Cheap-and-easy model rocket by tmartin

Hey! This thing is still a Work in Progress. Files, instructions, and other stuff might change!

Cheap-and-easy model rocket by tmartin Jul 3, 2011

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Description

Just in time for the Fourth of July! This is intended to be a semi-disposable dirt-cheap model rocket that can be produced in under an hour on a makerbot in only one print. It uses standard inexpensive estes C-class motors since these are not much more expensive than an A motor and much more powerful. It has been flown three times and has performed well each time. It does not have a parachute or any other recovery mechanism and on the occasions I've flown it I have yet to retrieve one since it travels extremely high and seems to disintegrate when the ejection charge goes off. I flew it mainly at night for the spark trail effects and couldn't find it afterwords, but judging by the impressive visible trail it flew very far and straight.

Disclaimer: This rocket has no method of retarding it's descent and presents a potential hazard to anyone in the area, fly only in uninhabited areas and at your own risk.

Design Features: The six fins towards the back give this rocket good stability despite its short height by packing a large surface area behind the center of gravity (provided by the weight of the motor). In order to keep the height within the limits of a standard makerbot I felt the extra fins were a good idea, and besides they look cool. The ring fin provides some extra surface area but mainly aids in durability to keep the thin fins from snapping off. The motor sits partway up the rocket body to bring the center of gravity as far forward as possible for stability reasons. The printed part tapers away from the rocket motor and seems to have enough clearance from the hot gasses, but nevertheless may present some fire hazard although this hasn't been observed in any tests yet.

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License

Cheap-and-easy model rocket by tmartin is licensed under the GNU - GPL license.

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Instructions

1) Print out the rocket body using a makerbot with ABS on standard default extrusion parameters. I used the Acetone-scrap ABS film trick (as detailed here: thingiverse.com/thing:7460) to avoid the need for a raft.
NOTE: this thing prints much more nicely with the Ducted cooling fan by Iwo thingiverse.com/thing:5756 If this is not available, the built in side-fan does acceptably, but some cooling is recommended because without it the main tube will be bumpy and uneven.

2) Trim up any bumps and brush the fins and outer surface with some acetone, this helps seal up any gaps in the fins and boosts strength tremendously.

3) Insert an Estes "C" engine in the tube as far as it will go. The end edge of the motor should be roughly flush with the beginning of the outward taper. The tube is deliberately slightly oversize for ease of loading and ejection. Wrap a layer or two of tape at a couple of points of the motor until it is just held in by friction. If you're lazy glue or acetone-abs paste works too, but it is definitely a one-shot flight then.

4) Connect the ignition wires and launch in a safe area. I recommend using a disposable cup turned upside-down with a hole cut in the bottom as a launch platform. Launch lugs are not needed, it will fly straight so long as the initial launch site is level.

Cheap-and-easy model rocket by tmartin is licensed under the GNU - GPL license.

By downloading this thing, you agree to abide by the license: GNU - GPL

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C-rocket.stl

Last updated: 11-07-03

Downloads: 565

Size: 88kb

565 88kb

Comments

anixie on Dec 21, 2013 said:

looks good indeed, but where is the launch lug ?

theMOIer on Feb 19, 2013 said:

scald down to 50% and it works as a pencil topper (more like a half-pencil cover :) )

r3becca on Jul 4, 2011 said:

If you are attempting to recover the rocket and night launching then perhaps consider glow in the dark filament:

http://store.makerbot.com/glow...

diabeetusman on Aug 8, 2011 said:

One problem with that: I (personally) wouldn't go looking to recover a rocket at night

hamjudo on Jul 3, 2011 said:

Since it blows apart anyway, why not have it become a streamer or a helicopter?

Putting the rocket engine at the base of the rocket doesn't hurt stability. (Very counter intuitive, I don't understand the physics.) That leaves more space at the nose for fancy stuff.

If there is a spiral of very thin material up to a relatively robust nose cap, my (untested) theory, is that th
e recovery charge would blow the nose cap off and the thrust would unwind the spiral. This would put a spin on the whole thing. And it would spiral down, relatively gracefully.

If the rocket motor snapped into its section, or was glued there, the whole thing might be recoverable as a unit. Once re
covered, it could be disposed of properly, since it could only fly once.

tmartin on Jul 3, 2011 said:

Those are all good ideas, my ultimate hope is to expand the nose section and place some sort of payload bay there so you can put a firecracker or parachute, or maybe a printed black powder charge in there so it explodes properly like a firework or becomes more recoverable. My hope with this one being loosely fit is that the charge would blow the motor out the back and the change in balance would cause the body to de-stabilize and tumble to the ground since the bodies aren't too stable without the motor. For all I know that may be happening, I need more testing during the day when I can spot it better. If it does turn out to disintegrate I may start using PVA so that it biodegrades. Feel free to post any derivatives, I'll upload the solidworks part so people can modify it once I can locate it.