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750 fps marble launcher

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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750 fps marble launcher

Unread postAuthor: Anatine Duo » Mon Feb 06, 2017 7:55 pm

Not ready for showcase yet... thought I'd post this now and maybe get some inspiration on how to finish this guy.

Short story: This is the Bullshark, rebuilt in bits from my MK 2 back in 2003, standard piston valve muzzleloader, .64 cal currently shooting marbles at 240psi. Overall length 38" , overall weight under 5 lbs, mechanically triggered

I'm quite proud of the pilot valve that I call the "Liftoff" valve (hopefully I can get these pics to work)

Chrono shows 630fps @150 psi with marble, 430 fps @200psi with 5/8" steel bearing

Since getting the pilot to stop leaking it has been awesome@240psi (that's as high as my bicycle pump goes) but it was snowing too hard to get the chrony out... data and video to come...

More of the story... part of the rationale behind the design of this launcher was to use as few plumbing parts as possible. The Liftoff pilot can be made of very basic materials. The pressure tube is ABS DWV but before the obligatory safety warnings get posted, it has 3 layers of Kevlar wrapped around it in aircraft laminating epoxy (plus 2 layers glass sanding veil)
The stock has minimal inletting, as all the mech is in one plane. Trigger has to be mechanical for me... originally I piloted this thing with a schrader at the end of a tube but I learned to shoot on real triggers and hate mushy valve triggers.

It's a "no excuses" sort of build... Any smooth tubes, scrap schrader, plus some gumption can be the basis for a similar build. I did have access to a lathe briefly so the end plugs are machined, but nowadays I would probably cast them from epoxy with additives.
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bullshark liftoff open (3).jpg
bullshark wip 2.jpg
Last edited by Anatine Duo on Sat Feb 18, 2017 2:54 pm, edited 3 times in total.
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Re: marble launcher bullpup

Unread postAuthor: jrrdw » Tue Feb 07, 2017 6:33 am

Stain the stock. A nice dark cherry or mahogany looks good...
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Re: marble launcher bullpup

Unread postAuthor: farcticox1 » Tue Feb 07, 2017 5:00 pm

I like it :bounce:
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Re: marble launcher bullpup

Unread postAuthor: Anatine Duo » Wed Feb 08, 2017 9:42 pm

Some 240psi damage video:
Better pic (not sinking in snow)

bullshark with pump small.JPG


The wood definitely needs some colour, but I'm not happy with the quality so it will probably get paint. Needs a trigger guard... so sketchy without.

Needs ramrod holder.

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Last edited by jrrdw on Fri Feb 10, 2017 8:13 am, edited 1 time in total.
Reason: Embedded video.
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Re: marble launcher

Unread postAuthor: nik282000 » Sat Feb 11, 2017 10:14 pm

Awesome, it takes a lot of force to poke a hole in a hard hat.
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Re: 750 fps marble launcher

Unread postAuthor: jackssmirkingrevenge » Mon Mar 06, 2017 10:05 pm

Interesting pilot setup, how do you force the seal against the nipple?

Reminds me of one of my first projects that was basically a barrel-sealing piston mechanically held in place.
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Re: 750 fps marble launcher

Unread postAuthor: Anatine Duo » Tue Mar 07, 2017 12:09 am

The seal is held against the nipple by a pivoting bar. The other end of the bar is held by a sear which is the end of another, longer pivoting bar. Pulling the trigger actuates the longer bar, moves the sear down, allows the first bar to pivot and the seal to move. Very low forces on the mech. The final reveal will show how it works.

I got the idea from my testing of the launchers by holding a thumb or finger over the pilot port. It's just a mechanical finger! The actual seal can be fussy (eraser doesn't work more than once) but grease on leather works, plastecine on leather also works (though I have a suspicion it slows piloting slightly if it gets in the nipple)

Currently it holds pressure overnight.

Got some paint on it yesterday and a trigger guard today (now it can be locked) but it needs a very high scope mount to be fabricated.

BTW it turns out marbles also go through hardhats!
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Re: 750 fps marble launcher

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Re: 750 fps marble launcher

Unread postAuthor: jackssmirkingrevenge » Tue Mar 07, 2017 7:37 am

Anatine Duo wrote:BTW it turns out marbles also go through hardhats!


Anything will if its going fast enough, velocity is king!

Just be careful of ricochets, I know.

The actual seal can be fussy (eraser doesn't work more than once) but grease on leather works, plastecine on leather also works (though I have a suspicion it slows piloting slightly if it gets in the nipple)


It would be much more reliably and good to higher pressures with an o-ringed spool, don't forget you share the same continent with some friendly machinists if you want something more professional done.
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Re: 750 fps marble launcher

Unread postAuthor: Anatine Duo » Wed Mar 08, 2017 1:35 pm

Thanks JSR, I see some endplugs in my future assuming you are way cheaper than a regular machinist! I'm happy to have them machined from scrap ;) I still own my lathe but during several moves it has not come to what is now a family home.

Part of the rationale for the Liftoff pilot was not needing machine tools.

Anyway, more progress, got the scope mount fabbed, painted, epoxy is curing I type. If anybody is interested in mounting a scope on a homebuilt this is my "one group zero"

In my version I center the scope in it's adjustments to give me the widest range after mounting. THen I shoot a group at first distance (ball still traveling up) after consulting ballistics calculators to optimize point-blank range. For this group I hot glue a laser to the barrel, shoot at a bullseye 3 times (use a larger backstop than you think you need... ask me how I know) at 9 yards

Now clamp the launcher so that the laser still points at the bullseye at the same distance. Mount the scope so it points at the point of impact (center of group) using shims, tape, whatever will hold it in position. If you have patience you can keep carving the mount until it sits just right. Mix epoxy and slather it on... usually some more shimming. Using this method the scope should be zero-ed without having to use the adjustments much.

First 2 shots were overlapping, third was touching (that one was harder to get in the barrel). NOt bad considering that was with a dollar store laser hot glued to the barrel, shooting dollar store marbles. Looking forward to actually shooting with the scope.
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Re: 750 fps marble launcher

Unread postAuthor: jackssmirkingrevenge » Thu Mar 09, 2017 10:26 am

If it's a simple job like a spool valve to help a fellow spudder I don't normally charge much beyond materials and postage.
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Re: 750 fps marble launcher

Unread postAuthor: Anatine Duo » Fri Mar 10, 2017 4:06 pm

The high scope mount:

quick high scope mount small.gif



It's all done! Started a showcase thread: pneumatic-cannon-database/topic26588.html
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