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Mjöllnir - 1.5" porting Handheld Piston Hybrid

Built a hybrid 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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Unread postAuthor: Ragnarok » Fri Oct 29, 2010 11:53 pm

MrCrowley wrote:Didn't need ear muffs since it was a shot in an open environment

This thing is still going to be way past the hearing damage threshold (which is generally thought to be about 120 dB for "short" exposures), open space or not.

The other thing is noise levels are often one of the causes of a firing flinch... and that in turn makes recoil control worse.

Even when hearing damage isn't a concern, it can still be worth wearing - when target shooting with my air rifle (which is reasonably hearing safe), my accuracy tends to go up slightly when I'm using hearing protection.
The less attention put into fighting reflexive blinking, the better I can focus on other aspects of marksmanship.

and didn't bring safety glasses because I didn't really need them.

Better to be wearing them and not need them than vice versa.

edit: Cannon weighs 15kg by the way. If anyone wanted to know :P

And that would mean... *hits calculator several times* ... about 80J free recoil energy. The weight kills the recoil quite well, but still more than I'd want to be shooting from the hip.
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Unread postAuthor: MrCrowley » Tue Nov 02, 2010 9:50 pm

New photos added:
Increased pilot porting to 25mm because piston bounce has been destroying my sealing faces. I also added a much better barrel support at the expensve of having to add a 1.5" ball valve (which I didn't want on the cannon originally). You will probably notice the 1" galv pipe sticking out of the chamber. I removed the second ignition electrodes and put the pipe in its place to help deal with recoil. Recoil will still be a [female doggy], but hopefully not so bad. The Steyr rifle sling is there to help distribute the weight.
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Unread postAuthor: SpudFarm » Wed Nov 03, 2010 10:26 am

I don't write on the forums alot anymore but this is looking really good. This would be exactly what my hybrid would look like if I built it back when I had the money to spare.
Good job!

BTW, have you considered what will happend to the more holy parts of your body if that pipe sticking out of the chamber burst of gets DDT or something? :P
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Unread postAuthor: POLAND_SPUD » Wed Nov 03, 2010 12:21 pm

have you considered what will happen to the more holy parts of your body if that pipe sticking out of the chamber burst of gets DDT or something
Sure, it would be better to use hydraulic tubing and fittings. However while hydraulic tubing is available, fittings are kind of hard to get
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Unread postAuthor: SpudFarm » Wed Nov 03, 2010 12:32 pm

The tube could be filled with something to stop the mix getting in there..

JSR, what was that? Ohh, you want me to suggest epoxy?

But it probably isn't going to fail anyway.
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Unread postAuthor: MrCrowley » Wed Nov 03, 2010 12:58 pm

The 2" pipe is far more likely to fail the way I see it. I thought about trying to block it off but it just seemed like too much hassle, it is a pretty big area to fill with epoxy.

Since it's Guy Fawke's this weekend, I should be able to get off a few night shots without the neighbours being able to complain. :P
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Unread postAuthor: Technician1002 » Wed Nov 03, 2010 1:12 pm

I have an antique gas engine with a Jet Ignition Chamber. It is initiated in a small separate chamber which is coupled to the main chamber with a small port. The theory was the chamber ignition would generate a muzzle blast into the main chamber to cause a rapid ignition of the main cylinder.

Do you think a faster burn rate could be achieved with the ignition in the small pipe to blast a muzzle blast into the main chamber?

I sometimes see this ancient technology making a comeback.

http://www.greencarcongress.com/2010/10/tji-20101027.html
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Unread postAuthor: MrCrowley » Wed Nov 03, 2010 1:20 pm

Interesting idea, I would need a member who is more familiar with flame fronts and combustion to comment on that one. While originally two ignition points looked like a good idea, I think it was at the higher mixes where it started to make little difference, boosting performance by a few meters per second compared to about 40 or 50ms I was getting at lower mixes (IIRC).
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Unread postAuthor: SpudBlaster15 » Wed Nov 03, 2010 2:18 pm

With the valve opening pressure set close to the peak combustion pressure, I see little advantage to elaborate ignition systems designed to decrease combustion time. Heat loss and total usable energy in the chamber may change some, but as the valve opening point is fixed at a time interval where combustion is nearly complete, the integral of force (barrel pressure*projectile area) over displacement will not increase significantly.

Such a setup may have some benefit in standard combustion launchers, and we have discussed them before. However, for this design, a jet type ignition system would likely do nothing more than increase the probability of DDT.

BTW, have you considered what will happend to the more holy parts of your body if that pipe sticking out of the chamber burst of gets DDT or something?


Shouldn't be an issue. The burst pressure of that assembly is well into the range of several KPSI, and DDT is not likely with ~75% buffer gas present.
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Unread postAuthor: MrCrowley » Fri Nov 26, 2010 10:21 pm

New video:
[youtube]http://www.youtube.com/watch?v=ZkGriGwCSJU[/youtube]

I'm not interested in hearing anything about lack of earmuffs. Most of the shots were filmed weeks ago (before the lecture I got from you guys about not wearing ear protection) and on a few shots I did have ear plugs in.
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Unread postAuthor: jackssmirkingrevenge » Sat Nov 27, 2010 2:25 am

Tsk tsk, no ear protection...

But seriously, nice video! Did someone in the house not approve of your shooting at 2:29 :D

I would have included less footage of launching golf balls into low earth orbit and more target shots, maybe with a little high speed stuff, but that's just me :)
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Unread postAuthor: MrCrowley » Sat Nov 27, 2010 2:38 am

I would have included less footage of launching golf balls into low earth orbit and more target shots, maybe with a little high speed stuff, but that's just me

It was a shame that I couldn't get any golf ball damage shots due to the location. I was staying with some mates up at a friends bach (holiday house) where I had a quite a few paddocks I could shoot on but unfortunately most were filled with cows. I also lacked targets to shoot at. There was a tin shed my mate sacrificed to the Hybrid God but it was rejected due to the risk of a golf ball ricocheting in to the nearby house or penetrating and hitting cows in the paddock immediately behind.

All the range shots were aimed in to large forest areas or empty paddocks (which were too far away and isolated for me to do any target shooting, not to mention the lack of target). You can see with the shot at the hillside I craved a target to shoot at but unfortunately the opportunity didn't arise.

Funnily enough, my favourite bit of the video is the very start with the Super-8-esque look :D
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Unread postAuthor: MRR » Sat Nov 27, 2010 3:38 am

"This video contains content from Sony Music Entertainment. It is not available in your country."

Sometimes I hate YouTube! :evil:
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Unread postAuthor: MrCrowley » Sat Nov 27, 2010 3:47 am

Ah yes, it is blocked in Germany. I have no idea why, perhaps Germany is still touchy about hearing Soviet-era music like Dance of the Knights by Sergei Prokofiev :D

I wonder, is it possible to view it if you change your YouTube settings to a country outside of Germany? What about if you used a proxy? I'm guessing it is blocked due to the music since all the video is mine but usually they just mute the audio if it is copyrighted.

Edit: if you know of some German Fair-Use copyright laws I can use to dispute the claim I can try and get the ban removed.
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Last edited by MrCrowley on Sat Nov 27, 2010 3:56 am, edited 1 time in total.
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Unread postAuthor: MRR » Sat Nov 27, 2010 3:56 am

The country settings don't work, it's more an IP thing.

I am searching for a proxy at the moment but wasn't able to find one with a proper bandwith. I might ask a friend, who has a VPN in Malaysia.

Edit: Apparently it is possible to watch your video by changing the country settings. I set it to YouTube UK and everything works fine.

Impressive performance of your cannon by the way :wink:
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