RWBY - Qrow's Harbinger (transforming sword / shotgun / scythe)

[mageus]

===== I - Introduction =====

I originally thought of cross-playing RWBY with the Crescent Rose. But by season 3 it was obvious that Qrow was the way to go. Following is my journey to replicate Harbinger. Any comments, criticisms, or advice would be appreciated.


DESIGN FEATURES

- broadsword
blade in 5 segments
central circular body with clockwork gears
handle (wrapped in red pleather)
hand guards with blades
shotgun barrels on either side of blade
- carry mode
last 3 segments of the blade retract
- shotgun mode
blade rotates to face the ground
trigger attached to the handle
- scythe mode
blade rotates backwards to face up, 90 degrees with the handle
handle telescopes open in 5 segments; trigger stays on middle section
guards / shotgun rotate with blade, stopping at 30 degrees from the blade
blade segments pivot at back edge to form curved scythe blade
red scythe edge is exposed on the back edge of the blade


Here are some excellent resources to start with:

Wiki - Harbinger

Benton's wooden, then foam build -
RWBY Qrow's Sword Scythe

Matthew Barrett's builds -

3d model by gibbygabe - Harbinger Scythe (Qrow's Weapon from RWBY) by gibbygabe10

3d model by Brian Chen - 3D Printable Qrow Sword non-transforming Prop by Brian Chen


See the next few posts for details.

 

[mageus]

===== II - BODY =====


The body is made of 5 stacked discs: one for the blade, two middle ones for the handle, and the two outer discs for the guard/barrels. Technically, the guard and barrels rotate separately, but I've never seen them do this in the show. I can use aluminum, plywood, or MDF for the discs, held together by a nut and bolt. A nylock bolt lets me manage the tension.


QUESTION: how to limit the rotation of the discs?

The three planes have distinct ranges of movement with respect to each other. I cut circular slots in each disc, within which a pin rides. The slots will constrain the rotation of each disc to a certain angle.


How to lock the discs together?

I cut a small notch radially from the circular slots, at each mode position. The pin sits in these notches, locking the discs. To transform, pull the pin radially outward, rotate the parts, and then push the pin radially back into the notch. You could even have a spring pull the pin into the notch.

The pin is anchored in the handle discs, with the blade and guard/barrels rotating around the handle. I've placed the slots opposite the blade, so the slot won't weaken the blade plate.


I've modeled this in small scale in foam and it seems to work.

- BLADE LAYER -

The central blade plate will include the first segment of the blade itself. This will anchor the blade to the body and provide strength and stiffness.


- HANDLE LAYER -

The handle mount will be embedded between the two handle discs. Since it will cross into plane of the blade, I'll cut material off of the blade plate, opposite the blade. Basically, there will not be a blade plate 'slot', just a 180 degree cutout at the back of the plate.


Two tabs will be anchored on the pins, and stick out the back. They will be connected to form a loop. You pull on the tab to pull the pins out of the notches. A spring will pull the pin back into the notch.


- GUARDS / BARRELS LAYER -

A foam ring will make up the bulk of the outer body.

The barrels are actually hexagonal, not round. I'm thinking of using foam rods, for weight and to avoid the wrath of the Peace Bond Police. To be realistic, one could use wooden dowels planed on 6 sides. I think that's doable with a table saw.

The guard blades would be MDF - rigid, but not sharp or dangerous. I'll try to make the guard base out of foam. If it's too flimsy, I'll use pine or bamboo.

 

[mageus]

===== III - HANDLE =====

The sword handle, which is ~12-16" long, magically extends into 5 segments. The top 2 segments and bottom 2 segments extend from each end of the main segment. Using 5 concentric tubes is not feasible with hobby level tools.

I found this at Home Depot:

https://smile.amazon.com/Shur-Line-...tension+pole&qid=1568763133&s=gateway&sr=8-40

The metal segments actually extend both above and below the red grip, probably using a rack/pinion. They lock in place using kayak clips. It has a standard 3/4" thread on the end. I'll use the end of a paint roller brush to mount it to the body.


Problem is, it's only 3 segments, and the graspable segment ends up at the bottom, rather than in the middle. I could shorten each segment, and add 2 more segments that screw onto the bottom. This would look more realistic, but would require manually attaching parts.


I would plether wrap the main segment, and paint the other segments.

 

[mageus]

===== IV - BLADE =====

The blade has several mechanisms:

- The segments pivot to form a curved scythe blade.

- Sharp edges magically pop out of the back of the blade to form the scythe edge.

- The distal 3 segments magically retract into the base for carry mode.


Matthew Barrett's pantograph mechanism for the blade is quite clever, and allows the blade to bend symmetrically in one connected motion. However, if you look at this animation:

//imgur.com/gallery/ff34MUl

you will see that the segments first extend (with a little puff of smoke), and then rotate. I want to use pins running in slots (common theme) within each blade segment. I made a card stock model that pivots correctly. Allowing the segments to slide then pivot will be harder.

Using this image:

there are 30 degrees between the first 4 segments, and 15 degrees between the last 2 segments.

I'm looking into aluminum plate for the pivoting frame. Otherwise I'll use MDF. This will all be covered in foam, so the surface and edge of the blade are harmless.

Since the blade is ~1" thick, there is enough space to make little red edge-lets that slide out of the back of the blade to form the scythe edge.

In reality, the blade couldn't retract into itself. I'll just make the distal segment detachable. I haven't figured out how to make it lock into place yet.

Unfortunately, I haven't found a way to make any of this automatic. Each blade segment and edge piece will have to be moved individually.

 

[mageus]

===== V - CLOCKWORK =====

I want to make the gears motorized. I would prototype with Lego Technic, like Benton did. The 3d files listed above have detailed clockwork models, which I could scavenge. More likely I would find 3d files for proper gears with common pitch/module. I'd need a pancake motor, and then figure out the reduction gear for a usable voltage.

I couldn't put the trigger on the handle, since I couldn't get the wiring to work when the handle extended. I'd have to hide the switch on the body.

 

[mageus]

===== UPDATES =====

9/27/19 - Foam core mockup:

10/15/19 - Pivot system:

 

[mageus]

I made a foam core mockup, which looks pretty good. The stops are working well.

 

[mageus]

The handle mount is ~1" thick. For stability it needs to be embedded a few inches into the body, so, I need to cut out a radius of the blade and guard discs for clearance. However, these cutouts limit the rotation, obviating the need for the slot system. I do need a new way to lock the discs' rotation to each other.

I found 12"x12" 3/32" aluminum plate for $15 on Amazon. It's plenty stiff. I'll keep the blade disc 1/4" ply, but make the handle discs out of aluminum, and the guard discs can be foam (with a central circle of aluminum or wood, for strength).

 

[mageus]

The blade pivot system works well in foam core.

 

[mageus]

Because I want the scythe blade edge to pop out of the back of the blade, I had to rethink the design of the blade layers. If you look at the pictures from the prior post, the triangular sections exposed when the scythe opens up are made of the inner layer (plywood). The back 1.5" of this layer have to be empty, to give space for the scythe blade edge pieces. That would leave a small triangular gap:

The blade is now 5 layers: inner plywood frame; 2 aluminum segments that pivot on the plywood; 2 foam layers attached to the aluminum for the outer shape of the blade. The plywood stops 1.5" from the back edge of the blade, but the aluminum goes to the edge of the back of the blade. This leaves a 1.5" wide by 1/4" thick channel between the aluminum pieces, within which the scythe edge can slide out of.

So, the aluminum forms the inner exposed triangles. It was getting very complicated, so . . .

CAD to the rescue!

(Inkscape, GIMP)

 

[mageus]

duplicate

 

[mageus]

I went with 0.0125" aluminum since it's relatively cheap on Amazon ($10 for 1'x2'). 1/4" sandy plywood. You can see there's a fair amount of overlap between the aluminum and plywood. The plywood segments are interesting. Pivot the sections to draw the overlap, then use a compass to make sure the interlocking sections clear each other properly. High school geometry has come to good use! The distal segment seems stable with the aluminum sandwich. Total cost for plywood and aluminum: $60 (including the 1/8" plate for the body).

For those wondering how I cut it all . . .


- Rough cut the plywood with a jigsaw.
- For the straight edges, the piece is taped to a cross-cut sled on a router table at low speed. I worried the table saw would make too much tear-out.
- For the curved edges, I just hand-trimmed them using the router table.
- Be sure to cut all outlines with a knife, to avoid tear-out of the top layer of plywood.
- Drill press for all the holes.
- For the slots, I tried a 1/8" spiral bit in a rotary tool, but was hard to keep steady. I ended up drilling holes along the path, and then filing out the slot.
- You'll notice the plywood pieces go all the way to the back of the blade. This was to facilitate alignment of the aluminum. I'll just cut the 1.5" off using a table saw and fence.

- The aluminum is thin enough to make a rough cut with shears.
- Then score a few times with a hobby knife, bend, and snap!

- M3 screws, washers and nuts, because #6 UTS (North American gauge) is coarse and junk. Lock-nuts on the pivot points, to allow for play.

 

[mageus]

I wanted the blade segments to stay locked in the closed or extended positions. I glued 6mmx3mm magnets onto the aluminum segments, and embedded 2 magnets in the plywood for open and closed positions. I can leave the nylock nut a little loose for smooth movement.

For the body, I used 1/8" aluminum for the handle plates. There's a tongue that slides into the handle and is screwed down. The outer plywood plates are for the blade guard / shotgun / clockwork layer. The cutout allows them to rotate into a 60 degree position in scythe mode. The blade slides in as the middle layer. Held together by a 1/4" bolt / nylon nut and large washers.