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"In the world of spuds today"

A place to ask general spud cannon related questions.
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Unread postAuthor: mark.f » Fri Jan 18, 2013 10:23 pm

Well...

I just recently dropped my current work in progress, breaking the barrel to chamber connection...





















Image

...freeing myself from finishing another boring combustion project!

:lol:
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Unread postAuthor: Brian the brain » Sat Jan 19, 2013 10:53 am

My claws, back, neck, shoulders and knees froze up today trying to fix the washer...
Pff..anytime I stress up this happens..

stumbling around like an old man...
I guess I'm not going to fix that barrelpump coax prototype I've started on..

I made all the parts on the lathe...but somehow I got newb issues with the piston not sealing right...
It's solid rubber...?

I guess 7+ years of spudding and building various other type of launchers before that, stretching my experience to well over 23 years are no guarantee to instant succes... :D
( the piston is too soft and needs to be held against the seat firmly with a strong spring)

Anyway, the pumprod I had at hand ( spoke and caulktubetip cut to size) worked nicely, but was too short to fully compress the air.
When the piston did seal I found it was very doable to pressurise it this way.
I just couldn't build up enough pressure to pilot the piston.
The spring I had to use to seal the piston was too beefy compared to the stored pressure.

This version is all aluminium and will be built for my son ( low power)...as soon as my bodyparts start working again.

It makes more sense to me to build something a little more advanced anyway.Why would I go through the trouble ( and pain) anyway if it's not that special?

With my condition it might be better to start a long term project and ease my way through the process..

I need to fix on a design and stick with it...that's my problem now..


I am leaning towards a Girandoni type thing, with my own twist on it.
A built in pump, ballreservoir under the barrel and a falling-block assisted by the triggerguard..

If possible, the fallingblock would be used to stop the ammo from rolling out the bottom tube.
The way I see it, it could be pressed up by hand ( or thumb) to load the tube, springing back into position after each ball.Kinda like loading a shotgun.

All this is not possible without a buttreservoir.In an over-under construction the reservoir will either be in the way...or will have to run on top of the barrel..wich is ugly..

I'd love to construct the Girandoni valve-hammer-trigger combo in a similar way...

For now I'm not doing anything apart from planning...
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Gun Freak wrote:
Oh my friggin god stop being so awesome, that thing is pure kick ass. Most innovative and creative pneumatic that the files have ever come by!

Can't ask for a better compliment!!
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Unread postAuthor: POLAND_SPUD » Sat Jan 26, 2013 10:04 am

Just a quick question

What do you think about having a tank full of air fuel mix and using it to fill the hybrid ??
I know it's not a novel idea or anything but the general consensus has always been that it just isn't safe

I must admit that I used to agree with it but then again the idea would greatly simplify things and I think there are ways to make it safe


a 20X mix of butane can produce up to like ~2100 psi... so in theory an average PB tank filled with the mix should survive it just fine... damn one might even make a custom tank rated to more than that of a pb tank


is there anything I am missing ?



You know I've been thinking about it and it strikes me that it takes quite a lot of effort to mix fuel and air in proper proportions, take care of dead space present in the meter, tubing, valves and all... plus weight and size of the entire setup needed for this: the microcontroller, batteries, solenoid valves, check valves, regulators, and stuff... and then on the other hand you just take a biga## syringe and add X ml of fuel, top it off with air and you're done
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Last edited by POLAND_SPUD on Sat Jan 26, 2013 10:14 am, edited 1 time in total.
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Unread postAuthor: ramses » Sat Jan 26, 2013 10:09 am

I would say as long as the tank is rated for the peak combustion presssure, go for it.


I would use flashback arrestors just in case, and be conscious of which direction the burst disk on the pb tank is pointed (ie. not at you)
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Unread postAuthor: jackssmirkingrevenge » Sun Jan 27, 2013 9:00 am

Given how bloody difficult it is to ignite a hybrid mix, I would say a check valve between main tank and firing chamber is all you need.

You would want a regulator though, otherwise as with a multishot pneumatic the mix would get weaker with every shot. Given hybrid power density though, you could have a tiny firing chamber vis a vis the main tank that would give you say 20 shots with no noticable power loss.
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Unread postAuthor: CS » Sun Jan 27, 2013 3:38 pm

What do you think about having a tank full of air fuel mix and using it to fill the hybrid ??


I would fire it remotely, and that isn't as fun.

Tech mentioned an appealing setup:

Propane->regulator->buffer tank->valve->orfice
Air------->regulator->buffer tank->valve->orfice

-regulated air/propane to same pressure
-regulator pressure higher then hybrid mix pressure
-valves open/close same time
-mesh to mix/ diffuse after the orfice
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Unread postAuthor: Lockednloaded » Fri Feb 08, 2013 12:18 am

ITWOST: working on an integrally suppressed copper co-axial, can decide to make it a cane gun or a nice wood stocked rifle...

Image

About 180psi with a sabot'd 3/8" ball bearing
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Unread postAuthor: mark.f » Fri Feb 08, 2013 12:23 am

Make it solenoid piloted, paint it black, add a pistol grip handle with two-stage piezoresistive trigger, slap on an EOTech with magnifier, and add a wire stock. :wink:

In the real world, go ahead with whatever style suits you best, and up the pressure to at least 300 PSI. I run my copper gun at around 320-360 with a 1" type L chamber.
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 08, 2013 12:37 am

Ooh, that's a healthy speed, and I'm sure you can do better in terms of pressure. How effective is the suppressor, and what's the chamber:suppressor length ratio?
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Unread postAuthor: Lockednloaded » Fri Feb 08, 2013 12:54 am

@mark.f
I'll check for some of those floating around in my spare parts box :D

@JSR
I doubt it's too effective, but the shroud 3/4" copper shroud around my 1/2" copper barrel is really an aesthetic addition, so I thought I'd drill some holes in the barrel for the hell of it. It's a pretty small chamber, so I'd say the suppressor volume's close to twice as large as the chamber without any measurements on hand atm.

I should be getting a fridge compressor from Mattyzip pretty soon, so I'm really excited to up the pressure and get some real results!
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Unread postAuthor: jackssmirkingrevenge » Fri Feb 08, 2013 2:20 am

I bet it takes away quite a bit of muzzle crack. As mark said, up the pressure to the 300-350 psi range and I'll wager you'll see velocities jump to the 850-900 fps range. What are you using as a sabot for the bearing?
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Unread postAuthor: jackssmirkingrevenge » Wed Feb 20, 2013 3:03 pm

http://cheezburger.com/47425281

Spuds gone slightly mainstream...
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Unread postAuthor: mark.f » Thu Feb 21, 2013 11:02 pm

[youtube]http://www.youtube.com/watch?v=HjR2kfkZ9YI[/youtube]

Mute it. I was watching Scrubs. :roll:
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Unread postAuthor: jackssmirkingrevenge » Tue Mar 05, 2013 3:32 pm

Those damn Mexicans are at it again!

http://www.guardian.co.uk/world/2013/fe ... zed-mexico

Apparently a pneumatic, I wonder what the valve is like.
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Unread postAuthor: mark.f » Tue Mar 05, 2013 4:15 pm

Interestingly enough, the overly-complicated PWM circuit I tried to make here was completely unnecessary... just found a circuit which can provide ~1-99.9% variable duty cycle PWM output with a single 555, although at a variable switching frequency.

It's just an astable oscillator with a diode in parallel with the R2 resistor, which can be a potentiometer used as a rheostat...

Don't you hate that. :lol:
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