Tank strap technology

[jimclarke]

For what it is worth rubber is linearly compressible but bulk incompressible.
Linear compressible - you can sqaush any one direction.
Bulk incompressible - squeezing hardly affects volume.

So rubber makes a good spring but (unlike noprene) has no effect on bouyancy as you change depth.

 

[fdog]

I'm one of the ones that is so sold on the Scubapro Super Cinch band that I have put it on all my BCs and STAs. I swear you could dent a tank with one.

However, when I switched to Tobin's' DSS plate, I recieved it set up for a single. One of the first things I noticed was the plastic cam bands and the elastomeric doodad, and I thought "okay, I'll have to replace those straps too..."

Fortunately, I dove it before making such a snap judgement! (in my defense, borne out of poor experience with plastic cam bands) The DSS bands with the elastomeric pad have:

Always held
Never slipped
Are so easy to close, your prior experience says they'll slip

It's one of those forehead-slapping moments. It's amazing what a simple piece of engineered flexible stuff can do!

Don't knock it unless you've tried it. I have tried it, and it really works, even better than all my Super Cinch bands.

All the best, James

 

[cool_hardware52]

What part of an innertube is incompressible? The stem, maybe, but I don't think he's using that.

I've used old innertubes for a large variety of jobs, and they are elegant, easy to work with, and "reusing" them helps me "reduce" my purchases of new things -- a big, big plus in my book!

--reduce, reuse, and recycle

A strip of rubber spread out under a good percentage of the contact area between the camband and the tank represents a lot of square inches ~18 x 2 or 36 sq in.
An inner tube is quite thin ~.05-.06 inches.

Our cam pads are short and thick, ~2 inches long thats about 2 x 2 or 4 inches of contact or 1/9 the area of your inner tube. Our cam pads are about .4" thick.

Consider this: If you wear to lay out a thin sheet of rubber and step on it would it feel "springy" ? I doubt you could feel any compression. Now step on a rubber hand ball.

By concentrating the available load (your weight) on to a small area and using a thick section of rubber you achieved deflection. It's deformation or deflection of the elastomer that makes the cam pads work.


Tobin

 

[cool_hardware52]

For what it is worth rubber is linearly compressible but bulk incompressible.
Linear compressible - you can sqaush any one direction.
Bulk incompressible - squeezing hardly affects volume.

So rubber makes a good spring but (unlike noprene) has no effect on bouyancy as you change depth.

Many years ago a old time mold designer in a rubber molding plant told me to think of rubber as a very viscus fluid. The volume of a fluid will remain constant, but it can be deformed into various shapes. Same with elastomers the volume is constant the shape can be changed with force.


Tobin

 

[SparticleBrane]

Personally I prefer the Halcyon tank straps.

 

[jimclarke]

Many years ago a old time mold designer in a rubber molding plant told me to think of rubber as a very viscus fluid. The volume of a fluid will remain constant, but it can be deformed into various shapes. Same with elastomers the volume is constant the shape can be changed with force.
Tobin

I like the analogy

 

[stillhope]

An inner tube is quite thin ~.05-.06 inches. ... It's deformation or deflection of the elastomer that makes the cam pads work

I certainly wasn't suggesting that your pads didn't work, or that they weren't the cat's pj's. I'd guess they're GREAT! based on what I've been hearing.

But that's a totally different issue from creating something useful from something that's on its way to the trash. To give something old a new use is a thing of beauty in itself. And it it's not easy, if it takes putting new batteries in the thinking cap, so much the better! (as long as they're rechargeable batteries )

How many layers of the innertube would it take to be effective? How would you secure them? Maybe something else would be even better? These exercises aren't for everyone -- when I was working long hours and raising kids, it would have been out of the question. But my situation is different now -- I have the time to appreciate the beauty of doing more things for myself -- and much more limited in my ability to buy stuff.

But gee, I have my old ScubaPro straps, so this is all academic to me!

 

[cool_hardware52]

I certainly wasn't suggesting that your pads didn't work, or that they weren't the cat's pj's. I'd guess they're GREAT! based on what I've been hearing.

But that's a totally different issue from creating something useful from something that's on its way to the trash. To give something old a new use is a thing of beauty in itself. And it it's not easy, if it takes putting new batteries in the thinking cap, so much the better! (as long as they're rechargeable batteries )

How many layers of the innertube would it take to be effective? How would you secure them? Maybe something else would be even better? These exercises aren't for everyone -- when I was working long hours and raising kids, it would have been out of the question. But my situation is different now -- I have the time to appreciate the beauty of doing more things for myself -- and much more limited in my ability to buy stuff.

But gee, I have my old ScubaPro straps, so this is all academic to me!

John,

It's not about how many layers. You need a deformable piece that can be point loaded. You'd be better off rolling up a 12" piece of inner tube and sticking the roll between the strap and the tank. Keeping it in place when you change tanks will be challenge.


Tobin

 

[skynscuba]

As an alternative look here.

http://www.deepseasupply.com/page13.html
(Scroll down to the bottom of the page)

Are one or two pads used for each strap?

Gary

 

[cool_hardware52]

Are one or two pads used for each strap?

Gary

One per strap.


Tobin