Demand valve spring tester

[GJC]

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.

For a normal breath, I suspect spring movement would be less than 1 mm.

You should be able to measure diaphragm movement while taking a breath. Then you can take the cover off and see how far the lever tabs move the poppet when the lever feet are moved to that measurement. I'll have to play with one of my 109s when I have time.

 

[GJC]

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.

Yeah, I think it gets exponentially harder to compress until the coils touch.

 

[Open Ocean Diver]

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?

No this is just a static test to compare spring compression from one spring to another.

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??

The old is a 216, the new 218.... differences are in an above earlier post. The new appears to be longer and stronger making all the difference.

 

[lexvil]

No this is just a static test to compare spring compression from one spring to another.




The old is a 216, the new 218.... differences are in an above earlier post. The new appears to be longer and stronger making all the difference.

I was just wondering if the tests would give us a better idea why the new spring helped, for the cost of a spring it’s not of deep concern just enlightenment

 

[Open Ocean Diver]

I was just wondering if the tests would give us a better idea why the new spring helped, for the cost of a spring it’s not of deep concern just enlightenment

I think it does that pretty well and it’s fun to test and discriminate bad part from your collection of parts. I now have a basic understanding of why the 218 performs better than the original 216 spring that came with the 108 when I purchased it used.

 

[Couv]

Could one of you kind people take the following dimensions from known good BA/250 spring please?

Overall length
Wire cross section
Total number of coils
OD of spring

Bonus if you can list all the models this spring will work in .

TIA

couv

 

[Open Ocean Diver]

Could one of you kind people take the following dimensions from known good BA/250 spring please?

Overall length
Wire cross section
Total number of coils
OD of spring

Bonus if you can list all the models this spring will work in .

TIA

couv

I can do that… Define what would be a know good spring?

 

[Kupu]

Results from a sample of twelve new/unused .216 springs. Tested with a cheapo caliper.

• Overall length = range of 23.7mm to 24.1mm, Mean 23.875mm. 1 each at 24.0mm & 24.1mm, and then 1 at 23.7mm. 23.8 or 23.9 for the remainder.
• Wire cross section = .8 on all samples
• Total number of coils = 6 on all samples
• OD of spring = range of 8.3mm to 8.4mm, Mean 8.325mm

Maybe not helpful to define a good spring, interesting to see the range in lengths.

 

[Open Ocean Diver]

Results from a sample of twelve new/unused .216 springs. Tested with a cheapo caliper.

• Overall length = range of 23.7mm to 24.1mm, Mean 23.875mm. 1 each at 24.0mm & 24.1mm, and then 1 at 23.7mm. 23.8 or 23.9 for the remainder.
• Wire cross section = .9 on all samples
• Total number of coils = 6 on all samples
• OD of spring = range of 8.3mm to 8.4mm, Mean 8.325mm

Maybe not helpful to define a good spring, interesting to see the range in lengths.

two new .218 springs:
Overall length 23.6, 23.9mm
Wire cross section cross .8mm
Total number of coils 6
OD of spring 8.38mm, 8.4mm

 

[halocline]

I read on this forum years ago that SP went through springs and picked the 'good' ones for use in the G250 and used the leftovers in the R190. I think it was DA aquamaster who posted that. But I have no idea what constituted 'good' in that case.

I will say that I have found replacing the spring periodically in the G250, B/A, 109, etc.. seems to help them tune, and recently I got one of my not-so-good performing 109s to breathe better just by trying a few different springs/lever combos until I found one that worked well. I have no ability to measure the compression other than by feel. It's basically trial and error.

I think those springs wear out in time, unlike 1st stage springs. It would be great to find a source of the springs with very consistent performance.