Centurion Update 25

Posted by Mangozac on February 16, 2014

Progress continues and I’m really excited with how the cannon is looking! You can see the detailing is coming along nicely (yes, those are more lifting points on top of the body). I machined up the muzzle today but I’m not 100% sold on it. I machined in three equally spaced muzzle brake slots, but in retrospect a muzzle brake on an energy/plasma weapon probably isn’t the brightest idea ๐Ÿ˜›

Centurion_WIP_100

This shot also dรฉbuts my new scale reference: a great little figure from my mate Steve at Mad Robot Miniatures. I’m sure he was quite chuffed with assembling this combination of parts for an Aussie like myself ๐Ÿ˜‰
The figure is standard 28mm heroic scale, so should give you an idea of just how much of a “big freaking gun” this is!

Centurion Update 24

Posted by Mangozac on February 7, 2014

Detailing of the cannon continues. I’ve actually been finding it a difficult process as the cannon body is quite large and has a lot of plain, flat surfaces which are just creaming to have some interest added. Of course, vents are always a staple detailing fallback (especially on something that would generate lots of heat like a plasma cannon), but there’s only so many of them you can add before it’s a bit overboard. I will of course add some lifting/tie down points and I have some more ideas for what to do with the outboard side.

The stumpy arm that connects the cannon to the shoulder has turned out really nicely. It looks quite solid and also passes a few power cables and the like. The entire cannon design is symmetrical and many parts, including the arm, are designed to be able to attach from both sides. While this may limit design choices slightly (everything has to be mirror-able), it’s a lot less work than having to build two of these things (even with the CNC cut parts).

I’m still deciding exactly how I’m going to split it up for casting, but I have a feeling it will be four parts: arm, cannon body, barrel assembly and front armour plate. I could mould it with the armour plate already connected to the barrels, but the mould lines would run through the centre of the plate, making them a pain to clean up…

Centurion_WIP_99

Oh, one other thing I wanted to talk about was the piping. I needed something about 3mm in diameter to use as pipes between the shoulder and cannon body and as details on the top of the cannon body. While I could use styrene tube wrapped in 0.7mm diameter solder for straight sections of ribbed tube, this looked really poor if tight curves are introduced.

I’m a massive fan of the Dragon Forge Pewter Power Cables, as they are so easy to work with and will facilitate bends as sharp as 90 degrees while retaining that nice, ribbed profile. Unfortunately, the largest size he does is 2.15mm diameter – a little bit too small for what I needed.

I tried heat bending some styrene rod but could not get a consistent, clean bend without any warping. Similarly using tube reinforced with some solder wire inside.

The solution is very similar to the pewter power cables. Metal rod facilitates sharp bends while retaining the circular profile so I decided that some thicker diameter solder wire would be the way to go. 3mm is 1/8″ and that sounded like it would be a common size. I knew I didn’t have any but I checked with another engineer friend of mine and he was kind enough to donate a 150mm length to me. It saved me having to buy an entire reel!

The solder behaves absolutely perfectly for this kind of application. To bend it I drilled a 3mm hole in a block of timer, inserted the wire and then just bent it over with my thumb. Because the solder is so soft it can be cut fairly easily using just a sharp hobby knife! It is easy to accidentally mark the solder though, so you have to be careful handling it. I inadvertently made a couple of marks with my fingernail, but not deep enough for me to worry about too much ๐Ÿ˜‰

Centurion Update 23

Posted by Mangozac on January 29, 2014

Quick update before I go to work to show you all the progress on the cannon design. It’s coming along very nicely! As I’ve said before I’m much happier with the larger cannon size. Obviously there’s still a lot more detailing to do (the muzzle is yet to be built too), which I’ll hopefully get completed in the next week or so.

Centurion_WIP_97

Centurion_WIP_98

Enjoy!

Centurion Update 22

Posted by Mangozac on January 21, 2014

I received some queries asking what exactly I did with my CNC router for making model parts, so having just finished cutting out the upsized cannon parts I thought I’d share:

The first thing I do is draw the parts in a vector graphics program called Inkscape (the open source alternative to Adobe Illustrator). It’s a great program! I then choose to make a copy of the artwork and convert everything to toolpaths. I’m using a 1mm diameter cutter for this so the toolpath will be 0.5mm (the cutter radius) outside of the line I want to cut. While there are automated tools for converting vector artwork into toolpaths, I’ve found that doing it manually doesn’t take that much longer and is less error prone. More importantly it allows me to precisely control the locations of the tabs which hold the part to the sheet. Kind of like sprue gates on injection moulded parts (although a different purpose).

Once I have the toolpaths drawn up I export them as a dxf file. This can be loaded directly into my machine control software.

I have an abundant supply of 1mm and 1.5mm styrene sheet, so I cut them up into approximately A5 sizes to fit on my router table. The styrene sheet is clamped down and I run the program. It generally takes anywhere between 5 and 15 minutes for most stuff I do. Note that I’m cutting out solely in 2.5D: cutting out 2D shapes.

This is what I end up with:
Centurion_WIP_96

I then cut the tabs and start assembling. Easy! While it’s not a 5 second process, it’s still WAY faster than having to cut out all of that detail by hand (especially if there are duplicate parts) and provides such precise curves and geometry I shudder at the thought of doing many of my parts any other way!

So tonight I’ll start assembling the new cannon. I’m really pleased with the design tweaks I’ve made too.

Centurion Update 21

Posted by Mangozac on January 17, 2014

I just wanted to drop off this quick update today and whet everyone’s appetites ๐Ÿ˜‰

My CNC router was temporarily back up and running (it was assembled to the bare minimum necessary to cut out the cannon parts but has since been disassembled again so I can tidy it all up and reassemble properly) so I got my cannon parts cut out!

I give you the beginnings of the cannon design:
Centurion_WIP_95

The basic design concept was drawn up by my friend Xeones, and it was then up to me to translate it into a physical design. There is one big problem: it’s not big enough! You see I scaled it around the sizes of styrene tube I had in stock but neglected to print out a 2D paper copy first to ensure it looks correct. It’s a smidge too small :(

Actually, at this point I should interject that realistically it’s probably quite an appropriate size as is, but the style I’m going for is that over-the-top sci-fi style we all know and love, where guns are far oversized.

So I’m now tossing up between just making modifications to this design or starting again and making it bigger (I’ll have to buy some larger sizes of styrene tube). The beauty of using the router is that I can just scale up the parts by ~20% and re-cut it out. Also, I’ve got a couple of tweaks that would make it even better so it’s very likely that’s what I’ll do.

I’ll have to hurry up and reassemble the router ๐Ÿ˜›

Centurion Update 20

Posted by Mangozac on January 8, 2014

Happy new year everyone!

I’m fortunate that my day job takes a 3 week vacation over the Christmas holidays. The first week was spend doing Christmassy stuff. The second week I spent on a yacht on the Gold Coast. Now here I am with my third week half way through and progress on the Centurion is starting to gather momentum!

I’m been focussing primarily on the cockpit detailing, which is a slow and fiddly task. I’m actually a little bit disappointed at how it looks in pictures (tiny model parts always look less impressive in photos) but with another layer of details (like structural details) it will be good to go!

Centurion_WIP_93

I’m sure you’ll be excited to see the first WIP shots of the pilot, as is being sculpted by my mate Marcus. The body is pretty much done, just the arms are left (which require me to complete the hand controls first, still WIP in the following shots). I’m really pleased with how it’s turning out!

Centurion_WIP_92

Centurion_WIP_94

After I took the above photos I gave everything an airbrushed coat of Tamiya Liquid Surface Primer and am very pleased with the results. The parts look better than I’d imagined when all a uniform grey colour!

I’m hoping to test out the new control system I’ve built for my CNC router tomorrow afternoon, so I’d better pull my finger out and draw up some patterns for the weapons so that they can be cut out…

Airbrushing Tamiya Surface Primer

Posted by Mangozac on December 30, 2013

Warning: epic blog post ahead!

OK so it’s no secret that Tamiya Fine Surface Primer (in the small and large spray cans) is the best hobby primer out there. Some people say they get great results with other brands but either they haven’t tried the Tamiya product or are not willing to pay for it (because let’s admit it, it’s expensive stuff). Note that some people highly recommend automotive primers as an economical alternative to specialist hobby products. That may be the case but I’ve not yet felt the need to try it out.

The Problem

I recently found myself looking for a primer that I could airbrush onto master parts (specifically for my Centurion project). There are two reasons I like to prime master parts:

  1. A single colour makes it much easier to get an appreciation for where the parts is at aesthetically, rather than if it’s comprised of many colours (like white styrene, yellow Milliput, clear 3D prints).
  2. It does some very light filling and will reveal any flaws with the surface texture.

Note that grey is my preferred priming colour – both for master parts and models to be painted. It’s very important that a quality primer is used, since it will often end up being removed by scraping and sanding. Good adhesion will prevent any flaking around scrapes and a smooth transition to sanded areas.

Usually I’d just hit the parts with the Fine Surface Primer from the spray can, but those who are familiar with it will be aware that it lays down a fairly heavy coat. For master parts you want the coat to be as light as possible to that details remain as sharp as possible. Also, for every square millimetre of primer applied to the part about 10 times that amount is wasted into the air (did I mention it’s expensive?)!

Potential Solutions

I did some research and came up with two options. The first was to decant some of the spray can into a jar and then spray it through the airbrush. Certainly improves control of application but is still relatively expensive. The other option is to use Tamiya Liquid Surface Primer thinned with Tamiya Lacquer Thinner. Here’s the three items:
Primers
So what’s the best way to determine suitability of a new product? Try it out, of course!

The Experiment

I grabbed a piece of scrap styrene sheet that had a bunch of holes drilled in it and prepped it for priming. I then divided it up and sprayed three separate test strips:

  1. Fine Surface Primer directly from the spraycan.
  2. Fine Surface Primer decanted into a jar, mixed with some Lacquer Thinner and sprayed using the airbrush.
  3. Liquid Surface Primer applied using the airbrush.

I used my trusty Iwata HP-CS airbrush (0.35mm nozzle).

This is what it looked like:
Primers

This is probably a good spot to mention that the Liquid Surface Primer does not thin with Mr Hobby Thinner. It just globs up. So there’s obviously something different about them. I didn’t have any automotive thinners handy to try out, but for what it’s worth just use the Tamiya brand stuff.

Results

My very first comment in this post stands: Tamiya Fine Surface Primer in the spray can is the best. It applies aย  much smoother coat than the airbrushed mixtures, however admittedly that is likely due to the high flow rate. To test the quality of the samples I used various techniques to scratch the paint:

  • Scratching the samples using my fingernails did leave marks but on none of the samples did it go through to the plastic.
  • Scratching with a bamboo skewer did eventually wear down to the plastic. It’s hard to tell but I think the spray can applied primer was a little hardier in this test.
  • Metal tools scratch straight through to the plastic. Kind of to be expected. Importantly though, this did not result in any flaking around the scratch, proving that the primer is exhibiting good adhesion.
  • There doesn’t seem to be any difference between airbrushed Fine Surface Primer and Liquid Surface Primer.

So my recommendation: for priming master parts airbrushed Liquid Surface Primer seems to be great. For actual models I’d still stick with the rattle can version, just to be absolutely sure (perhaps just airbrush on specific areas where detail preservation is of utmost importance).

Addendum

I should probably come clean: the reason for the above experiment is because I was very silly and after buying the Liquid Surface Primer and lacquer thinner I decided to apply it straight to a Centurion master part. Very bad idea! The primed part had a glossy finish to it and has remained with a slightly tacky feel. It seems it just won’t fully cure.

I must have thinned the primer too much, as it took many coats to get an opaque covering and not being too familiar with spraying lacquer paints it seems I made a rookie mistake. From whatย  have read applying too thick a coat of lacquer (especially when it is heavily thinned) will result in curing problems like this. Bugger.

I did the above experiment to ensure that the problem was actually with my technique and not the Liquid Surface Primer itself. That was proven. My tip is this: don’t shake up the Liquid Surface Primer bottle before sucking some out with a dropper for mixing in the airbrush. The primer and some of the thinners it sits in separate when it’s standing and it seems best to leave them that way.

TL;DR (Summary)

  • Tamiya primers are awesome.
  • Liquid Surface Primer (in the bottle) and Fine Surface Primer (in the spray can) seem to be the same base product, but the rattle can stuff is ever so slightly better.
  • Thin the Liquid Surface Primer with Tamiya Lacquer Thinner (yellow lid).
  • Don’t thin the Liquid Surface Primer too much for spraying and ideally don’t shake the bottle before dispensing the primer for thinning.
  • Apply only thin coats. Heavy and/or especially “wet” coats will result in curing issues.

I hope this will be useful to someone! Thanks for reading!

Centurion Update 19

Posted by Mangozac on December 18, 2013

Brass etch success! Yay!

The photosensitive coating kit I bought from ebay/China worked but it gave pretty poor resolution so wasn’t suitable for this. It may have worked if I experimented with it a bit more, but instead I decided to play around with the PRP photoresist spray again.

I’ve got applying a nice, even coating sorted but it seems that the biggest requirement is a fairly long exposure time. On this piece it was up around 15 mins (as opposed to around 1.5 minutes for pre-sensitised blank PCB). I get the impression that a slightly thicker coating and even longer exposure time would provide for even better results.

The etching went well (I should have heated up the etchant a bit more) and admittedly I pulled it out a little prematurely, but I preferred to have it under-etched than over-etched.

Anyway, enough talk; check it out!

Centurion_WIP_91

There’s a few bits that are unusable, but for the most part it’s pretty good! Once this is posted I’m going to go and cut some out to begin using them!

I also did some detailing on the inners of the shoulder rings:

Centurion_WIP_90

Centurion Update 18

Posted by Mangozac on December 9, 2013

I’ve been busy over the last few days and made some great progress – although I don’t think that the pictures really do it justice! The exterior of the torso is 99% complete. I’m just waiting for an order of Tamiya supplies to arrive so I can prime it all grey with the airbrush (rather than the difficult to control excessive spraying of the Tamiya Surface Primer cans I usually use).

Most notable recent additions are the spotlight just forward of the main hatch and the lifting points on top of the torso. I admit I’ve gone a bit overboard with the lifting/tie down points, but I like them as a detail ๐Ÿ˜‰

Centurion_WIP_87

Centurion_WIP_88

Centurion_WIP_89

As you can see I’ve also filled in the shoulder cylinders with a ball socket. I’ve machined up the matching ball which the weapons/arms will mount to. I still need to do some detailing around the sockets. Hopefully I’ll be able to get stuck into the interior very shortly!

Centurion Update 17

Posted by Mangozac on November 22, 2013

I’ve got a quick update this morning showing off the reactor detailing progress. Not the best picture, but I think it conveys the gist of it. I ended up going for a pair or fans with cylindrical cowlings and am pretty pleased with how they’ve turned out. The fans themselves a Kotobukiya Modelling Support Goods option parts (ordered from Japan – I don’t know any local retailers that stock them). I also added some lifting attachment points on brackets on the rear corners of the reactor. I’ve added similar points on the front of the shoulder discs on the torso (that I didn’t realise I hadn’t taken a picture of yet).

The lifting points have a hole in them that goes all the way through, but I have a thin disc of styrene edged in the middle so that they cast easily (this then has to be drilled out during assembly of the kit, although it’s thin enough that it could just be broken out using a sharp point).

Centurion_WIP_86

So with the reactor detailing almost done the torso is extremely close to finished. I just need to do the hinge for the hatch and finish off the neck. The interior still requires a lot of work, but that won’t stop me from hitting the exterior with some primer and even putting some of the exterior parts into silicone. Hopefully I’ll make a start on the cannons next week…