Full/Semi auto 27mm blowback bolt cannon. UPDATED new paint+

[ThornsofTime]

This topic is now relevant to my interest. Lolz have been had.

BACK ON TOPIC: great cannon man. Once you decide on a final operating pressure, and get that action timed in post another video. Seems like either your pressure is too low or the rubber band resistance is too high for a good rate of fire. I agree with others that it would look better redesigned, maybe with a 3way valve, but hey, you have full auto and I don't. Grats.

[jhalek90]

Nice.
What are you using for your magazine spring? is the magazine sealed from atmosphere?

It is simply as jack said. a rubber band. Also. the magazine is no where near air tight. it actually is filled with holes. to prevent it from making a quick exit in the event of a barrel jam. it is removable ya know. lol

lol @ the detent, love it

It works great, the rubber ball actually deforms to pass the detent, as apposed to the detent moving out of the way.

I was sitting around trying to find a way to make a detent, and had the idea of melting a shape into the PVC, Bic lighter, a ball bearing and a few seconds later...voila

Seems like either your pressure is too low or the rubber band resistance is too high for a good rate of fire.

Actually, the fill auto Fire rate is controlled by how far a ball valve between the air supply and air chamber is opened. In the video it was only slightly cracked. It will cycle much faster, but tends to not feed if you crank the RPM up to high.

Also, the pressure is set at 60psi due to the pop off valve.

I never intended for this to be a power house, simply wanted to get full auto working, and I did.

this breech could stand to be re built, i DID do alot of tweaking while building, and there are a few things i wopuld change.

@ Poland spud: I did have a 3 way valve attached,l but it created inconsistent piloting, so i removed it. and went with a ball valve, that springs shut.

[POLAND_SPUD]

I did have a 3 way valve attached,l but it created inconsistent piloting, so i removed it. and went with a ball valve, that springs shut

If 3 way valves are not the answer to all your problems then you must have fu##### up something

[jhalek90]

LOL. but ive already done that....
http://www.youtube.com/user/jhalek90#p/u/7/2aHkqTRIeRU

I agree, 3 way valves are nice, and very handy.

Does anyone know if you CAN fill a sprinkler from the pilot?

[mark.f]

LOL. but ive already done that....
http://www.youtube.com/user/jhalek90#p/u/7/2aHkqTRIeRU

I agree, 3 way valves are nice, and very handy.

Does anyone know if you CAN fill a sprinkler from the pilot?

When I tried this, it was pretty slow. I doubt it would be a good idea to integrate into a full auto cannon.

Nice job, by the way. Unique way of going about things...

[jhalek90]

update:

Fixed a few things with the magazine, and re built the bolt.
Also, paint job and new trigger.

Quick video.
[youtube][/youtube]

[ThornsofTime]

Looks better with print

[jhalek90]

I thought so.

Any questions from anyone?

[JDP12]

have you considered a spring instead of a rubber band? I feel like it may hold up better over time and require less maintenance

[POLAND_SPUD]

Yeah, that would require filling from the pilot... somehow I missed that

Have you considered using a solenoid valve and a 555timer/timer relay ?

[jhalek90]

Have you considered using a solenoid valve and a 555timer/timer relay ?

yes. but, this system allows me to do all the same things.
1. change the rof: open supply vale more or less
2. change "open duration" open pilot valve more or less
3. change closed time: close or open supply line valve.

Also, my system allows for changing these variables, on the fly, without swapping capacitors and resistors.

have you considered a spring instead of a rubber band? I feel like it may hold up better over time and require less maintenance

yes. i just purchased the parts to rebuild the breech/bolt and magazine

[irisher]

I used a 555 with potentiometers to vary the waveform which gives me on the fly tweaking of all the above mentioned variables.

[jhalek90]

I used a 555 with potentiometers to vary the waveform which gives me on the fly tweaking of all the above mentioned variables.

but, dependence on batteries.

The purely pneumatic approach offers all of the same features, but only requires one power source. Air.

Look at it this way, i can simply pick this gun up, open a single valve to "power" it, and pull the trigger to shoot once. Or hold the trigger down for full auto.

None of this requires any "programming" (turning of potentiometers or swapping of resistors)

Now, i dont argue that the 555 is a great way to accomplish a similar result. This 555 idea is a very very good one, with merits all its own.

My idea with this cannon was simplicity of use.
Which i feel i accomplished.

[LovableAirGuns]

can you take some pictrues of the bolt?

[JDP12]

look in his development thread... i believe its in pneumatic discussion forum.