pneumatic spearguns...

[jackssmirkingrevenge]

... are actually valveless single stroke captive piston pneumatics!

This was news to me.

No need for an external air supply, push in the spear compressing the air until the trigger sear locks et voila.

[PotatoEnemy17]

Interesting, I once considered building valve based on this.

[jackssmirkingrevenge]

Essentially similar tothis concept, except it doesn't rely on external air and uses a piston pusher that doesn't actually leave the barrel.

[PotatoEnemy17]

Are you planning on building this? BTW you always supply us with links, and what you link us to tends to have more links Ect. and in the end I spend about an hour going through all these links Thanks

[MRR]

I think this design could be improved with a balanced piston. There is too much stress on the trigger mechanism in my opinion.

[PotatoEnemy17]

What does the water go in for anyway?

[mattyzip77]

SPEARCHUCKER!!!!!!

[PotatoEnemy17]

Actually this would make an epic handheld air cann - er... not air cannon but uh... weapon thingy. Wait, these are already mass produced aren't they.

[jackssmirkingrevenge]

I think this design could be improved with a balanced piston. There is too much stress on the trigger mechanism in my opinion.

Could be done, but how much pressure can you really generate with a single stroke, it's not *that* stressed.

What does the water go in for anyway?

... because you're underwater?

You can't leave that part full of air, because it will resist the motion of the piston. Of course water does this too but it is incompressible so it is simply being forced out.

Found the diagram on a website suggesting a "dry" barrel, where the space in front of the piston is evacuated:



If they really wanted to increase power significantly though, it's easier to just stick on a schrader valve and pump a few extra psi.

*gasp* have I just suggested MOAR POWER! over better efficiency?!

[PotatoEnemy17]

Oh, I didn't think about that part.

[silentkill12345]

looks verry intresting want to see one in action

[jackssmirkingrevenge]

An interesting CO2 powered speargun I came across made by Crosman, it seems to be a "valveless launcher" with the spear held in place mechanically:

[hectmarr]

Interesting. :bounce: I tried to build a single-drive air pump, but I have not been able to pass about 5 bar and even with a lever it is extremely hard to use ... Maybe it was not built correctly I will read what is published here.

[jackssmirkingrevenge]

Interesting. :bounce: I tried to build a single-drive air pump, but I have not been able to pass about 5 bar and even with a lever it is extremely hard to use ...

Even the best commercial "single stroke" pneumatics are very limited in power compared to what multi-pumps can do. The Parker Hale Dragon comes to mind, it can manage 11 ft lbs of energy in 0.22" which isn't bad but other pneumatics with a pre-charged chamber can easily double that and more.

[hectmarr]

Very good this weapon. In my designs I have chosen multiple pumping because in the new pumps that I have built, which are small and compact, with not very long lever, with 6 pumps I can generate 150 ml of air at 15 bar. In the future I will try to re-plan and build a mono pump, although its benefits are lower.