Questions About ScubaPro 109 2nd
- Thread starter Litefoot
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Got it. Page 72 is definitely using unbalanced 109/G200 vs Balanced Adjustable/G250 as the example.
I can easily grasp the concept that the stronger 109 spring requires more energy to open the valve and maintain open position when compared with the lighter balanced poppet spring. But where he says the WOB is "dramatically improved", I lack the experience or technical knowledge to understand how his statements are in agreement with real world experience that breathing effort is quite similar when comparing 109/G200 vs Balanced Adjustable/G250.
A good question, hopefully someone will come along with the answer.
I can easily grasp the concept that the stronger 109 spring requires more energy to open the valve and maintain open position when compared with the lighter balanced poppet spring. But where he says the WOB is "dramatically improved", I lack the experience or technical knowledge to understand how his statements are in agreement with real world experience that breathing effort is quite similar when comparing 109/G200 vs Balanced Adjustable/G250.
A good question, hopefully someone will come along with the answer.
I think "dramatically improved" is dramatically overstated and exaggerated. I suppose if you had a 1970s unbalanced Mark 2 and a conventional downstream 109 and your cylinder is down to like 300 psi as you reach back to pull the J-valve and the second stage was set at full tank IP, yeah, I could see that. But I can also state with confidence that a Mark 2 Evo coupled with a well tuned balanced G250 does just fine.
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I'll get new prices on parts required, I'm thinking to include both a .216 and .218 springs sometimes the stiffer spring helps if your cracking is on the low side.
Once I get prices I total up about for full kit.
1x .141 curly feet lever
1x Long crown balance chamber
1x Plastic orifice (metal if you choose)
1x .216 spring
1x .218 spring
Given price I'll be asking for up front payment.
Sound good?
Absolutely. I think you should always take payment before.
- Messages
- 17,266
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- Location
- Somewhere between here and there
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I used to trust folk blindly but have been stiffed 3 or 4 times. If I "know" you I'm good with after pay but if you're unknown to me it's up front no exceptions
halocline
Contributor
Re: WOB for the balanced vs unbalanced poppets, the main difference has to do with the unbalanced using a fully mechanical spring to counter downstream force of IP, vs balanced using a combination of mechanical spring and IP in the balance chamber ‘pushing back’ against the downstream force. In a static setting you could set them identically and there is no difference in cracking effort. But in actual use, what happens is the valve opens and IP drops, we all understand that. That means that IP also drops in the balance chamber, which means the total force countering downstream force lowers. It’s as if you have a lighter spring pushing against the poppet when air is flowing.
That changes the character of breathing in my experience. I find the balanced poppet a little smoother. And they do hold a tune longer in storage.
That changes the character of breathing in my experience. I find the balanced poppet a little smoother. And they do hold a tune longer in storage.
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