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ALL THE INFORMATION BELOW CAME FROM WIKIPEDIA AND IS 100% FACT
Due to pinging (DETONATION), the CR in a gasoline/petrol powered engine will usually not be much higher than 10:1, although some production automotive engines built for high-performance from 1955-1972 had compression ratios as high as 12.5:1,
NOTE 12.5:1 MEANS 12.5 TIMES ATMOSPHERIC PRESSURE
In an auto-ignition diesel engine, the CR will customarily exceed 14:1. Ratios over 22:1 are not uncommon
Knocking (also called pinking or pinging)— colloquially detonation—in internal combustion engines occurs when air/fuel mixture in the cylinder has been ignited by the spark plug and the smooth burning is interrupted by the unburned mixture in the combustion chamber exploding before the flame front can reach it. The engineered combusting process ceases, because of the explosion, before the optimum moment for the four-stroke cycle. The resulting shockwave reverberates in the combustion chamber, creating a characteristic metallic "pinging" sound
Engine knocking has disastrous consequences for the engine, since it leads to the catastrophical wear of the combustion chamber walls, through particle wear for moderate knocking, to welding for serious knocking. This is due to the contact between those walls and high temperature gases resulting from the unwanted explosion. The processes also lead to a 'knocking' noise for the engine, that give its name to the phenomenon. TAKE NOTE THE ONLY DAMAGE TO THE ENGINE IS CAUSED BY TOO MUCH HEAT...
THE COMBUSTION CHAMBER WILL NEVER BREAK FROM PRESSURE EVEN ON NITROUS OXIDE (OXIDISER)
NOTE MANY ENGINES CYLINDERS ARE THIN ALUMINUM WITH A REALLY THIN LAYER OF NICASIL
IF ANYONE KEEPS SAYING DDT WILL BURST SCH 40 STEEL I WILL FIND OUT WHERE YOU LIVE AND
Last edited by pyro86 on Mon Sep 03, 2007 4:22 am, edited 5 times in total.
You're not factoring in things like the repeated stress of the steel pipe (which is not intended for hot pressurized gases anyway) expanding and contracting over and over, dealing with the shock of detonation repeatedly, etc...
It's very possible that there could be a minor manufacturing defect in a piece of pipe, and over time and many many detonations, it would cause a failure. You can't say it's impossible.
Also, even if it is sarcastic, please avoid comments like "I'll kill your dog", we don't like lawsuits around here
Wait did you just edit your post Pyro and take out all the stuff Pete edited?
I just saw it a moment ago edited by Pete and now all the changes are gone, If you haven't noticed Pete is a mod and so am I, this is defiantly not the best way to go about it if you want to carry on being a member here.
wait aren't engine cylinders encased in an engine block, which is pretty damn thick as I recal, or is the fact I haven't slept in two days messing with my mind?
And DDT does have the potential of rupturing sch 40 steel pipe, and if noname's test resulted in sch40 1/2" steel pipe bulging at the union end, I know it will rupture 2" sch 40 pipe, maybe lesser diamters too.
by the way just because something comes from wikipedia doesn't mean its 100% fact, since wikipedia can be edited by almost anyone, course usually its pretty accurate.
Last edited by Killjoy on Mon Sep 03, 2007 3:29 am, edited 1 time in total.
Stanford Class of 2012
"In the end our society will be defined not only by what we create, but what we refuse to destroy"- John Sawhill
No, he left my edits in, he just changed the name of the topic back. The only reason I renamed it is because his title seemed too long - it didn't fit in the "recent topics list", and "DDT in Steel Pipe" seemed like a better title to me anyway. But whatever, his thread :-p
PS - was just thinking about it, and... one of the properties of gasoline that makes it so widely used for a fuel is it's compressibility, so to speak. Data on gasoline and air at 12x + mixtures does not apply to propane and air, mapp gas and air, or especially fuel/oxygen mixtures, in spudguns.
Last edited by Pete Zaria on Mon Sep 03, 2007 3:47 am, edited 1 time in total.
Isn't that a bit of an oxymoron
gas and diesel motors factor in repeated stresses the steel pipe... expanding and contracting over and over, dealing with the shock of detonation repeatedly, etc...
BECAUSE THEY DO IT UP TO 150 TIMES A SECOND!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
SOME DIESELS INJECT PROPANE AND NITROUS WHICH MAKES IT A PROPANE/DIESEL/NITROUS HYBRID OPERATING SOMETIMES ABOVE 22X AND SOMETIMES THEY DETONATE AND MELT AFTER A COUPLE OF MINUTES
MELT NOT BURST!!!!!!!!!!!!!!!!!!!!!!!!!!!
Last edited by pyro86 on Mon Sep 03, 2007 4:21 am, edited 2 times in total.
as and diesel motors factor in repeated stresses the steel pipe... expanding and contracting over and over, dealing with the shock of detonation repeatedly, etc...
BECAUSE THEY DO IT UP TO 150 TIMES A SECOND!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
MY POINT IS THERES NO WAY A SCH40 STEEL GUN WILL HAVE A CHANCE OF BURSTING UNLESS YOU FILL IT WITH C4 OR SOME OTHER EXPLOSIVE
Since you ignored my PM, I'll copy and paste it here into this thread:
Since you've been a member of SpudFiles for almost a year, I thought I'd give communication a shot before taking action.
Your thread about DDT in steel pipes/gasoline engines is very arrogant; you cite a wikipedia article about DDT in gasoline engines as your only reference, which doesn't really even apply to spudguns anyway (since gasoline reacts very differently when compressed than propane or MAPP gas do). Additionally, you seem 100% sure of yourself, unwilling to consider other possibilities, and even went so far as to make a (hopefully sarcastic) threat if anyone disagrees with you. You also used all capitals in several places where it really wasn't necessary.
I edited your title (to make it shorter and more readable, and correct errors) and removed your threat, so you edited the title back and then re-posted the same thread again... Why did you feel this was necessary or intelligent?
Please try to show more respect for the forum patrons and moderators. I know MrCrowley has contacted you also; if farther action is required, it won't be as friendly.
For the most part, pyro, gasoline burns quite evenly and slowly. This is actually ideal. The higher octane gas you see at the pumps? It burns even stabler than the cheapo gas.
Detonation/knocking, despite what you've read, can be quite damaging at times, or if it persists. The reason there's not some huge explosion that blows up your hood and sends shrapnel through the firewall into your chest is because most cylinders are part of an engine block, made of iron, steel, or aluminum, sometimes with hardened inserts. Most of the time the parts of an engine that are most damaged, (although cracked blocks can happen), are the weaker components, like the gasket between the cylinder head and block, the head itself, the rings, or the valves.
Steel pipe can indeed explode if subjected to enough shock, which is the primary difference between a deflagration and a detonation, or pressure. With enough pressure, you are most likely going to have a failure at the fittings or along the seam on the pipe, (if it's welded pipe). If it's a detonation, there's no guaranteeing what will happen, as behaviours under shock are nowhere near as studied by pipe companies as failure characteristics under static loads.
I think the main reason so many people, (including myself), responded to this thread is your attitude. Running around screaming "Go ahead, do anything you want, as long as you've got steel pipe! It doesn't matter what loads you put it under!", is a surefire way for somebody to get hurt. I know steel pipe is strong, (my friend and his dad made a blackpowder cannon out of it, albeit reinforced with nearly 100 pounds of solid lead), but you need to take precaution with anything like spudguns. I am fairly confident any sort of gas detonation in steel pipe has the muscle to rupture it in some way.
pyro86: It's not the pressure of the gases produced by DDT but the SHOCKWAVE from the transition the gases make to faster than their local speed of sound. Anyway this severely damages the bonds between the atoms in the steel, so the pressure spike that occurs from the rapid heating of the gases and the energy they receive from rushing back into place behind where they expanded to(okay its not that easy to understand my explanation but I don't care) causes a pressure spike which, while not enough to rupture NORMAL sch 40 steel, it can burst the steel ALREADY stressed by the shockwave.
I didn't know you were a mod, Pete, and congrats on your hybrid work!
And now that I have explained DDT to pyro and I want to go play FEAR, I don't feel like telling him anything else.
If you really feel that DDT won't blow your steel pipe, why don't you set up a live webcam feed while you set off a 20x mix in sch 40 steel while holding your cannon?
I know I can blow up steel pipe using 30x mixtures. That isn't something you can really argue about. I'm going to *attempt* to get it to fail with much lower mixtures (10x), and hopefully that will be today.
Isn't high octane basically "watered-down" gasoline? aka Fuel that burns slower to allow for higher ratios without detonating.
It has already been PROVEN that detonations can cause extreme damage to even small diameter Sch 40 steel pipe. Noname should post the pictures of what that pipe looked like after he caused a detonation in it, just to shut this guy up.
Sch 40 steel isn't an engine block, and I can guarantee that 1" Sch 40 will not survive more than 2 detonations without some sort of failure.
_Fnord: I look forward to seeing the results of that test. What kind of mixes are you capable of using?
pyro: the shockwave would only act on the walls of the cylinder and the cylinder itself won't burst because that would require enough force to blast open the engine block, which CAN NOT be generated because the detonation moves the piston and releases the excess gas at the end of the stroke.
Guys, he is essentially saying that sch 40 won't burst with DDT......oh but it has to be encased in about 6"-8" of solid steel too.
_Fnord, can you get acetylene gas or maybe methane? I'd like to see a video of that !!!!
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