Looking at Armor Saves vs THACO

[Deleted]

From my understanding, Arneson moved from the Level vs Level chart with armor saves to the, now more familiar, Level vs AC chart sometime before submitting his rules to Gygax. I was thinking of trying to run normal D&D (B/X actually) using the original DatD attack method and was wondering how the two combat systems compared.

In the DatD system, armor blocks a set percentage of attacks and, strangely, having no armor at all still can block an attack. So, I took the 2d6-2 rolls, convert them to percentages and then subtracted out the 8.3% that having no armor will still save and here's what I got (discounting shields for simplicity):

Leather: 8%
"Hard" leather: 33%
Chainmail: 50%
Plate: 75%

Now, I took the Level vs AC chart from OD&D for a first level character and computed the change in percentage chance to hit for each of the armor types:

Leather (AC7): 18%
Chainmail: 35%
Plate: 55%

As you can see, armor is much more effective in the DatD rules than the D&D rules. To match the effectiveness you'd need to convert armor to AC as follows:

Leather: AC8
Hard Leather: AC5
Chainmail: AC3
Platemail: AC1

Similarly, converting D&D armor effectiveness to a 2d6 roll (ignoring the -2 for simplicity)

Leather: 4 or less
Chainmail: 6 or less
Platemail: 7 or less

Not that this means anything .....

If trying to play D&D with the DatD combat tables (but still using regular D&D weapon damage) I was thinking of giving large monsters a AF less than their HD while giving them a bonus that acts as a penalty to target's Armor Save (so armor will be less effective against a giant for instance). Also, some weapons, such as maces, might also get a anti-armor bonus (along with the possibility of making magical weapons with extra armor crushing powers).

[aldarron]

Apr 16, 2012 12:10:59 GMT -6 @hedgehobbit said:

From my understanding, Arneson moved from the Level vs Level chart with armor saves to the, now more familiar, Level vs AC chart sometime before submitting his rules to Gygax.

Not 'zactly. D@D's level vs, level chart is CHAINMAIL's fantasy combat table. It is reworked around the hit chances of Hero and Superheros and the numbers filled in to the rest of the columns from there by HD/level instead of particular creatures the way the original FCT is. So it is the same, statistically, but can be used for any monster.

Arneson used the FCT for a couple weeks and then rejected it in favor of a version of his own, which, Arneson had indicated was an adaptation of his ironclads game "to hit" tables. My guess would be that at some point, perhaps from the start, he used CHAINMAIL's list of 8 different grades of armor, thus the 1-8 AC. (edit 2017: we now know his "to hit system involved 2d6 rolls against a weapon skill target number that was individualized for the character).

Dave used a 2d6 saving throw after hits in combat but we don't know for sure if it was against AC or was simply a 7 or something. He does use a kind of AC save in AiF and it seems like something that he would at least have experimented with given the symetry with how he set up ability scores and given certain comments he made about them over the years.

Apr 16, 2012 12:10:59 GMT -6 @hedgehobbit said:

I was thinking of trying to run normal D&D (B/X actually) using the original DatD attack method and was wondering how the two combat systems compared.

In the DatD system, armor blocks a set percentage of attacks and, strangely, having no armor at all still can block an attack. So, I took the 2d6-2 rolls, convert them to percentages and then subtracted out the 8.3% that having no armor will still save and here's what I got (discounting shields for simplicity):

Leather: 8%
"Hard" leather: 33%
Chainmail: 50%
Plate: 75%

Now, I took the Level vs AC chart from OD&D for a first level character and computed the change in percentage chance to hit for each of the armor types:

Leather (AC7): 18%
Chainmail: 35%
Plate: 55%

As you can see, armor is much more effective in the DatD rules than the D&D rules. To match the effectiveness you'd need to convert armor to AC as follows:

Leather: AC8
Hard Leather: AC5
Chainmail: AC3
Platemail: AC1

Similarly, converting D&D armor effectiveness to a 2d6 roll (ignoring the -2 for simplicity)

Leather: 4 or less
Chainmail: 6 or less
Platemail: 7 or less

Not that this means anything .....

If trying to play D&D with the DatD combat tables (but still using regular D&D weapon damage) I was thinking of giving large monsters a AF less than their HD while giving them a bonus that acts as a penalty to target's Armor Save (so armor will be less effective against a giant for instance). Also, some weapons, such as maces, might also get a anti-armor bonus (along with the possibility of making magical weapons with extra armor crushing powers).

Wow that's a great analysis! particularly interesting how the numbers generate an almost perfect 1-8 AC in reverse (plate = AC1). Keep us posted on your further developments. Exalt!

[aldarron]

I've been thinking about this a bit more and I have some ideas in mind for a D&D style game, and I wanted to add to Hedge's discussion here with some thoughts on the Arneson's Adventures in Fantasy methods.

There he describes a one or two step process.

The first step is a saving throw which will result in no damage being done to the character if it is successful, as follows

Helmet 10%
Small Shield 25%
Large Shield 65%

The % given is the chance a save will be successful; in other words, you have to roll a 10 or less on a D100 for a Helmet based save to work. "Small shield" appears to refer to a buckler, while "large shield" is any shield of the standard variety. The helmet rule here is very interesting but unspecific. I presume that the Helmet category is a helmet only situation and that the other categories assume a helmet is being worn. So I think it would be reasonable to subtract 10% from the save percentage of the other categories if the defender failed to wear a helmet.

Anyway, the second step occurs only if the defending character is armored but either failed the shield saving throw, were attacked from behind, or if they weren't carrying a shield in the first place. This step does not save a character from damage, but does reduce the damage recieved.

Leather 55% (success reduces damage by 1/3)
Chainmail 60% (success reduces damage by 1/2)
Full Plate 90% (success reduces damage by 2/3)

So that's cool and all, but a bit much of a process for me to want to use it as is at the table. To my mind a saving throw involving more than one roll takes away from the sponteneity of the combat. The easiest and most interesting way I can think of to fix that is to make it a player option situation. What I mean is, a player wearing armor and carrying a shield who is attacked from the front can choose to make a shield throw in the hopes of getting no damage or an armor throw in the hope of better odds at getting only 1/2 damage.

A second thing I don't much like from a table use perspective is how the damage reduction of the three types of armor varies from 1/3 to 1/2 to 2/3rds. I'd prefer to just use a 1/2 damage reduction for all three.

If I were playing AiF, those are the only houserules I would apply. But part of Hedgehobbits goal was to use an Armor save in a D&D game - so how might we use the AiF system for that?

Of course, you could just roll percentile dice against the AiF percentages, or convert them to D20 numbers. However, since in D&D (and in D@D, for that matter) we have numbered Armor Classes, it would make sense to try to use those AC numbers rather than having yet another table TN's to consult. So let's look at a table comparing AC numbers with the AiF percentages. I'm cheating here a bit - I'm using the armor and shield AC because it lines up a little better and saves typing. The Aif % are the chances of failure of a Saving Throw.

Armor Type	AC #	AiF Save Failure %
Helmet	-	90%
Small shield	8	75%
Large Shield	8	35%
Leather (and shield)	6	45%
Chainmail (and shield)	4	40%
Plate (and shield)	2	10%

These numbers aren't radically different, and Chainmail is actually identical. The two that differ most are the AC for leather armor, and the AC for shields. Leather armor is notoriously variable anyway.

So, I'm suggesting that it would be perfectly acceptable to ditch Arneson's percentages and use the traditional AC number as a 1d10 target number, that you must score Equal to or ABOVE.

A successful save = 1/2 damage.


Theoretically, Helmets should be AC 9, but that doesn't make sense in D&D, so we will call them AC8, and, as seems to be the case in AiF, rule that lack of a helmet add 1 to AC.

If "helmet only" is AC 8, then shields only are something else, and that is because of Arneson's special no damage shield saving throw.

A player character attacked from the front and armed with a shield could choose to attempt EITHER an AC saving throw for 1/2 damage, OR a shield only saving throw for no damage at all. If the player chooses to make a shield saving throw and fails, full damage will result.

shield saving throws (1d10)

Buckler 8

Standard shield 4

Of course, all of this is just an initial proposal, so everyone feel free to jump in with comments if you have any.

[aldarron]

Mar 25, 2017 18:06:36 GMT -6 aldarron said:

A player character attacked from the front and armed with a shield could choose to attempt EITHER an AC saving throw for 1/2 damage, OR a shield only saving throw for no damage at all. If the player chooses to make a shield saving throw and fails, full damage will result.

shield saving throws (1d10)

Buckler 8

Standard shield 4

Of course, all of this is just an initial proposal, so everyone feel free to jump in with comments if you have any.

Actually I think I can simplify this even further to only one choice, like this:

To defend a hit:
The defender must roll 1d10 and score Equal to or ABOVE their armor class.
- If the character has a shield and is attacked to the fore, any roll of 8 or more equals no damage.
Otherwise a successful roll results in 1/2 damage received.
- a helmet alone is considered Armor class 8. Lack of a helmet adds one to AC.
A failed roll results in full damage taken.