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Hybrid ThorJack

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: Petitlu » Sun Apr 15, 2012 5:10 pm

Mix40 yes!
This will be the maximum for testing
I will shoot to the ThorJack to Mix20 or 30 max
'm careful
:D
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 15, 2012 5:12 pm

MrCrowley wrote:Just wondering if anyone has any qualms about using brass fittings at 40x mixes?


Assuming that to imply 4000 psi, would you think the threaded fitting would shear if you hung a 200kg weight from it?
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Unread postAuthor: al-xg » Sun Apr 15, 2012 5:20 pm

Nope, but add a bit of slack and drop say a 50kg weight from a couple of metres above and you probably will...
Or try hitting it with a hammer...

Just bashing the analogy really, static loads aren't really suitable in this case, hence the large safety factors usually applied.


Wow, typing scuba tank explosion into Google images, does return some impressive stuff...
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Last edited by al-xg on Sun Apr 15, 2012 5:24 pm, edited 1 time in total.
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Unread postAuthor: MrCrowley » Sun Apr 15, 2012 5:23 pm

I know the fitting would be sleeved by another fitting (the fitting it threads in to) but I'm sure you've broken a few brass fittings from over-tightening them ever so slightly. It's not the same type of force that would be applied during combustion but I could see a rapid pressure spike deforming the malleable brass fitting where it may not be sleeved. I think I would be more surprised if an unsleeved brass fitting survived at 40x than if it failed.

Doesn't matter now that we know Petitlu's fittings are rated for 5000PSI.
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Unread postAuthor: jackssmirkingrevenge » Sun Apr 15, 2012 5:23 pm

Naturally dynamic loads change the game, I was just trying to put the forces involved into perspective ;)

Maybe we can persuade Petitlu do some tests with a closed chamber :D

Still waiting for a taker for this...
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Unread postAuthor: Petitlu » Sun Apr 15, 2012 5:32 pm

I did some test ruptures on PVC-P up to 90bar!
But I can make your test!

http://patator.frbb.net/t9506-test-de-rupture-pvc-p
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Unread postAuthor: al-xg » Sun Apr 15, 2012 5:46 pm

Still waiting for a taker for this...


Skakarn on the French forum, is probably crazy enough to set something like that up :D

I think I would be more surprised if an unsleeved brass fitting survived at 40x than if it failed.
I reckon it would fail axially before it got close to failing radially.

If I was living in a more suitable environment, I'd happily test how much abuse the brass threads on this would take:
http://i156.photobucket.com/albums/t31/ ... 218a26.jpg
http://i156.photobucket.com/albums/t31/ ... cfef48.jpg
http://i156.photobucket.com/albums/t31/ ... 591639.jpg
(yeah I know, I somewhat underestimated the torque induced by tapping the 3/4" thread :roll: I'll make it shiny again...)
I'll start a thread I ever get anywhere near testing it :/


D'ailleurs PetitLu, tu n'avais pas remarque que tes disques de rupture tenaient bien plus de pression lors d'une mise sous pression lente, sur ton Eulrick ?
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Unread postAuthor: Petitlu » Sun Apr 15, 2012 6:08 pm

Oui lors des premiers essais sous 120bar

I will remove the quick connect to the Thorjack, I planned another system more convenient for the introduction of the disc and the bullet :wink:
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 16, 2012 12:30 am

Petitlu wrote:I did some test ruptures on PVC-P up to 90bar!
But I can make your test!

http://patator.frbb.net/t9506-test-de-rupture-pvc-p


hehe excellent!

I somewhat underestimated the torque induced by tapping the 3/4" thread


I saw the picture before I read that and knew exactly what had happened :roll:

What is it then? HPA burst disk pneumatic?
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Unread postAuthor: Petitlu » Mon Apr 16, 2012 1:45 am

it is a hybrid ...:D

Why you do not fully threaded 3/4?

I do not understand black spots ... :?:
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Unread postAuthor: MrCrowley » Mon Apr 16, 2012 1:47 am

Petitlu wrote:it is a hybrid ...:D

Image
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Unread postAuthor: Petitlu » Mon Apr 16, 2012 1:51 am

he is bald like me! :D
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Unread postAuthor: jackssmirkingrevenge » Mon Apr 16, 2012 2:19 am

Petitlu wrote:it is a hybrid ...:D


Ah, just noted the extra port for some sort of ignition :D I remember some questions about mini-hybrids, good to see you putting something together.
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Unread postAuthor: Petitlu » Mon Apr 16, 2012 2:34 am

it has a look of Thorjack! :shock:
:D
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Unread postAuthor: al-xg » Mon Apr 16, 2012 7:45 am

I will remove the quick connect to the Thorjack

Yeah, It seemed like a great idea when you used it on Eulrick, but a simple threaded union is actually a bit more practical on a small canon like this.

I do not understand black spots ...

When threading a cylindrical part on a lathe or milling machine, if the jaws aren't tightened down enough the part can slip in the jaws.


Oui lors des premiers essais sous 120bar

When PetitLu first added a burst disk to the ball valve pneumatic, he found that just opening the valve quickly would cause the disk to fail at a lower pressure. I wouldn't be surprised if burst disks actually fail prematurely on a hybrid shot.

Why you do not fully threaded 3/4?

Well it's a tapered thread, but a relief cut is planned to make it look like it's further in.

it has a look of Thorjack!
Well technically, the CAD files are actually older than Thorjack :tongue:
It will end up being very similar to Jack's 75SD, the original plan was just a smaller bore and not in a fixed barrel set up, but considering I don't have a workshop anymore or any useful tools of my own, it made more sense to start with a test setup and see how I got on.
It wasn't going to be a crazy high mix hybrid either, but then I realised that there was potential for matching basic 9mm loads in velocity and energy, which is all a bit too tempting...
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