My aim was to produce a near full-scale replica of the Halo 3 gravity hammer using materials and tools commonly found in households, or those easily available to buy locally. Some metalwork skill is useful for undertaking a project like this, and it helps if you're already familiar with Pepakura (See step 1), but this is a fairly easy concept to get the hang of.
Materials are as follows:
34 Sheets of 160gsm A4 card (Some call it cardstock)
150cm x 3cm Aluminium or PVC tubing
Several metres of Steel or Aluminium tubing (1-1.5cm diameter, square or round)
500ml can of expanding insulation foam (May require more if it is a low expansion variety)
Fibreglass and resin (Optional)
5mm Thick modelling foam for the head details
Spray / Acrylic paints (Greys, silvers, blue, black, white)
Fabric / Leather swatches for the handle grips
Step 1: Papercraft
The main shape of the hammer is created from a paper modelling tecnique known as "Pepakura". It's more commonly used for armour or masks, and strengthened with fibreglass, but it is also fairly effective for making weapon props. The program called "Pepakura Viewer" allows specially made 2D nets to be printed (Just use google to find the files, or search for them on 405th.com)
There's no point in me providing a step by step guide to Pepakura, as there are already so many guides, but the basic idea is print, cut out, and stick together. I prefer superglue as a method of sticking tabs, because it sets faster than hot glue, and has a negligible separation between the layers of card/paper.
The model I used was composed from about 6 main pieces, all intersecting on the virtual model, So I had to decide which I would create my own cuts/tabs for (All of the head, some bits on the shaft, and the hilt), and which I would make exactly as the net dictated, and cut to fit the main model after (Two blocks between the head and the blade). The blade itself only needed some holes cutting to fit the steel tubing through.
Step 2: Metal Reinforcment
When creating weapons from pepakura, you'll need to strongly consider replacing some of the design's parts with more appropriate reinforcements. I didn't construct the lower handle or hand guard from paper, nor the 4 bracing struts at the base of them blade (See later steps). I opted for a 160cm aluminuim pole (~3cm diameter) and some spare steel tubing for all the other parts.
The steel tubes all had a cutout running down them (They were from a swimming pool wall's rim) and so they were very prone to twisting/kinking when bent. I'd strongly suggest square, complete cross-sectioned tubing insead.
All were attached using 2 to 3 small bolts, by drilling a bolt-width-hole all the way through first, then widening the side that the screwdriver needed to go through (After marking out their required positions). Holding the paper sections up to it was vital to making sure they'd all fit together after.
To fill the air gaps in the hammer, I used expanding insulation foam. It helps fill them in multiple goes, or you'll risk overfilling it and causing it to warp severely. For some pieces, It's easier to fill them with foam before fitting the metal "skeleton".
For the larger sections like the head and the blade, it's worth creating several small holes to fit the nozzle from the can of expanding foam right into the corners of the shape (For the blade, I actually left one side un-constructed, and built it only when the completed sections had been filled). It also helped to clamp the blade between some flat pieces of acrylic to stop it bulging outwards when the foam expanded, and to string the head of the hammer up to the main shaft as the foam set.
I'd taped the joins between sections that I hadn't made tabs for to prevent the foam seeping out.
In the last picture, I filled the part with foam completely separate from the rest of the hammer, then cut it in half, and carved out the right parts to allow it to fit on after.
Step 4: 3D Detailing & Hardening
I had an old foam camping mat, which I decommissioned for the purposes of the head's details. Between 5 and 10mm thickness is ideal, and cuting out wedges from the inside of the fold makes it a much crisper bend. I'd recommend a smooth, dense foam, as the roughness can cause issues with the appearance and painting later on (Soft foam will cause the paint to crack more easily if dented).
Thin card details can be cut and stuck on wherever you feel is appropriate. All the details on the blade are meant to be recessed, but I felt it would be easier to have them protrude rather than engrave them, or cut out a whole sheet to stick over the blade (Although this would give a much smoother finish).
The 3 braces on each side (2 at the bottom, 1 at the top) were made from spare plastic rods (With a very wide "I" shaped profile, though rectangular would be just as good) and bent into shape using a soldering iron to melt it at the crease lines (Tsk tsk!)
I used screws and multi purpose glue to fix the braces and the block above the lower 2 braces, which were both authentic looking, and strengthening.
I used a polyester based filling compound to repair any dents caused by warping, and coated the whole thing in resin to harden it (Don't resin the foam though, as it will certainly crack and leave you having to repaint it later). I finally applied a single layer of fibreglass strips to the upper handle, becuase with the force of gripping it, the card and expanding foam would likely suffer some denting.
Step 5: Painting - Base Coats
For the fist stage of painting, simply spray the whole thing (Except the handles) in a grey primer.
I gave it a silver spray coat for the blade and raised details, and a dark acrylic coat for most of the shaft, and recessed sections. Ideally, refer to screenshots for these, because the actual shaft is more of a dark grey/brown.
Step 6: Painting - Details
The whole dark grey base coat had a horribly tacky look to it, so I made a dark brown colour wash to sponge on to give it a "dirtied" look (About half acrylic, half water). I then made a black wash from what was left over and painted inside all of the grooves to simulate accumulated oil and dirt (If you wipe it off just as you've painted the black wash on, it helps blur the boundaries and looks less like a sharp edged shadow). Repeat this wash several times to build up a nice smooth layer.
Paint on the blue "lights" in the head's grooves, and on the blade. If you mask them off, be careful not to let it build up too thick before removing the tape (I did, and I actually had to score the edges to get them off). If you have the spray paints available for these tasks, it will look much more professional, but I only had acrylics at hand.
Finally, the all important silver dry brush to give the idea of wear and scrapes. Try to only put it on the edges which actually stick out. Edges that are actually protected by other edges all around would only experience wear from the user, and not from the environment (Eg, being dropped). To protect all the layers of paint, I used a clear coat of spray on lacquer, and lightly sanded the areas the were supposed to be matte (All but the blade).
Step 7: Handle Grips
The last step was to create a realistic looking hand grip. I considered brown cotton herringbone tape, brown fabric, and even engraving the details onto a wraparound foam sheet, but eventually went for stitching some leather strips that I'd hand cut from some larger scraps, and wrapping them in a spiral. The actual pattern is more random, and a much darker brown, but I was limited by the availability of the leather and its colour, so I went for total coverage with minimum overlap wastage.
I ended each strip at an angle, and atteched the beginning by covering it in multipurpose glue, and performing a complete wrap around before starting to spiral upwards. I was running low on strong multi purpose glue, so I used PVA for the entire middle section, which, although slower to dry, seems to hold just as strong.
After gluing the ends down, I held them in place with a tightly wound velcro strap (Winding string around would work too). I sanded the overlapping sections to give them a scuffed look.
Step 8: Finished!
I'd painted over all the blue "lights" with a glow in the dark paint, but these were barely visible (not bad in UV light though!)
Anyway, after all those steps the hammer is finally complete
The final hammer is 160cm tall, and my old MA37 is just 80cm. I'm 182cm (6ft exactly), so it only just reaches my chin.
Its final weight is 2.08kg, and it's pretty difficult to hold horizontal with an outstretched arm (Picture 3!), but at least I'd be able to carry it around all day at a comic con without destroying my arm!