Since many of these components are sold in multi-packs, putting together a full set can get a little expensive. Buying everything on AliExpress costs around $45, while on Amazon it's closer to $90 — and depending on where you are and how much shipping runs, it can end up higher.
That said, many of the parts used here are shared across my other projects. So if you're planning to build any of my other designs — or you've already built them from the DIY guides — chances are you'll already have a lot of these on hand, like the buttons, bearings, springs and screws. That way you can save quite a bit.
But if this is your first build and you don't have much soldering experience, it may be worth getting my ready-made kit instead. It will likely work out both cheaper and easier to put together.
| Component | Qty | Specification | Where to Buy |
|---|---|---|---|
| Screw set | 1 set | M2.3 / M2.6 / M3 assortment, stainless steel | AliExpress · Amazon |
| Bearing screw | 2 pcs | M4x20 (It's better to buy two separately at a local hardware store, as ordering them is usually much more expensive) | AliExpress · Amazon |
| Trigger screw | 1 pcs | M3x16mm It’s often available as a spare part for printers (check before buying—you may already have them). It’s used to secure the heat break as well as pulleys on shafts. | |
| Hexagon Socket Allen screw | 2 pcs | M4x5mm It’s often available as a spare part for printers (check before buying—you may already have them). It’s used to secure the heat break as well as pulleys on shafts. | |
| Countersunk screws | 2 pcs | M3 × 5mm, flat head, stainless | AliExpress · Amazon |
| Nut for bearing screw | 2 pcs | M4 (It's better to buy two separately at a local hardware store, as ordering them is usually much more expensive) | |
| Bearing | 4 pcs | 4 × 12 × 4 mm 604ZZ | |
| Spring | 2 pc | 0.5mm wire, 30mm length, 5mm OD | |
| Battery compartment | 1 pcs | 8 AA Battery Holder 12v with wires | |
| Motor | 1 pc | JGA25-370 12V 400rpm (A deviation of ±100 RPM is acceptable) | |
| On/Off switch | 1 pcs | MTS -102 terminal 3 pin | |
| Display | 1 pc | 0.28 Inch DC LED Digital Voltmeter, 2 wires (For digits any color you want) | |
| Trigger button | 1 pcs | Micro Limit Switch NO-NC (without liver or simple remove it) | |
| 2 color wire | 1 pc | minimum 1 meter 28-22AWG | any hardware store |
| thermoshrink tubes | 2-3mm dia | any hardware store |
Printing
Almost every part is designed to print without supports — the only exception is the Main Body, which needs supports in the button-slot area. You don't have to set this up yourself: every part ships with a ready 3MF project file where orientation, settings and supports are already configured. Just open it, slice and print. A few parts (such as the gears) also print with integrated supports built into the model — these simply snap off after printing, and the spots are pointed out later in the guide.
Print Settings
For most parts, 2 walls and 10% infill are plenty. Use either a Grid or Cubic infill pattern — whichever you prefer, both work well. The Main Body is the exception: since it carries more load, print it with 3 walls and 20% infill. The blades and the handle should use those same heavier settings.
Exception —The Main Body, blade and the handle print it with 3 walls and 20%+ infill.
Some parts in the 3MF files also include modifiers to locally increase strength in specific areas.
Material
You can use almost any common filament — PLA, PETG or ABS all work fine.
Every part fits on a single 250 × 250 × 250 mm bed, and you'll need roughly 400 g of filament for a full set, depending on the wall and infill settings you choose.
When a part needs to be printed in more than one copy, the required quantity is noted in the filename.
Preparing parts
In this section of the guide, we'll prepare the electronics for assembly by soldering all the required wires.
Limit Switch
Solder two wires to the limit switch: an 80 mm wire to the C pin and a 160 mm wire to the NO pin. Solder them perpendicular to the pins rather than in line with them — otherwise the wires can get in the way during assembly. Try to match the photo as closely as you can.
Just to be clear: the short wire goes to the C pin, and the long wire goes to the NO pin.
Display
The display usually comes with its wires already attached, but if yours doesn't, solder a 100 mm red wire to the plus (+) terminal and a 100 mm black wire to the minus (−) terminal.
Motor
Solder a 180 mm red wire to the motor pin marked with a red dot.
Battery Holder
The battery holder normally comes with wires too, but they're usually quite short. Solder on extensions to lengthen them so the total length comes to 250 mm.
Main assembly
Fitting the Motor Gear
Take the motor and the smallest gear — this is the motor gear. It has a flat on its bore that matches the flat on the motor shaft. Line the two flats up and press the gear all the way onto the shaft, down to the stop.
The gear has two holes — install a set screw (M4×5) in each, one from each side. Tighten until snug, but keep in mind this is plastic: as soon as you feel the resistance increase, stop. Don't overtighten.
Mounting the Motor
Insert the motor, with the gear already fitted, into the holder. Line up the hole on the holder with the hole on the motor, then secure it with a countersunk M3×5 screw.
On the other side there's a second hole — install another M3×5 screw and drive it in with a hex key, reaching it through the dedicated access hole in the body. Tighten it all the way.
Preparing the Gears
The gears print with pre-made supports already in place. Remove these supports, then fit a bearing into each gear where the supports were. There are four bearings in total.
Assembling the Main Gear
The main gear comes as two separate parts, since it's difficult to print in one piece. Fit the two halves together; for extra strength you can glue them. Just make sure no glue gets into the bearing — this is very important, as it can damage the bearing later.
The last photo shows how the finished gear assembly should look.
Installing the Large Gear
Place the large gear into the body and center the bearing's hole with the hole in the body. Insert an M4×20 screw, fit an M4 nut on the opposite side, and tighten the screw into the nut. Run it down to the stop, but only so far that the gear still spins freely.
Fitting the Chain Sprocket
Take the sprocket and loop the chain over it with the teeth pointing counterclockwise, as shown in the photo. This sets the chain to run in the correct direction once everything is assembled.
Insert the sprocket together with the chain into the body so that its teeth mesh with the teeth of the large gear. Secure it the same way as the large gear — an M4×20 screw on one side, an M4 nut on the opposite side — and tighten.
At this point you'll have a fully assembled gearbox with the chain in place.
Installing the Gearbox
Take the main body and lay the chain into it down the middle. Then slide the gearbox into the body, as shown in the picture.
Take a spring and line up its eyelet (the loop at the end) with the hole, then fasten it with an M3×5 screw. Line up the spring's second eyelet with the hole on the gearbox and fasten it the same way, with another M3×5 screw. Repeat the whole process on the opposite side. In total you'll need two springs and four M3 screws.
Once both springs are in, check that they work properly — the whole assembly should travel smoothly along the rails without binding anywhere.
Installing the Blade
Line up the holes on the blade with the holes on the main body and fasten them with M3×5 screws — two screws on each side.
Fitting the Chain to the Blade
Now loop the chain over the blade. Because the gearbox sits on the springs, it can move to let you tension the chain. Brace your thumb against the blade, pull the chain with your index and middle fingers, and finally use your ring finger to draw the chain up and over until it seats onto the blade.
Installing Shell 1
Fit the Shell 1 part, fastening the countersunk section first with an M2.6×6 screw. Then take the bracket, set it onto the shell and the blade, and secure it with two M2.6×6 screws. Repeat the same steps on the other side.
Installing Shell 2
Take the Shell 2 part. Slip one end onto the blade first, then seat the part fully, lining up the holes. In the holes closer to the main body, drive in an M2.3×10 screw. Next set the bracket onto the shell and the blade and fasten it with M2.6×6 screws. Repeat the same steps on the other side.
Installing Shell 3
Set the Shell 3 part onto the main body, lining up the holes, and secure the upper hole with an M2.6×6 screw on each side.
Adding the Decorative Chain
Take the decorative chain, fit it onto the main body, and fasten it with a single M2.3×10 screw.
Next take the left bracket and hold it against both the decorative chain and the Shell 3 part. Fasten it to the decorative chain with an M2.3×10 screw, and to the Shell 3 part with an M2.6×6 screw. Repeat the same with the right bracket on the other side.
Installing the Button
Feed the button's wires through the hole in the main body. Angle the pins inward and slightly tilt the button, then push it all the way into place. Secure the button in the body with M2.3×10 screws.
Installing the Trigger
Next fit the trigger. The trigger has a flat cut on it — position it so that flat faces up, toward the hole, as shown in the picture. Then drive in an M3×16 screw, tightening it just enough that the trigger still rotates freely. Don't overtighten it.
Attaching the Handle
Screw the handle into the body.
Installing the Display
Take the display and insert it into the slot in the main body's cover, with the dots facing down — otherwise the digits will appear upside down. Then secure the display with M2.6×6 screws.
Wiring
This section provides the complete wiring/soldering diagram and a step-by-step guide for making all the necessary connections.
Routing the Battery into the Handle
Take the battery holder. To make the wires easier to feed through, bend both of them back 180° so they form a loop. Push the battery holder into the handle loop-first, together with its wires, then pull the wires out the other end.
Joining the Positive Wires
Gather the three red positive wires — from the motor, the display and the battery holder. Twist them together, solder the joint, and slide a piece of heat-shrink over it to prevent any short circuit.
Connecting the Motor Negative
Take the long black wire coming from the button's NO pin and solder it to the motor's remaining pin (the negative). Cover the joint with heat-shrink.
Wiring the MTS-102 Switch
Slip a piece of heat-shrink onto the battery wire first, then solder that wire to one of the outer pins of the MTS-102 (either the left or the right one).
Next take the two short black wires — the 80 mm one from the trigger/button and the one from the display. Slide heat-shrink on, twist the two together and solder them to the center pin of the MTS-102.
Once everything is soldered, slide the heat-shrink over each joint and shrink it down. That completes the wiring.
Installing the Switch
Take the toggle switch and push it through its hole. Align it so it seats properly in its mounting slot, then tighten the nut on the back side all the way down.
Closing Up the Body
Route the motor wires through the dedicated channel in the display cover, then tuck all the wires down inside the body.
Bring the cover up to the body, keeping a close eye on the motor wires — make sure they aren't pulled too tight, or you risk tearing them. Fasten the cover with four M2.6×6 screws. For the two screws located under the motor, press down on the motor with your thumb to push it inward — this opens up enough access to drive those last two screws.
Installing the Tube and Handle Bracket
Take the handle bracket and spread it open so you can slip it over the handle, past the threaded section.
Now take the tube and orient it so that the hole nearer its end sits against the handle bracket, while the hole set farther from the end faces toward the chain. Seat the tube into its slots and fasten it on both sides with M2.6×6 screws. Then secure the handle bracket itself with another M2.6×6 screw.
Loading the Batteries
Fit eight AA batteries into the battery holder, then slide the holder into the handle. Don't push it in too quickly — the wire can get pinched and jam. Take your time and feed the battery holder in carefully.
Final Step
Screw the handle cap onto the threaded end, and with that, your Ripper is complete.
Basic operation
How to Use the Fallout Ripper
Basic Operation
Flip the switch to turn the Ripper on, then pull the trigger to spin the chain. That's all there is to running it.
Reading the Display
The display shows the total voltage of all eight batteries combined. When you pull the trigger, the reading may dip slightly under load — this is completely normal, and it usually climbs back to its resting value once you release the trigger.
Which Batteries to Use
I recommend running this prop on either lithium AA batteries or nickel rechargeables (NiMH / NiCd), since both can supply the higher current the motor draws. Ordinary zinc-carbon ("saline") cells will still work, but they tend to drain quickly because they aren't built for these current levels.
What the Numbers Mean
Because the display reads the whole 8-cell pack, the full and empty figures depend on the battery chemistry. As a rough guide (resting voltage, no trigger pulled):
Lithium AA (1.5 V cells): a fresh set reads roughly 12–13.5 V; treat around 9 V as effectively empty.
Nickel — NiMH / NiCd (1.2 V cells): a full charge reads about 11–11.5 V; treat around 8 V as empty.
Under load the numbers will sit a little lower, so judge the charge level by the resting reading.
Painting
This section is currently under development. A more detailed painting guide may be added in the future. Below are the key points to keep in mind when painting your axe.
⚠ Important — protect moving parts
Do not apply primer or paint to the chain, chain guides, or any moving surfaces. Paint is a sticky substance — if it gets on the guide rails, the chain will stick or rotate poorly due to increased friction between the links. This can lead to motor overheating and potential electronics failure.
Before painting, cover all internal surfaces and guide rails with masking tape. If paint accidentally gets on the guides or chain, make sure to thoroughly clean it off. The chain must rotate freely and slide along the guides without resistance.
Painting the chain
Paint the chain elements either separately before installation, or very carefully while installed — making sure that primer and paint do not get inside the links where they slide against each other.
Surface preparation
Sand the plastic surface before painting to improve adhesion. You can then apply a filler primer or automotive putty to smooth out layer lines.
An excellent alternative for smoothing print layers is UV resin. Apply a thin coat of photopolymer resin to the surface, then gently heat it with a heat gun or torch to remove air bubbles. Cure it under a UV lamp. Sand away any drips or uneven spots, then apply primer followed by paint.
Paint options
You can use acrylic craft paints or automotive spray paints. I typically use FolkArt acrylic paints — they come in larger bottles compared to modeling paints, making them a good option in terms of both price and quality. Spray cans also work well, especially for base coats and large surfaces.
Always apply primer before painting, regardless of which paint type you choose.