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4 inch piston

A place to ask general spud cannon related questions.
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Unread postAuthor: Technician1002 » Tue Jul 20, 2010 11:57 am

It liquefies at slightly above boiling water. I don't know how long it will stay liquid or if it is chemically breaking down at that point.

I heated some ABS DWV Cellular Core pipe over a flame to see if I could bend it like PVC. No such luck, the inside remained stiff when the outside started to liquefy. The trapped gas in the cell core expanded and blew bubbles through the outer jacket as it started to melt. When bubbles appeared, I stopped heating. The bending test was over. I'll do another test later in an oven to see if it goes fluid or just like taffy. I didn't heat it enough to drip. It may behave like melted HDPE and be squishable like the inside of a grilled cheese sandwich.

I'll grab a photo of the bubble pocked pipe and post it here later.
Update: Photo is in a later post
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Last edited by Technician1002 on Wed Jul 21, 2010 10:49 pm, edited 1 time in total.
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Unread postAuthor: theBOOM » Tue Jul 20, 2010 2:46 pm

I say you cast it out of hot glue, but to make it lighter use something like 3 inch PVC inside of the cast, and on the outside use whatever your using to cast your piston, so that its hollow on the inside and not so heavy.
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Unread postAuthor: Mr.Sandman » Tue Jul 20, 2010 4:08 pm

theBOOM wrote:I say you cast it out of hot glue, but to make it lighter use something like 3 inch PVC inside of the cast, and on the outside use whatever your using to cast your piston, so that its hollow on the inside and not so heavy.
That is a LOT of hot glue sticks, and the only way to cast that, that i can think of would be to use a stove and and a pot. A cap would still be lighter and a lot easier to make into a piston.
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Unread postAuthor: deathbyDWV » Tue Jul 20, 2010 11:11 pm

Check out my coax... I've had a pressure rated 3" cap as the piston with no bumper for more than a year... It hasn't broken yet... :?
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Unread postAuthor: theBOOM » Tue Jul 20, 2010 11:27 pm

Sandman, the sticks would cost like 3 dollars tops, I've seen the bundle of 1/2" glue sticks x 10 for a few dollars at walmart, can't be THAT many or too hard...

You can heat it up with a torch or anything else
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Unread postAuthor: Technician1002 » Wed Jul 21, 2010 12:39 am

deathbyDWV wrote:Check out my coax... I've had a pressure rated 3" cap as the piston with no bumper for more than a year... It hasn't broken yet... :?


Yet.. Give it a few more shots. The end cap on the back of my Marshmallow Cannon finally failed after a year of hard use. Be carefull to be clear of flying objects when the back of the cannon does break.

Image
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Last edited by Technician1002 on Wed Jul 21, 2010 10:10 am, edited 1 time in total.
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Unread postAuthor: spudtyrrant » Wed Jul 21, 2010 8:26 am

theBOOM wrote: You can heat it up with a torch or anything else
been there done that......not a good experience, a non-viscous epoxy would work much better, glue sticks are more trouble then they are worth once you get over and inch IMO, not good on the stove either, it comes out a lot like pancake batter and ruins the pan.
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Unread postAuthor: c11man » Wed Jul 21, 2010 11:29 am

i use a 3inch coupler with washers on the ends. but i had to have mine lathed down to 3 3/4. but with a good bumper no damage has occured!
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Unread postAuthor: Mr.Sandman » Wed Jul 21, 2010 11:35 am

c11man wrote:i use a 3inch coupler with washers on the ends. but i had to have mine lathed down to 3 3/4. but with a good bumper no damage has occured!
You could probably lathe it down with a sheet of sandpaper and the coupler chucked into a drill press via threaded rod and washers. Just curious c11, how did you attach the washers to the ends of the coupler?
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Unread postAuthor: c11man » Wed Jul 21, 2010 11:40 am

there was no way i was gonna take off that much material with just sandpaper... plus it wouldnt be as precise

the piston is realy a endcap and a coupler. i cut off almost all of one side of the coupler then the washer fits into little bit of the socket that is left

<a href="http://s696.photobucket.com/albums/vv321/c11man/New%20Plague/?action=view&current=104_9975.jpg" target="_blank"><img src="http://i696.photobucket.com/albums/vv321/c11man/New%20Plague/104_9975.jpg" border="0" alt="Photobucket"></a>
the coupler is on bottom, and the endcap on top

<a href="http://s696.photobucket.com/albums/vv321/c11man/New%20Plague/?action=view&current=104_9977.jpg" target="_blank"><img src="http://i696.photobucket.com/albums/vv321/c11man/New%20Plague/104_9977.jpg" border="0" alt="Photobucket"></a>
and how the washer is recessed
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ABS Test bend photo

Unread postAuthor: Technician1002 » Wed Jul 21, 2010 8:49 pm

As promised, here is the photo of the test of heating ABS Cellular Core DWV pipe to bend it. It was gently heated to soften it over a torch by rotating it to evenly heat it all the way around the same way I bend PVC. The ABS started to become shiny (glossy) as it started to soften, and then as it softened to the core, it blew bubbles. An attempt to bend or dent it by pushing on the edge of a propane tank handle only dented it, but did not bend it. The bend test was a complete failure. This is a piece of 3 inch pipe.

A comparison photo of the results from an earlier PVC test is included.

There is an excellent possibility it may be able to be melted to cast the stuff as a stronger replacement for hot melt glue stick pistons. :D
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Attachments
ABS Melt Test.JPG
The ABS test. The pipe blew bubbles at the end of the test.
PVC Melt Test.JPG
Same test for PVC from earlier.
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Unread postAuthor: deathbyDWV » Wed Jul 21, 2010 9:24 pm

Technician1002 wrote:
deathbyDWV wrote:Check out my coax... I've had a pressure rated 3" cap as the piston with no bumper for more than a year... It hasn't broken yet... :?


Yet.. Give it a few more shots. The end cap on the back of my Marshmallow Cannon finally failed after a year of hard use. Be carefull to be clear of flying objects when the back of the cannon does break.

Image


Thanks for the warning. I already never stand directly behind the cannon anyways. I still wouldn't even it I had a good bumper...
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Unread postAuthor: urgle the danish cow » Wed Jul 21, 2010 9:29 pm

as theBOOM was saying with hot glue and the pvc to make a hollow inside but to save time you can just stuff the mould with glue sticks. bring out the torch, and muuwwaaahahahaha :twisted:

of course for melting the glue
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Unread postAuthor: SP00K » Thu Jul 22, 2010 2:21 pm

Well I made the piston out of 3" endcap with the round end cut off. I put a piece of 3" pipe inside and put a wooden disc on top of that. I used a cut up mouse pad as a sealing face.

Problem the piston is too tight in the chamber, and the end is screwed on too tight to get off :P

Well I was able to get a large hose clamp-esque thing to manually unscrew the end. So for now it looks like the piston will have to be manually placed up against the barrel before everytime I want to shoot it. But it works great!
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