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fueling biohazard

Post questions and info about hybrid (compressed gas with fuel) powered cannons here. This includes discussion about fuels, ratios, ignition systems, build types, safety, and anything else relevant.
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Unread postAuthor: SpudBlaster15 » Tue May 20, 2008 7:08 pm

Ever thought of using an air through meter design? I've never had a misfire that couldn't be attributed to something dumb such as a broken pressure gauge.

"Chamber pressure" meters have too small of an error tolerance at reasonable mixes to be practical. Anything but extremely accurate and expensive pressure gauges will be insufficient. Go with the better existing methods instead.
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Unread postAuthor: DYI » Tue May 20, 2008 7:33 pm

My chamber pressure meter only cost me about $120 total, and it's worked just as well at 2x oxy/MAPP as it did at 10x air/propane and 20x oxy/propane. The fueling gauge is 15 psi and +/- 1% of the full scale, leading to a margin of error of +/- .15psi on the fueling, well below what could cause an unignitable mix. The gauges cost $36 each from McMaster, not unreasonable by even the cheapest standards considering the quality (or lack thereof) of hardware store gauges.
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Unread postAuthor: SpudBlaster15 » Wed May 21, 2008 12:30 am

Only $120. That is more than I (as well as most people) have ever spent on a single launcher. My original air through meter design cost me all of $20 to build from scratch, and is more tolerant to error than a chamber pressure meter.

Keep in mind that there is a massive difference between an unignitable mixture and a mixture that yields sub optimum performance.
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Unread postAuthor: SpudFarm » Wed May 21, 2008 9:24 am

i think everyone overestimates how accurate a gauge needs to be. i am going to try the chamber pressure meter with a cheap 15psi gauge and if it works i am going to laught (?) at DYI for the money he spend.
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Unread postAuthor: psycix » Wed May 21, 2008 9:41 am

spudfarm wrote:i think everyone overestimates how accurate a gauge needs to be. i am going to try the chamber pressure meter with a cheap 15psi gauge and if it works i am going to laught (?) at DYI for the money he spend.

Ofcourse it works, but you may inject 10% too much or too less, while his fuel meter never injects more then 1% off the perfect injection amount.

10% isnt really notable to the human eye, but on ultra advanced guns, you will fight for every m/s you can get, and thus you will want to have accurate metering.

Note:
I just made up the numbers 10% and 1%, they may be somewhat different, but its not about that anyway. I hope you get the point.
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Unread postAuthor: SpudFarm » Wed May 21, 2008 9:44 am

well i will see it over the chrony if one shot is more powerfull than the other one.
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Unread postAuthor: DYI » Wed May 21, 2008 7:26 pm

My original air through meter design cost me all of $20 to build from scratch, and is more tolerant to error than a chamber pressure meter.


I can use my meter for anything from the size of Nova's Brass Bruiser to D_Hall's pipe dream with no modification, and the exact same set of numbers every time, which is more than anything you could hope to achieve with a volumetric meter. The range from my meter for propane would be from 3.2% - 5.2%. You will notice a very small performance difference within that range.
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Unread postAuthor: pat123 » Sat May 24, 2008 2:51 pm

So for any gun you would use th esame pressure of propane right?
1x would be .62
2x would be 1.23 and so on right

are those numbers right i think i did it right.
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Unread postAuthor: SpudFarm » Sat May 24, 2008 3:37 pm

if it is right it should be 1.24
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Unread postAuthor: pat123 » Mon May 26, 2008 11:16 am

1.24 for 2x?

400 posts :P :blob2: :blob3: :blob4: :blob5: :blob6: :blob7: :blob8: :wav:
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Unread postAuthor: DYI » Mon May 26, 2008 4:37 pm

Here's a hybrid fueling table for my system, up to 20x:

It used to be a nice pretty table, but the forum f*cked it up pretty bad, so I wish you luck :roll:

Hybrid Mix Tables

Air / Propane

Nx Propane Air Total
1 0.616psi 14.7psi 0.616psig
2 1.23psi 29.4psi 15.93psig
3 1.85psi 44.1psi 31.25psig
4 2.46psi 58.8psi 46.56psig
5 3.08psi 73.5psi 61.88psig
6 3.69psi 88.2psi 77.19psig
7 4.31psi 102.9psi 92.51psig
8 4.93psi 117.6psi 107.83psig
9 5.54psi 132.3psi 123.14psig
10 6.16psi 147.0psi 138.46psig
11 6.77psi 161.7psi 153.77psig
12 7.39psi 176.4psi 169.09psig
13 8.00psi 191.1psi 184.4psig
14 8.62psi 205.8psi 199.72psig
15 9.24psi 220.5psi 215.04psig
16 9.85psi 235.2psi 230.35psig
17 10.47psi 249.9psi 245.67psig
18 11.08psi 264.6psi 260.98psig
19 11.70psi 279.3psi 276.3psig
20 12.31psi 294.0psi 91.61psig


Oxygen / Propane

Nx Propane Oxygen Total
2 1.23psi 2.94psi 4.17psig
3 1.85psi 5.88psi 7.73psig
4 2.46psi 8.82psi 11.28psig
5 3.08psi 11.76psi 14.84psig
6 3.69psi 14.7psi 18.39psig
7 4.31psi 17.64psi 21.95psig
8 4.93psi 20.58psi 25.51psig
9 5.54psi 23.52psi 29.06psig
10 6.16psi 26.46psi 32.62psig
11 6.78psi 29.4psi 36.12psig
12 7.39psi 32.34psi 39.73psig
13 8.01psi 35.28psi 43.29psig
14 8.62psi 38.22psi 46.84psig
15 9.24psi 41.16psi 50.4psig
16 9.86psi 44.1psi 53.96psig
17 10.42psi 47.04psi 57.46psig
18 11.09psi 49.98psi 61.07psig
19 11.7psi 52.92psi 64.62psig
20 12.32psi 55.86psi 68.18psig
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Unread postAuthor: pat123 » Mon May 26, 2008 5:13 pm

so why do you need so many gauges if a 0 - 15 psi one will work from 1 to 20x?
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Unread postAuthor: Larda » Mon May 26, 2008 7:58 pm

I fixed the fueling table, hope you don't mind. :)
Edit: Something seems to be wrong with the Air / Propane numbers. :?
Code: Select all
Air / Propane

Nx   Propane          Air              Total
1     0.616psi        14.7psi       0.616psig
2      1.23psi         29.4psi       15.93psig
3      1.85psi        4 4.1psi       31.25psig
4      2.46psi         58.8psi       46.56psig
5      3.08psi         73.5psi       61.88psig
6      3.69psi         88.2psi       77.19psig
7      4.31psi       102.9psi       92.51psig
8      4.93psi       117.6psi     107.83psig
9      5.54psi       132.3psi     123.14psig
10    6.16psi       147.0psi     138.46psig
11    6.77psi       161.7psi     153.77psig
12    7.39psi       176.4psi     169.09psig
13    8.00psi       191.1psi       184.4psig
14    8.62psi       205.8psi     199.72psig
15    9.24psi       220.5psi     215.04psig
16    9.85psi       235.2psi     230.35psig
17  10.47psi       249.9psi     245.67psig
18  11.08psi       264.6psi     260.98psig
19  11.70psi       279.3psi       276.3psig
20  12.31psi       294.0psi       91.61psig


Oxygen / Propane

Nx   Propane       Oxygen           Total
2      1.23psi        2.94psi         4.17psig
3      1.85psi        5.88psi         7.73psig
4      2.46psi        8.82psi       11.28psig
5      3.08psi      11.76psi       14.84psig
6      3.69psi        14.7psi       18.39psig
7      4.31psi      17.64psi       21.95psig
8      4.93psi      20.58psi       25.51psig
9      5.54psi      23.52psi       29.06psig
10    6.16psi      26.46psi       32.62psig
11    6.78psi        29.4psi       36.12psig
12    7.39psi      32.34psi       39.73psig
13    8.01psi      35.28psi       43.29psig
14    8.62psi      38.22psi       46.84psig
15    9.24psi      41.16psi         50.4psig
16    9.86psi        44.1psi       53.96psig
17  10.42psi      47.04psi       57.46psig
18  11.09psi      49.98psi       61.07psig
19    11.7psi      52.92psi       64.62psig
20  12.32psi      55.86psi       68.18psig
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Unread postAuthor: pat123 » Mon May 26, 2008 8:05 pm

I think for total he means the total pressure that will be added
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Unread postAuthor: psycix » Tue May 27, 2008 3:48 am

Those "total" numbers seem somewhat screwed up.
Code: Select all
18  11.08psi       264.6psi     260.98psig
19  11.70psi       279.3psi       276.3psig
20  12.31psi       294.0psi       [b]91.61psig[/b]

How come that one is lower?

You should spend more time making your tables DYI .
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