Published January 31st, 2017 by

Well, I got so engrossed in completing this project that I didn’t update the blog for quite some time. I’m now going back and “filling in the gaps” with the build info. I’ll start by wrapping it up with the final summary and pictures.

I’m very proud of how everything turned out, especially since when I started I had little more than some metal and a saber saw. A lot of things were built along the way and every one of them was worth it since I learned so much. This project was one long education.

The final arm is fully articulated and I finished a acrylic display for it with some custom lighting. It took approximately two years of spare time from start to finish. In hindsight that seems extraordinarily fast when I include everything else that was built to help the process, not the least of which was my custom written CNC software & software (see the my blog section on MillDroid).


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4: Terminator T800 Hand - Metal Build

Published November 20th, 2014 by

Now we’re getting serious. I have spent about two years tooling up for this build and now I’m making real parts.

I’ll start with the three middle fingers bones. These are similar enough to be machines together and should save some time on tool changes and holding.

I started by rough cutting three bars of 3/4 6061 Aluminum on the bandsaw then truing them up on the mill with a carbide facemill.IMG_0008

One side of each of these phalanges gets milled down a bit. This makes it a bit of a chore to hold in a chuck because they are more difficult to center….so i use a four-jaw independent chuck.


I don’t have a lathe so I planned to mount my rotary table as a fourth axis and (slowly) mill out the center of the stock to create the “bar-bell” shape of the phalanges. I wrote a custom tool for my MillDroid code that makes setup simple and mills each one in about 40 minutes. A Lathe would undoubtedly be faster, but I don’t think i would want to subject a small mill to the interrupted cutting of taking a square piece of stock down to a cylinder….that’s a lot of abuse to the hardware.


The pieces moves past the 1/2″ end mill left and right, rotating the A axis every pass by several degrees.



Three barbells later! Good finish on the cylindrical parts is achieved with a quick pass of wet sandpaper grades 360-500-1000-1500-2000 in increasing order before I remove them from the rotary table chuck.

I wrote a Slotting custom tool for MillDroid to cut the slots that run through the core of the cylinder in the barbells.

Holding these odd-shaped parts securely for the next cutting operation required a bit of R&D. I built a jig for my tooling plate to keep the parts centered between two aluminum plates then clamped them down with an aluminum bar. The offset side it lifter with a metal shim to keep the whole thing square.


Now I could use a carbide flycutter to cut away the ends into the required L-shapes.


4: Terminator T800 Hand - Metal Build

Published January 28th, 2013 by

Since I was already finishing the new rocket I decided to clean up and refinish the old one at the same time. Besides, I hated the black/red color scheme (it seemed like a good idea at the time).

I polished and patched up the original Cobra’s old balsa fins lightly with epoxy and refinished the tubes and nose. It wasn’t worth filling the seems on this old girl. Several coats of primer for both with lighter and lighter wet sanding between coats. It was after taking hours to paint with my airbrush that I decided that I needed a faster method of painting….these babies were too large to paint with a small airbrush. I picked up a more “automotive-scale” airbrush and things went a lot smoother.

The newer version gets several light coats of thinned enamel with more wet sanding between coats. Then a few final coats to get a mirror finish. I was very please with the surface quality on this bird–it was my primary goal to get a mirror like surface and I pulled it off.

Some details that were painted separately, some masking/painting of the fins and the girls are ready to fly!


Published January 28th, 2013 by


When Moebius came out with a Lost in Space Jupiter 2 model I knew I had to build one. Unfortunately it had very little detail. I spent a good amount of time detailing it, although I was never really happy with my interior painting and lighting. I designed and built some circuitry to create the fusion engine core lighting on the bottom of the ship using some CMOS counters and LED drivers. I then put a small sound sampler chip with a tiny bit of memory inside and recorded a sample of the ship taking off from the original TV Series pilot. It could playback the sample and accelerate the engine lights to simulate takeoff with the sound fx of the original show!

Jupiter 2

Published December 28th, 2012 by

After doing my research on the Terminator T800 hand I started building some of the “bones” in plastic and resin. If this all worked out well I would proceed with the complete hand.

All the “bones” in the T800 arm are rod stock in diameters that are impossible to purchase. I then went looking for items that were the proper diameter from which I would then cast resin duplicates. AAA batteries, and X-Acto handle, a mechanical pencil and a few others were all tubes in the diameters I needed. I cast silicone rubber molds from these and resin casts were struck. I then sanded down the resin casts to make half and quarter round versions and made rubber molds from these for new casts. After about two weeks I had several quarter, half and full round stocks in the various diameters for the bones.

I then laminated various thicknesses of styrene stock together to build sheet stock in the sizes I would need for the “knuckles”. I laminated a bit thicker than the actual piece then wet sanded down to the true sizes. Several sanding passes to round off corners to the proper radii resulted in some very accurate knuckles.

At this point I experimented with CA glue and epoxies to cement and fillet the bones to the knuckles and test a prototype. No pulleys or non-structural details at this point.

Although it was very cool to see the structure and shape coming together I felt that the resin/glue was a bit flimsy. I had experimented a bit with adding glass fiber to the resin casts but it didn’t help much. I was also concerned that painting the hand in metallic would be even more difficult because of the moving parts. I began reconsidering the medium and started thinking about metal.

I already own a full compliment of woodworking tools but metalworking would require an entirely different setup. I spent about two months researching and talking online to people and came to the conclusion that I would need (at minimum) a lathe and a mill. I looked into Chinese mini-mills and several others and settled on a Sherline. Small enough for what I’m working on and expandable to within reason it seemed like a good setup for this and other projects. I’m also planning on designing my own encoder readers and software for measurement before I make it CNC compatible. Therefore the T800 arm will be on hold for a bit as I tool up for metalworking.

2: Terminator T800 Hand - Resin & Plastic Attempt

Published December 17th, 2012 by

I’ve wanted to build a Terminator T-800 arm for some time but couldn’t decide on the medium.

Machining the entire thing from Aluminum stock would be very cool but metalworking is not my specialty. A metal mill and lathe would be required.

I considered machining the parts from machinable wax then casting in resin. Since there are no duplicates anywhere in the arm casting wouldn’t be efficient. Casting is ideal for multiple parts that are identical so it seemed like overkill in this case.

I decided to approach the project as a buildup in styrene and resin. First I’d do a prototype of one phalanx of the index finger of the hand. This would allow me to test the strength of the build and the epoxy & glues I’d be using.

Since the project required some drilling into very small pieces I would need a new xy-table/vise for my drill press to accurately position parts. I did a lot of research and the general consensus was that almost all those available are from China and they suck. Online discussions led me to believe that the only way to get a decent xy-table/vise was to take one of these and fix it. I found one at Harbor Freight that had the basic capabilities. See my blog posting about getting the vise up to caliber.

New drill press centering jig, check. Fresh orders of silicone rubber, resins, sheet styrene, epoxies on the way.

I found some decent blueprints on the internet that someone had made from the actual movies prop and some very good reference photos.

T800 Arm

Published November 1st, 2012 by

I’ve wanted to build a Terminator T-800 arm for some time but couldn’t decide on the medium.

I considered machining the parts from machinable wax then casting in resin. Since there are no duplicates anywhere in the arm casting wouldn’t be efficient. Casting is ideal for multiple parts that are identical so it seemed like overkill in this case.

I originally decided to approach the project as a buildup in styrene and resin. First I’d do a prototype of one phalanx of the index finger of the hand. This would allow me to test the strength of the build and the epoxy & glues I’d be using.

I found someone on the internet that had had access to the original Terminator props and precisely measured them, transferring it all into very accurate blueprints. Nearly 60 pages of them.

I started the research and development for the plastic version in October of 2012.

I’ve broken the project blog into several categories based upon my attempted approaches.

Attempt One-T800 in Plastics was in plastics, which I abandoned after about a month of work. It wasn’t giving me the strength or heavy metallic feel I was after. I though metalworking would be much better but had no metalworking experience.

I decided to learn metalworking. That single sentence contains a LOT of work and about a year and a half of R&D learning and tooling up to be able to do it.

Attempt Two-T800 Hand Metal Prototype was practice–I learned CNC machining and wrote my own CNC Milling application….mainly because I though that what was commercially available was buggy and sucked. For details on that adventure, see my blog entry on MillDroid.

Most of the Shop projects on this blog are a result of the learning experience I spent on the T800 hand. Learning techniques, building my own tooling, restoring old metal tools that I could use. An expert metal worker could probable have done the hand in a week; I had to learn and build everything along the way. These distractions, while time consuming, helped me with the techniques I would need as I built the hand. I’m nothing if not very patient.

Attempt Three-T800 Metal Hand is my true build of the hand using all the tools and techniques I’ve learned over the last year and a half. Now I have to complete it without any new distractions or new tools 🙂


1: Terminator T800 Hand - Introduction

Published January 10th, 2012 by

After purchasing my Sherline Mill and customizing it to stepper motors and full CNC I spent a few months playing with scraps and learning some metal working techniques. What a different world from woodworking!

I used the ‘standard’ Mach3 software to control the mill, but have continuously found myself despising the software. I’m certain that when it was written it was the top of the heap.

However, this software is buggy as hell. It crashes a LOT. Many of the ‘features’ are either beta and never finished, or assumed to work and never tests. It handles the basics fine–give it G-code and it will run–but I really wanted to use it’s Visual Basic capabilities to program my parts manually. The VB interface (which isn’t really VB but is actually something called Cypress Basic) is also very buggy. I think it was patched into the code to claim VB capability but never truly debugged entirely. When I inquired only of Mach3 experts about some issues I was told I “wasn’t using Mach3 the way it was intended”. That may be so, but I was only doing things the software claimed it could do. If it crashed with just a little pushing what good was it?

It took a LOT of time to make the code work and I still see a lot of Mach3 crashes. The company that now owns the ancient Mach3 code base has been claiming a new version will be out any day for the last few years….I’m thinking they had no idea what they were getting into with that project. They’ve also said that the new code will no longer support VB scripting, chosing LUA as it’s new script language. I have nothing against alternative scripting languages, but LUA?? In twenty-five years of programming I’ve only seen one other application that used LUA and even they switched to Python after a few years. This is what happens when programmers make decisions that should be made by users. What to they say about eating your own dog food….?

I’ve been giving serious consideration to writing my own Mill controller. I don’t think I’d even use G-code as a base. It seems like something that could use an entirely new approach and it would be an interesting project. Right now I’m putting it off until I get some more chips made……

A few practice pieces from 6061 aluminum…..I have a local metal working supply shop that has a large selection of end mills in bins for a couple bucks each. It’s a great local resource and let’s me avoid shipping costs every time I need a simple tool. Need a 3/8″ double-sided 2 fluted high speed steel end mill? They’ve got 50 in stock for $3.00 each. At those prices you don’t feel bad experimenting and breaking a few end mills.

I’ve been making some parallels from hot rolled steel but doing most of my cutting with 6061 aluminum. I really like the aluminum better and think it will be a better material for the T800 hand. The Sherline Mill is a very nice piece of hardware. The main thing it is missing are covers for it’s ways, but that isn’t fatal. I figure that by the time I wear them out I’ll want to build a larger mill from scratch.

First T800 phalanges for a single finger. Lots of metal removal and some operations that would probably have been faster on a lathe but I figured out a way to do them on my CNC rotary table on the mill. Takes longer but worked very well once I figured out the math and code.

I purchases a vibratory tumbler with the intention of polishing the finished pieces. Through some trial and error I found that Ceramic media left the Aluminum with a black coating (Aluminum Oxide, perhaps?) After some experimenting I found that tumbling in Plastic Pyramid media for 2 days, then walnut shells embedded with red rough for 8 hours produced a nice polished chrome-like appearance. Too long in the pyramids caused the edges of the metal to “round” more than I wanted.

The quest for walnut media was interesting. Online suppliers wanted $50 for small quantities (several pounds) of crushed walnut shell media. An online metalworker suggested to me looking in a pet store for Amphibian/Lizard Litter used to line the cages of pets. Sure enough, they had twenty pound bags of the stuff (pure ground walnut shells) for $8.00!

The Red Rough I added to the walnut media was suggested online…..that stuff is messy. It sticks to everything including your hands. I’m going to try some tests without it and see if the difference is noticeable.

First programming lines, then block removal, then arcs, then slots….I practiced some of the basics. I wrote everything in VB/Cypress Basic and it generated the G-Code that ran in Mach3. I put a lot of error correction into the VB to catch Mach3 Exceptions.

Through the combination of the rotary table and the mill I’ve managed to avoid purchasing a lathe. It would definitely be faster to do some of these cuts but I really like the fact that I can do all the setups on the mill.

After a few weeks of practice I’ve started milling actual parts. I’m actually starting to get the hang of this metal stuff…..

Now I’m ready to begin doing finish parts.

3: Terminator T800 - Metal Prototype Attempt

Published December 8th, 2011 by

My original plan was to pilfer the two 36″ nylon parachutes from my never flown Sparrow rocket for recovery. However after feeling the weight of the new bird I’m starting to think I might need some beefier chutes. Also need to track down some heavy-duty shock cord to absorb the ejection charge.

One of the things that the original rocket had a problem with was that the nose would “bang” against the body during descent and do some surface damage to the fins and body tube. I could have the nose and body recover separately but I think some adjustments to the position of the chutes along the shock cord can cure this problem.

Have to work on recovery stuff a bit….also need to decide on launch guidance. This one is a little large for a standard rod/lug system so I’m looking into a rail-guide. Need to do a little more research on this.


Published December 8th, 2011 by

Now that the four fins have had their bases epoxied to the engine core using the outer body as a guide I can remove the core and begin reinforcing the fins and interior.

I purchased some heavy duty fiberglass cloth for the reinforcing of the engine mount tubes, fins and centering rings where they all will bond together. For this I used pure epoxy (no thixatives or micro-balloons) so it could saturate the thick cloth and seep into the wood surfaces for a secure bond.

Thanks to my old friend gravity, I could only do one side per day. This prevented the epoxy from dripping down fins or running down the body. The US Composites Epoxy I use is extremely thin in it’s purest form giving it a good soaking bond but runs are quick to appear. Even though the pot life was 15 minutes I wanted to make sure there was no chance of runs. The pure epoxy is very hard to remove or sand.

Three layers of heavy 6 oz. fiberglass cloth/pure epoxy across each fin root/centering ring/engine tube. Then a wrap of one layer of 6 oz. cloth around the entire remaining length of the engine core tubes for some added strength. This should help distribute the engine thrust across more of the length of the main body tube.

A test fit of the finished engine core/fin unit into the slotted body tube showed that it all fit together. Whew!

Side-by-side of the last version with the current version ready for final assembly and final primer & sanding. The new baby is a little taller because of the difference between the old Estes-BT101 nose cone and the PML 3.9 Nose cone but this couldn’t be helped without turning my own nose cone. Since I don’t like lathes this’ll have to do. I did shorten the body a couple inches to help compensate but the added length will help compensate for the heavier tail due to added engine weight. Looks like the center of gravity will be darn close to the location of the original helping to maintain stability. A trip through the RockSim software helped confirm this theory.


Published November 30th, 2011 by

It took another coat of primer, sanding with 220 grit then wet-sand/polishing with 600 grit paper to get the fins to a silky smooth surface. Now that I’ve completed the whole fiberglassing process for the fins I’m 95% satisfied with the results. I think the fiberglassing process gave me fantastic strength but the amount of labor to finish the outside of the fins and get a glassy-smooth surface just wasn’t worth it. Given another take, I’d triple up the heavy fiberglass on the interior of the fin between the perpendicular basswood layers but I’d skip the fiberglassing of the outside of the fins and go with multiple coats of sanding sealer. The pinholes and slight waves in the fiberglass surface just involved too much work to get a glassy finish.

First I scraped the root of the fin down to the wood and soaked the edge with pure epoxy to allow it to sink into the wood for a few minutes. After dry-fitting the engine core into the main body, I added cabosil thixative to the epoxy to keep it from running and applied it to the engine core fin location through the body slots. Now the fin could be inserted into the body slot without worrying about the engine core or fin being glued to the body. By not gluing the core or fins to the body I’ll be able to remove them and reinforce the fins and core later.

Second fin epoxied on (1 every eight hours, allowing time for the last fin to cure and not “drift”. Gravity is my enemy when gluing up. Pulled the engine core our to check that everything was still removable–didn’t want to find out it was too later after the fourth fin….then put it back in for the third and fourth fins.


Published November 26th, 2011 by

Before slotting the main tube for the fins (which are mounted through the wall and onto the engine motor mounts) I though I’d try a test. I wanted to be sure that my jib saw wouldn’t vibrate the tube too severly and shatter or crack the spiral seams I had to painstakingly filled. Glad I did. The jigsaw shook the test tube enough to rattle out some of the filler. Now that I know I tried using my Dremel with a cut-off wheel. Takes a bit longer because of the impregnated phenolic for it was worth it to avoid damaging all the labor I’d put into the seam filling. Cutting phenolic tubing is more like cutting oak than paper.

Now the tube has been slotted to the fins. After they’re completed I’ll do a dry bit of everything. A compressor comes in very handy for eliminating dust after sanding….just remember the goggles and respirator when blowing all that phenolic and fiberglass dust about.


Published November 26th, 2011 by

Although I learned a lot about fiberglassing by using it on these fins I’m not sure I’d do it again. Although the added strength is wonderful the work that I went through finishing the outsides doesn’t seem worth it. Too many air bubbles or waves to fill. Not sure how to reduce that and still get a perfectly flat surface. I think next time I would increase the number of fiberglass/epoxy layers within the fin’s layers, then stick with sanding sealer on the outside of the plywood. Here’s a few more shots of spot filling the surface of the fins and primer, gradually getting the smooth surface I wanted.

After one last coat of primer I’ll hit them with some wet sanding at 600 grit to prep them for final paint.


Published November 26th, 2011 by

Filling in the PML phenolic body tube spirals is definitely the most tedious part of this project. Three successive passes each of filling, sanding, priming to get them nearly seamless. I say “nearly” because I can still see them if the light is at the right angle. I will definitely try Quantum tubing next project if for no other reason than to avoid this labor-intensive process.

Pics of each pass getting gradually smoother. Also more squadron putty for pass two on the seams and injection points on the nose cone….


Published November 20th, 2011 by

The PML 16″ nose cone arrived with quite a few flaws–seams, grooves, injection dimples…and a ding from a surprise driveway bounce.  Time to break out the squadron white putty and go to work. That stuff dries (too) fast so you need to work quick. It also dries harder than stone which makes sanding into a workout.


Published November 19th, 2011 by

Now that the fins have fully cured I cut them down to size with a jigsaw and a fine plywood blade. Because of the fiberglassing I wore goggles and a respirator. It’s tough to work when your covered from head to toe but it beats getting fiberglass dust in your lungs and eyes. That stuff makes drywall dust look course by comparison. It gets into EVERYTHING. I keep my shopvac pointed at the saw blade while I cut to minimize floating material in my shop.

I half-rounded the leading edges and squared off the trailing, root and outer edges with a sanding block with progressively finer grains. I then brushed a thin pure epoxy coat onto the freshly cut leading, trailing and outer edges and allowed it to soak into the raw wood before sanding. This will seal the outer edges. I won’t do the root edge until the fins are mounted so that the raw epoxy will soak into the wood for a better bond.

The fiberglass and resin made the fins very tough and difficult to sand. I’d like to try a stress test sometime with some scrap to be sure but I’d guess offhand that the fins are at least 5-8 times stronger than bare wood.

The last Cobra’s fins were epoxied onto the outer body tube. This model’s body tube will be slit to allow the fins to be mounted “through-the-wall”. They will be fiberglassed directly onto the motor core. The notches in the fins allow them to mount over the motor mount’s 1/4″ plywood centering rings within the body.

The fresh-but edges of the fins clearly shows the glass-wood-glass-wood-glass layers. It’s a heck of a lot more work than the old balsa fin days!


Published November 18th, 2011 by

After sanding the filler, two coats of primer and sanding again the spiral grooves were better but still visible. Time for another coat of filler. This is a very tedious process that reminds me of rotoscoping. I can do about one inch per minute so a four-foot, four inch diameter body tube takes a while. Time to turn up some tunes and get in the zone.


Published November 17th, 2011 by

I don’t think we ever even though of filling the grooves in body tubes when we were kids but nowadays it’s standard operating procedure for a good finish. The main body four-inch phenolic tube has spiral grooves in it you could drive a truck through.

Filling them with a 4:1 mix of Elmer’s Carpenter Wood Filler and water works well. VERY tedious to fill these with a stick, then sanding them down lightly, repeating the whole process two to three times. Lots of dust, too.

Now it awaits some primer to really show off the flaws.


Published November 16th, 2011 by

Having settled on a six-engine cluster configuration I began building the engine core. I was also planning on the fins being mounted “through-the-wall” and directly into the core itself. This created a nice little puzzle for planning what could be built & glued first.

I started with the core “short”–that is, just past the length of the engines themselves–so I could work from both sides mounting higher power engine blocks. Later I would mount the ejection charge extensions and fins before mounting the completed core into the main body. The inner seventh engine tube is just a space-holder to keep the outer six in place while the epoxy cures–then it can be removed.

After cutting some 1/4 five-ply centering rings and dry-fitting everything I epoxied the core together. I used expended D-Engine slices as heavy duty engine blocks in addition to engine hooks to hold the engines locked in during ejection. Then a second pass of epoxy fillets thickened with Cabosil to keep it from running. After the fins are finished and epoxied to the engine core I will add heavy fiberglass and epoxy to strengthen the whole core mount.

Here’s the completed motor mounts awaiting fiberglassing for added strength when the fins are mounted to it. Can’t wait to see this puppy loaded with six E30s!


Published November 15th, 2011 by

During curing the surface epoxy developed two problems: Irregular surface dent from large bubbles between the epoxy and wax-paper protection layers, and micro-bubble pinholes from the plywood and fiberglass cloth degassing. Here they are highlighted because they are full of fiberglass dust after a light sanding.

I’d encountered degassing resin problems before while building my Arc Reactor prop and new that there was only so much you could cure with higher temperature epoxies and curing. Since this surface was to be painted I would deal with it post-cure.

I experimented with Cabosil-Aerosil thixatives and epoxy but found that an epoxy-based filler was far too hard to be able to sand down without damaging the existing epoxy finish down to the fiberglass cloth. I guess this is why we test on scraps.

I’d planned on using Elmer’s Carpenter Wood Filler as a patch for the body tubes and thought I’d give it a try here.

Worked great! Takes two or three passes of filling with a popsicle stick and sanding with very fine sandpaper. A mix of 3 parts Filler with 1 part water softens the filler enough to “flow” into the finer bubbles….but they do have to be filled individually. Too much filler on the larger surface means more sanding and that means risking sanding down to the fiberglass cloth and ruining the fin.


Published November 10th, 2011 by

My original cobras were tested the old-fashioned ways: you measured for center of gravity and center of pressure then “flew” the rocket at the end of a rope around you like a sling to test it’s stability before flight. THEN you launched and hoped you got it all right. Well now we have simulation software that lets you build and test your rocket before you even hit the hobby shop for parts. RockSim is a really nice simulation program and I used it to flesh out my designs.

Once I proofed my new design and had some simulation data to work with I settled on an engine configuration that could handle six D12s, six E9s or six E30s. I could probably jam in six F60s but that might be pushing it’s stability because of the extra engine length. Besides, big fields are harder to find now than when I was twelve years old.

First, fins. Although it worked well for my original Cobras, old-time Balsa wood is out of the question for this size. Some type of enhance composite was required. I had never done epoxy-base composites before so though I’d give it a try. New techniques keep my interest better. I experimented with carbon fiber, kevlar and fiberglass a bit to test some ideas. In the end, fiberglass was the most cost effective method and more than strong enough for this thrust class. Carbon or kevlar would be necessary if I get into the H engine and higher classes. Besides, they cost 4-10 times as much as fiberglass.

After doing some strength testing for a few weeks I settled on a five-layer plywood & fiberglass composite fin. By laying out the plywood layers with their grain perpendicular to each other I was able to increase the strength of the fin many times before even introducing the fiberglass layers.

I sandwiched a layer of heavy fiberglass cloth in epoxy between the two perpendicular grained, 1/8″ three-ply plywood bases.

This gave a very strong core for the fins.

Now for the outside. I layers a medium density fiberglass cloth in an epoxy soup with Q-Cells to make the layer softer to finish. Not enough to lose structural density–just enough to make the outside easier to finish sand. I sandwiched all the layers between two marble floor tiles–the smoothest, least likely to bend material I could find–and weighted them for 48 hours to cure fully.

Lost a test set because I didn’t realize that the epoxy lubricated the layers enough for them to slide out of alignment during the night even with weight on them. Learned a lesson–lock everything down tight!

The finished product is a lightweight, incredibly strong fin. But the finish left a bit to be desired.


Published November 7th, 2011 by

In 2011 I got the itch to fly again. I’m hoping to get my nephews out next spring for some flying so I decided to revisit the Cobra design. I think she’s still in my storage room…..

Well, she’s a little dusty and has plenty of dings (character!) and cobwebs but is still flyable.

OR…. I could build a better one with more power!

….Time to experiment with some newer building techniques first.


Published November 6th, 2011 by

I think I launched my first model rockets when I was around eight or nine years old at the local school fields. I remember my younger sister molly riding in my wagon as we hauled it and my fleet out for flight. She would chase them down as fast as I could launch them. When my other sister and brother were old enough they would accompany us as well. The early fleet was half store bought and half homebrew.

Polaroid! Those who remember Estes might recognize the SkyDart, Atlantis, Condor (sans Glider), Andromeda, Orbital Transport, Interceptor, Photon Disruptor, Mini-Saturn V, Mini-Beta (that was my little brother’s) X-Wing and Mercury Redstone. Also a homemade 110 Titan IIIc camera rocket I had worked up with Tony Campana, another bud. This was the fleet in January 1976. I took a lot of flack for painting the Photon with house paint. Hey, it was cheap and handy!

In Junior High I met Mike Aprile, Brian Hebel and Paul Candel with whom I would launch a lot of rockets. Between the three of us we flew anything Estes or Centuri made. Heilmann Park in Detroit was our field and the trees around that park probably still contain many of our birds that never made it back into our hands!

I entered the state competitions a few time back then and snagged a few ribbons. My dad would drive me to Ford Field for state matches and to watch the R/C Airplane competitions. He drove me around a lot for those things and always pushed me to enter those and join rocketry clubs and such and because of him I learned a lot.

I first saw the Cobra M1 missile in 6th grade in a military book. It was a four-inch diamter, four foot long anti-tank missle. I decided to build one in 1980 that was full-size, the actual size of the real thing. It used a D12 engine and gave a nice, slow, low flight at the state meet that year. I was mighty proud of it. This design became a foundation for me when trying new build techniques in the following years.

The same year one of the advanced rocketeers introduced me to medium/high powered rocketry…..WHAT? You mean there are engines bigger than an Estes D?! I’d never heard of such a thing! I was an E flight that year, and F and a G engine! I was stunned by the power of those things! The next year, I refitted my Cobra for an F100 and flew it at the state meet. However, I wasn’t prepared for the thrust the F100 could put out and it ripped the guts out of the Cobra. That was when I learned that Elmer’s Glue and Balsa were not up to the task.

In 1985 I built a new cobra using a three-D12 cluster (F100 engines were expensive!) and got several excellent flights. It was a good crowd-pleaser because it made lots of noise and flew slow enough to watch the exhaust. On it’s last flight I had a an engine core blowout and the remaining engines couldn’t eject the parachutes. After a nose dive from 900 feet she smacked the ground hard enough to wake the prairie dogs.

“What the heck went wrong?”

After repairs and a fresh coat of black paint she flew several more times before retiring to storage.


Published January 4th, 2011 by

I decided to create a stand for the whole thing by using my existing silicone ring mold and more urethane plastic resin but in a candy apple red/black to match the Iron Man armor. This combined with a bronze nameplate and a soft resting plate allows the arc reactor to remain removable for close examination or in the stand without scratching anything.

A power plug that matches the movie prop and we’re done!

About two month’s spare time went into it and I’m very happy with the final result.

When the lights are on it’s so bright that it’s hard to look at directly (perfect!).

Arc Reactor

Published January 2nd, 2011 by

I built each “layer” of the reactor so that each could be built independently of each other in case I made design changes along the way, and I was glad I did so.

I had planned on adding an inner ring of light to the interior of the reactor using an LED ring light used in car taillights. When I bought one it wasn’t as bright as I’d hoped to I scratched the idea. I decided to place eight more high-intensity LEDs behind the repulsor emitter in a 1/4″ area of space.

Here’s a pic of the layers disassembled and assembled:

The layers consist of:

The main ring, the repulsor shielding, the main power cabling, the repulsor emitter, the repulsor reflector, the light chandelier, the secondary lighting ring, the repulser emitter light, the electronics layer, the mechanical layer (gear) and the heat sink foundation.

Here everything is stacked together and some of the heat sink fins are removed.

An inner lighting test….neat!

Here it is with all parts assembled:

Arc Reactor

Published December 28th, 2010 by

I found some nice thin brass stock and brass wire for the transformer exterior wiring. I had intended to solder the fittings together but then realized that the plastic transformers would melt from the nearby heat. Time to make simulated solder!

After bending the brass wire to the correct shapes and sizes and cutting small brass mounting plates, I glued everything into place with medium-viscosity CA glue and CA accelerator. This causes the CA to cure before it levels too much and gives it a more “blobby” appearance. I augmented this appearance by moving the wires slightly as it cured to look more like manually soldered shaped. After all, Tony Stark built his in a cave from a box of scraps….it shouldn’t look too perfect.

A little solder-colored paint on each blob and the illusion is complete. I was very happy with this look.

Arc Reactor

Published December 27th, 2010 by

Winding the transformers was one of the more difficult tasks on the project. I experimented with painting fake surface to simulate wire windings and several other methods but I couldn’t come up with anything that looked as well as actual magnet wire. That meant manually winding the 10 transformers by hand since the ring was a single piece. Cutting the ring wasn’t an option although that would have made winding the transformers a heck of a lot easier. The process took about eight hours total spread over a few evenings.

It takes three complete windings of the 30 gauge magnet wire to completely cover the transformer and get the proper “rounded” look at the edges. The black cores you see are vinyl to block any light from leaking through the windings and spoiling the illusion of transformer thickness.

I would start by winding approximately 40 feet of magnet wire onto a small custom “spool” that I made. Then I could pass the spool around and through the ring the hundreds of times it took to wind each transformer.

Although magnet wire this thin can be stretched I was unable to do so because it would actually distort the resin ring if taxed too much! A lot of patience went into winding these buggers and trying to get the wires as straight as possible.

You can now see the little “fake screw” details on the transformer sides highlighted by the polished chrome paint–Floquil chome paint is nice stuff that take a light polishing very well.

Arc Reactor

Published December 23rd, 2010 by

Originally I planned to have the arc reactor be just the ring itself in thickness so it could be worn under a shirt. Like most of my projects it evolved into the complete prop including it’s base. The base as it appears in the movie looks very much like a heat sink (given some creative liberties). This added a few inches of thickness to it but also gave it more accuracy.

I started by trying to carve the heat sink “fins” (of which there are twenty total of two types) of styrene–my medium of choice. They turned out to be too thick for that approach so I went with plan B.

I carved a prototype from thin styrene, then “traced” that onto a rolled piece of Sculpy clay of appropriate thickness. I then baked this in the oven for hardness, finished it with files and coated it with a sealer so it couldn’t absorb moisture. This gave me a prototype fin (two different prototypes, one for each fin type actually).

Then I built a mold box to accomodate the Sculpy prototype and cast a negative mold in my old friend, Smooth-on Oomoo silicone rubber after spraying it with lots of mold release.

I did this one using a two-piece mold technique: I poured liquid silicone into the mold box while empty to the half-way point and let it level and cure for 90 minutes. This gave me a flat base thanks to our friend gravity. I then sprayed it with more mold release and place the sculpy heat sink fin prototype flat onto the silicone base. I then poured more silicone onto the fin to the top and let that cure. After 90 minutes this gave me a nice two-part mold in which one half contains the actual part. This has the benefit of keeping the “flash” caused by resin leaks at the very edge of the part and makes it easier to finish.

For the resin itself, I used Smooth-On’s “liquid plastic”, called Smooth-Cast 300. This stuff is fantastic! It’s very important to get the ratios precise–the tiniest amount off and your castings are too flexible and mushy. Even though the measurements are by volume, you need to be very precise about it–no eyeballing! The resulting urethane plastice is hard enough to be finished like plastic but it is difficult to get paint to stick to it. Washing it with a degreaser (I use Simple-Green) and a resin-prep compound it critical and it helps to rough it up a bit with 1000 grit we sandpaper before a base coat.

Because I made a creative change to the shape of the fins I had to start over, but it was worth it. The new shape I have for the fins utilizes them to actually hold the internal parts, eliminating several brackets that I was going to create. Now the fins become actual structure parts of the arc reactor.

Here’s the finished 20 cast heat sink fins of the final shape. The first two have been glued to their base….

They are so closely aligned that I had to create a jig to mount them properly after painting–I knew I’d never be able to get paint between them if I waited until after mounting.

The completed Heat Sink foundation:

Arc Reactor

Published December 20th, 2010 by

My original plan was the mount ten high intensity LEDs underneath the transformers. By lighting the ring from these hidden sources I thought I could hide the actual lights and cause the ring to appear to glow on it’s own. However, I cornered my self when I began to plan how to wrap the transformers with magnet wire. I found that I couldn’t wrap the transformers until after the LEDs were mounted, but I could mount the LEDs and run the wiring until after the transformers were wound.

I decided to redesign my lighting by placing the LEDs into a “chandelier” configuration underneath the repulsor emitter. This actually gave me a brighter light than my original plan.

Here’s a test lighting arrangement with LEDs and their current-limiting resistors….

Lighting also revealed my old enemy, the bubbles again. GAK! I hate those things!

Here’s the “Chandelier” arrangement I came up with to light the ring from within–it had to fit within a very small area of the repulsor emitter rings:

Arc Reactor

Published December 15th, 2010 by

The palladium ring–a roughed up copper wire ring painted with a thick, blobby mixture of aluminum paint to look like a cast piece of palladium.

Matches the movie piece pretty nicely…..

Needed a gear-like device with 200 teeth, so built that from styrene triangular stock and flat stock….one tooth at a time….

Not too painful. About two hours of work under a magnifier.

Now the circuitry layer–I mined a couple old computer motherboards I had for interesting looking pieces (chokes, larger electrolytic capacitors and diodes) then built a chassis for them. These are mostly hidden, but closer inspection of the arc reactor shows the inner detail even though the movie prop is never seen that close.

A little more brass paint and fake solder (chrome paint).

Arc Reactor

Published December 5th, 2010 by

Some small custom styrene circles painted with brass paint for the repulsor reflectors.

The Main Power Cable, from copper wiring and styrene tubing…..

Assembly of the main power cable, shielding and focusing ring holder along with flat metallic black paint for that nice “industrial build” feel….

Now add the repulsor focusing rings. The only “screen-type” material I could find at the proper scale was a tea-strainer! I painted it chrome, then cleaned out every hole in the screen because the paint had filled it in solid.

Arc Reactor

Published November 17th, 2010 by

I built the ten transformers from styrene sheet with the intention of hiding the lighting LEDs underneath; hence their need to remain hollow.

These were a tedious bitch to create. In hindsight I would probably have made one, then cast it in resin to make duplicates. Live and learn.

Time to test fit all existing parts on the earlier prototype resin ring (to avoid scratching the final ring)….

The transformers have a total of 80 tiny screw in the sides. I couldn’t find anything small enough so I experimented with carving my own using a template. I carved some brass into the shape of a tiny screw then heated it with a soldering iron and pressed it into the styrene. Took a little practice considering the scale.

Arc Reactor

Published November 10th, 2010 by

Time to make some of the internal parts (I was sick of clear resin at this point).

After trying to track down small, thin plastic or metal rings simliar to washers I decided to create my own. I created a circle cutter out of an old drafting compass by replacing the pencil with a finely sharpened steel pin. This made it easy to created the many circle cuts I would need, all smaller than 2 inches in diameter.

I started with the Emitter Shield….

I created a small jig for my drill press to make this a bit easier. Lots of fine filing involved in those oval vents.

Next, building the regulators and emitter brackets. Everything is carved from styrene at this point and glues with cyanoacrylate glues. I love CA….I use several different viscosities and epoxies but rely on the CAs the most. They’re very easy to control and predict because their speed of cure is so reliable.

I found some tiny scale screws and allen bolts that perfectly matched my requirements in my hobby shop’s scale railroad department. CA bonds them perfectly to styrene without the mess of epoxy. I also carved a few pieces from some sprinkler system hose attachments that were made of a very tough Urethane. One of these days I’m going to buy myself a lathe for this type of thing.

Arc Reactor

Published November 5th, 2010 by

Now that the silicone mold is working I can concentrate on the clear epoxy ring itself.

The first ring, with just a little blue/green tint, contained a massive number of large bubbles. I learned a lot online chatting with people who do casts for a living. Basically it all boiled down the temperature and pressure. The only way to totally remove the bubbles it to cast in a “pressure pot” that basically keeps your mold in a vacuum, causing all the bubbles to expand and pop. Since this requires an investment of about $1000, I decided to adjust the temperature. By arranging some light bulbs around my molds during curing (and testing about $12 in epoxy resin to make five or six test rings) I discovered that the ideal temperature was around 90 degrees Fahrenheit for 24 hours. Any lower and the bubbles continue to expand. Any higher and the epoxy cures too fast. This was the first attempt so you can see how many bubbles are created:

Ick. Looks like frozen Seven-Up.

Castin’ Craft, the company that makes the clear resin, also makes some nice tinting agents. I began adding those to get more blue in the color. I knew I would have to live with a certain amount of bubbles but I was determined to minimize it as much as possible without having invest in a pressure pot.

Notice that my ring is a bit less green than the movie prop pictures. Online research seemed to indicate that the actual prop had faded towards green or that the pictures weren’t color accurate–the actual ring in the movie was a bit more blue and I decided to go that way since the ring’s blue glow never looked green in the movies. Call it a creative decision.

After casting, I polished all sides and surfaces of the ring. I followed a regimen of grits as follows:

-300 light pressure passes with 80 grit dry sandpaper.

-500 light passes with 120 grit dry sandpaper

-750 passes with 220 grit dry sandpaper

-1000 passes with 400 grit wet sandpaper on glass

-1200 passes with 1000 grid wet emery paper on glass

This gave me a super-smooth surface (and hands that were sore for a few days). I intended to clear glosscote the ring, but experiments showed me that this gave me a bit more of a “wet look” than I wanted. Leaving it unglossed kept a slightly fogged look, but also helped hide some of my old enemies, the bubbles.

The final, color correct ring, after polishing:

I then drilled some holes for LED lighting that would be hidden under the “transformers” in my designs…Epoxy is an interesting material to work with; it remains a bit soft to work with and even after curing can be bent by squeezing it too hard. Caution is required when handling it.

Arc Reactor

Published October 24th, 2010 by

I built a full scale hollow ring prototype from styrene sheet plastic as a positive full scale ring and finished this perfectly smooth.

After building a mold box from styrene and locating a proper mold release agent, I poured and molded a proper silicone negative mold.

I decided to use an “open-face” mold as opposed to a two-part, sealed mold because it would allow me to better control the temperature of the epoxy during the curing process. I made the The prototype (and silicone mold) are therefor approximately 1/8″ deeper than the final ring to allow for later polishing. I used Smooth-On’s Oomoo 30 Silicone rubber–I recommend it highly. Good viscosity and tear strength and very easy to manage when it comes to bubbles.

Arc Reactor

Published October 15th, 2010 by

The first item to attack is the semi-clear ring that forms the foundation for the reactor. I looked into having clear acrylic milled (something for which I lack the tools) but most of the quotes I received were at least $60 each. I’d wanted to try casting polyester & epoxy resins for some time so I decided that this would be a good time to learn that skill.

Most of the casting methods I explored were expensive and toxic. Since winter temperatures were forcing this project indoors I decided to go with epoxy resins. My first attempt, after creating a plastic mold negative used a vegetable-based oil as a mold-release.

Major failure. The epoxy resin, normally clear, leached moisture out of the veggie oil and fogged the resin. As it turns out, moisture is the number one enemy of epoxy resins. Lesson learned.

I then obtained some mold release made by the same company that makes the epoxy. This failed to release from the plastic mold. What a mess….

You can also see some chunks of color from tinting that I added. During curing, the tint clumped together.

Arc Reactor

Published October 14th, 2010 by

While browsing online as some movie prop reproductions I noticed the large number of Iron Man Arc Reactors–hundreds, actually–created by fans. At the same time, I was amazed at how many weren’t even close to accurate. I don’t expect everyone to be able to build perfect replicas but I don’t expect tape, cardboard & 15 minutes work to garner hundreds of “wow that looks amazing” comments.

Of the Arc Reactors used in both Iron Man movies my favorite was the model he builds in the cave. It has a more “rustic”, built from leftovers feel to it. I found a few photographs of the actual prop used in the movie (which sold for around $50,000 at auction) and proceeded to attempt to duplicate it.

Here are two photos of the prop from the first Iron Man movie…..

Arc Reactor

Published January 3rd, 2009 by

This is a log of my adventure building a replica of the Super Star Destroyer Executor from The Empire Strikes Back. There never was a consumer released model of this ship and I’d always wanted to create one. When I found out that a resin cast model was available I knew I had to build one. The resin casts were well made but I wanted to add an entirely new level of detail to it including lighting. I’d built quite a few models in the past but never anything requiring such a wide range of skills so I looked forward to the learning process. Being deeply ingrained in computer graphics I enjoyed going back to old school techniques from before CG was feasible.

I began in early June of 2008 and finished near the end of November 2008. A few hours a night here, a weekend there. A few occasional week-long pauses waiting for toys like compressors or supplies to arrive as well.


Published January 3rd, 2009 by







I started to think about how the Executor just isn’t the Executor without some Avenger-class (or Imperator-class, if you insist) Star Destroyers flanking it. I remembered a small pewter Star Destroyer in a local collector shop. I checked the measurements of the Executor and sure enough, the Pewter SD was almost exactly the right scale (it’s about 1/2″ short).

Here you can see the size of the Avenger to scale. My original intent was to cast a silicone rubber mold and make a half dozen Avengers in resin to complete the fleet but I think I’ll scratch build an Avenger in closer scale. Seems like it I’m going to do it I might as well make it perfect.



Published January 3rd, 2009 by

Base still needs to be painted but everything else is finished!





Published January 3rd, 2009 by

Originally my intent was to enclose the entire ship in a plexiglass box. When the price of oil began to climb the price of plexi did as well (according to my vendors). I couldn’t get a quality case made for less than $400 and decided against it. So I spent some time building a base that mimicked the style of the destroyer itself. It was worth a week of work. The two verticals contain steel rods for strength and wiring. The large vertical has two aluminum rails that touch two screws on the bottom of the model to supply power.



Published January 3rd, 2009 by

Final assembly of the hull.

One thing I realized early on was that the internals–wiring, fiber, electrical–had no room for error. Because everything was glued as it was built, constant testing was essential. If I glued the hull together and something failed it was all over.

At one point I considered making the hull attach with screws or something, but it would have been impossible to do with less than a dozen or more attachment points and I didn’t want to mar the surface of the model with them.

It was a race to get the epoxy in place for the entire surface area around the hull before it’s pot time expired (30 minutes). I almost didn’t make it in time. Everyone should have dozens of these pony clamps on hand for projects like this. Note the sponge cloth protecting the surface of the model from scratching by the clamps.




Published January 3rd, 2009 by

I spent quite a bit of time experimenting with washes on scraps that I detailed and scribed.

Crushed pastel chalk in liquid medium was too “chunky”. It always looked dotted and didn’t flow well. Some liquids, even with wetting agents just didn’t dry well. Ick.

Dry brushing didn’t work well. It took a long time before you noticed that it was too dark and by then it was not fixable.

During the course of things I made the decision not to use a flat coat after paint. Everything I tried dissapointed me or played havoc with the paint. I even tried the vaunted “Future” and Tamiya flat base, but could never get it flat enough without going milky. There was no chance I was going to risk it. So without a final flat coat, I had to stay away from dry brushing and anything that couldn’t seal on it’s own.

I really liked how a was turned out. A drop or two of my base paint darkened with a drop of Blue Angle Blue and thinned with 10 ml of thinner worked very well. It darkened surfaces sufficiently and flowed well and could be blotted if it got out of control. Two or three passes worked well on areas that needed “separation” from flat surfaces. I was really happy with this.




Published January 3rd, 2009 by

Like all projects there are a few surprises along the way. During a dry fit of the two halves of the hulls, I discovered that there were some substantial gaps in the seams. Since there was no way I was going to let something like that happen I spent a few extra days creating edge details to fill the varying gap heights along the edges.


More edge gap fixing….


Another gap in the front filled between where the equatorial trenches meet.



Published January 3rd, 2009 by

Bundling fibers into place. A toothbrush was handy to “comb” the fibers into place. Everything needed to be mounted down to the lower 1/2″ of the hull because the upper cities would require all the remaining space in the body cavity.


Circuit board for the lighting placement, more projector mounts.


I found some great aluminum tape (usually used for ductwork) that helped to seal projectors so that there were no light leaks. It turned out to be very helpful because the LEDs were so bright that they leaked a LOT of stray light. Anything that wasn’t totally sealed (like an unpainted glue seam) would show light behind it. The tape is easy to shape, and unlike paper tape won’t dry out and crack.


A final light test shows that all the electronics are working.



Published January 3rd, 2009 by

Mounting the LED “projectors”. I wanted to be able to easily adjust the color of the lighting in windows in case I didn’t like it after everything was mounted. Also moving the wiring harnesses and circuit board into place.


One of the many LED projectors.  White LEDs in one end, Fiber out the other. The tubing keeps the fiber at the perfect 90 degree angle to the lens of the LED for maximum brightness, and a tiny slot in between let me place colored filters of thin plastic. This way I could try different color filters until I likes the windows and they matched the film model.


A few standalone white LEDs with Yellow filters to illuminate the landing bays at the front of the equatorial trenches. Just enough of a light leak to spill out under some carefully carved edges. Some of the light leaks are visible along the edge of the trench.



Published January 3rd, 2009 by

Interior lighting of the equatorial trenches. The fibers had to be arranged to allow for room for the city fiber lighting as well as the internal hardware yet to come. A lot of planning went into this. I also wanted a couple of “landing bays” near the front of the trenches as visible in the Executor in The Empire Strike Back. Hence, the openings in the trenches near the front of the model that I bored with the FlexShaft.



Engine wiring and underside city fibers coming together.




Lighting tests are always fun!






Published January 3rd, 2009 by

Engine lighting. It was interesting that if an engine LED was 1 millimeter further out than another, the engine would look totally different. I wouldn’t have thought it would be noticable, but was glad I found out before gluing.







Published January 3rd, 2009 by

More city final assemblies…..I can only do 1 or 2 a night since the surrounding cities need to be dry fitted each time to be certain of alignment. It’s a very tight fit and the fiber makes it even tighter. No room for mistakes.










Because of the large amount of fiber I had crammed into the bridge/conning tower and the number of fibers in the surrounding cities, it got quite right in some areas of the center of the model. Snapping fibers happened often (along with cursing) as I jammed everything into place. Nothing like 30 minute epoxy for keeping you on a deadline.




Published January 3rd, 2009 by

Assembly after final painting. Paint was a mix of 6 parts ModelMaster Intermediate Blue, 1 part Blue Angel Blue, and 6 parts mineral spirits. Thin paint, just like the primer, to avoid filling in the surface details. Approximately 3 very light coats. I keep a large halogen lighting rig on the model as I paint to keep it warm–not enough to dry the airbrushed paint too fast as it sprays.

Time to epoxy the assembled cities and feed in their optics.








Hurray! The two smallest cities in place……26 more to go, ugh. Better stock up on epoxy.