Armor type/thickness and DR...

GoblynByte · 03-22-2009, 03:46 PM

I know I remember seeing guidelines (either in a book or on the forums) for calculating the DR of vehicle (or personal) armor based on the material and thickness, but I'm unable to locate them. Can anyone help me out?

Sam Baughn · 03-22-2009, 04:04 PM

Possibly the old Vehicles book? On page 4 it says that one inch of 'unsloped ahrd steel armor' is DR 70 and later it gives various options for armour (unfortunately without actually specifying the exact materials) which vary the weight of each point of DR over a square foot. I guess if you wanted to work backwards from that you could work out some more detailed statistics.

Page 559 of the Basic Set (4e) has a small table of DR ratings for various materials which seem to be consistent with the vehicles ones at a glance. This includes a few materials which probably don't appear on the vehicle table.

I don't think you can make a direct translation between vehicle and personal armour though. Strapping half an inch of armour to the side of a truck is going to offer different protection to a half inch thick trauma plate, especially if you don't wear sufficient padding.

EDIT: Here is a thread where someone tries to assign realistic weights to various low-tech body armour types and gives a long list of options. Exact weight per point of DR is probably debatable, but the experts don't seem too offended by those given here...

http://forums.sjgames.com/showthread...5&page=1&pp=10

Anthony · 03-22-2009, 04:25 PM

Quote:

Originally Posted by Perfect Organism

EDIT: Here is a thread where someone tries to assign realistic weights to various low-tech body armour types and gives a long list of options. Exact weight per point of DR is probably debatable, but the experts don't seem too offended by those given here...

Well, I'm not sure I see strong agreement on numbers there. Part of the problem is that GURPS may be overstating the penetration of melee weapons.

Oh, found an interesting reference: someone doing ballistics testing on some 17th century armor. The thickness scans are particularly interesting.

DanHoward · 03-22-2009, 04:34 PM

This is the main problem with modelling plate armour in GURPS. Historical armour was not a uniform thickness. Breastplates and helmets were deliberatly made thicker on areas that cover vulnerable locations. On top of that, each separate piece was of a different thickness. Helmets and breastplates were thicker than greaves and backplates for example. The best you can do is average the thickness for any individual piece and include rules that allow a suit to be built up from separate pieces - each with a different DR. Low Tech attempts to do this without making things too complicated.

Taking a look at Sylvia's examples, the second breastplate is atypical of historical examples. I am thinking that some serious "restoration" was done to wear down the front portion of the plate so that it is thinner than the sides. The first piece she tested is more representative of most extant breastplates, though the average thickness varies considerably.

Some random comments:
Breastplates generally left a great deal of space between the plate and the arming garment underneath. Even the large dent made on BP2 is unlikely to touch the wearer.

She made no attempt to simulate the arming doublet (or buff coat). There are several accounts of soldiers getting hit with firearms and they subsequently took off their breastplate and shook out the bullet fragments underneath. In other words the shot penetrated the plate but not the garment underneath (the wearer was uninjured even though the armour was compromised).

GoblynByte · 03-22-2009, 04:50 PM

My main target is just vehicle 'skin' rather than personal armor. I figure I can get some useful benchmarks if I can figure out how much DR an inch of, say, titanium provides. I just thought I remember seeing those formulas somewhere. Maybe not, though.

Again this is for the application of translating a handful of Star Wars vehicles. It doesn't need to be exact, but if I can bench mark them to 'real world' analogies than the scale will be less likely to break down from characters to vehicles to starships.

I could just take a handful of real world vehicles and say they have equivalent DR, but I just thought it would be useful to know the formulas for how 'official' stats were figured (if they exist). Again, this is working on the assumption that I did see them somewhere. If I didn't than I'll just eye ball them. ;)

Sam Baughn · 03-22-2009, 07:08 PM

A very rough guide to vehicle armour in GURPS:

Steel armour is DR 70 per inch and wieighs about 40 lbs per square foot at one inch thickness.

Titanium is about as tough as mild steel by volume, just lighter (about 2/3 the weight). Call it around DR 60 per inch. Aluminium is only about one third the weight of steel, but probably doesn't rate more than about DR 20 per inch.

Modern carbon fibre composites are maybe DR 50 per inch (EDIT: actually that might be a bit high - maybe DR 20-30 per inch might be more realistic, about twice as good as steel by weight is probably the best you can manage at TL 8), but much lighter (about a fifth the weight of steel). Future-tech nanotube stuff might be about twice as strong as that for a similar weight.

Modern tank armour probably has a similar DR per inch to steel, but it will weigh a bit less and probably count as hardened.

03-22-2009, 03:46 PM	#1
GoblynByte Join Date: Aug 2004 Location: Dayton, OH	Armor type/thickness and DR... I know I remember seeing guidelines (either in a book or on the forums) for calculating the DR of vehicle (or personal) armor based on the material and thickness, but I'm unable to locate them. Can anyone help me out? __________________ A man said to the universe: "Sir I exist!" "However," replied the universe, "The fact has not created in me A sense of obligation."

03-22-2009, 04:04 PM	#2
Sam Baughn Join Date: Aug 2004 Location: United Kingdom of Great Britain and some other bits.	Re: Armor type/thickness and DR... Possibly the old Vehicles book? On page 4 it says that one inch of 'unsloped ahrd steel armor' is DR 70 and later it gives various options for armour (unfortunately without actually specifying the exact materials) which vary the weight of each point of DR over a square foot. I guess if you wanted to work backwards from that you could work out some more detailed statistics. Page 559 of the Basic Set (4e) has a small table of DR ratings for various materials which seem to be consistent with the vehicles ones at a glance. This includes a few materials which probably don't appear on the vehicle table. I don't think you can make a direct translation between vehicle and personal armour though. Strapping half an inch of armour to the side of a truck is going to offer different protection to a half inch thick trauma plate, especially if you don't wear sufficient padding. EDIT: Here is a thread where someone tries to assign realistic weights to various low-tech body armour types and gives a long list of options. Exact weight per point of DR is probably debatable, but the experts don't seem too offended by those given here... http://forums.sjgames.com/showthread...5&page=1&pp=10 Last edited by Sam Baughn; 03-22-2009 at 04:11 PM.

03-22-2009, 04:34 PM	#4
DanHoward Join Date: Mar 2005 Location: Maitland, NSW, Australia	Re: Armor type/thickness and DR... This is the main problem with modelling plate armour in GURPS. Historical armour was not a uniform thickness. Breastplates and helmets were deliberatly made thicker on areas that cover vulnerable locations. On top of that, each separate piece was of a different thickness. Helmets and breastplates were thicker than greaves and backplates for example. The best you can do is average the thickness for any individual piece and include rules that allow a suit to be built up from separate pieces - each with a different DR. Low Tech attempts to do this without making things too complicated. Taking a look at Sylvia's examples, the second breastplate is atypical of historical examples. I am thinking that some serious "restoration" was done to wear down the front portion of the plate so that it is thinner than the sides. The first piece she tested is more representative of most extant breastplates, though the average thickness varies considerably. Some random comments: Breastplates generally left a great deal of space between the plate and the arming garment underneath. Even the large dent made on BP2 is unlikely to touch the wearer. She made no attempt to simulate the arming doublet (or buff coat). There are several accounts of soldiers getting hit with firearms and they subsequently took off their breastplate and shook out the bullet fragments underneath. In other words the shot penetrated the plate but not the garment underneath (the wearer was uninjured even though the armour was compromised). Last edited by DanHoward; 03-22-2009 at 05:02 PM.

03-22-2009, 04:50 PM	#5
GoblynByte Join Date: Aug 2004 Location: Dayton, OH	Re: Armor type/thickness and DR... My main target is just vehicle 'skin' rather than personal armor. I figure I can get some useful benchmarks if I can figure out how much DR an inch of, say, titanium provides. I just thought I remember seeing those formulas somewhere. Maybe not, though. Again this is for the application of translating a handful of Star Wars vehicles. It doesn't need to be exact, but if I can bench mark them to 'real world' analogies than the scale will be less likely to break down from characters to vehicles to starships. I could just take a handful of real world vehicles and say they have equivalent DR, but I just thought it would be useful to know the formulas for how 'official' stats were figured (if they exist). Again, this is working on the assumption that I did see them somewhere. If I didn't than I'll just eye ball them. ;) __________________ A man said to the universe: "Sir I exist!" "However," replied the universe, "The fact has not created in me A sense of obligation."

03-22-2009, 07:08 PM	#6
Sam Baughn Join Date: Aug 2004 Location: United Kingdom of Great Britain and some other bits.	Re: Armor type/thickness and DR... A very rough guide to vehicle armour in GURPS: Steel armour is DR 70 per inch and wieighs about 40 lbs per square foot at one inch thickness. Titanium is about as tough as mild steel by volume, just lighter (about 2/3 the weight). Call it around DR 60 per inch. Aluminium is only about one third the weight of steel, but probably doesn't rate more than about DR 20 per inch. Modern carbon fibre composites are maybe DR 50 per inch (EDIT: actually that might be a bit high - maybe DR 20-30 per inch might be more realistic, about twice as good as steel by weight is probably the best you can manage at TL 8), but much lighter (about a fifth the weight of steel). Future-tech nanotube stuff might be about twice as strong as that for a similar weight. Modern tank armour probably has a similar DR per inch to steel, but it will weigh a bit less and probably count as hardened. Last edited by Sam Baughn; 03-23-2009 at 04:04 AM.