1:144 Sumo

The Project

Recently the Hero Legends group delivered their subtitled version of Turn-A Gundam, and so I was able to see this most eccentric of Gundam series at last. At first my interest in the show was almost a morbid curiosity - I knew the show by reputation and I knew its designs (I already liked a few of them by that point, but still had my doubts about the show itself). But as I watched the show it really grew on me, and awaiting new episodes became the most exciting part of my anime hobby. So it won me over, I bought the kits, and I started thinking about projects. In particular, Otakon was fast approaching and I wanted to have something Turn-A related ready for display. But what to build? The 1:100 scale kits are great, but they also have some issues of their own, which could potentially be very time-consuming, especially since I know I'll want to get those particular kits right. I decided to go with the 1:144 Sumo, which is one of my favorite subjects from Turn-A Gundam... in fact, it is the Turn-A Gundam, or at least it could have been. I've decided to do the silver type, because I like the red/silver combination and I'm looking forward to using this project as an opportunity to try out Alclad Chrome paint.

Early Work

Before I started tracking the time spent on this project I did some reasonably substantial work. I modularized the shoulder armor so it could be removed and painted separately from the shoulder, I cut out the poorly molded detail from the upper arm so I could replace that, and I had begun tinkering with crude prototypes for the new arm parts. I had also glued some parts together, and already faced a problem with the hip pegs - one broke off, and I repaired it. (It's very good to have that behind me! It's not hard to fix that stuff but it can be time consuming, and much better to not have that at a critical time...)

The Plan

It is fortunate that I've already completed a few of the small but important tasks of this project. From here I intend to replace the elbow joints with large, spherical hinges, make the hands look better (without replacing them outright) and do a reasonably good job on any sink-holes or seam lines, so that the Alclad Chrome will look good on the surface.

About Alclad

Alclad metallic paints are probably the best metallic paints out there for modelers right now. They're available in a wide range of colors (at least three varieties of "Aluminum" alone). I honestly can't say how they compare to products like Model Master Metalizer or Gunze's Mr. Metal Color - I haven't worked with those products. The only metallic paints I've used so far have been from the regular product lines. But I've heard that Alclad's good stuff and so I'm excited to try it.

About Spherical Joints

Since I started in this hobby I've done a lot of experimenting with option parts. One of my favorites is the Wave L-Joint #3. It's a polycap joint which comes with plastic cover parts that completely encapsulate the joint inside a sphere. You can then seat the joint into a part on your model - the spherical shape can be used to provide a smooth transition between parts, but since it's a functional hinge, too, the parts can be mobile - but that continuity will never be interrupted because the hinge can go through its full range of motion and still be a sphere. It's a great part and I've found it useful on a lot of kits. The Sumo's elbows are also spherical joints, and luckily they even have the center line just like the L-Joint. But at 1:144 scale the elbows are much bigger than an L-Joint, so I need to build my own spherical joint. I ordered plastic hemispheres from Plastruct, which makes the work much easier. (Believe me, I've scratchbuilt hemispheres before and I like this way much better!)


2005-08-15: Arm work

Cumulative Time logged: 6 hours

Creating a pair of spherical hinges took about two hours work. They're just slightly misaligned, which is unfortunate, but I don't think it'll be a big deal for this first Sumo. I also took another four hours to create a new uper arm cuff which I'll recast to create upper arm and forearm parts.

In the photos you can see basically how the new elbow hinges go together (if you look closely you can see the 3mm rod and polycap inside - when the hinge halves are pressed together, the joint appears as a solid sphere.) and roughly how the whole thing will look when completed. The modified hand part is also in the "Arm Progress" photo. The arm cuff took some time because I wanted it to look good for recasting, and to be convenient to fit onto kit parts with just minor alterations. Plus I was working with Bondo instead of my usual, preferred Doro Doro poly putty.... Don't get me wrong, Bondo's great for some stuff - Bawoo's done incredible stuff with it and I've done some reasonably good work with it, too - but in some ways it just can't compete with Doro Doro. There simply is no comparison. Now I'm off to make the mold to recast the upper arm cuff... (Mold preparation takes a lot of time, since the rubber needs to cure, so it's not something that can be delayed at this point!)

2005-08-16: More Arm work

Cumulative Time logged: 13 hours

After an emergency trip to the art supply store in Cambridge to get more mold rubber, I recast the cuff part for the upper arm and rigged up a simple test-shot of how the assembled arm will look, and comparing it to the original parts. Hopefully the results speak for themselves. In addition to being closer to the look of the original design, I also feel this joint looks better than the kit parts.

The reality of the deadline is looming. I've begun the process of sanding smooth the putty but it's tough to say whether I'll finish it before the con.

2005-08-31: New Elbow Joints

Cumulative Time logged: 21 hours

The Otakon deadline has come and gone, of course, and Patcon is coming up, most likely to zoom by me before I can finish this project. I've decided that I'm not entirely happy with the original elbow joints that I made (though I think they were nice work, and it's great to see how simply something like that can be accomplished - I just really feel the precision on my projects ought to be better than that.) so I'm working on new ones (to be recast) using the last two 14mm hemispheres I have on hand. I have ordered more hemispheres, but with a little luck I ought to be able to get by with what I've got.

The big change in this effort is that I'm now using the Dremel as a way to check the alignment of the hemisphere relative to the rod, and to correct it. My first attempt with this technique involved mounting the hemisphere on the rod, then chucking it into the Dremel and sanding it down until it was centered. This reduced the diameter of the part from 14mm to 13mm, and I'm concerned about the resulting part's uniformity as a sphere. But this part is very far along at this point - I scribed lines in it by holding a razor saw to it as it spun, and I puttied some minor mistakes and primed it to check the surface - it needs some more work but if I decide to move forward with it, it's nearly ready.

My second (and last, until I get that order of hemisphere parts) attempt at this was done by first sandwiching 3mm worth of plastic plate, drilling a hole in it, and mounting that to the rod. Then it was chucked into the Dremel and sanded down until it fit inside one of the hemisphere parts. From there, the hemisphere part was carefully aligned on top of the shaped styrene. Alignment was checked using a pencil touched to the hemisphere while it was spinning. (If the hemisphere was off-axis, the pencil would make contact with just one side of the hemisphere. If the hemisphere was on-axis, the pencil would make a complete circle around the part, or close to it, and that circle could be checked to ensure it was parallel to the edge of the hemisphere.) Minor alignment issues were corrected by sanding the outside of the hemisphere as it was spinning. I think with a little luck this version of the part will work out nicely.

My plan is to complete this hemisphere-on-a-stick part and scribe two lines in it on the Dremel - one about 20 degrees from the planar side and one about 20 degrees from the axis - the idea being that for different projects I could fill in these lines or take advantage of them, as needed. Then the part will be recast, and the castings will be performed in different ways in order to create both the male part and the female part of the hinge from the same mold. If the first mold works out, then I'd like to alter some of the cast parts from the mold to pursue my 3-part hinge idea.

2006-1-26: Three-part elbow joints

Cumulative Time logged: 45 hours

Since the last update I've abandoned the idea of creating a two-part spherical hinge for the elbow in favor of a three-part hinge. I could explain the design but I find pictures communicate these ideas better, so there's a mockup photo to see. Just picture the middle part attached to the model's shoulder, and the two outer parts pinned to the forearm. The middle part rotates about the axis and that's the hinge action.

I had a lot of false-starts on this effort. My first attempts involved creating the outer parts first - I trimmed down one of my plastic hemispheres (from the full 7mm radius thickness to 4mm) and attempted to mount that, perfectly centered, onto a strut. When that didn't work out, I tried spin-sanding it on the dremel (and then building the part back up again with poly-putty, and repeating) in the hopes of making the part more symmetrical about the axis. I think the (styrene) axis I'd mounted it on was a problem, though, subject to flexion. I got as far as mastering the part this way and recasting it, but now I'm not sure if I'll be able to use those castings.

From there I tried to use two of the castings to create the middle segment - I had all kinds of problems trying to do different poly putty casting maneuvers (many of which wound up stuck to the pattern rather than the part) and ultimately I wasn't happy with the results. This work went through the same process of spin-sanding and re-puttying as well, but I ultimately gave up on that approach.

My current approach is to build the middle segment first. I started by cutting twelve circles of .5mm styrene and stacking them into a cylinder. I used my new drill press (best Christmas present ever!) to drill a hole down the middle of the cylinder, and I created a turning template with which I'm attempting to form the spherical surface of the part. Once that is done I'll either re-use the end part I've already cast, or I'll make a new one.

The work so far is promising - more successful, I'd say, than my earlier attempts at using similar template-turning to create spheres. I think my template this time around is more precise, thanks to my circle-cutter and a slight bit more patience. However, there are still other problems. Mainly, the flat surfaces of the middle hinge part still aren't quite completely planar and perpendicular to the axis. However, I have a plan to correct this. I'll start with a thick plate - something I'm confident has parallel and planar upper and lower surfaces, and I'll drill a hole in it with the drill press, and install a 3mm rod in it. Then I'll apply putty to the hinge part and slide it down the rod until it comes in contact with the plate. The result should be a planar surface of poly putty perpendicular to the axis applied to the hinge part. This depends on the precision of my drill press and the straightness of the rod I use - both of which I'm reasonably confident in.

2006-4-29: New three-part elbow joints

Cumulative Time logged: 52 hours

In the last update I described work on a three-part hinge that was to start with the use of the drill press to drill a hole through a block of styrene, perpendicular to the bottom face of the block, and use this as the core segment of the hinge. This was the basis of my most recent prototype for the hinge. What I found early on, however, was that the two faces of the block were not parallel due to variances in how I stacked the styrene sheets to create the block, and I had various difficulties in creating the remainder of the hinge. This frustrated me for a while, and I began to consider other ways of making the hinge part, including recasting a 14mm ball bearing and attempting to drill through its center, then cut it up to produce the hinge. I did a couple trials, and found that the process was far too error-prone with the equipment I have, and all the approach's merits depend on being able to get it right the first time. In contrast, my other techniques have all allowed for initial imprecision, by emphasizing stepwise refinement.

I recently returned to the prototype I'd made with the help of my drill press, and refined my method to improve the work. Earlier work had all been done with a styrene rod as the joint's axis, when testing or spin-sanding the joint. I found a supplier for a 3mm steel rod to do those jobs: in comparison the styrene rod was a bit undersized (meaning it wouldn't totally fill a 3mm hole, meaning the parts would wobble) and it was flexible - meaning my precision was limited and my ability to detect precision problems was compromised. The steel rod solved those problems. I also began using the drill press to spin the parts both for sanding the sphere to spherical shape, and for sanding the planes flat and perpendicular to the axis. This combination made it easy to make a lot of progress quickly, and now I feel I have a prototype that is nearly ready for recasting.

I had debated on whether or not to create the counter-sunk areas where the outer hinge parts overlap the inner hinge parts before recasting what I'd built so far - I was concerned about the risk of destroying the work I'd done so far in the attempt to improve upon it. Ultimately, I decided to go for it, and so today I added the overlap between the hinge parts.

As for the joint's current state: I think it may have a slight wobble relative to the axis but if so it's minor enough that I'm willing to accept it. There are also minor problems with the planes where the hinge segments meet: as the hinge is turned the distance between the segments changes a little. But at all times there's a gap there, so the variation isn't as bad as it'd be as if the gap closed and opened as the joint was turned. The joint end cap was originally made with a hole all the way through it, and I've just started capping that hole so the entire outer surface will be spherical in form - that's a bit rough still. The whole joint is a bit rough in places, in fact, as a result of various poly putty work I've been doing, little bits of poly putty have wound up on the joint surface. That'll be relatively easy to correct. Also note that the pictures show an outer hinge segment on the end of the rod, an inner hinge segment next to it, and another outer hinge segment strung onto the rod: the second hinge segment is relatively crude because I stopped development on it. I had been working on all three parts but at a certain point I decided I had to choose which of the two would be recast (as they're not identical, and the outer hinge parts should be identical.) It's in the photos mostly just to show how the final joint will look. Obviously there's still a lot of cleanup to do - the joint is going to be painted in Alclad Chrome, so all these little pits and bumps have got to go.

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