Modular 1/25 Scale A4/V2 model rocket
by mechg, published
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The A4 rocket was developed by German scientists, including Werner Von Braun, during the 1930s and early 1940s. It was adapted for use as a weapon by the Nazis in WWII and renamed the V2. After the war it was used for research and helped pave the way for space programs in many countries.
This model is hollow with 1.2mm thick walls, allowing for two extrusion widths of .6mm. The Slic3r settings for some of the parts use an extrusion width of .63 to ensure good bonding between inner and outer walls. I used the Slic3r engine within Repetier for this project.
The entire rocket is 22" tall and 2.75" in diameter. The mid-section and fin sections are each about 7.6" tall. When printed at 100% scale, the fins fit within a print diameter of 6.2", just fitting within the print volume of an Orion Delta. Quarter-turn bayonet fittings connect most of the parts. The groove in the bayonet fittings includes a locking bump that will help lock the parts when turned 90 degrees. Index markers on the outside of the rocket help with alignment for assembly/disassembly.
Both the nose tip and nose cone base will bayonet-lock to the nose cone. The nose cone base then slip-fits into the mid-section. The jet-vanes assembly friction-fits into the tail of the rocket.
This model is mostly for display purposes, but I have added some features that should make it possible to use it as a flyable model rocket. The nose tip has a compartment for adding weight to position the center of gravity properly for stability. It is the same diameter as U.S. quarter coins, and will hold up to 136 grams in coins. The fin section has supports so a motor tube with 2.6" and 1.9" centering rings can be held in place when the mid-section is attached. Then, you would be able to swap motor mounts for 24mm or 29mm motors. You would need to file/cut four notches in the outer edge of the upper centering ring so it could be inserted past the four bayonet bumps.
The mid-section has an internal lug where a shock cord/static line could be attached. I have posted two versions of the mid-section, one with external 3/16" launch lugs and one version without.
I have included a verson of the nose tip that has the modified Wac Corporal second stage used in Project Bumper at White Sands and Cape Canaveral. It is just shy of 9" tall. I sloped the trailing edge of the fins of the Wac Corporal to make it printable without support. To make it truly scale, you would need to trim them to be perpendicular to the rocket body. http://www.wsmr-history.org/bumperaction1.htm
There is also a version of the mid section that has a simulation of the thin perforated section seen on many V2's. See Mid-ring.stl
If you build one of these to launch, please post photos and video of your rocket in action. I will seriously consider requests for modifications to the design that will help make it flyable.
Historical information and blueprints of the A4/V2 can be found here:
See the Slic3r settings I have uploaded.
Copy the Slic3r settings files into the filament/print/printer folders at
C:Users > yourID > AppData > Roaming > Slic3r
If you are thinking of printing this rocket, the first thing you should do is use the Test Slice file to check your slicer settings. It allows you to quickly iterate through tests of the critical part of the fin section without having to commit to a long print. The entire fin section takes about 6 hours to print at 45mm/second, while the Test Slice only takes maybe 15 minutes to print enough for you to check the quality.
It is important to set the "Only Infill where needed" box to unchecked/OFF, even when infill is set to 0%. Infill extrusion width should be zero, also. This will eliminate a lot of tiny bits of plastic that Slic3r puts in the corners of fillets reducing z-banding on the outside surface caused by unneeded travel moves and retraction.
A 5% Archimedean chord infill setting provides reinforcing ribs in the fins to make them strong at a minimal weight penalty. I tried using the Cura slicer, but it does not have a fill-in pattern that is as good as Archimedean chords is for this purpose. Other patterns might add strength, but they also add weight. This rocket is stubby with small fins, so the lighter you keep the fin section, the less weight you will have to add to the nose for stability.
When you slice each part, you must place it in the orientation shown in the third photo to avoid the need for support material.
If you get the warning that the fin section is not manifold, you can ignore this and go ahead and slice it, at least with Slic3r.
When printed on the Orion Delta using MARS PLA, the fin section depends upon retraction to keep oozing and stringing to a minimum. But the frequent retractions can cause the hot-end to partially clog, resulting in under-extrusion on the cylindrical parts of the fin section while the hot-end is catching up.
I solved this by using the retraction setting that pushes .5mm extra filament after retract. The price you pay for this is some extra material at the ribs within the fins. This is mostly hidden anyway, but you may have to experiment with that value to prevent the ribs from showing through on the outside of the fins, especially if you have a different printer or use a different filament. If a few of the ribs poke through, and you are using PLA, it is usually easy enough to sand the outside of the fin down to make them smooth.
If the bayonet fitting is too tight, you can sand the groove using sandpaper wrapped around a pen, or you can use a small candle to rub some paraffin onto the tight areas. You don't want to force a really tight fitting, because you run the risk of friction-welding the parts together and you won't get them apart again.
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Modular 1/25 Scale A4/V2 model rocket by mechg is licensed under the Creative Commons - Attribution license.
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