Batch 2017-batch-04
4 grains of 29mm intended to be a reloads for the second-longest GMA 29mm snap-ring case, and 6 grains of 54mm intended to be 2 3-grain reloads, all in one sorbitol melt.
29mm grain length 45mm with 1mm spacing per grain, so we'll make the casting tubes 46mm long. Delrin coring rods of 5/16" diameter.
54mm grain length 76mm with 2mm spacing per grain, so we'll make the casting tubes 78mm long. Delrin coring rods of 1/2" diameter.
Formula for a batch size of 1kg:
- 65% KNO3, 650g, taken from the big bucket
- 35% Sorbitol, 350g
- 1% RIO, 10.0g
- PolyStep B1, 15 drops
With left-overs from batch-01, this was enough for all but two of the 29mm grains. We added enough materials for another 100g and were able to finish up with a bit left over.
Presto Multicooker operated at 275F indicated.
These grains were cast on 1 June 2017.
Simulation says:
| 29mm 4-grain Sorbitol #14 | |||||
|---|---|---|---|---|---|
| Rating: | 99% G-180 | Max Pressure: | 6.47 MPa (939 psi) | ||
| Total Impulse: | 159 Ns | Specific Impulse: | 133 s | ||
| Max Thrust: | 228 N | Volume Loading: | 69% | ||
| Average Thrust: | 180 N | Fuel Mass: | 122 g | ||
Results
Average 29mm casting tube mass 1.25g.
29mm grains
- Grain 1, 29.3g gross, 28.05g net
- Grain 2, 29.1g gross, 27.85g net
- Grain 3, 28.9g gross, 27.65g net
- Grain 4, 28.5g gross, 27.25g net
Total of 110.8g propellant, vs 122g simulated.
With a 7.40" liner, 14/64" nozzle throat, buna-n o-rings, simulation says this reload will be a 99% G-180, 159 Ns, with about an 0.8 sec burn.
54mm grains
- Grain 5, 184.6g gross, ?g net
- Grain 6, 183.3g gross, ?g net
- Grain 7, 186.2g gross, ?g net
- Grain 8, 182.6g gross, ?g net (canted - casting tube tilted at pour time)
- Grain 9, 184.0g gross, ?g net
- Grain 10, 180.5g gross, ?g net