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cartridge fed combustion build log

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 2:46 am

Insomniac wrote:On a partly-used 4GB card, when recording at 1000fps it told me I had a bit over 16 minutes of recording left (16 minutes in real time). If my maths is correct, that would be over 8 hours of video when watched normally. So basically, more recording time than your ever likely to need.


Thanks for the info, gives me something to look forward too :)

uhmm sorry that was mean but it proves that it might be a good idea to invest more in some tools (like a drill press, or a mini lathe). IMO it has got slightly too dangerous and time consuming since you got that HPA tank (yeah I know it was a combustion)


It's a cash flow issue, my priority at the moment is finding living quarters as opposed to throwing money at what to fill it with, but yes, a drill press and mini lathe are certainly on the shopping list.

Lets face it, the materials can't be faulted for failing, it's usually either impatience on my part not allowing the adhesives to fully cure, or indifferent design that doesn't account for the forces involved.

I should have a contemporary project system, where I work on two things at once (and there are lot of drawing board ideas that need testing to choose from) and cut/hack/drill one while the epoxy on the other sets :)
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 1:03 pm

Ah, that's more like it :)

[youtube]http://www.youtube.com/watch?v=EfB2En9JibY[/youtube]

Power was a bit dismal though, a 9 x 0.177" steel BB buckshot round punched through a relatively flimsy acrylic box, but not the cartdboard backing:

[youtube]http://www.youtube.com/watch?v=xyz8WfVqCIk[/youtube]

Same results for a marble wrapped in tape:

[youtube]http://www.youtube.com/watch?v=Lcg4ooACjeo[/youtube]
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Unread postAuthor: Lentamentalisk » Sat Jan 23, 2010 1:43 pm

Maybe you need a longer section for the cartridge to slide into, before it vents to the atmosphere, as it kicks back? Calculate the length given the relative inertia of it verse the projectile, and all that. If the cartridge gets kicked out too soon, then the projectile may only be accelerating for a small fraction of the barrel length. You can test how much efficiency you are losing by the cartridge ejecting, by clamping it in and firing it like that.
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 1:59 pm

I tried with a much stronger spring that barely let the cartridge move and it didn't seem to make a difference.
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Unread postAuthor: POLAND_SPUD » Sat Jan 23, 2010 2:23 pm

hmm
I've noticed that I tell you to give up a give up your projects as I think they are not practical... and uhmm sorry but I am going to say something similar now :D

cartridges might work well with firearms and I understand that you're trying to mimic their operation with this... but maybe that's not the best idea

well you see cartridges, at least from my point of view, doesn't make much sense for spudguns... all you need is a a good source of HP air, a valve and a loading mech...

cartridge fed spudguns combine all the disadvantages of firearms and pneumatics / combustion spudguns into one design

I know that my construction methods are not ideal but cartridges put the word 'complicated' on completely new level...
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 3:23 pm

POLAND_SPUD wrote:cartridges might work well with firearms and I understand that you're trying to mimic their operation with this... but maybe that's not the best idea


I acknowledge it's not the best idea, cartridges are certainly a complication in this case, but as you said, this isn't about practicality. If it makes you feel better, I'm working on this at the moment ;)
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Unread postAuthor: jrrdw » Sat Jan 23, 2010 3:34 pm

POLAND_SPUD wrote:hmm
I've noticed that I tell you to give up a give up your projects as I think they are not practical... and uhmm sorry but I am going to say something similar now :D

cartridges might work well with firearms and I understand that you're trying to mimic their operation with this... but maybe that's not the best idea

well you see cartridges, at least from my point of view, doesn't make much sense for spudguns... all you need is a a good source of HP air, a valve and a loading mech...

cartridge fed spudguns combine all the disadvantages of firearms and pneumatics / combustion spudguns into one design

I know that my construction methods are not ideal but cartridges put the word 'complicated' on completely new level...


Counter point:

The direction I see this going is everything being loaded into the cartridge then pull the trigger, eject, reload. How much easier can you get for a combustion?

I'm waiting to see a nice spud revolver.... :D
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 3:41 pm

jrrdw wrote:The direction I see this going is everything being loaded into the cartridge then pull the trigger, eject, reload. How much easier can you get for a combustion?


True, a single shot bolt action version of this would be childishly simple to make.

I'm waiting to see a nice spud revolver.... :D


Not from me you won't, if anything it will be pump action :P D
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Unread postAuthor: jrrdw » Sat Jan 23, 2010 4:26 pm

JSR wrote:Not from me you won't, if anything it will be pump action :P D


Shangerla! Just keep from beating up the contact points, and or jumping a arc to them while in the magizine.
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 23, 2010 5:17 pm

jrrdw wrote: Just keep from beating up the contact points, and or jumping a arc to them while in the magizine.


The cartridge/bolt contact points are pretty hardwearing and should be able to take a lot of punishment, here's what the internals look like:
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Unread postAuthor: jrrdw » Sat Jan 23, 2010 5:54 pm

Nice design for the electrodes. Possitive contact no matter what.
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Unread postAuthor: USGF » Tue Jan 26, 2010 3:45 am

jackssmirkingrevenge wrote:
USGF wrote:JSR, setbacks build character. :cry:


Easy to say from your high end workshop :D but you know what they say, "if at first you don't succeed, you're probably JSR and you will invariably throw more epoxy at the problem" ;)

Nope, JSR, I got lots of character. USG Mike does too. "High end" workshop means our failures cost a lot more. :oops: Not for USG but we had a batch of PVC parts we had to rework, only 800 parts....


How about UV curing adhesives / epoxy? I understand they get to 95% strength in a few seconds. On a tangent, you use metric hardware or inch stuff?

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Unread postAuthor: Ragnarok » Tue Jan 26, 2010 4:35 am

jackssmirkingrevenge wrote:Power was a bit dismal though

One possible solution to that might be using a fuel-oxygen mixture rather than a fuel-air mixture. That could potentially up power by about five times, assuming the cartridges could take the pressures involved.

The most sustainable way (in that you wouldn't need to buy oxygen cylinders on a regular basis) to do something like that would probably be an electrolysis cell.

In my personal opinion, there just isn't the pressure behind an atmospheric fuel-air combustion to really be able to run a cartridge set-up that has any real power.
You probably need to up the ante somehow - whether it's by fuel-oxygen mixtures or hybrid cartridges is up to you.
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Unread postAuthor: jackssmirkingrevenge » Tue Jan 26, 2010 4:44 am

USGF wrote:"High end" workshop means our failures cost a lot more. :oops: Not for USG but we had a batch of PVC parts we had to rework, only 800 parts...


I guess it means there's more pressure to get it right the first time, but then again with CAD designs it's more likely that you will :) swings and roundabouts

How about UV curing adhesives / epoxy? I understand they get to 95% strength in a few seconds.


Now that's an avenue I never thought of, will look into it!

On a tangent, you use metric hardware or inch stuff?


The nature of where my epoxy batcave is located means that it's a mix of metric and imperial, but as time goes by the imperial is being phased out.

One possible solution to that might be using a fuel-oxygen mixture rather than a fuel-air mixture. That could potentially up power by about five times, assuming the cartridges could take the pressures involved.


I flirted with the idea here but never actually made anything because of a pathological fear of handling pressurised oxygen, but what I never though of was

an electrolysis cell


:idea:

So many ideas, so little time!
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Unread postAuthor: Ragnarok » Tue Jan 26, 2010 8:13 am

jackssmirkingrevenge wrote:So many ideas, so little time!

Yes. I see you are still talking when there's science to do.* :tongue3:

*Heck, I want to see you start one of your showcase threads with the line "This was a triumph".

...It'd make a change to your usual performance at least.
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