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sch 40 but not high pressure

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sch 40 but not high pressure

Unread postAuthor: dukesbb37 » Wed May 27, 2009 11:04 pm

i went to my local home depot today to make my first spud cannon... and i was planning on a 4" expansion chamber with a 2 inch barrel. The problem that i found was that all of the PVC pipe that was 3" or bigger had "not for high pressure" or someting like that. It was Schedule 40 but i was too scared to use it because i didn't know what would happen and i wasn't sure if it was still safe. How can it be SCH 40 but not high pressure? anyways here's what i ended up with

24" PVC 2" sch 40 (expansion chamber)
45" PVC 1.25" sch 40 (barrel)
2" T fitting with 1.5 inch split (makes a handle)
one of those bendable click lighters JB welded into the expansion chamber (ignitor)
pvc primer and cement on all contact points.

about to fire it off tomarrow ill let you know how it goes.


heres the pics. IS MY IGNITION SETUP SAFE? im planning on trying to run the butane from the lighter until its empty so i can just use the spark.

<a href="http://s728.photobucket.com/albums/ww287/dukesbb37/?action=view&current=IMG_0489.jpg" target="_blank"><img src="http://i728.photobucket.com/albums/ww287/dukesbb37/IMG_0489.jpg" border="0" alt="Photobucket"></a>

<a href="http://s728.photobucket.com/albums/ww287/dukesbb37/?action=view&current=IMG_0488.jpg" target="_blank"><img src="http://i728.photobucket.com/albums/ww287/dukesbb37/IMG_0488.jpg" border="0" alt="Photobucket"></a>
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Unread postAuthor: dukesbb37 » Thu May 28, 2009 1:54 am

been looking around and i think i found my answer that the not for pressure PVC is not good for spud guns. Still does my "ignitor" look safe?
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Unread postAuthor: inonickname » Thu May 28, 2009 3:40 am

It's probably alright. (ignitor) If you buy new PVC, drill the hole and mount the lighter tip through two layers of PVC.

If you're going to use non-rated materials definitely use abs. It's failure characteristics are undoubtedly more preferable. Though for the best safety margin, use a pressure rated PVC. It's only a matter of trying a different store, such as an irrigation supply place.

Looks alright so far, welcome to spudfiles.

By the way, beware of fittings that are shaped like that wye.
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Unread postAuthor: JEK3 » Thu May 28, 2009 11:06 am

A lot of the larger PVC sold at home centers is for drain use, so they sell "foam core" PVC. This is made lighter weight essentially by "whipping" the PVC during the moulding process to make it airy like foam (hence the name). As it is not solid material, it is not as strong. I know Lowes sells both foam core and regular, you just have to read the labels (and confirm it by weight - there is a noticeable difference).

The "schedule" of pipe refers to the thickness,not the pressure rating (http://en.wikipedia.org/wiki/Schedule_80).
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Unread postAuthor: jimmy101 » Thu May 28, 2009 1:08 pm

For a generic combustion gun cell core pipe is probably OK. Though pressure rated pipe should really be used.

BTW, that Y fitting is probably DWV only as well. Pressure rated parts generally don't have that "visible socket" look.

Your gun is going to be a PITA to get to fire. The long skinny chamber and lack of a fan is going to make fuel mixing very slow. You should probably wait a couple minutes after fueling for the propane to mix.

The long wait for mixing will make getting the fuel mix right a PITA.

Is the "ignitor safe"? Hard to tell. How well epoxied in place is it? If the "neck" of the lighter blows out that isn't a big safety issue. If hole in the chamber causes the chamber to fail then that is a much bigger safety issue.
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PVC

Unread postAuthor: Technician1002 » Thu May 28, 2009 2:03 pm

jimmy101 wrote:For a generic combustion gun cell core pipe is probably OK. Though pressure rated pipe should really be used.

BTW, that Y fitting is probably DWV only as well. Pressure rated parts generally don't have that "visible socket" look.

Your gun is going to be a PITA to get to fire. The long skinny chamber and lack of a fan is going to make fuel mixing very slow. You should probably wait a couple minutes after fueling for the propane to mix.

The long wait for mixing will make getting the fuel mix right a PITA.

Is the "ignitor safe"? Hard to tell. How well epoxied in place is it? If the "neck" of the lighter blows out that isn't a big safety issue. If hole in the chamber causes the chamber to fail then that is a much bigger safety issue.


I have had too many failures of PVC simply because it has some properties of glass. It cracks and shatters. If you are stuck using cell core DWV, it may be best to use ABS instead. It is more chemical resistant and impact resistant. It holds up to combustion pressure well.

Most older members have seen the following thread. I have even pressure tested ABS for an air cannon. The results are in this thread.

http://www.spudfiles.com/forums/abs-cellular-core-test-cannon-t17968.html
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Re: PVC

Unread postAuthor: jimmy101 » Thu May 28, 2009 2:43 pm

Technician1002 wrote:I have had too many failures of PVC simply because it has some properties of glass. It cracks and shatters. If you are stuck using cell core DWV, it may be best to use ABS instead. It is more chemical resistant and impact resistant. It holds up to combustion pressure well.

Most older members have seen the following thread. I have even pressure tested ABS for an air cannon. The results are in this thread.

http://www.spudfiles.com/forums/abs-cellular-core-test-cannon-t17968.html

I've got a ~10 year old "advanced combustion" that uses 3" cell core pvc for the chamber. Been fired several hundred times. No problems.

If it is glued correctly, cell core can handle 1x propane + air.
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Re: PVC

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