Introduction: Working Mercy Staff V2

Welcome to v2 of the original Working Mercy Staff!

The original can be found here (thanks Corwin!):

This version 2 was made a year after the original staff. There are many improvements over the original, such as standardized hardware, a lighter and more rigid design, and a simplified and more robust battery solution. The entire staff was designed in Fusion 360 from scratch!

To make this guide, I completely disassembled my original staff to document how I put it back together. You'll probably notice things such as chips in paint and silicon grease in parts that are more well worn. I've taken my staff to many a con and the various blemishes bring along all the history. This is a pretty long build so I'll be covering a lot of the main assembly in more detail than things such as paint.



The 3D printing files are available for purchase here: (STAFF V1 FILES NOT COMPATIBLE)

You'll also need:

  • 100RPM motor
    • (
  • Wires
  • JST Connectors
  • Soldering Iron (and solder)
  • 3 position 6 pin slide switch
    • (
  • 2 carbon fiber rods 8mm 372mm long
    • (
    • I was also informed aluminum 5/16" rods work if holes are bored out with a drill bit. The aluminum rods might be easier to find.
  • 6mm magnets
    • (
  • Li-ion battery
    • (
  • Battery charger circuit
    • (
  • M2 and M3 screws
  • Spring from a pen
  • Glue (super glue or epoxy)
  • Various Lego axles
  • 4 Lego Universal Joints
  • 4.5ft 1in PVC pipe
  • Wood filler
  • Filler primer
  • Paint in different colors in order of frequent use (Spray paint makes things easier)
    • Black
    • white
    • Gold
    • Silver
    • Clear-coat
  • Blue tape (painters tape for masking)
  • Legos (The piece list was made to simplify the building process. If you are proficient at Legos, feel free to use what you have on hand. The universal joints are the only non-optional pieces. Bricklink might be useful!):
    • 3x Technic Axle Connectors
    • 4x Technic Universal Joint 3L
    • 2x Technic Axle 6
    • 3x Technic Axle 4
    • 2x Technic Axle 3
    • 2x Technic Axle 2 (notched or not, doesn't matter)
  • Hot glue (optional)

Step 1: Step 1: Get 3D Printed Files Printed and Painted

The link to the 3D printed parts can be found in the supplies section. These parts will be finished and painted for the most part, so you'll need to print with at least 3 shells so you have enough material to sand down. Material doesn't matter as long as it is easily printable and rigid. A lot of the files are also split up into multiple parts to account for smaller printer build volumes or printing orientation.

For the entirety of the staff, you'll need:

Most of the files are one time prints, exceptions being any gears or mechanism parts and the Winglets.

One Winglet consists of:

  • 1 Top Winglet
  • 1 Bottom Winglet
  • 1 Linkage Arm
  • 1 Winglet
  • Anchor

You'll need 3 Winglets total of course. If you have a smaller format printer that can't fit the Top or Bottom Winglet models, I included the full model for you to cut up as needed using MeshMixer or another program. You also might find it easier to print the Rail models (part of Top) by splitting the part in the middle and gluing them together. Be sure to glue any split parts together before the later steps.

As for the mechanism, you'll need:

  • 3 Short Barrel Gear Stabilizers
  • 2 Long Barrel Gear Stabilizers
  • 2 16 Tooth
  • 2 Gear Rings
  • 3 Rails in the "Top" folder

Everything else you only need one part. You may want to print two 12 for Motor Shaft gears in case you have trouble with fit.

The first thing you need to do before painting anything is ensuring the seam at the glue-line between your Winglets (and any other parts that were split) is nice and smooth. I used wood-filler for this; nice and cheap and easy to work with. Fill in the cracks with filler, wait to dry, and then sand smooth using sand paper. Parts like the two pommel pieces and the rails can be glued later.

After seams are filled, it is time to start the painting process. You'll want to mask off areas that will be fitted together. I'll highlight those in the photos.

  1. Apply two coats of filler primer, waiting for the coats to dry before applying the next as per rattle can instructions.
  2. Once dry, sand smooth with 180 - 200 grit sandpaper.
  3. Apply another coat of filler primer.
  4. Repeat steps 2 and 3 with successively higher grits of sand paper until the desired surface finished is reached.
  5. Apply a final coat of primer to ensure no plastic is exposed on the parts.

The process for prepping models for final color is pretty standard across the 3D printed prop scene. A good video demonstrating this process is this one from Punished Props:

I use wood filler instead of spot putty mostly because it is cheaper! The PVC pipe also needs to be sanded and primed, but since it is smooth the sanding is only to help the paint stick.

Note that not every part needs to be painted since they're on the inside of things. These parts are as followed:

  • Battery and Charging Tray
  • All the gears
  • All the stabilizers and the motor mount

It may help if you move on to do a dry assembly of the entire staff before doing final paint to see for yourself what parts will and won't be seen. It'll also give you some practice in putting it together without scratching up the final paint! The entire staff is designed to be easily serviceable, so you should be able to get things apart relatively easily.

To apply the final colors, you can use rattle cans, paint brushes, or anything you're used to. The original staff was all hand painted with brushes, but I bought a cheap airbrushing kit for this newer version. For color reference, you can use the included images. There will also be annotations to see where parts should be masked and other notes.

Step 2: Step 2: Assemble the Battery Pack and Pommel

Now we get into the assembly!

  1. The battery clips into the Battery and Charging Tray, with wires going out the back of the tray and wrapping underneath the battery.
  2. The input of the charging circuit is on the side of the board, which means it is inaccessible when fitted inside the pipe. You'll need to solder a female JST connector (the same one that would fit with the plug of the battery) to the leads of the plastic connector of the board. This allows us to plug in the battery anywhere we want. I recommend adding hot glue on the connection so that the wire doesn't accidentally get pulled up when connecting and disconnecting the battery.
  3. Another JST connector (male) can then be added to the positive and negative outputs of the charging board, which will connect the battery pack to the rest of the staff later.
  4. The charging circuit board can then be screwed to the tray with two short M2 bolts, the USB port for charging facing away from the battery.
  5. After the battery pack is assembled, it can be inserted in one end of the pipe. The two pommel pieces (or one pommel piece if you've already painted and glued them together) should be pushed on. To keep the pommel on the end of the staff, you'll notice a hole for a bolt near the top of the pommel. That hole should be used to mark a place on the pipe for a corresponding hole to go. This hole should be slightly smaller than an M3 bolt so that the bolt will thread itself into the pipe. The hole should be drilled without the battery pack in place. Once drilled, ensure the hole is in the right position with the battery pack and pommel in place.

Step 3: Step 3: Assemble the Handle

This is where the staff really starts coming together! Every other step is Bolded to make this wall of text easier to follow.

  1. The first thing you'll need to do is cut a length of wire that is the length of the pipe and solder JST connectors (female) to both ends. This long wire will connect the battery pack to the rest of the staff.
  2. While we're soldering, we can get the switch soldered up. Our switch has 3 positions and 6 pins. This will allow us to eventually switch the direction of the rotation of the motor! Check the pictures for the wiring diagram.
  3. Take your PVC pipe and add your "Handle 1" piece to the end that doesn't have the pommel. Just like before, we want to mark the location of the hole that will bolt the handle to the pipe. The hole should be on the opposite side of the pipe such that the white of the pommel lines up with the black side of Handle 1 (according to the color scheme outlined in the first step).
  4. The carbon fiber rods should now be cut to 372mm. Try to be as exact as possible, slightly longer is better than slightly smaller! Wrap the tubes in blue tape to mark accurately. Cut using hacksaw preferably outside or a well ventilated area. This kind of dust is real nasty!
  5. Before assembling the rods into the handle, check how they fit into the Anchor piece (Top folder). It is imperative that they are neither too loose or too snug in the anchor, as you don't want to pull the entire handle apart all at once while disassembling. You want the rods to be a relatively light friction fit in the Anchor. If both ends of the rod are too tight, sand the rod down (well ventilated area!). If both ends are too loose such that they fall completely out, you can either use tape to get the diameter up or you can use super glue to build up thickness. To do so, add a line of super glue to the end of the rod and wait for the glue to completely dry. Then check the fit and sand down the super glue until the desired fit is achieved. Once both rods are a light friction fit in the Anchor piece, set the Anchor aside for later assembly.
  6. Insert the rods a quarter way through the "Handle 2" piece. Then Insert the "Handle 1" piece to the end, pushing both pieces together. The fit should be tight, a friction fit. These pieces do not need to be taken apart later if painting was already done. I would not recommend gluing the rods in place, instead wrap the tubes in tape to increase the friction fit tightness. The "Handle 4" piece can then be pushed into position.
  7. Insert the switch into the "Handle 4" piece from the front. The Switch Plate should sandwich the switch in place, back side towards the switch. Feed the wires through first! After the switch is in place, the longer battery wire can be fed through the handle. Ensure the switch can move to all three positions after installation. Keep the switch at it's middle position (off position).
  8. "Handle 3" can now be pushed onto the rods in place. The wires have to be on the right of the carbon fiber rods for the next piece to fit! Feed the motor wires through the Handle 3 Piece to ensure wires aren't pinched. The entirety of the handle should fit without any major gaps, so be sure to push things together well and ensure nothing is caught!

Step 4: Step 4: Mechanism Assembly

Ah yes, the heart of the staff: clockwork. This is the most touchy feely part of the assembly, so don't be discouraged if it takes you a few assemblies and disassemblies to get it running just right! Also time to get out the Legos. Every other step is Bolded to make this wall of text easier to follow.

  1. Assemble your Legos into four parts listed in the picture. They will be referred by their numbers in the picture.
  2. Next, install the magnets into the barrels and the gear rings. There are three magnets per piece. These magnets should be facing such that the gear rings stick inside of the barrels. Be wary of the magnets orientation! They can be stuck in with super glue. Go ahead and attach a gear ring into the Short Barrel.
  3. Add the first Short Barrel Gear Stabilizer to the rods, with the axel hole on the left side of the rods. Put the Short Barrel with the Gear Ring inside onto the rods, the gold ring towards the handle. Have it sit on the stabilizer. now, push the stabilizer down from the middle just until there is a small gap between the Short Barrel and the handle. See picture for an idea of what that looks like. Spin the Short Barrel to ensure the gap there all the way around. The first stabilizer can then be tightened down. If the nut spins in place as you're tightening it, use a pair of needle nose pliers to prevent the nut from spinning so it'll tighten properly. Remove the Short Barrel from the assembly.
  4. Add a gear ring to the rods, followed by a second Short Barrel Gear Stabilizer. Before sliding it down, add the short side of Shaft A to the second stabilizer. To the other side of the stabilizer, add a 16 tooth gear. Slide the stabilizer assembly all the way down, ensuring there's enough room for the gear ring to rotate freely by rotating the Lego axle before tightening the second stabilizer down. The third Short Barrel Gear Stabilizer is a surprise tool that will help us later :D
  5. Add a Long Barrel Gear Stabilizer to the rods (symmetric part, so no orientation relative to rods). It should sit right above the Lego axle connector. Ensure axle still spins freely before tightening. Add the second gear ring, followed by sliding the second Long Barrel Gear Stabilizer to the rods. Before sliding it all the way down, add the long side of Shaft C to the unoccupied shaft followed by the second 16 tooth gear on the other side of the stabilizer (just like step 4). Slide stabilizers together, testing how parts spin before tightening. Add Shaft B to the exposed end of Shaft A.
  6. Add the Initial Reduction Gear Stabilizer to the rods now, with the hole nearer to the middle of the rods on the side of Shaft C. Feed Shaft B and Shaft C through the stabilizer, then secure the stabilizer down after testing looseness. Add a 12 tooth gear followed by a 10 tooth gear to Shaft B, then a 9 tooth gear to the end of Shaft C.
  7. Solder wires and a JST connector to the motor. The JST connector at the end should plug into the one coming out of Handle 3 (just check, we'll plug it in for good after mounting it to the rods). The location of the black and red wires doesn't really matter, as with DC motors we reverse the positive and negative lines to change direction anyway. The motor mount should have nuts and bolts installed as shown in the picture. The motor can then be added and locked in place. The face plate of the motor should not be flush with the mount! Instead, when a gear is put on the motor shaft, the shaft should be flush with the gear (see picture). Find the 12 for Motor Shaft gear and press a small washer into the rectangular slot. This is so that the D shaft of the motor doesn't dig into the plastic over time.
  8. Put the motor gear onto the motor shaft and add the motor mount to the rods, gear facing towards the other gears (see pictures). Once fully down, ensure all the gears are loose and free to rotate before tightening down the motor mount. Add Shaft D to the exposed end of Shaft B. The last Short Barrel Gear Stabilizer can now be added, with the axel hole above the motor (the universal joint should not go through this last stabilizer).
  9. Feed the motor wire down and through the stabilizers and plug it into the connector coming out of the handle, being careful to not obstruct any gears or have the wire be loose enough to catch in the ring gears. Use zip ties or tape to hold the wire in place. The barrels can be added to the mechanism. The gold ring should be on the side of the handle for the short barrel. The rounded side should be on the side of the handle for the longer barrel.
  10. The Anchor piece goes on next, with the orientation such that the axel hole is on the same side as our universal joint. Align the 4u axel with the axel hole and the rods with the rod holes, then push the Anchor on just enough so that there is a tiny bit of axel sticking out where the final gear goes. Push the final 8 tooth gear in place, then fully seat the Anchor. You'll probably have to spin the gear to make sure it gets onto the axel. If the Anchor is rubbing against the Long Barrel, pull it up a bit.
  11. The last part in this assembly is adding the rails. There are three ways to do so: friction fit, magnets, or glue. Friction fit is as simple as pushing them into place and seeing if they stay there. There are also holes for seating magnets to keep them in place, but I ended up not using them as friction fit worked for me. You can also glue the rails in place, but that might make it harder to disassemble. Your choice!

Step 5: Step 5: Winglet Assembly

The Winglets are the biggest and most fragile part of the staff. I've broken a Winglet in half by being careless, so be careful how you hold and store the staff!

  1. Start by press fitting two nuts into the linkage arm. These are designed for M2 size nuts.
  2. Attach the linkage arm to the Winglet Support with a 15mm M2 bolt (see picture).
  3. Screw the Winglet Anchor to the Winglet Support with two M2 screws. Make sure your screws are long enough to go through both sides of the Winglet Anchor! These are threaded directly into the plastic.
  4. Screw in a 20mm long M3 bolt into the hole at the top of the Winglet Anchor.
  5. Add a Winglet to the Winglet Anchor by pressing them together. They can then be locked together by screwing the M3 bolt.
  6. Repeat steps 1 - 5 for the two other Winglets!

I would really advise against turning on the staff with the Winglets as they are right now. You need the Winglets to be out! Here's how:

  1. First, unscrew the bolt that held the linkage arm in place halfway.
  2. Move the winglet until the other hole in the linkage arm aligns with the bolt that was unscrewed.
  3. Screw the bolt back in.

Winglets retracted for storage, winglets out for spinning!

Step 6: Step 6: Final Assembly

You've got your handle assembly, your winglet assembly, and your battery pack ready to go. It is time for the final assembly! You might want to do this on the floor for space.

  1. Plug in your battery pack and get that long length of wire fed through your PVC pipe. You'll need access to the wire from both ends, so I recommend taping or weighing one side of the wire down to get it through the pipe. Before continuing, ensure the switch in the Handle assembly is in the middle position. Connect one end of the long wire to your battery pack and one end to the wire from your Handle assembly.
  2. Slide the PVC pipe into the handle section, making sure the bolt holes drilled earlier line up. If they don't when the pipe is slid in as far as it can, it is because the wire is getting pinched. Pull the wire from the pommel end so that the handle sits properly, then bolt the Handle to the pipe using a 5mm long M3 bolt (length of bolt doesn't matter too much here).
  3. Slide the slack wire and the battery pack into the other end of the pipe. The board side of the battery tray should be facing towards the pommel bolt hole. Add the Pommel, and screw it in using an 5mm long M3 bolt in the hole you drilled earlier. The bolt must be 5mm or shorter to avoid any potential of damaging the battery. This is not optional. By now you should have both the pommel and the handle bolted to the pipe.
  4. Add the Winglet Support piece to the very top of the staff. You may have to prop the staff on a chair to make sure the winglets aren't damaged by the entire staff's weight resting on them on the floor.
  5. Add a spring from a pen to the top of the Anchor piece at the top of the handle. Secure by any convenient means as long as the spring can still compress. Then add the cap, securing by pushing lightly down on the cap and twisting clockwise until the cap depresses. Then without pushing down on the cap, continue turning clockwise until the cap pops up slightly, locking in place.
  6. Finally, the Handle 5 piece can be snapped into place. Turn it on to see if it works. You're done!

Step 7: Staff Maintenance

Congratulations on conquering this mechanical monstrosity! You have my utmost respect if you made it this far. There are a few things you want to keep in mind when owning this thing:

  • This is a delicate prop so treat it as you would with a big, thin, spinning glass rod. Don't hit your friends with it. Be very mindful and aware of how long it is.
  • It runs better at full battery. You'll notice it start to chug along.
  • If the mechanism doesn't seem to run smoothly, make sure the gears and everything else has room to breathe and spin freely. Feel free to add some silicon grease or graphite powder as I did in the gears and especially the Anchor at the top where it slides against the Winglet Support.
  • The staff may spin better in one direction than the other. That's fairly normal. It is also normal for the staff to spin better when it is vertical.
  • Staff might sound whirr-y. That's normal! There are a ton of moving parts, so don't expect utter silence from this machine.

How to charge:

  1. Unscrew the pommel.
  2. Take out battery pack.
  3. Unplug battery pack from rest of staff.
  4. Charge.
  5. Assemble in reverse order.

How to disassemble for maintenance:

  1. Push down and twist the cap counter clockwise until it pops off.
  2. Take the Winglet Support piece off with the Winglets.
  3. Gripping by the center shaft, wiggle off the Anchor (This is why the "light friction fit" is so important. If it were tight, the entire handle could rip apart when trying to take the Anchor off). Be careful not to let that little 8 tooth gear run away!
  4. Slide off Barrels one at a time to expose mechanism.

To store, disassemble according to charging instructions. Unplug battery from charging circuit and reassemble.

That's all I got! The making of both versions of this staff has been a really fun and educational experience. Special thanks to Engineer_Corwin for hosting the original Instructables. Thanks for stopping by!

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