Is this dangerous?

[ilcmuchas]

Heres the deal, I built a spud gun today (which ive done before with sucess) I used sch 40 PVC, I have a 13 inch long 4 inch diameter combustion chamber, and a 1 1/2 inch diameter 42 inch long barrel. Now my problem is I wasnt able to find pressure rated connectors but the guy at home depot assured me that it would be ok, and after reading on some websites about people using ABS which isnt pressure rated (correct?) for spud guns and getting away with it that it was prolly ok.


The only thing Im scared of is that my connectors ad about 4 more inches to the combustion chamber, and Im making a pretty sharp change from 4 inches to 1 1/2 diameter, is this a little too risky since my reducers and bottom cap arent pressure rated? Thanks in advance

[jook13]

the problem I see if I am reading it right is the transition from pvc to abs. they dont bond together correctly.

you can buy pressure rated abs but not at home depot. it is really expensive.

I wouldnt use it if you tried to glue abs to pvc.

[biggsauce]

Just use some DWV parts. Idon't think they make a 2" to 1.5" bushing, but if they do, use that and a 4" to 2" reducer.

Or, a 4" coupler, 4" to 3" bushing, and a 3" to 1.5" bushing. If they have that at the Depot...

I wouldn't try an ABS and PVC mix...

[D_Hall]

Note that there ARE cements specifically formulated for bonding ABS to PVC.... But you have to pay attention and read the lable.

[BigGrib]

I believe what ilcmuchas was trying to get at was not using ABS and PVC but the fact that people who build ABS cannons sometimes don't use pressure rated parts for their cannons. For me, I have always used cell core ABS, which is not pressure rated, but have used pressure rated parts. As far as reducers go, I usually advise against using bell reducers just because the formation of which is a weaker structure. The use of a bushing is more recommended just because of the structure is a lot stronger. To get from 4" to 1.5" is quite tricky. I would use a 4" to 2" bushing set in a 4" coupler glued to your chamber. Then in the 2" hole you can use a 2" to 1.5" bushing or use a 2" threaded fitting and the go to a 2" to 1.5" deal or something like that.

If you are worried about using non rated parts you should switch over to ABS because my opinion on that is that ABS is safer than PVC for combustions just because ABS rips on it's seams and PVC shatters, which I have first hand experience with. There really is no need to worry however. I have installed on my biggest combustion cannon I have a pressure gauge with a secondary peak needle that stays at the peak pressure. I have never had it peak over 100 psi so I don't think it'll be a problem.

[ilcmuchas]

Im not mixing ABS and PVC, I have all PVC but the couplings are not pressure rated and im wondering if that dangerous because especially since im going from a 4 inch combustion chamber to a 1.5 inch barrel.

BigGrib I used a 4 inch coupler and then the bushing style (not the cone style) reducer for 4 to 3 and 3 to 1.5 do you think thats a safe enough reduction, even with non pressure rated coupling, reducer, and end cap?

[TurboSuper]

As long as it's a good ol-fashioned spray-n-pray, you should be able to get away with it.

[jimmy101]

Basically all PVC combustion guns use at least one non-pressure rated fitting. Cleanout plugs are rarely pressure rated, they are strickly DWV parts.

So, I wouldn't worry about a DWV bell reducer. Most people do avoid the clearly DWV shapped parts where the OD at the socket is greater then the OD outside the socket area. Evil non-pressure rated fittings that look like it:

[ilcmuchas]

ended up working great, good noise, awesome range compared to my last one. Thanks for the reassurance.

[FLONE]

ended up working great, good noise, awesome range compared to my last one. Thanks for the reassurance.

Perhaps not related to your original question, a 4" x 13" chamber can handle more barrel length, even with pray and spray. You'll be amazed at the distance. Good luck.

[Boom_erang]

True - I have a 42"x2" barrel and a 4"x8.5" chamber on my main gun, and it throws pretty far. Your chamber is oversized, which is OK if you want a loud gun, but wastes some of the power of the combustion.

-B