Printing an Ogive Nosecone for Model Rockets


I took my own advice and bought the Flashforge Creator X 3D printer. It has two MK8 print heads, for printing two colors, and an aluminum plate. So far I like it. I’m using ABS plastic and so far have had no jams. I’ve replaces the Kapton(tm) build plate covering once so far. I beat it up after seven or eight builds. The initial instructions suggest a plate temperature of 90C. I’ve had better luck with parts sticking to the build plate at 110C.

 

My initial interest in 3D printing is to make model rocket nose cones with a capability of carrying small payloads. Getting a 3-D printer has given me a opportunity to develop some ideas. I’d like to have a nosecone that can carry small circuit board payload. The version described here does not have that capability, but it is a step toward that goal. It includes a shell of a nosecone. I’ve included some internal bulkheads, though I’m not sure they are needed. The nosecone needs to survive the launch pressures. The bulkheads will need to be reduced, but could be thickened, to carry a payload.

Printing a nose cone

Printing a nose cone

The ogive shape is based on a circle. A 2-D arc of a circle is spun in three dimensions to form a curved cone. This example constructs a ‘near’ ogive by a series of cords. The total arc for the ogive is calculated from the arctangent of the height-to-radius ratio, 180° – 2*atan(h/r). This gives a smooth transition to the rocket body. Once the total arc is known, it can be evenly divided into smaller arcs, or cords, to give a relatively smooth curve.  This nose cone looks pretty good with ten cords or facets.

 

The nosecones are developed using the OpenSCAD 3D design software. A scalable program is written on the interpreted scad language, including adjustments to nosecone length, rocket body tube inside and outside diameter.

 

Finished nose cone still in printer

Finished printing Nose cone

Variable Names, measurements in mm:

ratio: height-to-diameter ratio,

r1a: outside radius of body tube [r-one-a],

r2a: inside radius of body tube,

hcy: height of plug (insert into body tube,

dz2: plug lip height (insert into nosecone),

dx0: shell thickness,

dx1: radius reduction, to make plug fit inside nosecone,

nof: number of ogive facets, number of conical sections to use to build ogive.

 

I’m including the scad code I’m using. I haven’t yet figured out how to provide straight text as a attachment under WordPress, so I have encapsulated it in a MSWord document.

BT-50 Nose cone assembled

BT-50 Nose cone assembled

 

The model should be sanded, and painted with acetone, to smooth it out.  The plug should be glued, or set with acetone, into the nose cone.   & No, I haven’t flown it yet. RSN:)

NoseOgive2_scad

Update:2016-06-14: Updated code to improve fits, now that I located a BT-50 Body tube.

Thingiverse: http://www.thingiverse.com/thing:345464

Update 2016-06-15:  The nose cone weighs 15 gr, [w/ waste 20 gr]?  The ABS runs $30 t0 $40/ kg.  So the cost is about $.70 /pc excluding experimentation.  But … The pieces can be made to specification, rather than as-close-as-possible off the shelf. Also, It takes 90-120 min to print.

(c) David B. Snyder, 2014

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