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Hybrid short question topic

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: MrCrowley » Sat Apr 14, 2012 6:17 pm

Aluminium disks from a soda can to be used in a 3/4" union. If it takes four 3/4" disks for a 10x mix in a 3/4" hybrid and you get about 12 disks from one can that takes 15minutes to cut out; imagine how long (and how many soda cans) it would take to cut enough large disks for a 10x 2" union hybrid.

Burst disk hybrids are great... if the disks are already cut out and ready to be used :D
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Unread postAuthor: Petitlu » Sat Apr 14, 2012 6:24 pm

must take steel disks made ​​in cans of beer.
I make mine into the cans "1664"!
For MIX10, one would suffice!

I think that no system can match the performance obtained using a disk
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Unread postAuthor: DYI » Sun Apr 15, 2012 8:31 am

I think that no system can match the performance obtained using a disk


Well, that's not entirely true in all cases - in fact, I'd say that beating the performance of the burst disks typically used by members here wouldn't be too difficult, seeing as good chunk of the disk typically ends up being propelled out the barrel (especially with aluminum foil disks).

Any system which provides the same flow with the same opening time will be similar in performance. Folding skirts as implemented by Utron, or shear skirts, will perform similarly. The only case in which a rupture diaphragm is necessarily superior is when the intended projectile mass is very low in comparison to the bore. In that case, a rupture diaphragm which is scored to open in a "petal" pattern and stays fixed in the breech after opening is the typical choice.
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Unread postAuthor: D_Hall » Sun Apr 15, 2012 11:18 am

DYI wrote:Any system which provides the same flow with the same opening time will be similar in performance. Folding skirts as implemented by Utron, or shear skirts, will perform similarly. The only case in which a rupture diaphragm is necessarily superior is when the intended projectile mass is very low in comparison to the bore. In that case, a rupture diaphragm which is scored to open in a "petal" pattern and stays fixed in the breech after opening is the typical choice.

Even that's not necessarily true.

As has been so often noted in the pneumatic section of this site, with heavy projectiles the speed of the valve isn't as important as one might think.

Also, the scored diaphragms that open up in a petal pattern and stay fixed (which are the only type I have any experience with)? They work just fine regardless of projectile type. Yes, you may have to move the projectile a bit forward in the breech so that it isn't whacked by the disk opening up, but that's an easy accommodation to make. Heck, plan for it and put the disk in a slightly over sized section of breech and they don't even restrict your flow.
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Unread postAuthor: DYI » Sun Apr 15, 2012 11:46 am

Ah, I thought we were talking about valve performance here, not performance of the gun as a system.

Also, the scored diaphragms that open up in a petal pattern and stay fixed (which are the only type I have any experience with)?


Most members here use either layered foil or sheet metal without scoring, a good deal of which tends to follow the projectile out the barrel. This is what I was drawing comparison to. I'm not aware of whether that method sees any use in more "professional" applications.

I don't see where I implied that scored diaphragms didn't work well certain projectile types. I simply mentioned that in applications where one wouldn't want excess mass being accelerated down the barrel along with the projectile, folding skirts or shear skirts would be inferior to a scored diaphragm.
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