Friday, September 14, 2007

Problems with an enclosed and inaccessible structure

Appears that I can't maintain enough friction on the ball joints. Since repair involves me disassembling the entire structure to get access to the ball, it's near impossible. The legs are still operational, but posing is now limited to non-acrobatic non-aerial poses. I still have the old legs as backup, but that involves removing a small part of the hips (the ball and socket pin part) to allow them to be reused.

I also erred on the paint mix, so her legs are slightly off shade. I'll have to correct that later.

Thursday, September 13, 2007

Redesigned hip structure with partial assembly steps

It's been only two or so months of service, and sad to say, the hip structure I designed started to show structural wear. Originally a ball joint approximation with hinge structures, it wasn't user friendly in design, and required a lot of proper manipulation to pose properly. This was due to the lack of proper ball joint design.

There are a few issues with ball joints made of paper/wood derivatives:

1) Making a uniform sphere. The best thing you can get is an approximation of a sphere by rolling a length of paper around a shaft, with some trapezoidal cross sections. For this exercise, I needed small spheres, otherwise, the housing would exceed the desired dimensions. The older unit used a 20mm diameter circular plate to flesh out the hinge area. I decided to use an 8mm diameter sphere, created by wrapping an 18cm long x 8cm tall strip of 110lb cardstock trimmed to taper down from 8mm to 2mm wide around a wooden bamboo skewer for structural support.

Two spheres were made, and placed on the ends of a 32mm long bamboo skewer. The spheres are force fit and removable, for later disassembly and maintenance.

2) Making the housing. The housing needs to be strong enough to support the outward force of the sphere, restrain the sphere in all directions except for rotation, allow for movement, while keeping enough friction to allow for posing the leg without need of external supports. It also must not occupy too much volume. For this, I'll need a strong material. The first housing consists of two 15mm x 87mm Macetail Hystrodon card sections rolled around an 8mm diameter cylinder as a guide. These strips were pre-sanded to allow for maximum adhesion, rolled, and form an outer diameter of 12mm. The bottom housing was done in the same manner with an Abjure. One 4mm wide by 7mm long cut was made down one housing, while the other was cut to fit around the other, making a crude T-Section pipe.

These are the end results of the housing manufacture process.

The design ultimately ends up with an 8.3mm sphere fit inside a 8mm inner diameter tube. The housing will bulge outwards a bit due to the force fit, but this will be corrected by adding the rest of the assembly, namely the end caps.

The next element to build is the lower leg attachment assembly.
This piece was rolled around a 36mm long bamboo skewer to form a stepped rod. this was inserted into the housing bottom, and the rest of the Macetail Hystrodon and Abjure card scraps (about 30mm x 87mm) were rolled along the thinner end to form the pin housing.

The next step is to thicken the legs. Random pink cardstock was used to flesh out the legs as needed, and the 110lb white cardstock was used to cover the upper part of the knee assembly.

The red bag like objects are made of rolled cardstock tubes glued around a straight 110lb cardstock cylinder over the thigh assembly. The top part has the end caps in place, made of a Malicious Advice. It is composed of a 5 walled box with a slit cut through the center.
This piece has a 14x4mm slit in the middle to allow for 90 degree movement, and was placed on the end of the housing. I've trimmed the box to fit better in the space allotted, so the actual dimensions needed are unknown. After the end cap was placed, it was glued and secured with layers of cardstock to hold it in place. Then the process of fleshing out the leg was freehanded with simple primitives covered by a tube of 110lb cardstock. The end result was sanded and painted.
The legs actually look better since it's smoother, shows less mechanical elements (the screw access holes for tightening), and hides nearly all of the elements that make it work.Here is a finished shot of the legs in action. These hopefully will last longer than the original legs.

Tuesday, September 04, 2007

More Head development

It would be unfair to not credit the creator of the model which Hotaru and Lucy are built upon. The paper modeling master at the now defunct Mizuirogakuen site produced several exquisite models which I built over the past year. Rather than build a new head sculpt from the ground up, i simply took the template for one of his model's heads and adapted it as a blank sculpt. Unfortunately, there were only two suitable candidates:

The Shinku head sculpt, without the extra bits, makes a good base. And the other candidate is Ruri Hoshino, from Martian Successor Nadesico. This one also worked well if you remove the extra hair bits too. I opted for this one as the default template was bigger.
The boxed in components are the necessary parts. I scaled the page to 96% or so to fit the doll. After acquiring the template, I simply placed a Magic the Gathering card underneath the sections and used a stylus to transfer the template. You can use carbon paper if you like, but it's messier. For this, you will need to omit the tabs on every part.

The process of fabricating a head takes a good half a day to complete, for reasons about to be explained. I'll document the exact process used.

1) Transfer the template onto a Magic the Gathering card. Centaur Veteran tends to be a common choice for me to use.

2) I like to use small pieces of masking tape to hold the parts together as I assemble the head. Using small strips of printer paper, I cover all the crevices from the inside. This leaves a smoother outer finish for better appearance. A Magic the Gathering card is stiff, and needs ample time to dry. Two layers is ok, but one layer is sufficient.

Make sure you cut a hole at the bottom of the triangular piece for the neck, if you plan on mounting it on a doll with a ball bearing support neck.

The best way to do it is to build the purple part separately, cut it in half (with the cut going along the join seam), and assemble it to the lower half ofthe face/neck region.
It should look like this. This one was formerly a Glory Seeker.

3) You should sand the outer face smooth, to remove any defects and protrusions caused by shoddy handiwork. My newer method involves taking an array of thin printer paper strips and covering the outer side (the back face in the case of the photo), going perpendicular to the join seams, trying to overlap as little as possible. After that dries, I like to sand the overlaps smooth.

4) Trace over another set of the parts, but this time on printer paper. Use pencil or something light if possible, as it will show up during the painting process. Glue those over the exterior surface now covered by strips of paper. You will now have something close to this:
(Yours will likely look like crap. Don't worry, it happens to all of us. This is my second one, which I never used again. Hotaru is my third attempt, and Lucy is the fifth.)

4) Use this time to draw facial features. Good luck. Drawing on a curve sucks. Be prepared to draw lightly and erase often.

5) If you are satisfied with the appearance, and have sanded the head smooth as you like, you should add the ears now. You can paint now as well.

6) Now, you have the back of the head to complete. You should have a small, quarter sphere piece for the top of the head that may or may not fit. Mine never do, so I solve that problem by enlarging the shell. Make a third purple part template, with cardstock. Assemble that fully.

Place the quarter sphere on the head, then fit the cardstock shell onto that, to complete the sphere. I'll document the hair making process and more of step 6 in the future.

Monday, September 03, 2007

Suigintou Cosplay: full version

This cosplay set features a few new elements worth showcasing. First off, the costume is more complete with white wig and headband like accessory on her head. Notably, the biggest improvement is the new face.

Now, you might have (not) noticed that the newer head has adjustable eyes to allow it to track you from different viewing angles. (Go look again, if you don't believe me. I'll wait for you.) However, that is true, as I've hollowed out eye holes and provided a new eye system that also allows for eyelids to be adjustable too. But the beauty of this system is that the eye tracking is actually an optical illusion. Yes, for all the shots, the eyes were not adjusted at all between shots.

What's happening is that due to the nature of the facial structure, the eye sits farther back than it should. When the eyes are set to look straight on, the pupils are surrounded by the white part of the eyes. As you move around, the lip that exists around the eye obscures the white part, making the pupil look like it has been adjusted to your direction. When combined with both eyes, you get an illusion that it is actually following your movements as you look at it.

Back view of the hair

For the interested party: here is an idea of how the system works.
The left side shows the possible eye colors to use. Right now, a purple set is inside the setup.

This is the inside of the head. The orange/red ring is a structural component to allow the head to not sink too far downwards on the neck. The black strip is what holds the eyes to the eyeholes securely. It allows for movement and simple adjustments.Here is a shot of the eyes in place.

Default scheme
With eyelids added With eyes positioned off center to allow for more extreme sideways glancing

This 2nd generation dynamic head design effectively replaces the original "Hotaru" face template. The 2nd generation head will now be referred to as "Lucy", and will be used for all future demonstrations.