Easy Meg Calibration Revisited

bgpartri

I have been diving one of these for about a year and I can't imagine not having it now.

I think every Meg diver should have one. It's easy, quick, and almost impossible to screw up the calibration.

I just wish John Routley would build them (with Ken's permission of course) so you could buy them on RebreatherWorldStore. I have to keep my eye on mine at all times with Meg divers around.

Bruce

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mempilot

I keep walking away with Padipro's calibration kit. One of these days he is going to press charges.

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Benthic

I too use one of Ken's plugs. I managed to talk a friend with a lathe into making one for me since I have ZERO machine tool skills.

When it came to the flow restrictor, I just used the one provided to me with my Oxycheq Expedition Analyzer. Kens plug even fits nicely in the box with the analyzer so it all stows away neatly.

Brian

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netmage

For those of us w/o access to a lathe....

Wouldn't the ISC dust caps suffice? Same size, you get two... remove the string, modify existing hole for the new barb and orifice combination...?

Calibration kit is $63...
2 dust caps are $20...

barbs, orifice and tubing can't be ~$86 worth of materials for two calibration plugs.

-Tim

-Tim

Benthic

Tim,

I had similar thoughts. However, if memory serves, the caps for the top of the head (where the loop connects) are a different size than the opening at the bottom of the head where the scrubber fits.

Brian

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Skipbreather

That is correct- the dust plugs are notably larger in diameter. Also, one of the key elements that makes the contraption work is the length of the cal plug (It is roughly 3x to 4x longer than a dust plug). Idea is to extend all the way through the chamber where the cells see loop gas and ½ inch or so into the channel just beyond w/ a 0.022 gap all around. Mass of plug in cell chamber reduces volume of O2 needed for complete O2 flood and 0.022 inch gap allows cal gas to flow past w/o measurable back pressure at the low flow rates used (was tested w/ a very sensitive Magnehelic gauge).

Ken

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netmage

I was wondering what the other piece in the kit was for...

Looking at Stuart's tear down/buld up pics this is do-able. Just need to source a plug for the bottom of the head. I would imagine a PVC cap would be sufficent. Get it a little big and put it in the oven to make maliable

http://www.rebreatherworld.com/megal...reak-down.html

---edit---
Ok, the lightbulb has finally gone off and I get it... the shop drawing for the plug always errored out for me... today it works....

With this design, only the sensor carriage sees the O2, via the drilled holes, and the end of the plug effectively plugs the rest of the head...

netmage

Made a mock up at eMachineShop and ran a few variations through...

Just for the plug, mind you, at qty 50 it came in near $14.
Removing the Threading, $11
Removing two side drilled holes, $7/per
Dropping qty to 25 brough it back up near $10/per

Unless we could get commitments for sufficient quantity or really abuse a hobbist in the community, this is appearing to be more trouble than its worth...