By using this as a guide, you will hopefully be able to copy my project and have a HMMWV turret for your games. This will cover materials needed, the actual building process, and some tips.
You will need some thin card, I use cereal or cracker boxes; some good super glue, my favorite "Loctite" gel which comes in the blue and silver squeeze bottle; thin clear plastic sheet, mine was from a name card holder; and of course the regular stuff for measuring and cutting. Something optional is a clear gel gloss glue, mine is "glossy accents," some artsy craftsy stuff in a pink bottle; I use it for filling in the armored windows.
The main steps are preparation, building the floor, building the walls, adding the details, then the optional roof armor which is a bit tricky.
i) take the turret ring and trim either the TOW control box, or machine gun mounts off of it. You want a completely flat surface.
b) Building the floor
i) cut out a section of cardboard approximately 15mm wide, by 20mm long.
ii) trim off the two front corners about 5mm from the end to make the end a triangle, as in picture 1.
Optional) once the glue is very dry, you may want to cut a circle in the floor for putting the figure through. I left the one with the roof closed, and cut the crewman in half, but it is more noticeable on the roofless version.
c) Building the walls
ii) cut window holes where you want them on the sides and front. I built the six window version here. Use a picture for size and placement of the windows.
iii) super glue them in place, then cut some of the clear plastic sheet to fit behind them in the inside of the turret walls.
d) Adding the details.
i) cut four strips of card per window for building up the armored frames. The best way of doing this is by your own eye judgement; you want a nice tight fit all around the cut out window.
iii) to build the gunner shield use picture 4 as a guide
following just the steps above, you will have a nice turret with no roof like this, and this. If you want to continue with the roof assembly which is very tricky to get correct, please follow the guide below. This will cover the steps of the actual assembly.
a) The roof assembly
i) begin by cutting out a piece from the clear plastic using picture 5 as a guide. As seen in picture 3, the turret roof will only be as long as the wall up to the bend. Mine was a total of about 26-27mm wide, you will have to eyeball yours for the best fit though.
ii) now assuming you follow the measurements above, scribe with a blade at the 5mm, the middle [~13mm], and the 21mm sections.
iii) bend each scribe and test fit. Make any adjustments needed. Once you are done, super glue each end to the top of the wall.
v) frame in the two windows in as you did with the others.
vi) there will probably be a gap between the roof and the walls, so cut a piece of regular printer paper and fit it over the gap on the sides as in picture 3. (you could also use some type of filler putty or clay to fill the gaps. There will also be a gap on the peak of the roof, cover that with a strip of the paper card as well as in picture 1.
With that you should have a decent roof assembly for your turret. Just remember that step is optional, so if it didn't work out, don't worry about it because it is very difficult to get the measurements correct.
Working with these materials pose a few tricky problems, but nothing big. These include flimsy paper that shreds and sometimes holds a weak bond, and the fact that the super glue fogs clear plastic.
I have worked with this type of paper card for years mostly with making buildings and wargame bases, as well as conversions like these. These are made like chipboard, having many layers of very thin paper, these will sometimes disintegrate especially when cut with a dull knife, sanded, or rubbed. I cure this with a large dose of wood glue. I painted it on all the edges, window frames, and super glue bonds. This also adds another element of strength, as well as helping the paint go on better.
For some reason super glue, or CA, fogs up clear plastic with this horrid white powder as you probably know. I didn't worry too much about that with this project because the windows are so small, and because I used the clear gel I mentioned earlier. This stuff goes on in a gel, and dries with in a very hard, extremely glossy finish, I think it gives a good impression of armored glass even when the original layer is fogged. If you don't have access to this stuff, I would white glue the clear plastic on, instead of CA.
Anyway, I hope this helped anyone who was interested, especially Torvic who requested a tutorial. Good luck to all, and if anyone attempts this, please share your results with me! If you have any questions just comment.