer.

There are some regs that by design and virtue of the materials used will trend. This is because the high pressure can influence the valve closing position because of the combination of these two things. The worst problem is the material, but sometimes the design doesn't help, especially when you look at how air flows around valves.

If you've ever set an airgun reg you'll know that to move perhaps a Bar takes a fraction of a turn of a screw which normally has a fine pitch in sub mm. So we're talking about nths of a mm that can make a difference. If you've got a part that allows the reg valve to stop in a different place when it's under 200 bar than if it's 100 then you'll see a pressure change on the outlet.

In reality I'm not convinced even a bar or so makes any noticable difference down range (say 50m) on tight groups (say 1/2") (and wouldn't on larger).

I'm also not sure 300 bar makes a difference either to a working reg, but if you've got a reg that doesn't settle the same at 100 bar than it does at 200 then 300 is only going to make it worse.

Mick Dawes was using 2 regs decades ago in FT.

Walther dominators had steel cylinders that go up to 300 bar. They're using them on the 400's but I'm not sure of the fill advice because mine has an ally one which is 200 max suggested fill. They both use the same single reg though.

I'd say 300 is more about shot count so perhaps if you're chasing that and have a reg implementation that really trends then you might use two regs, but I'm not sure of the point because if the regs move that nth degree twice it can't be far off that distance once... perhaps they're using a soft material that just can't take 300 bar without going squidge.

Thing is, if you use one reg that works, the second one won't because there's no pressure differential to operate it.

[Spray1Mark]

Walther used to have 300 bar cylinders, do they still have them? As diving cylinders only go up to 300 bar though I don’t understand (no surprise there ) the point. I thought most rifle cylinders were 200 bar or has that changed since I stopped FT a few years back. It’s of no consequence to me now, I just find the topic interesting.

As home compressors are now widely availible and can fill to 300 it's the natural choice, the carbon bottles are already rated to 300 bar anyways, I am sure Walther still do it, ATAMAN also and maybe EDGUN I think.

[hmangphilly]

Walther used to have 300 bar cylinders, do they still have them? As diving cylinders only go up to 300 bar though I don’t understand (no surprise there ) the point. I thought most rifle cylinders were 200 bar or has that changed since I stopped FT a few years back. It’s of no consequence to me now, I just find the topic interesting.

walther cylinders are rated to 300 .
The design of the reg doesn't lend itself to 300 bar fills though . Stay under 200 and all should be fine

[xbow]

As home compressors are now widely availible and can fill to 300 it's the natural choice, the carbon bottles are already rated to 300 bar anyways, I am sure Walther still do it, ATAMAN also and maybe EDGUN I think.

So most folks don’t use diving bottles these days? I only stopped shooting FT about eight years ago so it’s surprising how things change.

[RobF]

So most folks don’t use diving bottles these days? I only stopped shooting FT about eight years ago so it’s surprising how things change.

I’ve not got a compressor but my shop serves emergency services so if it was essential I could get a fill.

But my cylinders have all been 300 bar because it’s far more economical instead of 232. I still only put 200 in because that’s all my gun cylinders are rated to.