Home  Guides Gearbox Science I: Predicting Rate of Fire for Gearsets
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Gearbox Science I: Predicting Rate of Fire for Gearsets |
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Written by Jay
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Monday, 07 February 2005 |
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Page 9 of 10 Experimental Results
Do these theories and formulas actually work? Do the predicted rate of fire numbers bear any resemblance to actual measured results? To verify the formulas derived above, our AEG test platform was tested using 4 available Prometheus gearsets.
Test Platform Configuration:
| AEG: | Tokyo Marui G3 SG1 | | Main Spring: | Systema M120 | | Spring Guide: | Systema spring guide with bearing | | Piston: | Systema aluminum | | Piston Head: | Systema polycarbonate with bearing | | Bushings: | Systema metal bushings | | Mechbox: | Stock Tokyo Marui V2 | | Cylinder Head: | Stock Tokyo Marui | | Cylinder: | Stock Tokyo Marui type 0 | | Motor: | Tokyo Marui EG1000 | | Battery | Sanyo Cadnica KR-1800SCE 7 cell 8.4v |
The Prometheus gearsets exhibited the following ratios:
| Prometheus Standard | 18.72 | | Prometheus Double Torque | 23.79 | | Prometheus Triple Torque | 26.43 | | Prometheus High Speed | 16.46 |
With the standard ratio gearset installed in the test platform, the audio-analysis measurement yielded a rate of fire of 1018.87 RPM. Using the formula for mechbox torque load:
mechbox torque load = (- (1018.87*1407*18.72)/27552 + 1407)*18.72 = 8105.48
Now that the mechbox torque load is known, the expected rate of fire can be calculated for the rest of the gear ratios:
Double Torque ROF = ((27552/1407)*(1407-(8105.48/23.79)))/23.79 = 877.69
Triple Torque ROF = ((27552/1407)*(1407-(8105.48/26.43)))/26.43 = 815.23
High Speed ROF = ((27552/1407)*(1407-(8105.48/16.46)))/16.46 = 1088.04
The calculated expected rates of fire show a significant drop when going to a double or triple torque gearset, and a slight rate of fire gain with the high speed gearset. Let's see how these values correlate with actual experimental values:
| Gearset | Measured Battery Voltage | Predicted Rate of Fire | Measured Rate of Fire | Percentage Difference | | Standard | 9.97 | - | 1018.87 | | | Double Torque | 9.98 | 877.69 | 866.77 | 1.3 | | Triple Torque | 9.98 | 815.23 | 808.38 | 0.8 | | High Speed | 9.99 | 1088.04 | 1105.72 | 1.6 |
The results show a less than 2% error between the predicted results and the actual experimental results, supporting the validity of the equations. The error may be reduced further if the difference between measured battery voltage and rated battery voltage for the motor speed/torque curve are taken into consideration, but that discussion will be reserved for the upcoming AEG Motor Science article.
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