• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Smaller Guns / Reasonable Power

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
O

onefish

New Member
Feb 5, 2008
63
6
0
OK, my previous thread raised a heap of questions and answers about if it is possible to obtain reasonable power from a smaller pneumatic gun. Please let me begin by saying this is a somewhat hypothetical scenario and I know that an obvious solution is to use a bigger/longer cannon.

It appears that the mass of shorter spears is a severely limiting factor in obtaining suitable power out to any distance.

The other limiting factor is the energy a smaller pneumatic can transmit to the spear.

The energy transmitted the spear is limited by human strength (that is until some manufacturer finally works out that a simple internal winch is easily achievable). And also the efficiency of the transmission. So practically speaking, we can build more muscle so more internal pressure can be used, we can use a dry barrel system and increase internal port sizes. That's about it.

This will transmit as much energy as is practically achieved with current technologies. The problem is now that the spear will quickly loose inertia because of the reletively low mass. The solution..... use a heavier spear. This can be achieved by using a spear that is much longer, but this would really counteract the benifits of having a small gun. The other way to do this is to utilise a heavier metal, such as a tungsten alloy (which is heavier than lead).

Has anybody ever experimented with heavier metals for spear shafts? It could be an expensive experiment but you never know.

Am I on the wrong track?????

Cheers,
TJ
 
Last edited:
no i havent but it would be possible for me to set you up wit the diffrent metals possibly but i would need to know the specs of your current spear and depending on the metal might me more or less than ur current
 
Aaron,

Thanks for the offer. Do you know anything about the mechanical properties of tungsten and tungsten alloys? I'm not sure what grade or alloy would be suitable. I know the thoriated tungsten electrodes used in TIG welding SS are a bit brittle. It would be an interesting experiment if not too costly. My gun is set up for 9/32 (7.14mm) shafts. Any engineers out there?

Cheers,
TJ
 
i can check it out at work on mon or somethin wats the lenth of ur shaft for now so i know how much metal each one will take? and u say 9/32 would you be able to go up or down a size or so depending on the metal? wats ur max and min. diameter(s)?
 
Aaron, the Tovarich kit I have ordered for my gun seals on 9/32 shafts only. The shafts can't be shorter than 21". There are other heavy metals that may work also/better. I'm no engineer though so I'm not really sure but possibly molybdenum?

Cheers,
TJ
 
in my opinion,(just an opinion ) based on my experience, gus shorter than 42 inch are useless. it is too hard to get close enough to spooky fish, with smaller guns. plus there isnt enogh barrel lenth to have more than 6 or 8 inces of band stretch, (if you subtract the slack bands position from length of barrel(measured to notches)) you only get like 5 inches of stretch or so on a 36 inch ab biller, for instance, and a 24 inch is more of a toy than anything else. pneumatics are probably the way to go on little guns, if you must use one. the mass of spear is still an issue. also with these little guns, you end up wounding fish, but not keeping it, which is kinda uncool, in a way.
 
I think there is a place for specialist short guns. In Cornwall, I swam in confined gulleys and had a large bass swim under me, knocking me as it pushed passed. Minutes later another swam out from under an old boiler in the same gulley, again too close to shoot. Watching an Italian spearo DVD last week (Daparin?), the diver could have shot many of his fish with a vets' humane-killer he was so close, as they were in caves or under overhangs. It seems like short guns (60-70cm) are not that uncommon further east on the south coast of the UK (e.g. Sussex) where viz. is often poor and there are some reefs & wrecks. Or even Dorset in winter it seems.

Re. short pull on the bands. Pastor mentioned recently that a few companies use trigger mechs that are "sort of backwards" (like a mid-handle gun) so there is a few more cm of stretch available - which could be critical for a short gun. So I guess using a short version of a popular long gun might not be the best policy (although the 60/65cm Commanche seems well regarded). Anybody have any experience of a well designed/optimized short gun?
 

You are correct about band guns, we were discussing smaller pneumatics. An interesting statistic. 17-4ph stainless steel is roughly 45% the weight of Tungsten. this means that a 50cm tungsten spear would weigh roughly the same amount as a 111cm SS spear of the same diameter.

Cheers,
TJ
 
Jtkwest wrote ''guns shorter than 42 inch are useless. it is too hard to get close enough to spooky fish, with smaller guns.''


Bottom time bottom time
 
Last edited:
You must log in or register to reply here.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…