SpudFiles

nice website.

i hope someone can help with my question.

this summer i built an advanced combustion launcher. it's been working well up until it started to get colder. now the propane refuses to turn to gas. it stays in a liquid state while in the meter. i'm guessing my meter is too small but i haven't got the money for a new larger one.

does anyone know the math to figure out what the minimum temperature i can use my meter at?

some info you might find useful:

chamber: 190 cu. in
meter pipe dia.: 1/4 in. or 0.364" ID
meter length: 6.5 in. between two s.o.v.
my elevation: 9,275 ft above sea level

according to the fuel-tool downloaded from burnt-latke i should be running about 123-124 psi on my gauge.

i have tried double shots at 60-ish psi with less than favorable results.
this place is full of dipshits who suck cock
any help would be appreciated

Welcome to SpudFiles.
Right of the bat, thanks for posting in the right section, using readable English, and appropriate grammar. We like new members like you I'd encourage you to read around on our Wiki and How-To sections if you haven't already.

I have the same problem, living near Seattle, WA. For instance, it's 49F outside right now.

This chart shows you the vapor pressure of propane at various temperatures, which is the max pressure you'll get out of it at any given temp.

http://www.engineeringtoolbox.com/propa ... _1020.html

So in my case, at 49F, I could expect around 76psi max pressure.

I have a slightly-too-small meter pipe (it was recycled off an old cannon, simple setup with two ball valves and a pressure gauge) for my chamber.
On warm days (anything over 60F) I use two "shots" at 65psi. On cold days, I use 3 shots at 43psi. You may end up figuring out a similar "fuel schedule".

You shouldn't have any different results using two lower-pressure shots of propane as opposed to one higher pressure one, as long as the total fuel injected is the same. Do you have a fan to mix the fuel?

Your other option is to build a larger meter pipe that could sufficiently fuel your chamber at less than propane's vapor pressure for your given temperature.

I have no idea how altitude effects propane except to say that the air up where you are is less dense, so you'll probably want to run a slightly leaner than normal mixture.

I hope that helps.

You can see my cannon here, if it helps at all: http://www.spudfiles.com/forums/pete-za ... 11054.html

Peace,
Pete Zaria.

thanks for the chart. it looks as if i'm sort of screwed using my current meter for the rest of the winter. i only used the 1/4 in. because it was just laying around.

i'll probably just have to go back to static guard for the time being.

bluerussetboy wrote:thanks for the chart. it looks as if i'm sort of screwed using my current meter for the rest of the winter. i only used the 1/4 in. because it was just laying around.

i'll probably just have to go back to static guard for the time being.

No need... Just keep your propane tank inside before you shoot. It'll stay warm enough to fire a few times.

Run your meter at a lower pressure, and use more "shots" of propane, like I explained above.

Propane is infinitely better than any aerosol fuel I've come across, and you have a meter setup good to go... it'd be a shame.

Peace,
Pete Zaria.

OR measure out liquid propane and let it evaporate in your chamber

i'll probably go with the triple shot at 40-ish psi. i've got a small regulator laying around that i can probably use for consistency. i was just trying to keep everything as compact as possible. this will give me a chance to play with other metering options.

thanx again