SpudFiles

Some one plz help me,I'm really new at combustion cannons.
And i'm trying to make a mini one first,i used a chamber fan,a spark ignitor, using a mix of butane and propane.But a can't get it ignited!! some body plz tell me why and what's the basic things i need to make a good mini combustion cannon?thanks

How are you getting fuel into your chamber? Getting the correct fuel/air ratio (around 4% in your case) is very important for reliable function, especially in smaller combustions.

You might want to consider using a syringe:

how does it works, i do like to build a fuel inject system,but don't know how

Ok, what is the volume of your chamber?

i think is about 300cm2

So, grab a syringe and lighter setup like in the photo above, measure 12mL of fuel, inject it into your chamber, voila

so i have to take out the syringe for the lighter frist?than inject in to the chamber?

Yes.

Don't worry about the gas leaking out of the nozzle while you do that

ok,that's easy.but is there some way that i can do it with out move the syringe?

what do you mean by

with out move the syringe

??
you can use manometric metering but, AFAIK, it is a bit trickier to get right than this method

You could also have a valve between the syringe and the chamber, which is closed when you fill the syringe, then open it and push in the plunger.

You'd also need a way to vent the chamber though.

thanks,this helps a lot