SpudFiles

Following on from here I've written this section for those who feel the need to buy a cannon, for whatever reason you wouldn't want to make your own. Rather than providing an infinite list of "this is good"/"this is bad" I thought it would be a good idea to set out a basic list of things to look for in purchasing a cannon.

Sections marked * apply to pneumatics only.

*I have messaged Gort and Jagerbond requesting permission for use of their images, hopefully will get a response back soon*

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*Basic safety features:
These include, but are not limited to:
-Pop-off, safety valve, relief valve, calibrated burst disk etc.
-Accurate gauge with a suitable pressure range for the cannon.
-Use of rated fittings with matching threads etc. Using slightly incompatible threads in commercial cannons has no excuse! Also such things as launchers made from soda bottles and the like is unacceptable when purchasing a cannon!

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Safety of mounting:
First and foremost, valves, fittings, igniters etc should ALWAYS be placed through two layers of material, such as at a coupler for increased strength. Check for this extremely closely. Schrader valves are commonly mounted through a single layer, creating weak points.
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Rated fittings:
This is absolutely crucial. While in general practice DWV is acceptable on simple combustion cannons, it's in your better interest to purchase a cannon that only uses rated parts.

Unfortunately for manufacturers, unrated fittings are not a selling point so odds are they won't tell you. Luckily, DWV fittings are easily distinguishable from rated fittings by several factors.

This is a good link to help people identify rated components.

From the text:
"* Shallow sockets, DWV fittings have shorter socket depths in their fittings.
* Ring around fitting, DWV fittings usually have a 'ring' around the outside of the sockets, Pressure Rated fittings, don't.
* Thickness, DWV fittings and pipe are very thin compared to their Pressure Rated counterparts.
* Odd shape, some DWV fittings look very odd and drastically different to Pressure Rated fittings."

" * Deeper socket lengths
* 'Full' fitting, no rings around the fittings.
* Thickness, thicker then DWV fittings.
* Symmetrical look to the fitting, no odd shapes. "

Also, bell reducers are nearly always unrated, however rated ones are available, but very rare. Unless known otherwise, a bell reducer should be considered unrated.

Contact the manufacturer if in doubt.

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Manufacturer reliability:
Unfortunately, not all manufacturers are honest or forthcoming about flaws in their cannons. Unfortunately, this can become a safety concern.

Firstly, a common scam for many things is purely made up or false user feedback on the site. An indicator of this is stuff all contact information, or generic names. For feedback on a cannon, it's best to check spudgunning forums or ask around, rather than relying on the manufacturer's claims.

It should usually be identifiable if unsafe practices are used in construction. If it's as simple as a single valve through one layer of PVC, then you could simply contact the vendor and ask them to mount it through two layers. There would really be little reason for them to refuse. However, if the cannon is riddled with flaws throughout then reconsidering your purchase may be advisable.

If in doubt, ask.

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Purchasing pre-made components:
Things such as pre-made valves, triggers and cannon kits are available from many spudgun manufacturers. In general, as long as these comply to safety considerations there is little risk in purchase.

For example, there are several kinds of large piston-valved tees around. These obviously differ in price, size and quality. Rather than relying on the vendor's claims, it's always a good idea to ask for a comparison from a completely unbiased source.

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Doubt?
Sometimes considering safety, quality and other factors are difficult with information supplied. For example, while some sites may offer reasonable cannons, the small thumbnail photos and lack of information make it completely impossible to judge many factors. Contacting the manufacturer is an option (for more detail), or asking for a review.

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Quality of joints:
This is extremely hard to judge on photographs or information supplied. Often the only way to tell is to ask people who've used the product, or ask the manufacturer.

For aesthetics purposes, most manufactured cannons joints (PVC glued) will be done extremely cleanly, however in unpainted cannons the smallest amount of primer is usually visible. (many manufacturers now use clear cement and primer)

Just contact them and ask if they use a pressure rated primer and solvent welding glue.




Any more contributions or suggestions are welcome.

Work with both Jagerbond and sgort87 on this to get permission to use their cannons for pointing out good things to look for in both pneumatic and combustion and I'll sticky it. But not until it includes both type cannons and permissions and help and approval (via PM's) from our sponsors.

Who's image did you use to point out things to look for in your opening post?

jrrdw wrote:Work with both Jagerbond and sgort87 on this to get permission to use their cannons for pointing out good things to look for in both pneumatic and combustion and I'll sticky it. But not until it includes both type cannons and permissions and help and approval (via PM's) from our sponsors.

Who's image did you use to point out things to look for in your opening post?

One was gort's (the good one, surprise surprise), and one was SGD.

I've messaged them, thanks.

Edit: While I've messaged Gort and Jager requesting images of their cannons, I still need examples for the 'worse' side of things. So if you have any old cannons that include the following:

-Unrated fittings
-Unsafe construction practices
-Unsafe in general

Et cetera.. Photos would be greatly appreciated.

If a cannon is all ready displayed here on Spudfiles by the building member (member has laid claim of ownership) go ahead and use it, if they complain remove it. Plenty to use here.

The reason for permission from sponsor's is because they sell their cannon's and part of profit goes to keep Spudfiles up and running, so by getting their permission they get say on what cannons to use.

We need to show the utmost respect to our sponsor's, they help us greatly. They will also be a great asset to this thread.

After a bit of cleanup and perhaps additions, this would be a great SpudWiki page.

I would add an intro outlining why safety is an issue ... something along the lines of "you're holding a potential bomb in your hands, wouldn't it be nice if it didn't explode?" Or, "the energy in the chamber is comparable to a real rifle but the gun is made out of plastic. You would like for that plastic to be up to the job".

I would add a section on barrel supports for over-n-under designs (both pneumatics and combustions)

On pressure rated parts ... if you are buying a kit I would say that the parts must be pressure rated, even if it is a basic combustion cannon. Anyone selling kits really should have found a source of pressure rated parts. Besides, I would be concerned if a kit maker made both combustion and pneumatics and parts that are potentially common between the two designs were of different ratings. To much chance of'm shipping the wrong "2" to 1" reducer" if they have a bins of both rated and unrated parts.


Installing spark gaps by hammering a nail through the chamber is a really dumb idea. Is it that hard, or expensive, to get two fine thread screws and drill a suitable pilot holes?

Considering that from an engineering standpoint..... glue, primer, epoxy and plastic pipe intended for water transmission at relatively low and constant pressure, when used for any application other than it's original design use has potential risk and danger. How then can it be said that one manufacturers plastic product is "safe" and another manufacturers plastic product is not?

I guess a better way to say it may be whose is "less dangerous".

This was a good idea inonickname. However I feel it requires major refinement and organization. It seems it was put together quickly, but with the help of the SF community and sponsors we can provide a powerful resource for curious newcomers.

I also agree with jimmy101 concerning the Spud Wiki page(and because my name is Jim ). This allows any number of us to add missing info to the page and also edit existing pieces to better strengthen the page as a whole.

velocity3x wrote:Considering that from an engineering standpoint..... glue, primer, epoxy and plastic pipe intended for water transmission at relatively low and constant pressure, when used for any application other than it's original design use has potential risk and danger. How then can it be said that one manufacturers plastic product is "safe" and another manufacturers plastic product is not?

This is a good point but legitimate spud gun manufacturers state "PVC pipe is not intended by the manufacturer to be used in the construction of spud guns" or something of that nature. This can be seen either on the front page or in the safety disclaimer. I guess this can be expressed by saying "Safety is in the eye of the beholder." What one views as safe can be viewed as dangerous by another.

velocity3x wrote:Considering that from an engineering standpoint..... glue, primer, epoxy and plastic pipe intended for water transmission at relatively low and constant pressure

Not true. PWS systems can reach 100+ PSI static pressure. I Know because my city water line will do that occasionally. Shock pressures will give pressure spikes considerably higher than that. (Much higher shock pressures can be tolerated than static pressures.) PWS rated PVC will handle the loads and pressures, and indeed is designed with those loads as their "normal" operating pressure range.

Pressure rated PWS PVC pipe is designed for higher static pressure than are found in most spud guns. Most pneumatics are operated at 120 PSIG or less since that is what a typical shop compressor will do. A 1X combustion is limited to about 120 PSIG, and that only when the round jams in the barrel, usually the peak pressure is more like 60 PSIG.

Only hybrids and pneumatics at >120 PSIG significantly exceed the normal operating range of pressure rated PVC. Even then, for the pipes sizes used in pnuematics the pipe's pressure rating is typically at least 200 PSIG if not 300 or 400 PSIG.

...when used for any application other than it's original design use has potential risk and danger.

The issue with compressed liquid versus compressed air is all about the consequences of a failure, it has nothing to do with the chances of a failure. If a 100 PSIG PWS fails it makes a mess. If the same system fails with 100 PSIG pressurized air in it then you have an explosion. An explosion has much greater consequences than simply spraying water around.

How then can it be said that one manufacturers plastic product is "safe" and another manufacturers plastic product is not?

Who said that? What people have said is that there is a difference between pressure rated pipe (and fittings) and non-pressure rated pipe (and fittings). Most PVC pipe manufacturers make both types of pipe (and fittings). They are different products, made in different ways, to different spec's, and generally used for different purposes.

King_TaTer wrote: I guess this can be expressed by saying "Safety is in the eye of the beholder." What one views as safe can be viewed as dangerous by another.

That says it best.....I'm in total agreement! Without "industry standards" and data from actual lab testing, any endorsement given to a manufacturer will be based only on the opinion of the person giving the endorsement.....for what it's worth.