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Toxn
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So I got a request recently from {NAME REDACTED} as to whether we have a how-to guide or something for competitions. After a few moments of bitter, bitter laughter at the decade-plus of my life that I've spent cobbling together things that can maybe, sort-of, squint-your-eyes produce a facsimile of a realistic vehicle, I thought I'd share my process:

 

Quote

Hi {NAME REDACTED},

 

I'm going to post this on the forum, but thought I'd sent it to you first.

 

So I don't think there's a comprehensive how-to guide for anything at the moment, and all of us seem to prefer different approaches to modelling things. There are plenty of smaller tools out there for, for instance, calculating bullet velocities given a certain barrel length, bore diameter, shell weight and powder charge.

 

Generally the way I'd do something like a tank is to decide on the general layout and armament first, get some rough sketches done, and then start modelling the results. Normally I'll start with the fun bit: the main gun. For this you can either use an existing gun or else one of the afore-mentioned calculators + DeMarre and/or Longrods depending on the era in question. Once you know what size and configuration will work to hit parameters, you can then model that component individually and add it to the vehicle model. I do this for all the major components, using things like bulk densities for transmissions (to get the correct weight) and volumetric power outputs for given engine configurations (to get the right power output for a given size of engine). For some components, such as suspension and tracks, I either model and weigh the parts directly or else use available information to make good approximations for component weight. I work out the shape, configuration and volume of the rounds, and where they will be placed. I also use mannequins to model the crew compartments, although that's an area where I still make rookie mistakes (not having spent any real time in a turret and thus not knowing what might be important for a gunner, for instance, to have at hand). I use lots of reference material to sanity-check all my designs - mainly things like cutaways of real world vehicles and YouTube videos where people crawl around inside museum tanks.  

 

I use Sketchup a lot because I know it well and there are lots of parts publicly available if you want to, for instance, plonk a good-looking model of an M2 HMG on the turret roof. The best approach, however, would be to use something like Solidworks, because that allows you a fine degree of precision when it comes to estimating part masses and the like.

 

Anyway, once my initial model is done I tot up all the weights and start working on things like range, armour fraction, power-to-weight ratio etc. Often this is where whatever concept I had for my initial design breaks down completely and I have to go back to the drawing board. Generally I'm only happy after a few goes at the process, which having a quick workflow makes possible (a guy who spent two weeks making a good Solidworks model is not going to want to scrap it, whereas if I only take a few hours to lash something together I'm more amenable to starting over).

 

Some stuff I have to learn from scratch use things in ways they were never designed for - for a recent competition I decided that my tank absolutely had to have an ATGM, so I had to read up on control methods and laws and use hobby rocket modelling software to mock up the missiles and get an idea for their performance. For other stuff I've kludged together things like excel spreadsheets to help design shaped charges and composite armour packages.

 

I've been doing competitions like this for close on a decade now - ever since the World of Tanks days where the people that eventually started this forum would just sit and shitpost on the forums there. So I've gotten into a pretty comfortable groove ITO designing and I've got tools and approaches that work for me.

 

For planes, I'm also lucky enough that my dad has always been very into scale modelling and remote-control gliders, so I learned a couple of basic concepts at my dad's knee. So I'm decent at slapping together conventional aircraft designs with relatively benign flight characteristics. We're also lucky that there are a lot of available tools, rough simulation options and information out there which can be used to help the design process.

 

Ships I struggle a bit more with (not too much water where I live, so there have been fewer opportunities to experiment and learn directly, although I used to sail so at least I know the basics of ship handling) but thankfully there's also a wealth of information out there on how to design hulls and the like.

 

Anyway, I hope this helps.

 

All the best,

 

Toxn

 

Note: I was half-right - we definitely have supplementary info for aspiring pretend tank designers pinned to this very board.

 

Finally, I'm inviting our forum grognards and past winners to share their process for folk that haven't been here since before the last ice age, so that all can benefit.

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  • 3 months later...

Having very recently finished a design cycle, I can now offer insight into how I do things.
The first thing I do is look at the requirements, and the available options (whether limited by name or simply similar in performance), and try to figure out a first order approximation of what it is I'm hoping to get done. It's usually at this point that I sketch out the design in pencil and make a list of design features I intend to include in the design - this typically helps solidify the concept in my mind, as well as making sure I don't miss anything major along the way. I set myself certain design goals to guide myself along the way at this point, as they shape to an extent how I want the design to end up.
It's also at this stage that I tend to obsessively google ballistic charts, gun blueprints, and internal pics of relevant vehicles, for cribbing the designs off later.

This approach is very "front heavy", in that it requires you to have a very good image of what you want to get done in your mind before you ever really touch the CAD software, but it does mean that other than minor tweaks, you only CAD once. The Norman, Fox, .224 Rapier, and now BT-5-76/43 were all substantially first shots. Some details were ironed out as the design progressed (typically, precise dimensions are initially guessed and then adjusted as needed), but the concept, down to, say, the location of the extra periscope on the roof, was sketched out on day 0. This approach also means modelling is easier, as you are focused on carrying out the decisions of the design committee (you) and not making the decisions themselves.

As the design progresses, the day 0 first order approximations may turn out to be incorrect. The BT-5-76/43 was initially supposed to only have thick side-skirts along the fighting compartment, with thinner ones to the rear, but then I realized I had a sufficient mass budget to allow me to go wild, so I did.

As you go, it's important to keep whatever goals you set for yourself in mind. With a sufficiently blank slate, it's easy to get lost and start designing spaceships with All The Features TM, when you should be focusing on core capabilities. For the Norman, the core was a tank on par with late Centurions; for the BT-5-76/43, the core was "I do not want to touch the driveline or the turret ring in the process of improving this vehicle". Some features (like vision cupolas) are basically free improvements if you remember to include them; others (like fuckoff big guns) require substantial tradeoffs which must be viewed in the context of their effect on the bottom line of the design goal.

I tend to start from the turret, then the hull, then the armament, then systems, and finally suspensions and the like. The wonders of parametric modelling mean you can make a rough hull shape, design components to fit, and then rejigger the hull as required by the systems.

There's no good replacement for pencil sketches and barely legible scribbles on paper, in terms of focusing one's design intent into practice. CAD is just a way of translating that scribble into something others can understand too.

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12 minutes ago, N-L-M said:

Having very recently finished a design cycle, I can now offer insight into how I do things.
The first thing I do is look at the requirements, and the available options (whether limited by name or simply similar in performance), and try to figure out a first order approximation of what it is I'm hoping to get done. It's usually at this point that I sketch out the design in pencil and make a list of design features I intend to include in the design - this typically helps solidify the concept in my mind, as well as making sure I don't miss anything major along the way. I set myself certain design goals to guide myself along the way at this point, as they shape to an extent how I want the design to end up.
It's also at this stage that I tend to obsessively google ballistic charts, gun blueprints, and internal pics of relevant vehicles, for cribbing the designs off later.

This approach is very "front heavy", in that it requires you to have a very good image of what you want to get done in your mind before you ever really touch the CAD software, but it does mean that other than minor tweaks, you only CAD once. The Norman, Fox, .224 Rapier, and now BT-5-76/43 were all substantially first shots. Some details were ironed out as the design progressed (typically, precise dimensions are initially guessed and then adjusted as needed), but the concept, down to, say, the location of the extra periscope on the roof, was sketched out on day 0. This approach also means modelling is easier, as you are focused on carrying out the decisions of the design committee (you) and not making the decisions themselves.

As the design progresses, the day 0 first order approximations may turn out to be incorrect. The BT-5-76/43 was initially supposed to only have thick side-skirts along the fighting compartment, with thinner ones to the rear, but then I realized I had a sufficient mass budget to allow me to go wild, so I did.

As you go, it's important to keep whatever goals you set for yourself in mind. With a sufficiently blank slate, it's easy to get lost and start designing spaceships with All The Features TM, when you should be focusing on core capabilities. For the Norman, the core was a tank on par with late Centurions; for the BT-5-76/43, the core was "I do not want to touch the driveline or the turret ring in the process of improving this vehicle". Some features (like vision cupolas) are basically free improvements if you remember to include them; others (like fuckoff big guns) require substantial tradeoffs which must be viewed in the context of their effect on the bottom line of the design goal.

I tend to start from the turret, then the hull, then the armament, then systems, and finally suspensions and the like. The wonders of parametric modelling mean you can make a rough hull shape, design components to fit, and then rejigger the hull as required by the systems.

There's no good replacement for pencil sketches and barely legible scribbles on paper, in terms of focusing one's design intent into practice. CAD is just a way of translating that scribble into something others can understand too.

So our processes are basically opposites of each other :lol:

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6 hours ago, N-L-M said:

Having very recently finished a design cycle, I can now offer insight into how I do things.
The first thing I do is look at the requirements, and the available options (whether limited by name or simply similar in performance), and try to figure out a first order approximation of what it is I'm hoping to get done. It's usually at this point that I sketch out the design in pencil and make a list of design features I intend to include in the design - this typically helps solidify the concept in my mind, as well as making sure I don't miss anything major along the way. I set myself certain design goals to guide myself along the way at this point, as they shape to an extent how I want the design to end up.
It's also at this stage that I tend to obsessively google ballistic charts, gun blueprints, and internal pics of relevant vehicles, for cribbing the designs off later.

This approach is very "front heavy", in that it requires you to have a very good image of what you want to get done in your mind before you ever really touch the CAD software, but it does mean that other than minor tweaks, you only CAD once. The Norman, Fox, .224 Rapier, and now BT-5-76/43 were all substantially first shots. Some details were ironed out as the design progressed (typically, precise dimensions are initially guessed and then adjusted as needed), but the concept, down to, say, the location of the extra periscope on the roof, was sketched out on day 0. This approach also means modelling is easier, as you are focused on carrying out the decisions of the design committee (you) and not making the decisions themselves.

As the design progresses, the day 0 first order approximations may turn out to be incorrect. The BT-5-76/43 was initially supposed to only have thick side-skirts along the fighting compartment, with thinner ones to the rear, but then I realized I had a sufficient mass budget to allow me to go wild, so I did.

As you go, it's important to keep whatever goals you set for yourself in mind. With a sufficiently blank slate, it's easy to get lost and start designing spaceships with All The Features TM, when you should be focusing on core capabilities. For the Norman, the core was a tank on par with late Centurions; for the BT-5-76/43, the core was "I do not want to touch the driveline or the turret ring in the process of improving this vehicle". Some features (like vision cupolas) are basically free improvements if you remember to include them; others (like fuckoff big guns) require substantial tradeoffs which must be viewed in the context of their effect on the bottom line of the design goal.

I tend to start from the turret, then the hull, then the armament, then systems, and finally suspensions and the like. The wonders of parametric modelling mean you can make a rough hull shape, design components to fit, and then rejigger the hull as required by the systems.

There's no good replacement for pencil sketches and barely legible scribbles on paper, in terms of focusing one's design intent into practice. CAD is just a way of translating that scribble into something others can understand too.

 

This is why you're a genius, and I'm not. I'm a very dedicated idiot.

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I’ll add more context later, but here’s what (I have figured out) NOT to do when designing your tank/ gun/ boat/ thing: 

 

1. Don’t hyper fixate on one aspect or feature of your creation; get the idea into the rough area that you’re going for, then move on. Trying to get all those details perfect as you put them down will only slow you down, and drive you crazy. 
 

2. Don’t make your ideas too small; make your creation 50-100mm longer/ wider/ taller (for vehicles) than you think it needs to be, I’ve found that it’s easier to make a thing smaller than it is to make them bigger. Also, it allows for growth if you find an aspect lacking. 
 

3. Don’t be too “experimental” with it; fancy technology is always tempting to use, especially weight and space saving technologies to meet requirements in a competition. But are those technologies actually used in real world, production vehicles? Were there teething problems when it was implemented? Know the technology/ features you’re applying to your creation before you try to utilize them. 

 

I might think up more things when I finally get home, but those are the biggest things that held me back in the cascadia and californium competitions. 

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    • By N-L-M
      Restricted: for Operating Thetan Eyes Only
      By order of Her Gracious and Serene Majesty Queen Diane Feinstein the VIII
      The Dianetic People’s Republic of California
      Anno Domini 2250
      SUBJ: RFP for new battle tank
       
      1.      Background.
      As part of the War of 2248 against the Perfidious Cascadians, great deficiencies were discovered in the Heavy tank DF-1. As detailed in report [REDACTED], the DF-1 was quite simply no match for the advanced weaponry developed in secret by the Cascadian entity. Likewise, the DF-1 has fared poorly in the fighting against the heretical Mormonhideen, who have developed many improvised weapons capable of defeating the armor on this vehicle, as detailed in report [REDACTED]. The Extended War on the Eastern Front has stalled for want of sufficient survivable firepower to push back the Mormon menace beyond the Colorado River south of the Vegas Crater.
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      Over the past decade, the following threats have presented themselves:
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      Despite being approximately the same size, these 2 vehicles seem to share no common components, not even the primary armament! Curiously, it appears that the lone 120mm SPG specimen recovered shares design features with the M-8, despite being made out of steel and not aluminum like the light tank. (based on captured specimens from the battle of Crater Lake, detailed in report [REDACTED]).
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      Fitted on a limited number of tank destroyers, several attack helicopters, and (to an extent) man-portable, this missile system is the primary Cascadian anti-armor weapon other than their armored forces. Intelligence suggests that a SACLOS version (BGM-1C) is in LRIP, with rumors of a beam-riding version (BGM-1D) being developed.
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      C.      Deseret tandem ATR-4 series
      Inspired by the Soviet 60/105mm tandem warhead system from the late 80s, the Mormon nation has manufactured a family of 2”/4” tandem HEAT warheads, launched from expendable short-range tube launchers, dedicated AT RRs, and even used as the payload of the JS-1 MCLOS vehicle/man-portable ATGM.
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      B.      Requirements definitions:
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      b.      Width- 4m transport width.
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      Appendix 2- operational requirements
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    • By Sturgeon
      @Toxn
      @Dominus Dolorem
      @Lord_James
      @A. T. Mahan
      @delete013
      @Sten
      @Xoon
      @Curly_
      @N-L-M
      @Sturgeon
       
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      Estimated range
       
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    • By Monochromelody
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      Thank you. 
    • By Sturgeon
      The LORD was with the men of Deseret. They took possession of the hill country, but they were unable to drive the people from the plains, because they had chariots of steel.
      —The Book of Latter Day Saints, Ch 8, vs. 3:10, circa 25th Century CE
       
      BULLETIN: ALL INDUSTRIAL-MECHANICAL CONCERNS
       
      SOLICITATION FOR ALL-TERRAIN BATTLE TANK
       
      The Provisional Government of the Lone Free State of Texas and The Great Plains issues the following solicitation for a new All-Terrain Battle Tank. The vehicle will be the main line ground combat asset of the Lone Free State Rangers, and the Texas Free State Patrol, and will replace the ageing G-12 Scout Truck, and fill the role of the cancelled G-42 Scout Truck. The All-Terrain Battle Tank (ATBT) will be required to counter the new Californian and Cascadian vehicles and weapons which our intelligence indicates are being used in the western coast of the continent. Please see the attached sheet for a full list of solicitation requirements.
       

       
      Submissions will be accepted in USC only.
       
       
      Supplementary Out of Canon Information:
       
       
      I.     Technology available:
      a.      Armor:
      The following armor materials are in full production and available for use. Use of a non-standard armor material requires permission from a judge.
      Structural materials:
                                                                    i.     RHA/CHA
      Basic steel armor, 360 BHN. The reference for all weapon penetration figures, good impact properties, fully weldable. Available in thicknesses up to 4 inches (RHA) 8 inches (CHA). 
      Density- 0.28 lb/in^3.
                                                                   ii.     Aluminum 5083
      More expensive to work with than RHA per weight, middling impact properties, low thermal limits. Excellent stiffness.
       Fully weldable. Available in thicknesses up to 4 inches.
      Mass efficiency vs RHA of 1 vs CE, 0.9 vs KE.
      Thickness efficiency vs RHA of 0.33 vs CE, 0.3 vs KE.
      Density- 0.1 lb/in^3 (approx. 1/3 of steel).
      For structural integrity, the following guidelines are recommended:
      For heavy vehicles (30-40 tons), not less than 1 in RHA/1.75 in Aluminum base structure
      For medium-light vehicles (<25 tons), not less than 0.5 in RHA/1 in Aluminum base structure
      Intermediate values for intermediate vehicles may be chosen as seen fit.
      Non-structural passive materials:
                                                                  iii.     HHA
      Steel, approximately 500 BHN through-hardened. Approximately 1.5x as effective as RHA against KE and HEAT on a per-weight basis. Not weldable, middling shock properties. Available in thicknesses up to 1 inch.
      Density- 0.28 lb/in^3
                                                                  iv.     Fuel
      Mass efficiency vs RHA of 1.3 vs CE, 1 vs KE.
      Thickness efficiency vs RHA of 0.14 vs CE, 0.1 vs KE.
      Density-0.03 lb/in^3.
                                                                v.     Assorted stowage/systems
      Mass efficiency vs RHA- 1 vs CE, 0.8 vs KE.
                                                               vi.     Spaced armor
      Requires a face of at least 1 inch LOS vs CE, and at least 0.75 caliber LOS vs fullbore AP KE.
      Reduces penetration by a factor of 1.1 vs CE or 1.05 vs KE for every 4 inchair gap.
      Spaced armor rules only apply after any standoff surplus to the requirements of a reactive cassette.
      Reactive armor materials:
                                                                  vii.     ERA
      A sandwich of 0.125in/0.125in/0.125in steel-explodium-steel.
      Requires mounting brackets of approximately 10-30% cassette weight.
      Must be spaced at least 2 sandwich thicknesses away from any other armor elements to allow full functionality. 81% coverage (edge effects).
                                                                  viii.     NERA
      A sandwich of 0.25in steel/0.25in rubber/0.25in steel.
      Requires mounting brackets of approximately 10-30% cassette weight.
      Must be spaced at least 1 sandwich thickness away from any other armor elements to allow full functionality. 95% coverage.
      The details of how to calculate armor effectiveness will be detailed in Appendix 1.
      b.      Firepower
                                                                    i.     Bofors 57mm (reference weapon) - 85,000 PSI PMax/70,000 PSI Peak Operating Pressure, high quality steel cases, recoil mechanisms and so on are at an equivalent level to that of the USA in the year 1960.
                                                                   ii.     No APFSDS currently in use, experimental weapons only - Spindle sabots or bourelleted sabots, see for example the Soviet BM-20 100mm APFSDS.
                                                                  iii.     Tungsten is available for tooling but not formable into long rod penetrators. It is available for penetrators up to 6 calibers L:D.
                                                                  iv.     Texan shaped charge technology - 4 CD penetration for high-pressure resistant HEAT, 5 CD for low pressure/ precision formed HEAT.
                                                                   v.     The subsidy-approved GPMG for the Lone Free State of Texas has the same form factor as the M240, but with switchable feed direction.. The standard HMG has the same form factor as the Kord, but with switchable feed direction.
      c.       Mobility
                                                                    i.     Engines tech level:
      1.      MB 838 (830 HP)
      2.      AVDS-1790-5A (908 HP)
      3.      Kharkov 5TD (600 HP)
      4.    Detroit Diesel 8V92 (400 HP)
      5.    Detroit Diesel 6V53 (200 HP)
                                                                   ii.     Power density should be based on the above engines. Dimensions are available online, pay attention to cooling of 1 and 3 (water cooled).
                                                                  iii.     Power output broadly scales with volume, as does weight. Trying to extract more power from the same size may come at the cost of reliability (and in the case of the 5TD, it isn’t all that reliable in the first place).
                                                                  iv.     There is nothing inherently wrong with opposed piston or 2-stroke engines if done right.
      d.      Electronics
                                                                    i.     LRFs- unavailable
                                                                   ii.     Thermals-unavailable
                                                                  iii.     I^2- Gen 2 maximum
                                                                  vi.     Texas cannot mass produce microprocessors or integrated circuits
                                                                 vii.    Really early transistors only (e.g., transistor radio)
                                                                viii.    While it is known states exist with more advanced computer technology, the import of such systems are barred by the east coast states who do not approve of their use by militaristic entities.
       
      Armor calculation appendix.
       
      SHEET 1 Armor defeat calculator 4in-54 1200 yd
       
      SHEET 2 Armor defeat calculator 4in-54 2000 yd
       
      SHEET 3 Armor defeat calculator 6in HEAT
       
      Range calculator
       
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