WTF is this disc-looking thing in the tank's bottom?

[stretchthepenn]

I just bought some used tanks for cheap. One is resale-worthy. One is definitely recycle-only. The third is puzzling me.

This third tank is a Canadian-made Catalina, manufactured in November 1988, and marked for 3300 psi. I know it's older and some shops may not fill it, and I also know that it's not a 6351 alloy tank, so those points aren't at issue. What is at issue is this...thing that's attached to the tank's bottom interior.

What am I looking at?

 

[Eric Sedletzky]

??????
I can’t wait for someone to explain this one!

 

[inquis]

Someone glued a weight in to keep the tail down?

 

[bakodiver391]

Just the way it's machined. Seen them before. BTW that tank is very dirty inside, someone did not change their compressor filters often enough.

 

[iain/hsm]

I just bought some used tanks for cheap. One is resale-worthy. One is definitely recycle-only. The third is puzzling me.

This third tank is a Canadian-made Catalina, manufactured in November 1988, and marked for 3300 psi. I know it's older and some shops may not fill it, and I also know that it's not a 6351 alloy tank, so those points aren't at issue. What is at issue is this...thing that's attached to the tank's bottom interior.

View attachment 868853

What am I looking at?

Aluminium cylinders were made with a solid around 12 inch long circular block
the same diameter of the finished product. This block was placed inside a female die and then a male hydraulic pusher was used to extrude an open ended shell and around 200 tons of force
In a second op the shell of the cylinder was necked down to the external shape of the finished cylinder and then the neck thread was machined.
The shape of the internal base is the direct result of the shape of the male pusher.
Some manufacturers used a smooth semi ellipsoidal shape others a 10% torispherical

Now the other option is a compartment concealment and the best one I received ( I should add from our law enforcement folk) had an internal length 4 inches shorter than the external length. Two cylinders were used. Each threaded internal and external then shot blasted inside and out to remove the joint line and repainted outside.

Maybe you should measure the external length to internal length before you fill it. Just in case. LOL

 

[happy-diver]

well obviously then, some stoned disgruntled guy stuck a half dollar on the end of the pusher as a joke

oops $1.00 CAD

 

[BoundForElsewhere]

That's the fizzy tablet to make your air more exciting to breathe.

 

[JohnN]

well obviously then, some stoned disgruntled guy stuck a half dollar on the end of the pusher as a joke

oops $1.00 CAD

No, you’re the Loonie

 

[Wibble]

A zinc anode for damp fills?

A drilling point for an Avelo valve (a few years early)?

 

[happy-diver]

No, you’re the Loonie

Well here's another version for you then chief, just in case you can't see the trees for the smoke

well obviously then, some drunk disgruntled guy stuck a half dollar on the end of the pusher as a joke

oops $1.00 CAD