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Posted: Mon May 09, 2011 11:52 pm
by 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.

Posted: Mon May 09, 2011 11:59 pm
by Lockednloaded
You could just have a stronger spring in the 2nd check valve

Posted: Fri May 20, 2011 7:57 am
by 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.

Posted: Fri May 20, 2011 12:11 pm
by 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.

Posted: Sat May 05, 2012 12:22 pm
by rustlerdude987
is the ideal concentration of butane always 3%

Posted: Sat May 05, 2012 12:30 pm
by Crna Legija
nope its 3.23% :lol:

Posted: Sat May 05, 2012 12:33 pm
by rustlerdude987
haha ok tanks :D

Posted: Sat Jun 23, 2012 8:11 pm
by JDP12
sorry to kick this up, but how do you determine the dead space volume of your air pump?

Posted: Sun Jun 24, 2012 1:50 am
by 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.

Re: How-to: Syringe Fuel Metering

Posted: Tue Mar 17, 2020 12:18 pm
by 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?

Re: How-to: Syringe Fuel Metering

Posted: Wed Mar 18, 2020 8:58 am
by jackssmirkingrevenge
Welcome from the land of the lurkers!
Stabilizing Finn wrote:
Tue Mar 17, 2020 12:18 pm
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.