SG 110 "murderlizor" trying again

doochman · Mon Dec 01, 2008 7:34 am

Hey guys
just joined. this is my second attempt at a first post. the first one "disappeared" so if this appears twice, please forgive me.

I built this baby 'bout a year ago. It was my first attempt ever at anything like this and i must say the bug has caught. I'm currently workin on a
pneumatic rifle which i'll post as soon as its done.

I call it the "SG110 Murderlizor" he he
I live in South Africa so all my measurements are metric i.e m,cm and mm
The chamber is 110mm * 300mm (length)
with a 50mm T section for the trigger mechanism
I made two barrels 1: 50mm * 1.6m (which is great for golf balls!!)
2: 40mm * 1.6m with a breech loader( quick and
easy loading)
I also added a fan at the back (which has subsequently been blown to pieces :/ )with an external battery chamber. i'll fix it later...

The trigger is a barbeque gas ignitor which i modified. added some longer electrodes and covered the lot in heat shrink to seal it. The trigger is also removable for servicing.

Credit to PVC Ballistics for the breech design. Used that idea and modified.
I took a few quick pics and i'll get some damage footage soon.

Radiation · Mon Dec 01, 2008 9:57 am

I love it. Especially the name.

Interesting breech load, any insight as to how it works? I didn't see a bolt or anything. Great gun!

starman · Mon Dec 01, 2008 12:24 pm

Good work here. I like the ignitor "radiator cap" a lot actually.

Work on getting your fan replaced and adding a metered propane system and air inlet valve where that battery box is in the back.

Welcome to Spudfiles!

jor2daje · Mon Dec 01, 2008 5:33 pm

Cool cannon, but could you please explain the breech design a little more thanks.

doochman · Tue Dec 02, 2008 4:27 am

thanks for the comments. i've added some more pics and explanations of the breech design. busy uploading a quick vid i made of the breech action. i'll post the link as soon as its done

doochman · Tue Dec 02, 2008 7:00 am

link to video of breech action

spudtyrrant · Thu Jan 08, 2009 6:13 pm

the radiator cap was a very good idea they can take heat and pressure so it makes sense to use them in a spud gun

inonickname · Sun Jan 11, 2009 9:31 pm

spudtyrrant wrote:the radiator cap was a very good idea they can take heat and pressure so it makes sense to use them in a spud gun

Yeh, except he has non pw parts on there :\ Endcap looks a bit flat..

doochman · Mon Jan 12, 2009 3:21 am

by non pw parts i assume you mean non-pressure rated?
if so, then i doesn't really matter cos this is a combustion cannon. the pressures reached are far lower than pneumatic and therefore you dont really need high pressure parts.
Up till now i've had no real problems except for the a section of the back blowing off cos i didn't glue it properly. fixed that with better glueing and pop rivets.
the "radiator cap" works great though!

inonickname · Mon Jan 12, 2009 4:31 am

doochman wrote:by non pw parts i assume you mean non-pressure rated?
if so, then i doesn't really matter cos this is a combustion cannon. the pressures reached are far lower than pneumatic and therefore you dont really need high pressure parts.
Up till now i've had no real problems except for the a section of the back blowing off cos i didn't glue it properly. fixed that with better glueing and pop rivets.
the "radiator cap" works great though!

Thanks for the tutorial on combustion cannons. (:\)

Though being the simplest cannon of all, a well-made pneumatic or hybrid is usually more powerful then a combustion. The pressures in a combustion usually do not rise above 50-60 psi on spray and pray cannons and about 70-90 psi on advanced cannons. Jimmy101, a member of spudfiles showed that in closed chamber experiments the maximum pressure possible with a propane mix is a little more then 100psi in a closed chamber.

(spudfiles wiki)

DWV/non rated pressure parts are rated at 0 psi. This is basically so people can't sue the company when they put any pressure in the pipe. The main problem is the FLAT endcaps. A curved face holds pressure well, but flat surfaces are VERY poor at it. Your probably safe the first time, and so on.. But deflagrating propane inside plastic pipe which ISN'T rated for pressure won't make it stronger.

That aside, a fair few people use DWV + flat endcaps (also bell reducers are prolific) without any trouble. It's up to you to exercise what caution you think due.

Aside from that, awesome cannon. Enjoy it

EDIT:

Non pressure rated "DWV" pipe is used so now and then in combustion cannons and it is generally accepted that this is safe with basic spray and pray; however some of these cannons have blown up. If you want to be safe you should definitely use pressure rated pipe and fittings, especially on advanced combustions. As stated above specific fuels such as acetylene, hydrogen, and any oxygen enriched mixtures are not safe to use in a gun made out of PVC or ABS. When using a normal fuel, pressure rated pipe and fittings and have properly solvent welded all of the joints, you can be considered 100% safe.

Some people, like parents think it is unsafe because it is an "explosion" and thus dangerous. In that case point them on the facts that it is just a deflagration and not a detonation creating no huge shockwaves, but creating just heat and pressure. This pressure is lower then the rated pressure of pressure rated pipe and fittings and that means the gun simply can't explode.

Note that cold weather makes pvc brittle and you should not use a frozen gun. However a gun that has been frozen some time but is up to normal temperature again is safe to use. Dropping the gun isn't recommended, especially frozen guns, since this might create tiny cracks; a starting point for completely cracking open and blowing up.

http://www.spudfiles.com/spud_wiki/inde ... ion_cannon

doochman · Tue Jan 13, 2009 2:47 am

thanks for that. didnt mean to lecture anyone

let it be noted that although i trust my workmanship (except maybe i can go for glueing lessons) i NEVER stand behind my cannon. :0

im busy building (almost finished) a pneumatic cannon. used pressure rated parts, but its very expensive. more than double the price (here in South Africa) and also hard to find cos i live in a small coastal town. stuff is not readily available.

inonickname · Tue Jan 13, 2009 6:30 am

doochman wrote:thanks for that. didnt mean to lecture anyone

let it be noted that although i trust my workmanship (except maybe i can go for glueing lessons) i NEVER stand behind my cannon. :0

im busy building (almost finished) a pneumatic cannon. used pressure rated parts, but its very expensive. more than double the price (here in South Africa) and also hard to find cos i live in a small coastal town. stuff is not readily available.

I know you didn't, but it's the norm round here. Use dwv/non pw and people will hammer you for it. Don't worry, it'll get to you as well

.

I know, I live in australia 200 km's from anywhere with good prices and conveniently, I'm not old enough for my license.. So non-pw parts are expensive here, but as far as spudgun stuff goes our local rural supply store has only pressure rated abs and pvc parts (steel + copper pipe/fittings also) and they have regular schrader valves cheap AND screw in schrader valves to their credit. When ever I need an ignitor I just destroy a cheap camera/pull apart a lighter.

SG 110 "murderlizor" trying again

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