a spark question.

[stevenarroyo]

ok people i have a new question......
am going to use a electric BBQ ignitor and i spark plug. first do you think it can work?? and am planing on having it on the elbow before the barrel.
here is a picture of what an talking about....
<a href="http://s217.photobucket.com/albums/cc21 ... G00295.jpg" target="_blank"><img src="http://i217.photobucket.com/albums/cc21 ... G00295.jpg" border="0" alt="Photobucket"></a>
my question for that is do you think it will work there?? if not where can i put it that will not get in the way??

[psycix]

Why do you ask this question both in your existing thread AND in this one?


Yes, it will work, no matter where it is placed in the chamber.
Do note that when it is somewhere far away form the injection point you need to mix it well with a fan.
Also, burn rates are better when the gap is more to the center of the chamber.

[stevenarroyo]

o ok thanks

do u know what type of treads are on the spark plug??

[jimmy101]

Like psycix said. You probably want the gap on the central axis of the chamber (which a spark plug can't do since it is too short) and you want the gap near the front to back center of the chamber.

Oh, and it also helps if the gap is near the fan. As drawn, there won't be much movement of the fuel at the spark gap, even with a fan running.

But you probably want the fan near the clean out plug or else it'll get destroyed when the gun is fired.

Net result of all this? Do it the way 90% or all combustion guns are done when they have a single gap;
1. Use pointy screws (like fine thread drywall screws) for the gap, not a spark plug.
2. Position the gap at about the center of the chamber (you can ignore the volume of the elbows when determining the "center" of the chamber).
3. Mount the fan near the cleanout plug with the air directed at the spark gap.

Also remember that for an over-and-under design you need pretty good bracing between the barrel and chamber, the elbows aren't enough.

[stevenarroyo]

i know i need more bracing, am going to use wood or maybe some pvc i have around

[nickz]

o ok thanks

do u know what type of treads are on the spark plug??

Use A 1/4" NPT tap, It will fit tight.

[stevenarroyo]

thanks nickz.

but will the spark plug work? cause i was looking on the site and some1 was talking about it not working?? and i want to know before i make a big hole in my cannon.

[DYI]

Use A 1/4" NPT tap, It will fit tight.

I've never encountered a spark plug in my life that had 1/4" NPT threads. Not saying they don't exist, but you'd probably have a bit of trouble finding one.

Most modern spark plugs have some oddball metric threads (or at least they're odd on this side of the pond). Ye olde fashioned Model T spark plugs are 1/2" NPT threads (yeah, they're really big), but they're also kind of weak. I doubt this would be a problem on normal combustion guns, but I've blown 2 of them in half, consecutively.

but will the spark plug work? cause i was looking on the site and some1 was talking about it not working?? and i want to know before i make a big hole in my cannon.

Do you mean "will a device that is designed to allow electric arcs to occur inside the cylinders of an engine to ignite a gaseous hydrocarbon/oxidiser mix (at over 100 psi in some cases) be able to ignite a very similar gaseous hydrocarbon/oxidiser mix inside my spudgun at the same voltage, with better mixing and lower pressure?"

[stevenarroyo]

yes i am

i was looking on the site and the guy said it was not working then he put 2 screws and started to fire good.

[nibbler125]

make a bracket inside of the combustion chamber using wood and set 2 to 3 spark gaps just two wire pieces stapled to a 1" 1" 1" piece of wood spanning the distance of the cannon and use hot glue to make sure it wont go nowhere but make sure to test it to make sure it can gap ok before you glue it together.

[stevenarroyo]

am thinking of making something like that.... but out of some PVC i have around. maybe i do that am alright getting some good ideas in my head

[nickz]

Use A 1/4" NPT tap, It will fit tight.

I've never encountered a spark plug in my life that had 1/4" NPT threads. Not saying they don't exist, but you'd probably have a bit of trouble finding one.

Most modern spark plugs have some oddball metric threads (or at least they're odd on this side of the pond). Ye olde fashioned Model T spark plugs are 1/2" NPT threads (yeah, they're really big), but they're also kind of weak. I doubt this would be a problem on normal combustion guns, but I've blown 2 of them in half, consecutively.

but will the spark plug work? cause i was looking on the site and some1 was talking about it not working?? and i want to know before i make a big hole in my cannon.

Do you mean "will a device that is designed to allow electric arcs to occur inside the cylinders of an engine to ignite a gaseous hydrocarbon/oxidiser mix (at over 100 psi in some cases) be able to ignite a very similar gaseous hydrocarbon/oxidiser mix inside my spudgun at the same voltage, with better mixing and lower pressure?"

I didnt say it was 1/4 npt I jsut said to use a 1/4 npt tap.

compare them for yourself.

[nickz]

Use A 1/4" NPT tap, It will fit tight.

I've never encountered a spark plug in my life that had 1/4" NPT threads. Not saying they don't exist, but you'd probably have a bit of trouble finding one.

Most modern spark plugs have some oddball metric threads (or at least they're odd on this side of the pond). Ye olde fashioned Model T spark plugs are 1/2" NPT threads (yeah, they're really big), but they're also kind of weak. I doubt this would be a problem on normal combustion guns, but I've blown 2 of them in half, consecutively.

but will the spark plug work? cause i was looking on the site and some1 was talking about it not working?? and i want to know before i make a big hole in my cannon.

Do you mean "will a device that is designed to allow electric arcs to occur inside the cylinders of an engine to ignite a gaseous hydrocarbon/oxidiser mix (at over 100 psi in some cases) be able to ignite a very similar gaseous hydrocarbon/oxidiser mix inside my spudgun at the same voltage, with better mixing and lower pressure?"

I didnt say it was 1/4 npt I just said to use a 1/4 npt tap.

compare them for yourself.