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Bofors - GB Coax - Video!

Built a pneumatic cannon? Then post it here! This section is for completed, finished cannons that you have built. Please include pictures and information.
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Bofors - GB Coax - Video!

Unread postAuthor: starman » Sun Mar 09, 2008 3:55 am

Bofors Little Brother - GB Coax

I started on my mission to build my first pneumatic only knowing that I wanted to a) build a golfball gun, b) a coaxial model and c) somehow utilize one of those dumb 2' pieces of 3" PVC that Home Depot and Lowes love to sell these days. After considerable time and effort, I came up with "Bofors Little Brother", named after the Swedish 40mm anti-aircraft guns used on allied ships in WWII because they have similar look and share a similar caliber.

Features include:

- 48" 1.5" SDR 21 barrel
- c:b = 1:1
- overall gun length about 5'
- 3" barrel sealing piston, multiple plastic paint coatings to build out to ideal diameter
- 3/8" to 1/2" piston travel
- 3/4" Orbit Watermaster pilot valve, 3/4" brass and sched 80 piped, blowgun actuated
- schrader air fill
- screw ball stop and barrel dimple, holds ball in place reliably
- cool 2 tone flat black/glossy black paint job
- cool looking but useless barrel noozle
- deep throated, fast pulse shots, 50 - 100 psi feels about right in this gun. Laser beam GB shots...

After this project, I guess I still count myself a combustion man at heart. The whole air compressor requirement for medium and big guns makes me really enjoy the advanced combustion's always ready-to-go anywhere appeal. However, I wanted some pneumatic experience and this has been invaluable. The toughest part was getting the piston right and figuring out what order and what type adhesives to use when finally gluing the coax body and barrel together. You need a set of octupus arms to do everything you need to do almost all at once. You don't get a do over with a socket weld. Epoxy is my new best friend...:-)

Check out a plywood-shot video here:
[youtube]http://www.youtube.com/watch?v=xzfnXruYvxw
[/youtube]

And damage closeup:
[youtube]http://www.youtube.com/watch?v=tGnaGFtSeMs
[/youtube]
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Attachments
bofors 064 ss.jpg
Damage front, 1/2" plywood from about 30' away.
bofors 064 ss.jpg (36.38 KiB) Viewed 3815 times
bofors 031 s.jpg
Piston, used a slice of 2.5 " PVC pipe to build out the "ring" on a 2" socket to male NPT adapter. Most of the NPT threads were sanded off. Used multiple paint passes to build out ideal ring diameter.
bofors 029 s.jpg
Piston cylinder and pilot valve system
bofors 025 s.jpg
Sealing barrel face and airtank. Barrel standoff was made by using a tablesaw to slice the first 3/8" face off of a 3" / 1.5" reducer bushing. It is welded to the 3" only and floats around the 1.5" barrel. Screw ball-stop visable, barrel dimple on opposite side and is 7/8" in front of the stop.
bofors 043 s.jpg
Valve and piston assembly
bofors 045 s.jpg
Rear view
bofors 049sm.jpg
Business end of the BLB
bofors 059 trim s.jpg
The BLB with Cool McCool. Reasonable ergonomics and power aplenty.
Bofors40mm.jpg
The namesake, 40mm of whoop A.
Last edited by starman on Tue Jul 08, 2008 9:21 am, edited 14 times in total.
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Unread postAuthor: Antonio » Sun Mar 09, 2008 6:44 am

lol must be damn powerfull!
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Unread postAuthor: jackssmirkingrevenge » Sun Mar 09, 2008 7:31 am

Very nicely made, epsecially for your first pneumatic venture :) some videos, perhaps?
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Unread postAuthor: Rokmonkey » Sun Mar 09, 2008 8:48 am

Hmmm, the 2ft sections they sell at the Lowes and Home Depot near me are PVC-DWV, gotta replace one on my cannon same reason. Pass it off as pressure rated...


Aside from that, beautiful gun, Nice job with your first cannon, jumping right in on a piston. Very clean!
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Unread postAuthor: ghostman01 » Sun Mar 09, 2008 9:00 am

very nice looking gun i like the black paint i love painting all my guns that colour whether they look real or not
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Unread postAuthor: bigbob12345 » Sun Mar 09, 2008 9:07 am

Very nice job.
We havnt seen many upper scale coax's lately, nice to see a really well made one like this.
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Unread postAuthor: Gippeto » Sun Mar 09, 2008 10:44 am

That's very good. In fact it's one of the nicest "hole punches" i've seen! :wink:
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Unread postAuthor: starman » Sun Mar 09, 2008 10:49 am

jackssmirkingrevenge wrote:Very nicely made, epsecially for your first pneumatic venture :) some videos, perhaps?


Yes indeed there are! Just need to get them downscaled and uploaded...they are HD and way too large at the moment.

Rokmonkey wrote:Hmmm, the 2ft sections they sell at the Lowes and Home Depot near me are PVC-DWV, gotta replace one on my cannon same reason. Pass it off as pressure rated...


Ding ding ding...You win the rubber ice-pick! First one to mention DWV. Your homework for today...trip on down to Lowe's and check again for yourself. The 2' sections of 3" and 4" are pressure rated PVC and wayyyyy over priced. Longer 5' and 10' foot sections are cell core. If they are substituting cell core for the 2' items in your area, complain to the store manager.
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Unread postAuthor: bluerussetboy » Sun Mar 09, 2008 12:01 pm

It truly depends on the individual store. Currently our local Lowe's only stocks 2' sections of ABS. The only NSF-PW PVC that they are stocking now is 2" and below. Their reason is, it's what they have had requests for. No need to stock what people aren't going to buy.

Nice coaxial btw
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Unread postAuthor: starman » Mon Mar 17, 2008 12:39 am

Updated with video: http://www.youtube.com/watch?v=xzfnXruYvxw About 70 lbs psi.
And Damage closeup: http://www.youtube.com/watch?v=tGnaGFtSeMs (Sorry turned off the camera too soon on the other vid)
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