Community Project Poll

[Ragnarok]

Why are power requirements are mentioned only for no1 (2" and 10x mix) but not for the rest??

Smartarse answer: Because that's what got stated by the person who submitted it.

no3 would be something new when completed ... many people said it would be a cool to build a semi auto/full auto hybrid but it got only 1 vote

People may be mistaking what "working on a 4 stroke cycle" means. Some may be assuming that it needs to be built like a 4 stroke engine with a crank/motor driven piston, flywheel or some such.

Not at all. My auto hybrid uses works something that's functionally similar to a ICE cycle, using an idea I borrowed from Jo years back. (She posted it on Spudtech)
The chamber has a spring loaded piston that runs the chamber's length. When under pressure, the piston is pushed back to the far end of the chamber. After firing, pressure is lost, so the piston gets pushed back by the spring to the other end of the chamber, pushing out the exhaust gasses as it goes.
It's so simple, but so bloody f***ing clever, I really wish I could pretend I'd come up with it myself.

So, what I've designed is similar to a 4 stroke engine.
However, at first glance, it visually appears to only have 2 strokes (in that the chamber piston reciprocates once during a firing cycle)... not the case, because the fuelling and compression strokes are combined into one movement and the power stroke is directed at the projectile instead of the chamber piston.

The basics aren't really all that complex. The harder part is sorting out the valve system that controls the flow of both fuel and air as appropriate.

[noname]

I'm very surprised that design isn't more popular, Ragnarok. When put together with GalFisk's idea of possibly pulling and pushing water in and out of the chamber for cooling, it could work very effectively. The biggest problem I can see is getting an airtight piston that would cycle, but wouldn't leak due to hot gases and high pressures. I'm sure there's a way to get around that though...

[rcman50166]

I'm all for that design. I support it cause I have designed something very similar to what is proposed. It is not self actuating but rather a long-travel bolt action. It can be found here

[POLAND_SPUD]

well actually I've been thinking about the same design that rag proposed... pretty obvious solution I must say.... but I've never been into hybrids/combustions

You have three days

what does this mean?? will the guidelines be changed after that or the voting ends then ?

[jackssmirkingrevenge]

I think we're ignoring another route available for the development of a select fire hybrid - preloaded cartridges.

I would leave specifications on calibre and size open, but the cartridges should be relatively easy to manufacture. Magazine capacity would be at least 5 rounds, with a simple blowback action that need not be more complex than the Sten, full auto only would be acceptable.

Cartridges should be reusable, and power should be at least 10-20 ft/lbs assuming sub 6mm ammunition.

Of course we could scale it up and replicate the 88

[Moonbogg]

Can't the addition and complexity of the piston be eliminated by simply adding more air or oxygen than usual? You could simply live with a chamber filled with expent gasses and compensate by adding a little more O2 to the mix. This eliminates unnecessary complexity. Just a thought.

[Ragnarok]

I'm very surprised that design isn't more popular, Ragnarok.

Me too. I think the thing is that it never really got noticed when it originally got posted. That's very much the case at times - ideas that really have potential (at least if tweaked a little) just don't get noticed.

The biggest problem I can see is getting an airtight piston that would cycle, but wouldn't leak due to hot gases and high pressures.

Well, as long as it's airtight against pre-ignition pressure, losing a little on ignition isn't too catastrophic, as long as there's a vent on the other side of the piston.
Of course, that would exclude the use of an air spring, which although I think could be convenient here, I also think it's better to have that volume available to the outside air to draw in air and help with cooling.

As I noted (in the chat I think), the auto hybrid as I designed it is capable of kicking out multiple kilowatts of heat at full ROF, which is something you'll need to get rid of somewhere.

@Jack: It's a possibility, but it does call for a lot of cartridges (and time spent charging them) if you want sustained fire.
Although a couple of years ago I threw around some ideas about cartridges (although primarily for pneumatics), the issues with losing or damaging them put me off the idea.

@Moonbogg: Technically, if you're just injecting fuel/air in the normal proportions, you don't need to compensate for the inert combustion products - other than to adjust the pre-ignition pressure so the same amount of fuel/air was present.

Anyway the piston isn't complex in the slightest. It might not be so practical on a large launcher, but on a small launcher (given I designed it as a small launcher), it should be fine.
I may eventually omit it if I think getting a reliable seal is going to be a problem (at the rates of fire I'm looking at, it may be problematic), but there are notable benefits to using one.

[Pookydarts]

It appears that the 4-stroke charge cycle idea has had a 'failure to launch'

It just seemed that the engine manufacturers have been working on the high cyclic ROF (rate of fire, not rolling on floor...) problem for us for the last 150 years. (Rolling on floor I can do!)

The next topic to tentatively broach is, since there are 3 distinct groups of individuals beginning to emerge, who by voting I assume are hoping to contribute to the community project with brains, brawn, or bread (read: technical knowhow, building ability, and ability to provide tools and materials) are we going to focus on the poll winner only or split into 'splinter cells' and play the:

Hybrid with high ROF team
v's
Pneumatic with high ROF team
v's
Gatling style with high ROF team?

[Technician1002]

It appears that the 4-stroke charge cycle idea has had a 'failure to launch'

It just seemed that the engine manufacturers have been working on the high cyclic ROF (rate of fire, not rolling on floor...) problem for us for the last 150 years. (Rolling on floor I can do!)

The next topic to tentatively broach is, since there are 3 distinct groups of individuals beginning to emerge, who by voting I assume are hoping to contribute to the community project with brains, brawn, or bread (read: technical knowhow, building ability, and ability to provide tools and materials) are we going to focus on the poll winner only or split into 'splinter cells' and play the:

Hybrid with high ROF team
v's
Pneumatic with high ROF team
v's
Gatling style with high ROF team?

I won't head them but I have no problem on participating with all 3. I do fine with both pneumatics and electronics. I've studied combustion, but have not built any yet.

[Moonbogg]

I am willing to contribute to any project or projects in any way that I am able to be of service.

[jackssmirkingrevenge]

It's a possibility, but it does call for a lot of cartridges (and time spent charging them) if you want sustained fire.
Although a couple of years ago I threw around some ideas about cartridges (although primarily for pneumatics), the issues with losing or damaging them put me off the idea.

Valid points, however on the plus side:

1) Flying brass is cool!

2) A properly constructed hybrid isn't going to need more than 5-10 rounds to devastate a target. Say they were constructed with a piston instead of a burst disk as per attachment, loading them would not be a problem. Also worth considering is what SPG had proposed a while back, where the projectile is the valve.



Agitating the idea in the spudfiles think-tank will doubtless facilitate matters in terms of adding simplicity

[Technician1002]

Agitating the idea in the spudfiles think-tank will doubtless facilitate matters in terms of adding simplicity

In terms of adding simplicity on this design, eliminate the spring in the "Pilot" and fill from the pilot. Add fuel first, add air. This purges fuel from the pilot and then brings up the chamber to pressure with the correct mix. On ignition, the sudden pressure rise opens the valve. Doesn't get much simpler.

[jackssmirkingrevenge]

Interesting idea, you could eliminate the o-rings on the piston too. The problem though in my opinion would be guaranteeing a correct fuel-air mix in the chamber.

I think the "projectile seal" idea with no moving parts would probably be the easiest route to take however.

[airheadnoob]

i think Caselman would be a great contender

[jackssmirkingrevenge]

i think Caselman would be a great contender

It would be awesome to own one, however I don't think building something from established plans is really in the spirit of what this is meant to achieve.