Alright, most experienced people on here agree that DDT=Death.
As we know, DDT occurs when a flame front starts burning fast enough to break the local speed of sound, and the gasses in front of it are compressed and ignite all at once, thus the pressure spike.
That being said, I want to hear your opinions on an idea I had to avoid it:
Don't allow one flame front to exceed the SoS. More specifically, create as many flame fronts as possible and allow them to collide, so that no particular front accelerates too fast.
The short version is: can multiple spark gaps be used to avoid DDT?
A question/theory about DDT
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iPaintball
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Fnord, I'm not that experienced with DDT, but your idea seems logical.
BTW, DDT means Deflagration to Detonation Transistion.
BTW, DDT means Deflagration to Detonation Transistion.
Summer Projects:
CO2 tank hybrid: Gotta fix the meter
Cane gun: Needs a pilot/fill setup
1.5" piston valve gun: Almost done
CO2 tank hybrid: Gotta fix the meter
Cane gun: Needs a pilot/fill setup
1.5" piston valve gun: Almost done
Your idea does seem logical, to use iPaintball's exact wording. 
In my opinion, I don't think DDT=death, as long as you're using the right materials. Steel, even Sch 40, has a burst pressure in the tens of thousands of psi, and there's no way that any hybrid mixture below 10x, even if DDT occurs, will rupture the pipe. It may bulge a bit ( 
), but then you just need to get a new piece of pipe for a chamber, and that shouldn't cost a huge amount.
In my opinion, I don't think DDT=death, as long as you're using the right materials. Steel, even Sch 40, has a burst pressure in the tens of thousands of psi, and there's no way that any hybrid mixture below 10x, even if DDT occurs, will rupture the pipe. It may bulge a bit ( ), but then you just need to get a new piece of pipe for a chamber, and that shouldn't cost a huge amount.-
Novacastrian
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I would have thought multiple spark gaps increase the speed of the burn thus INCREASING the chance of ddt, although if it did occurr you would have a smaller effect because the relative area to ddt has been reduced by having 3 or more flame fronts. Does using a fan increase or decrease the chance of ddt? My guess is that it would increase it, but i'm no Einstein :joker:
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 5:32 pm, edited 1 time in total.
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Novacastrian
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What pressures could be expected at ddt in a smallish Hybrid? (say 500ml)
Lets assume a 4x mix, anyone know?
Lets assume a 4x mix, anyone know?
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 5:32 pm, edited 1 time in total.
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Novacastrian
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That's quite a lot, now, what are chances of ddt occuring in said example?
I ask because i'm own a smallish Hybrid (500ml)
I ask because i'm own a smallish Hybrid (500ml)
According to SpudTech members (written 3+ years ago), most Sch 40 steel pipe has a burst pressure of ~35,000 psi. He said knock off 5,000 because it's made in China, then cut it in half because of threaded joints. Give it a further safety factor of 10:1 and it's rated to 150 psi.
Novacastrian, there's almost no way you can incur DDT with just a 4x propane/ 4 bar compressed air mixture.
When I was messing around with DDT, I needed a 5 foot long chamber with a single spark at the very back, along wiht a 6x mixture, to get the gases to detonate.
Novacastrian, there's almost no way you can incur DDT with just a 4x propane/ 4 bar compressed air mixture.
When I was messing around with DDT, I needed a 5 foot long chamber with a single spark at the very back, along wiht a 6x mixture, to get the gases to detonate.
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 5:31 pm, edited 1 time in total.
What's the average pressure of a 6x propane/compressed air detonation?
I can see how close I was to blowing up the pipe that I was experimenting with.
I would download GasEq myself, and I have tried it, but my computer won't run anything I download, from GGDT and GasEq to Google Earth and other random programs.
I can see how close I was to blowing up the pipe that I was experimenting with.
I would download GasEq myself, and I have tried it, but my computer won't run anything I download, from GGDT and GasEq to Google Earth and other random programs.
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Novacastrian
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Thanks heaps for the info, i have 6.5mm thick s/s tube as my chamber.
I feel alot safer now
I feel alot safer now
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SpudBlaster15
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Last edited by SpudBlaster15 on Wed Jul 14, 2021 5:31 pm, edited 1 time in total.