2.375" Nozzle Update

I finished the back cut on the shoulder area. In an attempt to get really clean flow into the throat area, the convergent starts at a steep 45 degrees that leads into a shallower 22.5 degree section leading into the throat. This can be clearly seen on the back of the convergent side in the photo. I also chose a shallower divergence than the "standard" 12 degrees. A couple more hours and I should have a finished nozzle.

2.375" Motor, Nozzle Progress

I'm making pretty good progress on the nozzle. The black line in the top few photos is about where it'll get parted off. I still need to cut the 0-ring and insulation grooves, do the back cut behind the shoulder, and index the retaining screw locations. Then I'll part it off, flip it over, and finish the convergent side.

2.375" Motor, Starting Nozzle

I managed to start the nozzle. I'm starting with 2.75" diameter stock which is less than ideal; I would prefer to start with some thing closer to the OD of the finished part, but it's what I have on hand. It shouldn't be too bad though since I added a new, larger motor to the lathe a while back. I've only done some light turning with the new motor, so I can't wait to find out how aggressive a cut it'll handle. The starting piece is about an inch and a half longer than the finished part will be and weighs nearly nine pounds. I would guess that the finished nozzle will come in at around 1/2 lb. The general plan is to machine the divergent section, throat, shoulder, and index the retaining screw locations. Then part off the nozzle, flip it, and finish the convergent side

2.375" Motor Casing Completed

I finished the casing for the motor. I realized that I made a mistake in the CAD drawing that I posted earlier today. There should be six retaining screws for both the nozzle and the bulkhead versus twelve. I also made a slight change to the length of the casing, opting to make it 3/4"shorter which allowed me to true the ends on the lathe. I hadn't planned on being able to do that but by turning the tool post backwards I was able to extend it's capacity by just enough. Since just a very light cut was needed this worked fine. The design is pretty generous in the propellant segment spacing, so I'll make up the deficit by reducing the spacing slightly.

The bottom photo shows the new extended casing next to the older motor design. The new casing still has it's rust preventive zinc coating. The coating doesn't add any structural strength and has a fairly low melting point so I'll remove it with a quick dip in some muriatic acid.

2.375" Motor, Completed CAD (nearly)

I'll need a few more dimensions, but I'm pretty much ready to start. I'll start with the casing , then I'll be able to determine exactly what the OD of the nozzle and bulkhead needs to be.

2.375" Rocket Motor Design, Nozzle

I haven't done a lot of additional work on the design. I'm not sure that I'll remove the material indicated in red in the first image, back cuts like that can prove to be pretty time consuming. I should be able to shorten the shoulder a bit once I add the bolts into the design; that would make it a bit easier. I'm not too concerned about making as lightweight a motor as possible, but the aft end of the motor is a good place to remove weight from since additional weight in this area pulls the center of gravity aft. This isn't necessarily what you want since the likely result is larger fins to compensate. I'll wait and see how it goes while I'm machining it; I can always revisit the nozzle at a later date.

Cadillac Launch

I don't think of myself as someone who is easily influenced, particularly by advertising, but the other day I saw a car commercial that totally convinced me that I wanted to have this car. I've been considering getting a new car, but a Cadillac. Never! But it seems as if GM geared this commercial directly at me (or at least anyone interested in rockets, aviation, etc). After seeing it once, I decided I really wanted this car. That has to be good advertising!

Here is the commercial: