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making the blow-forward breech work

This area is for the discussion of BB or airsoft sub machine guns, and or other small arms such as pellets.
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Unread postAuthor: Antonio » Sun Jan 27, 2008 11:46 am

BigGrib wrote:
ant wrote: its kinda tricky to explain.


Yeah you should try a little harder cause I have no clue what the hell you're talking about


A spring cannot act as a damper. As the dependent of time is not affected. Force=k*x
For a damper force =c*v (v=speed)
... dont know how else to put it
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Unread postAuthor: Ragnarok » Sun Jan 27, 2008 12:05 pm

Excellent plan, using magnetic sesame seeds to power the hammer valve will cure all your former problems.

Ok, just ignore that, I seem to have gone hyper for some reason. Perhaps I should turn off the selection of fight music from the Matrix films

"Mr Ragnarok, why is it that you persist?"
"Because... I just don't like you."

Yep, definitely need to turn off the music ...but that would have been a better ending to the films.

Yeah Jack, this idea looks like it should be a lot more reliable than all the old ones, but by your own logic, you'll need to cut down the required deadspace from those animations you have.

Ant's explanation makes perfect sense to me. The problem is that you are both going by different definitions of damper. Ant is going by the engineering definition, but most people think that damper is something quite different.

Dampers are strictly an element in a system that would normally under go simple harmonic motion (think about a weight on the end of a spring, bouncing up and down, that's simple harmonic motion) that will reduce the amplitude of the system's oscillations over time.
Without damping in their suspension, cars would bounce up and down along the road for some time.

When you add damping in a system, it's aim is to bring the system to an equilibrium in a shorter time (or in a critically damped system, the shortest time). Or in the case of a car, stop it bouncing around and making everyone sick.

So, damping was the wrong term in this circumstance, because it means something quite different to what was intended. I know what was intended, I just can't for the life of me think what I'd call it. Probably a retarder.
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Unread postAuthor: Hotwired » Sun Jan 27, 2008 12:30 pm

I'm slightly worried that I appear to be listening to exactly the same thing as Rag.

Currently playing "Juno Reactor - Don Davis - Mona Lisa".

No idea whatsoever where that was in any of the films, only watched the last two once.
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Unread postAuthor: Antonio » Sun Jan 27, 2008 12:48 pm

Ragnarok wrote:
Ant's explanation makes perfect sense to me. The problem is that you are both going by different definitions of damper. Ant is going by the engineering definition, but most people think that damper is something quite different.

Dampers are strictly an element in a system that would normally under go simple harmonic motion (think about a weight on the end of a spring, bouncing up and down, that's simple harmonic motion) that will reduce the amplitude of the system's oscillations over time.
Without damping in their suspension, cars would bounce up and down along the road for some time.

When you add damping in a system, it's aim is to bring the system to an equilibrium in a shorter time (or in a critically damped system, the shortest time). Or in the case of a car, stop it bouncing around and making everyone sick.

So, damping was the wrong term in this circumstance, because it means something quite different to what was intended. I know what was intended, I just can't for the life of me think what I'd call it. Probably a retarder.


Hey thnx for makin this a bit more clearer. I think ppl should look at the physics side of this a bit. Or use a simulation program; I wish interactive physics would also include air :(. Btw what do u think of my valve theory. I have posted it 2-3 times now but its seems like nobody is really into it.
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Unread postAuthor: Ragnarok » Sun Jan 27, 2008 1:33 pm

@Hotwired: That's the music from the Freeway chase scene.
The other really noticable ones are "Spybreak" from the lobby shootout in #1, "Burly Brawl" from the Neo vs. 12,786 Smiths in #2, and "Navras" from the Final fight from #3 where only one Smith gets involved for inexplicable reasons.

@ant: I'm always impressed by your valves and designs.
I personally am not particularly interested in making hammer valves and loading systems like this myself, I'm more of a piston valve person, but I do like a good design... yours are damn good.
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Unread postAuthor: Skywalker » Sun Jan 27, 2008 1:47 pm

I'm pretty sure you'll need the pop-off assist, otherwise the thing will operate like an automatic hammer valve, which probably means flow-rate, spring, and piston mass would need to be tuned. With the pop-off action, it'll definitely cycle.

I can't believe the forum has come out with so many concepts so quickly. I love these flurries of design activity, it's fun!
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Unread postAuthor: Hotwired » Sun Jan 27, 2008 2:58 pm

@ ant: Your hammer valves are good and work on sound principles even if they are a little ghetto in places :wink:

People who appreciate good design don't always say so and whether theres a reply or not, you've shown how it is possible to create a working hammer valve at not particularly high pressure and with easily available components.


@ damper/spring talk: a spring opposing the main spring would merely steal force from the hammer before it hit the poppet.

For a simple solution to slow down the RPM on a sprung bolt/hammer the mass of the bolt could be increased as is done to automatic firearms to reduce the rate to more suitable levels.

For a demo you can see how having a smaller and therefore lighter bolt ramps up the RPM in the decreasing sizes of Uzi SMG.

Uzi = 600rpm
Mini Uzi = 950rpm
Micro Uzi = 1250rpm
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Unread postAuthor: Antonio » Sun Jan 27, 2008 4:02 pm

Hotwired wrote:For a simple solution to slow down the RPM on a sprung bolt/hammer the mass of the bolt could be increased as is done to automatic firearms to reduce the rate to more suitable levels.

For a demo you can see how having a smaller and therefore lighter bolt ramps up the RPM in the decreasing sizes of Uzi SMG.


Hey thnx man! Thats a real boost for me.
Yeah what u said really makes lots of sense to me. The problem in our guns is though that a heavier hammer will also increase the dwell time thus the power exerted on the projectile will increase. Ofcourse at some part the dwell time must have reached its maximum flow rate. From there on this statement is true I think. I find this hammer weight a very interesting topic. Ill maybe look at some dynamic behavior formulas for some concrete theory for our airguns. Hotwired thnx for the insight (tumbsup)
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Last edited by Antonio on Mon Jan 28, 2008 3:08 am, edited 2 times in total.
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Re: making the blow-forward breech work

Unread postAuthor: jackssmirkingrevenge » Mon Jan 28, 2008 12:28 am

ant wrote:Btw jack is this a breech now or a standalone system? I dont get how this would work with your other prototype u made as it has no way of running in synchronize.


This would be a reloading breech and valve combined, it's basically a marriage of the blow forward breech and the auto-piston.

I think with the pop-off feature it would work better, not only would the chamber have time to pressurise before firing, but also all you have to do to control rate of fire is to vary the flow into the chamber.
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Unread postAuthor: Sticky_Tape » Thu Feb 14, 2008 6:01 pm

Do you think that a really strong spring behind the piston would create a higher pressure in the chamber and fire the projectile with more forse? Or will the pressure relieve too much when the piston makes a gap and not get enough air into the barrel because the piston would be supplied with a heavier spring therefore pushing the piston back too fast and making a seal? I don't see you getting too much power from this design unless you use the right spring.
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Unread postAuthor: BigJon » Thu Feb 14, 2008 6:18 pm

I think this is a good idea and would most likely work, but I would just like to point out that this is very similar to something I posted here a while ago with slight variation.
http://www.spudfiles.com/forums/another-semi-full-auto-idea-t12647.html
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Unread postAuthor: POLAND_SPUD » Thu Feb 14, 2008 6:20 pm

why not just combine a blow-forward bolt with a QEV and snapvalve... much easier than trying to do this without a firing valve and it will work.....
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Unread postAuthor: jackssmirkingrevenge » Thu Feb 14, 2008 11:30 pm

BigJon wrote:I would just like to point out that this is very similar to something I posted here a while ago with slight variation.


It's the same concept here and in many other designs, there's nothing new about the idea. As to making it work... :roll:

why not just combine a blow-forward bolt with a QEV and snapvalve... much easier than trying to do this without a firing valve and it will work.....


It's complex, wastes air and I doubt it will give the chamber time to refill adequately.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 07, 2008 2:20 pm

After proposing this idea, I didn't actually follow it up with a prototype, and following some recent discussion I was persuaded to give it a go. I have modified the idea slightly, it should now look something like this, with a separate bolt and valve stem, though the concept remains the same.

Image

The attached diagram shows how I'm actually building it in terms of materials. I used some bits left over from my second blow-forward breech as a starting point. So far I've made the pop-off segment, it works beautifully with different springs at anything from 20-80 psi attached to a track pump, though there is a hint of honking. There's still going to be tweaking involved - namely spring strength and flow into the chamber.

I hope to have it finished by early next week, will keep you posted with my tales of success (or lack thereof :roll: ) as always :D
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Unread postAuthor: Sticky_Tape » Fri Mar 07, 2008 3:40 pm

That's awesom JSR it's definently not (bovine excrement :) ) Keep up the good work as I know you will :) . BTW where is the spring behind the bolt?Has anybody thought of this yet?
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