Burnt Latke
references and information



Fuel Tool Live still has a few rough edges. We are working on this to bring FT Live up to the standards of the Excel version.
Known bugs: The +/- buttons wreak havoc on the rounding functions in some display fields. To remedy this, Use the 'tab' key to cycle through the fields after calculation, this will help you read long numbers. The 'fuel mix' input also freaks out but can be entered by hand if needed.
The 'enter' and 'return' keys will not submit the form. Either click calculate, click a spinner or use the pulldown to update the calculator.



OnLine Measurement Conversions http://www.onlineconversion.com



Calculate Your Atmospheric Pressure (PSIA) http://www.turblex.com/altitude/index.cfm



Propane and MAPP - MSDS http://www.bernzomatic.com/littr.htm



Plumbing pipe is notorious for confusing naming conventions. A 3/8" plumbing nipple from Schlomo Depot actually has an inside diameter of almost half an inch. Fuel Tool uses the figures shown in the yellow column.

plumbing pipe and fitting conversions
Type ID decimal
1/8" pipe 1/4" 0.25
1/4" pipe 23.3/64" 0.364
3/8" pipe 15/32" 0.46875
1/2" pipe 5/8" 0.622
3/4" pipe 13/16" 0.8125


The lower and upper flammable limits of propane and MAPP gas are shown to the right.

Lower and upper flammable limits with air
Propane 2.10% 9.50%
MAPP 3.0% 11.0%

Fuel Tool was used to calculate the proper meter volume for our L1 launcher. Originally the L1 had a standard 3/8"x6" meter pipe and no regulator. This worked perfectly for the chamber's 2600cc volume and average propane pressure of 90 PSI. During testing , a problem with this setup became evident. The propane was having a hard time keeping 90 PSI because after a few shots, the bottle would start getting cold. This required a larger meter that could run at lower, controllable pressures, and a regulator of course.
The large meters were fitted with a pressure gauge and it was found that it takes a couple seconds for the pressure to equalize between the supply and meter pipe. These funky shaped meters were difficult to measure using formulas so they were measured with water. Fluid volume measurement provides a high degree of accuracy as it takes into consideration all the area between valves, fittings, etc. The gauge was removed and water added in a way that vented any air pockets.
The pressure regulator proved to be the key element. A mid range base pressure of 37 PSI was established with the choice of meter volume. This combination gives a calculated 4% propane to air ratio by volume. The regulator is used to accurately adjust the mix up or down. When using Fuel Tool, we kept an eye on the required 41ml meter volume then adjusted the pressure until the desired 4% mix was reached. It took about 10 seconds and let us preflight the designs.

BurntLatke L1 - Propane Experiments
10/27/02   design - Failed
Fuel Propane  
Chamber Size 2600cc  
Meter Pipe mixed  
Meter type 3 position variable, regulator  
PSIA 14.7  
Target Fuel Mix 0.04 Req. pressure
Meter Vol. 1 65.66 ml 23 PSI
Meter Vol. 1 90.66 ml 17 PSI
Meter Vol. 1 93.66 ml 16 PSI
Conclusion: This meter is too big for a 2600cc chamber. 3 position config. offers no benefits, requires regulator. Required PSI seems kinda' low. If your meter looks like this, you've done something wrong.

BurntLatke L1 - Propane Experiments
10/27/02   design - Failed
Fuel Propane  
Chamber Size 2600cc  
Meter Pipe 1/2" > 3/8 valves  
Meter type fixed w/gauge, regulator  
PSIA 14.7  
Target Fuel Mix 0.04 Req. pressure
Meter Vol. 1 39 ml 39 PSI
Conclusion: This meter seems to be the perfect size. True regulation dial and gauge replaces 3 pos. meter. Stepless adjustments. Required PSI at acceptable level. Too big to fit gun : (

BurntLatke L1 - Propane Experiments
10/27/02   design - Passed
Fuel Propane  
Chamber Size 2600cc  
Meter Pipe 1/2" > 3/8 valves  
Meter type fixed w/gauge, regulator  
PSIA 14.7  
Target Fuel Mix 0.04 Req. pressure
Meter Vol. 1 41 ml 37 PSI
Conclusion: Switched and replaced fittings to get meter to fit into launcher guide slot. Looks wicked. After testing, the meter gets dipped in blue rubber stuff to finish. The meter gauge reads 7 lbs. Higher.?.Bad gauge??

Tests Results. 2600 ml Chamber, 41ml meter. 10/28/02
PSI mix % comments
23 2.5 no ignition
25 2.7 weak, no flame
27 2.9 stronger, no flame
30 3.2 sharp, no flame
33 3.6 sharp, slight red flame
35 3.8 strong, slight orange flame
37 4 strong, orange with blue flame
40 4.3 softer, blue with orange flame
43 4.6 weaker, blue flame
45 4.9 very weak, blue flame
47 5.1 very weak, large blue flame
50 5.4 very weak, blue flame, smoke in chamber
53 5.7 very weak, giant blue flame, smoke in chamber
55 5.9 very weak, giant blue flame, smoke in chamber
65 7 no ignition, smoke in chamber
70 7.6 no ignition, smoke in chamber

Comments: A wadding made from a cotton t-shirt was used for these tests. The pressure gauges were switched and it was determined that one or both of them are off. Tech rep from manufacturer says, " those things all read different". Gauges were compared against a calibrated gauge which gave a reading right in the middle of my two gauges. Both dials will be opened and recalibrated. It's interesting to note the LFL and UFL are different from the quoted limits of 2.1-9.5%. This large meter/low pressure thing looks promising. Power and distance tests next.

UPDATE 11/3: Just finished rifled barrel tests at 50' and 150'. 37 PSI kicks ass, strong every shot. It was also easy to maintain a constant pressure, even with a half empty lp bottle. 37 PSI gives a calculated 4% propane on a 41ml meter. Of note, during the recent tests at 4% mix, the was no noticable muzzle flame at all, as opposed to the tests on the chart above.?. No flame may be a result of using potatoes instead of t-shirt wadding.