Contents 1 PVC Motors 1.1 Propellant 1.2 PVC0 1.2.1 PVC0-1 1.2.2 PVC0-2 1.2.2.1 Video 1.3 PVC1 1.3.1 PVC1-1 1.3.1.1 Video 1.4 PVC2 1.4.1 PVC2-1 1.4.1.1 Video 1.5 PVC3 1.5.1 PVC3-1 1.6 PVC4 1.6.1 PVC4-1 1.7 PVC5 1.7.1 PVC5-1 1.8 PVC6 1.8.1 PVC6-1 1.9 PVC7 1.9.1 PVC7-1 1.10 PVC8 1.10.1 PVC8-1,2,3 1.10.2 Video 1.10.3 PVC8-4 1.11 PVC9 1.11.1 Video 2 Nozzles 2.1 Gallery of designs 2.1.1 Water Putty 2.1.2 Ceramic

PVC Motors

Propellant

I designed these motors using Richard Nakka's SRM.xls spreadsheet. For PVC0 and PVC1 I accidently chose KNDX, the dextrose based propellant, rather than KNSU, the sucros (table sugar) based propellant. I've updated the design sections with the new calculations, and learned that my initial tests were a lot less conservative, pressure wise, than I had intended.

As I am using Jimmy Yawn's skillet cooking technique, and have not yet characterized the burn rate myself, I static tested these 'conservative' motors behind a concrete block barrier.

PVC0

Motor Specification

Length	110mm
Inner diameter	25mm
Class	F - 76 N
Total Impulse	66 N-sec
Max Pressure	377 psi
Throat diameter	5.5mm - 7.98mm

PVC0-1

PVC0-1 static tested May 13, 2007 at Potter's. Design puts this at an F-56 with 64 N-sec total impulse.

PVC0-2

PVC0-1 flown May 13, 2007 as a bottle rocket at Potter's. The motor landed in the pond, which was nice, as the burning was stopped abruptly, showing that post-burn the inhibitor is in very good condition. Design puts this at an F-56 with 64 N-sec total impulse.

Video

PVC1

Motor Specification

Length	137mm
Inner diameter	25mm
Class	G - 181 N
Total Impulse	111 N-sec
Max Pressure	871 psi
Throat diameter	5.8mm

PVC1-1

Static tested. The motor became quite warm after being fired, and while initially the PVC casing showed no deformation with time it became hotter and softer outside until it became quite flexible. PVC, apparently, can withstand a lot of heat and pressure briefly, but as the heat soaks through the pipe it becomes softer.

The nozzle, one of the smaller ones, broke at the throat. I dont know if it was the heat or the pressure.

Video

PVC2

This motor was just a little fun with one of my smaller nozzles and a single 25mm OD, 8mm ID 40mm Length grain I had left over.

PVC2-1

Unfortunately I lost it. I decided to just tape it to a fiberglass driveway marker and shoot it off like a bottle rocket. It had trouble building pressure and took off pretty slow.... It shot off towards the old peoples' home and I couldn't find it. It is probably just stuck in a tree somewhere.

Video

PVC3

Motor Specification

Length	150mm
Inner diameter	25mm
Class	G - 122 N
Total Impulse	82 N-sec
Max Pressure	696 psi
Throat diameter	5.13mm

PVC3 is designed to be a Reloadable PVC Motor. The nozzle is fitted into a plug that unscrews. It uses one of the smaller first series ceramic nozzles, #5.

PVC3-1

PVC4

Motor Specification

Length	145mm
Inner diameter	25mm
Class	G - 203 N
Total Impulse	124 N-sec
Max Pressure	874 psi
Throat diameter	5.46mm

PVC4 is designed to be a Reloadable PVC Motor. The nozzle, one of the larger first series ceramic nozzles, is fitted permanently in the aft end, with 2 o-rings and some RTV sealant.

The fore end of the motor has a threaded plug.

PVC4-1

PVC5

Motor Specification

Length	140mm
Inner diameter	25mm
Class	G - 131 N
Total Impulse	84 N-sec
Max Pressure	865 psi
Throat diameter	4.75 mm

PVC5-1

Uses one of the larger ceramic nozzles but at a lower pressure.

Static tested at Matt's house. Motor ran fine, looked good. Disassembly revealed basically intact but burnt grain liners. Nozzle held together, but shows some cracks. Pictures to follow.

PVC6

Motor Specification

Length	150mm
Inner diameter	25mm
Class	G - 212 N
Total Impulse	127 N-sec
Max Pressure	1012 psi
Throat diameter	5.5 mm

PVC6-1

Uses one of the smaller ceramic nozzles, but it is completely epoxied into the reducing coupling in which it was molded. Maybe this will either prevent it from breaking or at least it may retain the peices.

Static tested at Matt's house 9/1/07. Nozzle broke exactly like all other ceramic nozzles of same design. I was assuming this would be the case, but I had one last one to try and figured I would make sure.

PVC7

Motor Specification

Length	160mm
Inner diameter	25mm
Class	G - 166 N
Total Impulse	119 N-sec
Max Pressure	514 psi
Throat diameter	7 mm

PVC7-1

This motor uses a new nozzle made of a brass plumbing fitting that I am trying out. It was difficult to get the hole for the brass fitting centered and straight on the domed 1" pvc end-cap, so this motor is marked for static tests only as the thrust will not be straight. I will track down flat end-caps if the motor tests well.

Static tested at Matt's house 9/1/07. Burn looked good, a little different because of the larger nozzle. The grain liner was completely ejected towards the end of the burn. I will have to consider something to mitigate this if I increase the pressure, as I have seen others' motors fail from the pressure spike.

The brass nozzle came through like a champ and cleaned up nicely. The PVC around the nozzle began to melt a bit a minute after firing. As usual it takes time for the heat to soak through the plastic.

PVC8

PVC8-1,2,3

Three static tests with my Test Stand. Overall performance was about 60% of theoretical.

From discussion on SugPro I think that I need a larger ignition charge to get the motor up to pressure faster and not waste propellant on startup. Calculations indicate about 1g BP should do the trick.

Video

PVC8-4

This will be a static test with a ~1g BP ignition charge, otherwise identical to 1,2,3.

PVC9

This motor is a G class motor made with KNSU. I tried case bonding the first three with mixed success. The problem seems to be that KNSU made via recrystallization or casting is not flexible enough and cracks when subjected to the uneven pressure.

Of the first three motors two worked fine and one ejected the nozzle immediately on ignition. The nozzle design of the third was slightly different, which is unfortunate from a scientific perspective, because the quality of the finished fuel was slightly different too. PVC9-1 and 2 were both recrystallized propellant taken right from the skillet and molded into the grain. PVC9-3, which CATOed, was mixed and kneaded as normal with skillet fuel before it was molded into the grain. 1 and 2 took much longer to cure up and dry and were softer and more flexible.

I do not know if it was the weaker nozzle design or the difference in fuel processing that caused the difference. I will look into this more under Recrystallized Sugar.

Video

Nozzles

I have tried nozzles both made of Water Putty and Ceramic, but I am still looking for the right thing. I am not quite ready to spend the money on the tools to make steel nozzles.

Gallery of designs

Water Putty

Durham's water putty is strong, but erodes.

Ceramic

I have used a cone 5 earthenware clay (Miller #10T) suggested to me by my local ceramicist after discussing what I was making. I wanted a smooth surface, high strength, high resistance to thermal shock. He had used this clay for raku before.

The nozzles show zero erosion, but have been breaking. The PVC shrank a little when heated, and I had trouble getting the nozzle pictured below out, and may have broken it worse. The scorch mark on 2 of the crack surfaces shows that it had at least the one fracture during firing, not extraction.