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marker gun project - epic fail!

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Unread postAuthor: Carlman » Tue Jan 06, 2009 10:43 pm

you could just use a similar size metal tube and use the label from a marker on it...
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 07, 2009 12:45 am

psycix wrote:YOU forgot to roughen up the inside before casting epoxy?


I didn't forget, I figured since the casting would be all around the chamber it wouldn't be necessary. Evidently I was slightly mistaken.

This doesn't look good on your record JSR
You're going to have a graveyard for all your failed prototypes soon enough


I don't hang on to the fail, useful parts are cannibalised and the rest is confined to the trash. I might not have a shining record but you'll note that I post all my projects, in such a way that others might learn from the errors of my ways :p :D

Have you considered a wrap or two of glass cloth around the chamber?


There wasn't much space for that.

It's metal chamber or bust, as soon as I find something suitable I'll give it another go :)
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Unread postAuthor: psycix » Wed Jan 07, 2009 8:33 am

JSR wrote:I didn't forget, I figured since the casting would be all around the chamber it wouldn't be necessary. Evidently I was slightly mistaken.

You figured? Well, this makes me say:
Figuring,
You're doin it wrong!
:D


Figuring means that you assume something.
Taking the assumption "ahh what the heck, I guess that will hold it" in the world of engineering can be disastrous.
You were just slightly mistaken because this was on a small scale.
On larger scales, slightly becomes gigantically as the consequences are greater.

Well at least there's another lesson learned: never figure that you dont need to roughen before applying epoxy. :)
Nonetheless, you still did a great job!


I might not have a shining record but you'll note that I post all my projects, in such a way that others might learn from the errors of my ways :p :D

I noticed that, and I think that is very honest from you. Its very educational.

People should follow your example. ALL ABOARD THE FAILBOAT! :D
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 07, 2009 1:32 pm

I know I took a risk, but on such a small scale it was a calculated one and no harm was done :)

I'm dismayed to note however that the massive truck of fail is no longer sufficient to contain all my projects and we've had to get a boat instead *sniffle* :roll: :D
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Unread postAuthor: starman » Wed Jan 07, 2009 2:01 pm

jackssmirkingrevenge wrote:I might not have a shining record but you'll note that I post all my projects, in such a way that others might learn from the errors of my ways :p :D


And for that you are applauded sir! Let's see, what was that story...something about a guy named Edison......and some hairbrained idea he kept pushing....I think he called it the lightbulb...... 8)

I readily admit to NOT publishing my failed stuff....
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Unread postAuthor: jackssmirkingrevenge » Wed Jan 07, 2009 2:10 pm

It does expose one to a certain amount of ridicule, but I know that I have enough non-fail achievements under my belt to be able to shrug it off :D
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Unread postAuthor: inonickname » Wed Jan 07, 2009 10:25 pm

I made a pen gun similar to your second one (except shorter and from aluminium) but the piston didn't seal the barrel. I just got some stainless tubing so I'm making another today with a cast piston.

I like it, quite honest how you show all your projects. Maybe you show try get some copper pipe from hot water systems. The stuff we have over here would be about the correct size.

EDIT: question. I'm casting a solid hot glue piston for this pen-gun, but I can't find neoprene or any very soft rubber. Could I use (soft) rubber from the plunger of a syringe to seal the barrel?
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Unread postAuthor: Big Boom » Wed Jan 07, 2009 10:52 pm

You could make a rather large Marker gun and put it inside of one of the humungous Marks A Lot s (after it has been hollowed out, of course). This was actually what I was planning on doing, since these things have such a large diameter.

Here is a link to the first image i found using google search:
http://www.db-r.com/repairs/A600.2/A600.2-37.jpg
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 08, 2009 1:37 am

I'm casting a solid hot glue piston for this pen-gun, but I can't find neoprene or any very soft rubber. Could I use (soft) rubber from the plunger of a syringe to seal the barrel?


Surely you can easily get your hands on a vehicle tyre inner tube? Excellent source of sealing material.

One thing to make sure with small high pressure pistons is that the breech area of the barrel doesn't have sharp edges and is provided with adequate surface area to rest on - note that both this design and the pen gun v2 have collars around the breach end of the barrel for this very reason. Otherwise, the pressure will make the barrel cut into your seal.

You could make a rather large Marker gun and put it inside of one of the humungous Marks A Lot s


Interesting, must pay a visit to the stationer :)
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Unread postAuthor: cheeseboy » Thu Jan 08, 2009 2:37 am

probably to late for this, but after failing in a copycat of your pen gun project, and being to cheapskate to buy more tubing, I took an empty lipstick thing (metal of course) and used it. all I had to do was drill a whole in the lid for a schrader to to fill and pilot the gun, put in a very dodgy coaxial piston and cut off the other end to open the barrel. after copious amounts of araldite to connect the lid to the main body and to secure the barrel part to the outer casing/chamber it was done, being 13 I don't have a camera, but I am getting a new phone so I'll try to post a pic soon. I have only taken this gun up to 100 psi as I don't know how high I can take it before the epoxy fails and the lid bursts off. I thinks its my most simple build yet! and its so James bondish (that's assuming he uses lipstick :D)
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Unread postAuthor: jackssmirkingrevenge » Thu Jan 08, 2009 6:50 pm

I think you're headed for the next episode of fail if you take it to higher pressure. It would be cool to see pictures though :)
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Unread postAuthor: cheeseboy » Thu Jan 08, 2009 6:56 pm

hehe; my birthdays early march, but I might be able to do something with my web cam, apparently the type of lipstick case Is very odd as most of the time it is like a glue stick but In my case it was pretty much already a coaxial, can I please have a number on the strength of epoxy in this case? as I would love to take it to higher pressure!
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