Sunday, 24 February 2013

Hot Wire Polystyrene Cutter–Part 2

I gave the base of the cutter a coat of wood filler and then sanded it down. The next step was to go to the electrical supply store. Off we went.

I bought a single throw switch (push button), an inline fuse holder, a couple of 5V slow fuses (in case one blows, I now have some spares) , a couple of speaker wire holders and a 4m length of NiChrome wire.

I wanted to mount the switch in the arm so that it would be easy to turn the cutter on and off. The plywood for the arm was a little thick, so I drilled a hole through it for the switch (1/4”) and then cut a rebate into the front so that the switch would be slightly recessed.

Switch Mount

The washer and nut were then put on the other end of the switch and tightened.

The power supply hot wire attaches to the switch and then goes into the fuse.


I am using some speaker wire clamps to hold the NiChrome wire. The clamp in the top arm is attached to a small plate inside the arm so that the wire is held over the hole. This gave me a little bit of a problem, because turning the knurled head is difficult in the space that I’ve left myself. Bad design, but OK for what I need. I can tighten the head with a pair of pliers.

Top Connector

The other end of the fuse attaches to the clamp.


Underneath, the job isn’t very hard. There is just so much space underneath that it is a dream.

I made a small barrier under the body that will hold the lower speaker wire clamp in place. Then I wired it up.

Bottom Connector

The AC Adapter is then threaded through the back of the arm and we are done.


The last thing to do was to take the cutter out to the shed and see what I could do with it.

Turns out … not very much.

The cutter does indeed cut, but it does it very slowly. I think that the adapter that I am using just doesn’t have the chutzpah that I need. However … it is more likely that I just have to wait for the NiChrome wire to heat up sufficiently. I certainly didn’t give it that much time. Oh well, I’ll give the cutter some warm-up time and see if that makes much difference, although I am leaning toward the point of view that if 5V ain’t enough, then maybe 12V will … I’ll start hunting for a 12V AC Adapter.

The bottom line here is that, I made a Hot (Warm) Wire Polystyrene Cutter for a total cost of about $20. If I had to buy the plywood for this project and the AC Adapter, then it would probably have cost me closer to $60. But that is still a hell of a long way shy of the $600 that I’ve seen these puppies advertised for.

I will repost when I have jiggered around more with the power for the cutter.

Saturday, 23 February 2013

Hot Wire Polystyrene Cutter

There are definitely two schools of thought when it comes to carving polystyrene. On the one hand, there is the sharp knife, saw, rasp and sandpaper camp. The benefits of using hand tools is that you have the pleasure of being able to handle your material and the designs can be more organic. The down side to this method is … polystyrene dust. I have seen some truly awesome models using this method of carving. On the other hand, there is the hot wire camp. Hot wire gives you a clean, crisp. The down side there are fumes from burning polystyrene.

I’ve tried using the saw and knife method and, clean-up is a pain in the ass. I used to have a little hand-held hot knife that I used to use for making terrain for wargaming. It was a little 9V battery in a plastic grip connected to a U bar with a wire running between the ends of the U. This was a pretty easy way to cut polystyrene.

Finish is the other determining factor with the choice of methods. Knife, rasp and sandpaper leaves you with a rough surface. Hot wire leaves you with a sealed surface … but one that has been melted.

I’ve decided to make a bench hot wire cutter. The machine will have a opening that is about 12” high and the bench itself will be about 12” x 24”. The first job is to make the body of the cutter. This is basically a 12” x 24” box with a L shaped box added to the short end. The L has a hole in it for the wire to pass through and the bed has a hole that takes the other end of the wire.


Add a wall adapter, a fuse and a switch and we should be away.

I had an old mobile phone charger (5V) which is, basically an AC to DC transformer that steps the power down from 240 to 5V. I’ve cut the plug from the end of the adapter and exposed the two wires (black and green). I have soldered a red wire to the green and a black wire to the black wire of the adapter.

I’ll put an in-line fuse into the wire and mount a switch onto the arm so that I can easily turn the cutter off.

The cutting wire attaches between the red and black wires to complete the circuit. I am planning on using fine steel guitar string as the cutting wire, so I’ll either take one off the Fender, or go and buy another one.

I plan to put a spring loaded connector at both the top and bottom attachment points to that the cutting wire is held taught.

Today I did the timber work. I had some old plywood sitting around with nothing to do, so I did some cutting, gluing and screwing in the workshop. Tomorrow it’s back to the electrical store to get a switch and fuse. If the music store is open tomorrow (Sunday in Hobart) then I’ll get a guitar string as well.


To get the position of the wire hole in the base, I had the arm detached and positioned in the right place in relation to the body, but with the arm resting on the base and then drilled a pilot hole through the arm and base at the same time.

The arm is attached to the base with four bolts that pass through the inner wall of the arm and then into the wall of the base. I want the arm to be able to be removed for when I want to store the tool on the shelf.


Well … now I’m going to go to the electronic store and get some more electronic stuff to make the hot wire circuitry. If they have NiChrome wire at the store, I’ll get that instead of using a guitar string.

Wednesday, 20 February 2013

Steampunk Firepower–Prototype Encased

Well, I think that I have given the prototype gun enough coating to make it sturdy enough.


There are some small bits that still need touching up due to the fact that I can’t give it an all-over coat at once, but have to build the coat up in stages (I have to hold it somewhere while I apply the filler). But, overall, I’ve given the prototype 5 coats of filler. There are also some coats of 2 part epoxy and paint under the filler, but I’m not counting them.

The last couple of coats have been very thin so that the finished surface is as smooth as I can make it. I’ve rubbed the prototype with 120 grit sandpaper between coats to knock off some of the grainy bits in the filler and to smooth out some streaks left by the paintbrush.


You can see the overall shape of the prototype now too. Large body, thick barrel, chunky pistol grip, wavy bottom of the body and flat top.

Next I’m going to be drawing the design onto the prototype to mark out all of the areas that I’m going to etch with the Dremmel rotary tool and the cut-line where I’m going to cut the prototype in half.

Etching the surface is going to be another experimental stage. I know that the directions for the filler say that it can be drilled, sawn and sanded, but the subsurface has a lot of give and the vibration from the rotary tool may cause the filler to lift from the prototype. If it does, I’m going to go over the whole thing with a clear acrylic paint to help to stabilise it.

When the etching is done, I will be moving on to the next stage … making the prototype ready for investing. That’ll involve cutting it in half, removing the polystyrene core using acetone, building up the interior surface with more filler (so that the shell is at least 5mm thick), and of course … fixing anything that goes contrariwise to me.

So far … so good.

I’ve now ordered a truckload of electronic components from eBay (resistors, transistors, capacitors, timer IC, decade counter IC, LED, potentiometers, PCB, e.t.c) so that I can do some more work on the prototype electronic gubbins. I want to have a pulsing LED glowing through some cut-outs in the body and some lights chasing around the barrel of the gun. Here is a crap visualisation of the lights.


The cut-outs will be covered with some inset resin panels and will have a single large LED with a pulse circuit while the chasing lights will be some 3mm LED. Chasing just means that each light comes on in sequence (kinda like the “eye” of a Cylon). The above picture is pretty bad … just something I knocked up in MS-PAINT in a couple of seconds.

The body will not be that colour when it is in the final material, so don’t worry about that!

I want the circuitry to be fairly simple and I’m going to use trim pot resistors so that the cycle time can be varied manually.

Saturday, 16 February 2013

Steampunk Firepower–More Prototyping

Today I bought some water based multipurpose filler … Agnew’s Water Filler. This is a great filler and works on lots of different materials, but, importantly, it works on polystyrene.

The filler mixes 3 parts powder to 1 part water to make a thick paste. I made a mix of 1 to 1 to make a thin slurry of the putty and applied it directly to the polystyrene with an artist paintbrush. So far, I have applied 3 layers and it takes about 10 minutes for the putty to dry sufficiently to apply another layer. So that’s about 30 minutes to get about 2.5mm thick coverage over the polystyrene.

The putty can be sawn, sanded, drilled and carved, so I’m pretty pleased with the scope for the putty as a modelling medium.


I needed to extend the grip on the gun as it was about a finger too short. To do this, I used a hacksaw to cut the end of the original handle off and then carved a 1” polystyrene block and glued it on to the end. The putty slurry was then painted on to the stock to start building it up and blending it in. I also painted the slurry on to the new barrel of the gun and started to smooth out some of the lumpy bits.

Now I’m waiting for the putty to cure entirely so that I can start to sand and smooth the surface. The putty is still very thin on the gun, so I’ll probably need to give the surface some protection. I will use a clear matt finish acrylic paint to achieve that.


Soon, I’ll be able to start carving the detail into the surface.


I have an old urchin shell on the veranda, I’m going to fill the interior with some plaster to make the shell less fragile and then I’m going to cover the outer surface with some silicone moulding medium. The shell has such a fantastic texture, and I reckon that, if I flatten it out, the texture will look awesome as a surface on the gun … maybe on the grip.

When the prototype is all surfaced and carved, I’ll need to cut the gun in half along it’s length so that I can remove the polystyrene from the middle. I will also need to make the shell a bit thicker by adding more filler on the inside of the shell. When I’ve done that, I can start making the transparent sections of the gun. Oh well, that’s probably a long time into the future yet … how many chickens do I have now?

Friday, 15 February 2013

Steampunk Firepower–Design Sketches

As promised, I have compiled a bunch of scans of the sketched designs that I have done. These are designs inspired by various sources, mostly science fiction fantasy novels, television and movies.

I’ve tried to honour the feeling of the sci-fi genres that I have drawn from while still thinking about how the props would feel in the hand.

I must stress that these are NOT real guns, they will not work.

Rocky Horror

This is the Rocky Horror design, it’s a basic shape. The movie version was such a lovely and slick design. The ray gun here seemed to have no moving parts and was a simple shiny metal object.


The Marshall is a pistol design based on the Colt Navy. The addition of a bayonette onto the end is a bit of a unnecessary hardware, but it gives the impression that the hand holding the gun is resolute.

Plasma Freestyle

This is a plasma gun. The idea is that the panel at the rear of the gun would be a transparent plastic panel with glowing swirling lights.

Flame Thrower

A personal flamethrower is always something to pack when you are heading out for a night on the town. Especially when the likes of Nyarlhotep are about.

Angels Wings

The Angels Wings is a personal cannon for the fashion conscious lady adventurer.

Big Mumma

Another in the personal cannon range. The Big Mumma packs the kind of punch that even Dagon would envy. This is the kind of firepower that would be handy when the odds are stacked against you.

Heavy Handed

The third in the personal cannon range, the Heavy Handed is simple and straight forward. Point and Kablooie … problem solved. The Heavy Handed is the sort of gun that makes even the smallest adventurer a force to be reckoned with … although an enhanced arm would not go amiss when trying to cope with the recoil.

Duelling Pistol

The Duelling Pistol is a reproduction flintlock pistol, this sketch is more about the lines and the dimensions. The old duelling pistols were pieces of art.

trigger plate - duelling pistol

As were  the trigger plates for the duelling pistols…

Ray Gun

I am very fond of the design of The Ray Gun. There is a very satisfying balance to this sketch, when I have completed the Unearthly Power, this will be my next project.

Unearthly Power

The Unearthly Power is a fairly simple design and the overall shape is based on a Bosch drill. This is my first design that I am producing as a physical prototype. So far … so good. I’m going to have to remake the prototype as I am also experimenting with materials, but … meh, whatever. The prototype is based on the sketch, I will be making deviations from the design as my skill limits are reached.

Backup Powerpack

I also plan to make a backpack device that can plug in to several of the designed guns.

Steampunk Firepower–Prototype

Building the prototype

So far I have built the basic body of the gun. The body is made from several layers of polystyrene glued together with Poly Vinyl Acetate (PVA).


The polystyrene was harvested from a bunch of old computer and tool packaging. The hardest part was cutting out usable pieces of polystyrene … most of it is holes and voids so that the manufacturer can save cost.

The laminated polystyrene was then cut using a bandsaw, hacksaw and craft knife, and then smoothed using a 120 grit sandpaper.

I needed to fill some of the holes in the polystyrene, so I did some experimenting. First, I tried filling the voids with more PVA. This worked OK, but the glue is not able to be sanded very well.

Next, I used plaster of Paris. This worked fairly well, but it chips and breaks easily and it also takes a while to go off.

Next, I used a two part epoxy resin. This sands better, but it also eats the polystyrene.


To counteract the corrosion, I applied a coat of an acrylic paint. This worked well and showed up the rough spots well. The paint and epoxy solution takes even longer than the plaster solution … so on with the experimentation.

My next option was auto-body filler. I used a Selley’s multipurpose filler. This is styrene based, and so, also corrodes the polystyrene. I did this in a couple of layers. First, a thin layer that would corrode the polystyrene somewhat, and then build it up with subsequent layers and sanding.

Next I will use a water based wood filler. This will allow me to make the consistency of the filler according to my needs as well as being non-corrosive. I’ll start with a fairly thin layer of filler to seal the polystyrene and then build it up with thicker layers until I have about 3mm coverage. This should give me the thickness that I need to carve with the Dremmel.

The body is now made up of several different materials and so it can only be considered “experimental”, that is, it will not work as a usable prototype.

Electronics Prototyping

I’ve started to solder up some of the electronic circuitry for the bling of the gun. At the moment, my plans are to have a pulsing LED light being expressed through a set of resin “port-holes” in the main body and for a set of chasing LED lights circling the “barrel” of the gun. In total, there are only 9 LED lights (8 x 3mm and 1 x 5mm).

The prototype circuit for the pulsing LED light is under way and I will start on the chasing LED lights next. At the moment, this will be prototyped on two separate PCB, but I will reorganise the circuits so that they will fit on one later.

Pulsing Circuit with 556 Dual Timer replacing 555 Timer

The above circuit is the schematic for the pulsing LED light. The schematics that I found on the interweb call for a 555 timer, I’ve adapted the schematic to use a 556 dual timer instead, as that’s what I had to hand. I may expand the prototype later to utilise both timers in the 556 such as:

Dual Pulsing Circuit with 556 Dual TimerThis circuit will give me two pulsing LED lights, rather than just the one. If I change the resistor of the second LED, then the two LED lights will be out of phase too … that would be groovy. Anyway, the single LED will do for now. I am a novice in electronics, so it may be a bridge too far at the moment.

The main challenge for the lighting of the gun will be manufacturing the epoxy domes. The electronics themselves are fairly straight forward and reasonably inexpensive.

I plan to stow the 9V battery in a compartment in the grip of the gun so that I can easily change the battery when it needs it.

What I have learned

I’d like to get some thicker polystyrene, I will pay for some and get it in sheets. The hardware store sells polystyrene sheets, so some more investment is needed.

Using a non-corrosive filler, such as a water based wood filler is much better and causes far fewer toxic fumes in my workshop.

I will always end up with a lumpy surface after filling, so sandpaper and rasps are my friends.

The most important thing for me to remember is that, starting over is not such a bad thing. The prototype will be invested in silicone so that I can make solid reproductions of it, so getting it right at the start is far cheaper (in time and money) than trying to fix it later on in the process.

When planning your model, plan for space for the electronic gubbins if you are going to add any, it will dramatically reduce the amount of anguish later on when you try to fit the electronics.

Steampunk Firepower–Introduction

I’ve been toying with the idea of building a Steampunk gun or two. I’ve seen some cosplay props online and, while they are very pretty … they are not very durable. Virtually all of them are cast resin. If you are out there cosplaying, do you really want to break your $800+ prop? Not really.

From what I’ve seen, these props range from $200 – $2,500, so that’s a pretty hefty investment to risk breaking. I can’t see it happening, myself.

My plan is to make a prototype Steampunk cosplay prop out of aluminium and add some electronics into the mix to make these props really stand out.

I’ve started with a fairly simple design, using a drill as my template I’ve carved out the grip and body of the gun in polystyrene and then coated it in resin and filler to give it a smooth and workable surface. When I’ve finished modelling the surface, I’ll go to town with the Dremmel rotary tool to add some more detail.

I’ve added a barrel to the gun and I’ll do some more building up of the surface to make it look better.


I’ve also started designing some electronic circuits so that the gun has some dynamic visual interest. This will be delivered as a set of LED lights that do pulsing and chasing. I’m also investigating using electroluminescent wire to deepen the visual identity of the prop, but from what I’ve seen so far, electroluminescent wire doesn’t have a very long lifetime … that may have to wait for improvements in the technology.

Anyway, that’s the plan for now.

Paypal Donations

Donations to help me to keep up the lunacy are greatly appreciated, but NOT mandatory.