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Tips on scratch builting a tank turret?
harry5518
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Australia
Member Since: October 08, 2011
entire network: 12 Posts
KitMaker Network: 4 Posts
Posted: Tuesday, November 12, 2013 - 06:01 PM UTC
hello. i am wondering how i would build a custom tank turret? im going for the IS-7 tank as a scratch built tank, but i have little clue how i am going to make the turret.

what do i do? what should i use? etc.
Thudius
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Uusimaa, Finland
Member Since: October 22, 2012
entire network: 1,194 Posts
KitMaker Network: 96 Posts
Posted: Wednesday, November 13, 2013 - 12:29 AM UTC
Howdy,

Always glad to hear someone doing a bit of scratch. First off, the approach is going to be determined by what you want in the end. Will hatches be opened or closed, will the gun elevate and so on. Scale will also be a bit of a factor, what sort of plans you have to work from and your own comfort and skill level.

Basically, there are three ways to go about this: building up layers of styrene (or thin wood), making a sectional form and filling (think ship hulls or airplane fuselages) or carving out a solid block of wood (or carving resin). Building up layers is probably the simplest option for this type of turret and will give you a better chance of having things end up in the correct position and also will allow a little more precision in getting the shape right. Think of the turret as a contour map: each layer is cut to the shape of the elevation, and the elevation is the thickness of the material you use.

Start off with marking elevation on the side and front/back view of your plans (verticals), then you need to figure out what each contour is going to look like extrapolating from the top (horizontal)and vertical views. This is actually easier than it sounds; draw a box around your top, front and back views, make sure the dimensions match and mark each with a centre line. At each elevation, simply figure out where the outer edge is in as many different locations as possible and create your contour. To ensure alignment, mark and drill holes at a known position through each sheet and use rod or toothpicks to line them up vertically as you go. Don't glue until you're satisfied you have the shape correct, just clamp it for now. When all looks good, and you've removed any material or marked for hatches, gun mantlet, etc then glue and putty and sand for final appearance.

Hope that helps. If I have some time tonight, I'll see if I can do a quick drawing to better illustrate the process.

Kimmo

jon_a_its
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England - East Midlands, United Kingdom
Member Since: April 29, 2004
entire network: 1,336 Posts
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Posted: Wednesday, November 13, 2013 - 12:55 AM UTC
Hi Harry

First you will need reasonable drawings, preferably the right scale, and LOTS of reference.

Not knowing Russian tanks, It looks like that the IS7 is a Development of the IS3, so you may find the Tamiya/Zvesda IS-3 may be a good starting point, eg it might be easier to heavily modify an existing kit than to errr. start from scratch...

Google Tamiya IS-3 for loads of pics & links

I'd recommend Scale Military Vehicle Conversion by Duncan Howarth , or similar books

Basic tools, hobby/craft knives, saws, etc,
Scrap card/plastic, spares box of useful bits like barrels, storage, cupolas,
Glues suitable for your materials,
Fillers,
sandpaper & files...
the list, never NEVER, ever ends...
good luck
vahleof
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Quebec, Canada
Member Since: December 17, 2010
entire network: 189 Posts
KitMaker Network: 61 Posts
Posted: Monday, January 06, 2014 - 04:58 PM UTC
A scratch built IS-7 from Chinese forum
Hope it helps ya!
http://bbs.xiaot.com/thread-917775-1-1.html
tankmodeler
#417
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Ontario, Canada
Member Since: March 01, 2004
entire network: 3,123 Posts
KitMaker Network: 330 Posts
Posted: Tuesday, January 14, 2014 - 04:34 PM UTC
The key to scratchbuilding a tank is drawings. Good, clear and really accurate drawings. At least 3-view and preferably 5-view. On top of that, for cast or rounded shapes, you need a ton of photos to get the subtle curves just right.

For something like the turret of yon beastie, I would use the drawings to create a good longitudinal bulkhead, and a good transverse bulkhead, cut these bulkheads out of .030-.040" plastic and mount these on top of a ring the size of the turret ring. Make these bulkheads a tad undersize (I like to be about .050" under) and then use the top view to flesh out a horizontal planar bulkhead that shapes the bustle. You now have a basic armature that defines the outline of the turret in the 3 or 5 views from your drawings.

Then use the drawings to create and locate the machined surfaces; things like the hatch holes, the radio antenna mount surfaces, the openning for the main gun, etc. With these major fixed features located in space (on individual pieces of plastic, if need be) estimate the curvature of the front arc of the turret and create a series of curved ribs that will recreate the majority of the shape of the front of the turret. At least put a rib at 1, 2 10 and 11 o'clock (if the gun is a noon) and more if you can.

Use a similar process to create and place ribs to rough out the shape of the turret bustle. Remember to make outer surface of the ribs all about .050" smaller than the final shape.

With these ribs dry and any supplimentary shaping to correct the curve of the ribs completed, you are now at the "wattle and daub" or "plaster and lath" part of the process. Considering the ribs to be the ""studs", use strips of .030" plastic placed as close to gether as possible to bridge across all of the ribs. These are the lath. Leave as little open space as possible. Plate over the entire turret and make sure to add small "laths" to join up the fixed points (hatches, antenna mounts, etc) you established earlier with the new turret shell. Make sure the shapes you add reflect how these feature really merge together.

With all _that_ dry and possibly shaped, you get to the "plaster" stage, which is to cover all of the lath with a thin layer of epoxy putty. The key to this first layer is to close over all the voids and create the first homogeneous shell. Make it as smooth as you can and when it's cured, wet sand it with 200 grit to smooth it and start the shaping process.

From this point on it's add layers of epoxy putty and sand most of it off over and over until you get a turret shape you like and matches your photos. I've taken as many as 8 full and partial layers of putty to achieve the shape I need, but you shouldn't be counting them, do as many as you need to achieve the shape, that's critical. Be careful while sanding that you don't press too hard and delaminate the epoxy from the plastic underneath, remember it doesn't bond well to plastic and once it starts to flake off, it can be a bugger to correct. Don't sand so much that you expose the lath as you are then about .020" too shallow.

Once the shape is correct and the major elements all in place you can add the cast texture and then the fine details (grab handles, gun mounts, etc.), and she's done.

If you just want to open a hatch to put in a crew figure, use a dremel and scoop out the hatch opening so that you can place a half/three quarter figure and call it a day.

If you want a truely hollow turret you can make the bulkheads and ribs hollow, but frankly that's a pain and is very hard to get right. Make a solid turret, make a master from RTV, cast it in rubber, cut it in half on a band saw and hollow out the innards like a gourd. Then bond the two halves back together again adding a shim of the same size as a kerf width of the saw. Putty up the seam and then add your cast texture on top.

Easy peasy!


Not. But still a lot of fun and very satisfying when you get it finished! Real modelling.

HTH

Paul
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