Demand valve spring tester

[Couv]

As I read through, and do my best to process, all of the data you've posted it seems to come down to a short weak spring at the start. A new spring (longer and stronger) solved the issue.

I'm still curious to know if a shim would have accomplished the same thing. It would also be interesting to know if simply stretching a spring back to it's original length is worth trying-but I don't know enough about springs to know if that would have a lasting effect.

Bottom line is to start with a good spring-so my thought is the purpose of this experiment is how to determine that.

 

[lexvil]

My curiosity is along the line of how much does the spring compress during normal use how the rate reads in that swing.

 

[Open Ocean Diver]

Sorry, I had forgotten that the 108 inlet fitting is counter bored... So now the math looks like; [installed spring length] = [depth of bore] - [thickness of poppet face] + [1mm]
That look right?

Installed spring length = 10.5mm
Uncompressed spring length = 23.5mm
Bore depth = 16mm
Seat thickness = 4mm
Seat face above bore = 1mm
Spring compressed = 13mm

 

[Open Ocean Diver]

My curiosity is along the line of how much does the spring compress during normal use how the rate reads in that swing.

I will test now that I know installed spring length, above 13 mm. At 1/2 in I was getting 7 lbs, so now I’ll increase the compression beyond 1/2 in.

 

[Open Ocean Diver]

As I read through, and do my best to process, all of the data you've posted it seems to come down to a short weak spring at the start. A new spring (longer and stronger) solved the issue.

I'm still curious to know if a shim would not have accomplished the same thing. It would also be interesting to know if simply stretching a spring back to it's original length is worth trying-but I don't know enough about springs to know if that would have a lasting effect.

Bottom line is to start with a good spring-so my thought is the purpose of this experiment is how to determine that.

Yes I think so... but I still don’t understand why the newer 216 didn’t work, and purchasing from from eBay or VDH, you really never know if they’re new they could already be used and worn out.

I can’t find a shim that will work may have to make one.

 

[Open Ocean Diver]

My curiosity is along the line of how much does the spring compress during normal use how the rate reads in that swing.

Pushed lever all the way down an increase of 3mm of spring compression, spring force up from 7lbs on the 218 to 8.4 lbs. not exactly linear in this range.

 

[lexvil]

Pushed lever all the way down an increase of 3mm of spring compression, spring force up from 7lbs on the 218 to 8.4 lbs. not exactly linear in this range.

That’s pretty much the full travel as opposed to the actual movement of the diaphragm during a breath, I assume a precise measurement would be hard to get but that is where the spring change matters.

 

[Open Ocean Diver]

That’s pretty much the full travel as opposed to the actual movement of the diaphragm during a breath, I assume a precise measurement would be hard to get but that is where the spring change matters.

Basically fully open to fully purged. I think with all the numbers we can extrapolate what the force would be within the 3 mm travel window.

 

[lexvil]

Basically fully open to fully purged. I think with all the numbers we can extrapolate what the force would be within the 3 mm travel window.

My thought is, is the tester accurate enough the test the actual spring in operation, how open is the valve during taking no breath and taking a breath?

The fact that the replacement spring made it work better is good but where is the real difference in old spring, replacement old # and the one that is working best??

Purging is vastly different than breathing, just curious.

 

[GJC]

As I read through, and do my best to process, all of the data you've posted it seems to come down to a short weak spring at the start. A new spring (longer and stronger) solved the issue.

I'm still curious to know if a shim would have accomplished the same thing. It would also be interesting to know if simply stretching a spring back to it's original length is worth trying-but I don't know enough about springs to know if that would have a lasting effect.

Bottom line is to start with a good spring-so my thought is the purpose of this experiment is how to determine that.

Vance Harlow's Scuba Regulator Maintenance and Repair book makes mention of compressing a spring that is too strong and stretching a spring that is too weak and that some manufacturers like Zeagle mention spring compression to correct a spring that is too stiff (and is causing a high cracking effort). He cautions that it is possible to ruin a spring by trying to compress or stretch it.

There is no mention of compression force numbers or spring lengths. Shimming is mentioned as an option to correct a weak spring.