-# Test 1 #
+# Test 2 #
Trying again using the same formula as [test 1](test1.html), but different
handling logistics for pouring the grains.
mandrel, for 4 grains total. That left enough to form a test burn rod about
3/8" diameter and in excess of 4" long.
+## Results ##
+
+* Grain 1, 55.42g net
+* Grain 2, 54.57g net
+* Grain 3, 55.90g net
+* Grain 4, 56.33g net
+
## Observations ##
+Went much better than trying to pour one large "grain" to cut later, but we
+still seemed to have lots of bubble inclusions. Either need to use more
+surfactant or keep everything warmer to get better grains. Possibly pour
+on a vibration table?
--- /dev/null
+# Test 3 #
+
+First attempt using Erythritol. Simulation suggested that putting 5
+long grains in a 38/720 case would yield a reasonable motor.
+
+Formula is a simple mix of 65% KNO3 and 35% Erythritol. Both used in
+granular form directly from stock. Because Scott Fintel's site
+indicated near infinite pot life in the multi-cooker, We decided to
+melt enough for 8 grains, or a 520 gram batch size.
+
+Before starting this batch, we cut our two delrin mandrels in half to
+get 4 single grain mandrels.
+
+[Tru-Core](http://www.rocketsaway.com/html/casting_sets.html)
+casting set with four bases each set up with 0.5 inch mandrels. Four
+pieces of casting tube cut to grain length of 2.250 inches.
+
+## Process ##
+
+The multi-cooker was preheated to about 250F with the lid on. Temp was
+increased during melting to 300F indicated.
+
+We poured/scooped one grain at a time, leaving the multi-cooker heating
+and putting the lid back on between grains to keep the propellant at
+temperature. The propellant was really hard to pour into the 38mm grains
+with mandrel already in place. Lots of drips over the side. We reduced
+heat to about 225F while waiting for the first 4 grains to solidify. It
+was easy to pull the coring rods after an hour or so. The caps were a
+bit hard to remove.
+
+Given how much trouble we had pouring into grains with the mandrel already
+in place, we paused to fabricate some new casting bases using the CNC
+router and left-over hickory flooring material. The resulting bases are
+used with aluminum foil to hold a casting tube each. The casting tubes
+are marked with a fill line on the inside ahead of time, then the mandrels
+are pushed into place after the propellant is poured, penetrating the foil
+bottom. A cap is then placed over the mandrel and casting tube to keep the
+mandrel centered. This worked a lot better! We called this test 3B.
+
+## Results ##
+
+* Test 3, Grain 1, 61.78g net
+* Test 3, Grain 2, 61.54g net
+* Test 3, Grain 3, 61.84g net
+* Test 3, Grain 4, 61.89g net
+
+* Test 3B, Grain 5, 60.36g net
+* Test 3B, Grain 6, 61.23g net
+* Test 3B, Grain 7, 60.40g net
+* Test 3B, Grain 8, 60.79g net
+
+## Observations ##
+
+The new casting bases worked very well, but we did notice a problem with
+the caps. When the propellant is carefully controlled to completely fill
+a grain, it touches the bottom side of the flat caps when still hot and
+wet. When it cools and contracts, this leaves a thin skin above a ring
+of mostly air. Cutting the "skin" off the top and scraping a bit to leave
+each grain with a slightly concave top so there'd be burn space between
+grains left us with remarkably consistent looking and weighing grains. In
+future, we might want to either fill the casting tubes slightly less, or
+perhaps switch to caps with an explicit air space above the poured
+propellant in hopes that all bubbles would "surface" leaving the propellant
+solid and with a bit of air gap at the top of each grain's casting tube.
+
--- /dev/null
+# Test 3 #
+
+More KNER grains. Since we had 8 plausible grains from test 3 and
+want to burn 5 at a time, we decided to cast another 4 so we'd have
+enough for two motors plus a couple single-grain open air burn tests.
+
+Formula is a simple mix of 65% KNO3 and 35% Erythritol. Both used in
+granular form directly from stock. A 275 gram batch for 4 2.25"
+38mm grains.
+
+Used our new casting bases, now with the mandrel holes drilled all the
+way through.
+
+## Process ##
+
+Same as Test 3B.
+
+## Results ##
+
+* Test 4, Grain 1, 61.50g net
+* Test 4, Grain 2, 62.38g net
+* Test 4, Grain 3, 60.18g net
+* Test 4, Grain 4, excessive visible inclusions, set aside
+
+## Observations ##
+
+Not surprisingly, results were essentially identical to test 3B.
+
+Seems pretty clear that the post-casting process of having to cut off
+the "skin" at the top of the grain and impart a concave shape is
+losing .. means we'll never get uniform grain masses. REally need
+to figure out how to do this better.
+
+The last grain was "poured" by spooning in material that seemed
+to be clumping a bit, and we probably didn't tap it down enough.
--- /dev/null
+# Test 5 #
+
+Trying again using KNSO with our new casting bases. We also have a real
+eye-dropper now for measuring the surfactant. 4 38mm grains of
+1.875" length, using formula of
+
+* 65% KNO3
+* 35% Sorbitol
+* 1% red iron oxide
+* 3 drops Polystep-B1
+
+## Process ##
+
+The multi-cooker was preheated to about 250F with the lid on. Temp was
+increased during melting to 275F indicated.
+
+Individual casting tubes with fill marks, coring rod inserted after pour,
+cap installed and grain tapped down.
+
+## Results ##
+
+* Grain 1, 51.56g net
+* Grain 2, 52.80g net
+* Grain 3, 52.30g net
+* Grain 4, 51.23g net
+
+## Observations ##
+
+Pour went really smoothly. One grain looked "perfect" with the propellant
+settled evenly and a couple mm of open gap at the top of the casting
+tube. We think this one may have been slightly under-filled compared to
+the others, all of which had some evidence of propellant sticking to the
+cap and leaving an uneven top surface. This resulted in some quick trim
+work with a knife, ergo final grain masses not matching all that well.
+
+## Flight Test ##
+
+These four grains were assembled in an AT 38/480 case with a random AT
+delay grain from the pile of left-overs, and flown in Robert's Madcow
+Little John at Tripoli Colorado Spring Fling 2015. We used a Slim Gem
+igniter from Quickburst. Great flight! The motor seemed to come up to
+pressure quickly, and burned brilliantly.
+
+The original simulator data:
+<pre>
+Propellant : propellants/knsb.xml
+Nozzle diameter : 0.739 cm (0.291") (19/64")
+Number of grains : 4
+L/D ratio : 5.550
+Port-to-throat ratio : 2.952
+Mass Flux : 1.374 lbs/inch^2
+Mach number : 0.697
+Propellant length : 18.440 cm (7.260")
+Web Thickness (max) : 1.026 cm (0.404")
+Burn rate : 0.773 cm/s (0.304"/s) (a=7.852mm/s; n=-0.013)
+
+Total propellant weight: 216.00 g (7.619 oz/0.476 lbs)
+Average grain weight : 54.00 g (1.905 oz)
+Theoretical density : 1.841 g/cm3 (0.067 lb/in3)
+Actual density : 1.582 g/cm3 (0.057 lb/in3)
+Density ratio : 85.953%
+Specific impulse (Isp) : 106.342 s (estimated)
+Initial Thrust : 169.37 N (38.08 lbs)
+Peak Thrust : 182.21 N (40.96 lbs) at 34.00% (0.45 s)
+
+Kn Ini : 309.48 (488.04 psi)
+Kn Max : 330.39 (520.59 psi)
+Kn Fin : 248.87 (393.56 psi)
+Kn Avg : 309.70 (488.40 psi)
+
+Total Impulse : 225.104 Ns (40.69% H)
+Burn Duration : 1.328 s
+Average Thrust : 169.555 N
+
+Motor : H170
+</pre>
projects / web / gag.com / commitdiff