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Accurately Measuring Your Chamber and Meter

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Accurately Measuring Your Chamber and Meter

Unread postAuthor: noname » Thu Aug 09, 2007 11:59 am

This is mainly for hybrid users or those who are planning on making one. This would work for combustions, but it is mainly for hybrids because of how accurate your measurements need to be. Miscalculating a propane meter by even a millimeter can screw up your mixture and keep it from igniting.

1st Step: Measuring the Meter
Get your propane meter, and detach it from the gun. This step is easier if you strip the meter of everything up to the two ball valves. Open one ball valve, and slowly fill the meter with water. If your meter has elbows and T's coming off of the main pipe, the close the ball valve and turn the meter every now and then, to make sure water fills the T's and other sections of the meter. When the whole thing is full. pour it into a cup or something. (*) Then, get a medicine dropper and fill a graduated cylinder with the water from the meter. Hopefully, your measuring cup/graduated cylinder is graduated at every mL or every 2 mLs. When you have all the water from the cup into the cylinder, write down how many mLs the meter had.

Note: If you use a syringe, starting from (*), you can skip most of the 1st step.

2nd Step: Measuring the Chamber
Repeat Step 1, only do it with the chamber this time.
Again, record your data.

3rd Step: How Much Propane do you need?
Go over to your computer (if you're reading this, I know you have one) and go to www .advancedspuds.com . Go to the navigation bar at the bottom of the page. Scroll down and click "propane injection" underneath FUEL. At the bottom of this page, there is a link to SpudTool Online. I bookmarked it, because I can never find it. Keep the window with SpudTool open, and open another tab. Go to Goolge with the new tab. Get your piece of paper that showed your chamber and meter volumes. Enter "X ml to cubic inches" into the bar, "X" being your number. PRess enter, and you will have your answer. Write that down also. Do this with both your meter and your chamber. Now, go back to SpudTool. Go to the Chamber section and click 1/2" Sch 80. Then extend it until it is closest to your chamber volume. Using small diameter pipe in a simulation allows you to get the most accurate results. When you have the closest possible to your chamber volume, go down to the Fuel Meter Calculator section. All you need to do here is keep changing the pressure needed until the "vol of propane meter" bar matches your meter volume from your piece of paper. Write that down as well.

You are done! This how-to is a lot longer than I expected it to be, but it will hopefully save you guys some time, and it isn't this long when you're actually doing the measurements.
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Unread postAuthor: SpudBlaster15 » Thu Aug 09, 2007 5:01 pm

If you are using a hybrid design that injects air pressure through the propane meter, measure the whole launcher volume (meter and chamber) rather than just the chamber volume, and use this measurement in the 'chamber volume' section of whatever calculator you are using.
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Re: Accurately Measuring Your Chamber and Meter

Unread postAuthor: jimmy101 » Thu Aug 09, 2007 5:42 pm

noname wrote:...
1st Step: Measuring the Meter
Get your propane meter, and detach it from the gun. This step is easier if you strip the meter of everything up to the two ball valves. Open one ball valve, and slowly fill the meter with water. If your meter has elbows and T's coming off of the main pipe, the close the ball valve and turn the meter every now and then, to make sure water fills the T's and other sections of the meter. When the whole thing is full. pour it into a cup or something. (*) Then, get a medicine dropper and fill a graduated cylinder with the water from the meter. Hopefully, your measuring cup/graduated cylinder is graduated at every mL or every 2 mLs. When you have all the water from the cup into the cylinder, write down how many mLs the meter had.

Note: If you use a syringe, starting from (*), you can skip most of the 1st step.


Alternative #1:
If you have a reasonably accurate scale (a kitchen scale should be OK) simply weight the meter. Fill with water and weigh it again. Subtract the numbers. The result is the weight of the water in the meter. Since 1cc of water weighs 1 gram, the volume of the meter in cc is the same as the weight of the water in grams.

Same for the chamber, but since the volume is so much larger you'll need a scale with a larger capacity.

Alternative #2:
Fill you syringe with water, record the volume of water in the syringe. Use the syringe to fill up the meter. When the meter is full record the volume of water in the syringe. Subtract the two readings, that is the volume of the meter.
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