How-to: Syringe Fuel Metering

[Zeus]

But in my experience (which is minimal), the check valve would pop before the syringe was pushed back.

Also if too much gas was put in the syringe then there would be no way to vent it. I like your thinking though.

[Lockednloaded]

You could just have a stronger spring in the 2nd check valve

[jackssmirkingrevenge]

Helpful tip: you can get 100mL syringes a couple of dollars that will allow you to fuel combustions with up to 2.5 litre chambers in one go, so this method is not strictly limited to "mini" launchers.

[Technician1002]

By making your own pistons you can make metering syringes of any size.

I have toyed with making a dual syringe for metering air and fuel together much like an epoxy syringe. Either a pair of pipes with the proper ratio in cross section is needed or a lever to push the plungers in the proper ratio would be needed to dispense a purge fuel air cycle into a launcher. It would be for rapid reloads.

In medical supplies, they are not IV syringes. They are feeding tube syringes. The tip is larger than an IV syringe so a needle won't fit on it.

[rustlerdude987]

is the ideal concentration of butane always 3%

[Crna Legija]

nope its 3.23%

[rustlerdude987]

haha ok tanks

[JDP12]

sorry to kick this up, but how do you determine the dead space volume of your air pump?

[jackssmirkingrevenge]

You can fill it with water for a precise measurement, or guesstimate based on internal diameter. It's critical for small items like cartridges, but not so much for larger chambers.

[Stabilizing Finn]

Hi everyone!

I've been reading this forum long time now and I have built few hybrids aswell.

Recently I have cranked up my mixes and I started to think about that if I have chamber,
lets say 30ml and I go for X20 mix with MAPP gas with 4,66% mixture. So equation is then 0,0466 X (30ml + 1,5ml) = 1,4679ml
If we take that figure and multiply that with mix numer, 1,4679ml X 20 = 29,358ml fuel.

So far that look like it's about right figure.

Now this topic tells me that I have to put 29,358ml fuel in to the chamber and pump 19 BAR of pressure, right?

But now here comes my question, because my chamber is 30ml there is only ~0,6ml of atmospheric air in the chamber left,
far off of stoichiometric ratio. So should I pump 20 BAR insted of 19 to get right ratio, or am I missing something here?

[jackssmirkingrevenge]

Welcome from the land of the lurkers!

But now here comes my question, because my chamber is 30ml there is only ~0,6ml of atmospheric air in the chamber left,
far off of stoichiometric ratio. So should I pump 20 BAR insted of 19 to get right ratio, or am I missing something here?

That's an interesting point, I never accounted for the fact that at higher mix numbers, the amount of air in the chamber displaced by the fuel becomes significant.

You would be correct in saying that going by the formula, the mix would indeed be too rich for an ideal burn.