Actual weight of lead weights

[cool_hardware52]

I've weighed quite a number of scuba weights on an accurate, repeatable, high resolution digital scale.

Most commercial soft weight pouches are pretty close to the claimed weight.

I would expect that part of the soft weight production process involves some automated means of dispensing or batching the shot.

In my experience many cast weights are under weight. The reason is simple, the mold was not fully filled. Hand ladled hot lead induces inaccuracies and so does "stretching for yield", in other words you can cast more "4 lbs" weights if you don't completely fill the mold.

I recommend that anytime somebody tests the buoyancy of their exposure suit that they actually weigh the total ballast used, and not rely on summing the marked values on the weights.

I have a couple "4 lbs" block weights that weigh 2 lbs 12 ounces...........

Tobin

 

[LeadTurn_SD]

Interesting topic, and something I'd never really thought very much about.

I used a digital postal scale to measure shot for the soft pouches on my wife and kids' weight belts, but never even considered double-checking the true weight of the old "marked" block weights I use on my own belt... now I'm curious!

Guess I'd better go weigh my weights!

 

[SteveC]

I think it’s fairly important to have accurate weights. For one thing you want to have the same weight on each side, or be able to compensate for a dive light on one side. I poured my own weights, with the mold on a scale, so they are fairly accurate.

 

[spectrum]

I was just finishing up a day of gear prep when I noticed some weights and my postal scale. Here is what I found.

1 pound local castings:
1LB 1.3 OZ
1LB 3.7 OZ
As one would expect these vary considerably.

Sea Pearls, Vinyl Coated, 2, 3 & 4 pound:
2 Lb 1.3 OZ
2 Lb 1.2 OZ

3 Lb 2.3 OZ
3 Lb 1.8 OZ

4 Lb 1.3 OZ
4 Lb 2.0 OZ
4 Lb 1.2 OZ

The Sea Pearls weights were all slightly over the stated weight however the overage seems to represent the vinyl coating. The overage was quite predictable indicating accurate base weights. Since the vinyl is probably close to neutral they do not contribute to the actual buoyancy in a significant way. The product appears to have meaningful weight values.

Pete

 

[1_T_Submariner]

Get that man a copy of Mini Tab quick!

What is the capacity of this balance first of all? If you are talking about a digital bathroom scale with something like a 300 pound capacity you are working in the lower 1-2% of the range. Accuracy will suffer in this case.

Secondly is it repeatable? Take the same weight and weigh it 10 times, is the result consistent?

These are the some aspects of a Gauge R&R (Resolution & Repeatability) study or an MSA (Measurement System Analysis).

Have I gotten carried away?

Getting back to the weights, yes they are known to vary. According to the sea pearls website: Weight tolerance is -0 to +0.025 pound.

Pete

 

[spectrum]

Get that man a copy of Mini Tab quick!

LOL

I half thought of doing standard deviations and throwing up a graph but said what the heck.

 

[XS Scuba]

Hey Pete:
You're exactly correct.

Mike Piantoni
mike@seapearls.com
Sea Pearls - Worldwide Supplier Of Scuba Diving Weights & Cylinders

Sea Pearls, Vinyl Coated, 2, 3 & 4 pound:
2 Lb 1.3 OZ
2 Lb 1.2 OZ

3 Lb 2.3 OZ
3 Lb 1.8 OZ

4 Lb 1.3 OZ
4 Lb 2.0 OZ
4 Lb 1.2 OZ

The Sea Pearls weights were all slightly over the stated weight however the overage seems to represent the vinyl coating. The overage was quite predictable indicating accurate base weights. Since the vinyl is probably close to neutral they do not contribute to the actual buoyancy in a significant way. The product appears to have meaningful weight values.

Pete