Quesions about tank bands & bolts

[trevorrowe]

I'm trying to pick out a set of bands/bolts for my two HP 100 (worthington x7-100) tanks. I know the tanks are 7.25" inches, so thats the general size I will need, but heres what I'm not 100 sure about:

* I see 6" and 5.5" bolts for these, I'm guessing because they are 7.25" tanks and not 8" I will want the shorter bolts. I have a size medium DSS backplate as well. I have heard they have a shallower bend and so many bolts are too long for them (or rental ones at least). This also pushes me towards the 5.5"... would the 5.5" also work on 8" tanks?

* I see bolts come in two thicknesses, 5/16" and 3/8". It seems that the 3/8" are more common. Would that be the best fit, or are 5/16" a better choice because they are smaller and therefore able to fit more plate holes ( I don't even know if these vary much or at all)... I have also seem the very uncommon 8mm... meh - right now I would guess I want 3/8".

* band width : most appear to be 2.5" but there are those at 3"... I assume if the bands fit the extra width wont make much of a difference, any reason to pay more for the 3"?

* band gauge (thickness) : most appear to be 16 gauge (if listed at all). I assume this is pretty much standard I can generally ignore this measurement.



* nuts : wing nuts, delrin wheels, thumb knobs, etc. As long as they are stainless / rust resistant is there any big difference?

[boydski]

* I see 6" and 5.5" bolts for these, I'm guessing because they are 7.25" tanks and not 8" I will want the shorter bolts. ?

I have 5"x 3/8" bolts on my HP 100's, so I'm guessing the shorter bolts would work. My 8" bands have longer bolts, but I can't find them to measure them.

* I see bolts come in two thicknesses, 5/16" and 3/8". It seems that the 3/8" are more common. Would that be the best fit, or are 5/16" a better choice because they are smaller and therefore able to fit more plate holes

The 3/8 bolts are bigger, stouter and more secure. I use them whenever I can. We use the 5/16" bolts on the Aluminum 80's that we dive in Mexico. I keep spare wing nuts for both on the boat and in the save-a-dive kit.

* band width : most appear to be 2.5" but there are those at 3"... I assume if the bands fit the extra width wont make much of a difference, any reason to pay more for the 3"?

The 3" bands are needed for the larger steel tanks (130's, etc), but optional for the HP 100's. I have both and prefer the 3" bands since they are rock solid, but dive the 2.5" bands as well and they do work.

* nuts : wing nuts, delrin wheels, thumb knobs, etc. As long as they are stainless / rust resistant is there any big difference

You do NOT want the delrin wheels or knobs. They strip out easily and I actually had a set of 80's pop off my backplate in a cave due to a delrin thumb wheel failure. The SS wing nuts can be found at your local home center or you can get fancy SS knobs (I like those as well). Keep some spares around as wing nuts have a tendancy to get lost or get loaned out.

Good Luck,

[BDub]

Ditto to everything Scott said (I didn't measure my bolts though), but especially this

You do NOT want the delrin wheels or knobs. They strip out easily and I actually had a set of 80's pop off my backplate in a cave due to a delrin thumb wheel failure. The SS wing nuts can be found at your local home center or you can get fancy SS knobs (I like those as well). Keep some spares around as wing nuts have a tendancy to get lost or get loaned out.

[boydski]

I have 5"x 3/8" bolts on my HP 100's, so I'm guessing the shorter bolts would work. My 8" bands have longer bolts, but I can't find them to measure them.

I did locate my 8" bands and they have 5.5" x 3/8" SS bolts on them. If you use studs rather than bolts, you do have to add an additional half inch. I personally prefer the bolts.

[LCF]

Thanks for the info about the thumbwheels. I have never invested in them, but have thought they were interesting. I'll stick to my wingnuts, I guess.

[CaptnJack]

Thanks for the info about the thumbwheels. I have never invested in them, but have thought they were interesting. I'll stick to my wingnuts, I guess.

Edge broke one on doubles (admittedly hard use)
Sockmonkey broke one on a STA which was a bit of a "poof" wtf? moment

While the tensile strength etc etc is "stronger than steel" yada yada the fact of the matter is they don't hold up. in time they end up being a massive weak point on the backplate to tank connection.

[boydski]

While the tensile strength etc etc is "stronger than steel" yada yada the fact of the matter is they don't hold up.

Actually, the tensile strength of Delrin is pretty low (typically 9,000 psi yield) vs marine grade stainless steel (typically 60,000 psi yield) or cheap 304 stainless (~ 31,000 psi). It's no wonder it doesn't hold up well as a threaded retainer for our tanks.

[Paulicarp]

I have a size medium DSS backplate as well. I have heard they have a shallower bend and so many bolts are too long for them (or rental ones at least).

the shallow bend in the DSS plate actually has the opposite effect. you run the risk of the bolt being too short, not too long. with my 5.5in bolts on my 119s there's just enough length to have two bolts and one washer on the back side of the bands and I can still put my wing, large DSS plate and the wingnuts turn far enough to fill the threads in the wingnut.

[trevorrowe]

The 3" bands are needed for the larger steel tanks (130's, etc), but optional for the HP 100's. I have both and prefer the 3" bands since they are rock solid, but dive the 2.5" bands as well and they do work.

What about HP 119s (x8-119) tanks. WIth the 8" bands, would you recomend 3" on those, or do they fall into the 2 1/2" is fine? Also, you mentioned studs (and how they need to be longer). What exactly are the studs and how do they hold the tanks to the backplate?

Thanks for everybody's feedback!

[boydski]

What about HP 119s (x8-119) tanks. WIth the 8" bands, would you recomend 3" on those, or do they fall into the 2 1/2" is fine? Also, you mentioned studs (and how they need to be longer). What exactly are the studs and how do they hold the tanks to the backplate?

Hi Trevor,

I would recommend 3" bands on 119's, just because they are so heavy. If you are thinking about doubling up a set, you should consider borrowing a pair from someone and trying them out. I started out with a set of 119's (in 3" bands) and just never really felt comfortable in them so eventually sold them. Some of the bigger guys like them and they do hold a ton of gas.

Studs are like bolts, but with no head (all threaded usually), so you have to put a nut (and a lock washer) on the back side of the bands where the bolt head would normally be. Because they have the second nut, they do offer the benefit of being adjustable in length, but tend to be much harder to fit just right (it's hard to keep them parallel). The back nut will sometimes come loose when you really don't want it to, so most divers prefer bolts if they can get the right size.

[CaptnJack]

While the tensile strength etc etc is "stronger than steel" yada yada the fact of the matter is they don't hold up.

Actually, the tensile strength of Delrin is pretty low (typically 9,000 psi yield) vs marine grade stainless steel (typically 60,000 psi yield) or cheap 304 stainless (~ 31,000 psi). It's no wonder it doesn't hold up well as a threaded retainer for our tanks.

Shhhhh don't say that in front of Tobin!

[CaptnJack]

I have 2.5" bands on some 119s and 3" bands on some 95s and really can't tell the difference. I don't think anyone's making 7.25" bands in a 3" width but I'm probably out of touch - I haven't bought any bands in years.

Note: 8" tanks will always have 5/16" bolts in the bands, there's not enough room between the tanks for 3/8" bolts which will rub on the tanks as they bulge and flex. 7.25" bands commonly come with 3/8" bolts since there's more room between the tanks. Depending on how your plate is drilled, the fatter bolts can either be great or a pita. I've never heard of a bolt breaking but the threads can get munged up when slightly misaligned bolts/bands are forced onto a plate with barely large enough holes. I've had to clean up 3/8" bolts with a die a few times since those fit tighter. Being smaller, the 5/16" bolts are rarely "fit with a hammer" onto a plate.

[no excuses]

some plates will not take a 3/8 bolt (hammerhead) so you have to drill out the holes to accept the 3/8 bolt.

[trevorrowe]

the shallow bend in the DSS plate actually has the opposite effect. you run the risk of the bolt being too short, not too long. with my 5.5in bolts on my 119s there's just enough length to have two bolts and one washer on the back side of the bands and I can still put my wing, large DSS plate and the wingnuts turn far enough to fill the threads in the wingnut.

That makes sense. The shallow bend doesn't go back as far in btween the tanks requiring the bolts to go further to get to the plate.

[spatman]

any recommendations as to where i could find threaded 5/16th bolts?

[trevorrowe]

any recommendations as to where i could find threaded 5/16th bolts?

http://www.piranhadivemfg.com/category/ ... -Bands-109

Its a long page, scroll down 2/3rds of the way and you will see the 5/16ths bolts at 6". As for stores not online, no clue.

[spatman]

nice! thanks.

[Raydar]

any recommendations as to where i could find threaded 5/16th bolts?

Locally, I've had good luck at Mclendons for SS hardware.

[selkie]

Matt,

Try W C Winks http://www.winkshardware.com/

Or Parkrose Hardware

[spatman]

Matt,

Try W C Winks http://www.winkshardware.com/

Or Parkrose Hardware

i forgot about parkrose! i'll check out winks, too. thanks!