Along the lines of weight difference to thickness.

5.000 .1196
4.375 .1046 -12g.
3.750 .0897
3.125 .0747 -14 g.
2.813 .0673
2.500 .0598 -16g.
2.250 .0538
2.000 .0478 -18 g.

this is by sqr foot of metal.



RPM

Here is the complete chart
http://www.thedirtforum.com/sheetmetal.htm

All did you take pictures? It sounds interesting for sure.

RPM

Would heat treating explain why historical helms seem to be of lighter gauge steel yet still as strong? If you compare an 18 gauge steel helmet that is not heat treated with a exact duplicate that is heat treated, would the heat treated helm hold up better than its non heat treated counterpart?

Jonathan,

IN some cases yes but heat treating of armour is a fairly late occurance in Medieval Europe and the vast majority is not. Until the 15th most armour seems to have been wrought iron and a small percent of low carbon steels. It is not until the 15th that northern italy gets a limited production of it and till the end of the same century for areas in south germany.


RPM

But before the 15th century head defenses were often layered. A great helm was worn over a skull cap. A bascinet was worn over a mail coif.

Since it is quite posible to make helmets that are thicker than 18 gauge, the use of 18 gauge helmets would indicate that they where deemed sufficient by their users (or at least the people paying for them.)
This could very well be due to layering with other armour; a thin helmet over a mail coif and padding is less encumbering than a heavier helmet, in my experience.

Dan,

I agree, often this was done to increase the protection offered pre 15th century. It may have been done so that once the helm was removed you had beeter vision and breathing not solely protection.
Though it is not always the case wearing two layers of helmet or a coif. There are many examples of both equipment req's for soliders and art that show men wearing just a helmet and padding. Of course wearing more would be better in most cases but especially with great helmets, the more artwork I look through for examples of the dual helmet the more with only a mail coif comes up. I am starting to wonder how wide stread or common the practice was. Who did it etc. The Why they did it not so much as I think of it being more obvious.

RPM

Elling,

I think they clearly could make clearly thicker helmets than 18 gauge as most seen from the late medieval period are thicker than that. I think it is less them being deemed sufficient at 18 gauge and more them likely being of cheaper quality as the helmets that have context with suits (Churburg 13 for example) is much heavier than a 18 gauge helmet would be. Some people, especially poorer infantry would have no other choice.

RPM

See these experiments:

http://www.thearma.org/photos/Gathering03/testcutting.htm

I think that part of the variation in helmet thickness is simpley the fact that these guys were doing it by eye and starting from plate that wheather battered out themselves or later bought in sheets from a battering mill was already going to be of varying thickness through out. Theres alot of room for variation just based on those two factors alone.

Hello Dan
The MRL helm, I bashed,was on a fence post.You`re right,it didn`t have the ,"give",a person would have, if hit.
And a mail coif,would add that much more, thickness,of steel. But it would have still, hurt :)

Allan,

I agree but it still is possible that control was used to thicken or thin areas. It would seen strange to be that the crest of the skull is almost always the thickest in helmets as it the center ridge of most breastplates. I am sure much variation comes from those factors but it would be hard to see them not controlling thickness in those areas to me.

RPM

Randall, I agree completely and there are obvious examples of this being done, I simpley meant that based on those two factors alone, if you were to take two lets say chapel de fers that are to be of the same type as part of a 100 piece commision that those two helmets would have at least slightly different weights.

Allan,

No I agree completely with that.
It seems very accrate.
RPM

Hey something to bring this one back up in interest. I found reference to the King of France ordering a huge number of armours and open faced bascients in 1384 for an infantry force. That in itself is interesting but more so is one of the requirements is that all the harnesses weigh over 25 pound and the bascients over 4. I can only assume as he makes these weights required as a) they made armour and bascients lighter at times. b) these were not desirable to his force because how thin they were even for munitions armour as he was buying was going to be lower quality anyways he was trying to avoid helmets and armour he felt were not effective. I got it from osprey's French Armies of the 100 years war but sounds like the inventory of the clos of galees or something from the regnal records of france there. I will look about and see what I can find. It always suprises me what can be found in the most random of places...

RPM

on the point of thickness vs protection:

Even against pollaxes the thickness seems relevant, in that the weight itself is inertia to be overcome in accelerating the cranium when struck. this means concussive dameage from acceleration will decrease significantly with the weight of the helmet.

i assume the (temporary) deflection of the metal under the blow will be less in thicker steel, giving less chance for actual direct transferal of energy to the skull (as opposed to the energy being transferred through padding and large contact surfaces).

Also is mettalurgy not ma major factor in the damage to the occupant of the armour? Is thick spring steel not stiffer than thin mild steel?
I fight regularly with steel pollaxes in armour of various sharpnesses and thickness and hardness make a real difference, i feel

From my personal experience and from reenactment battles I have seen.

18 ga would offer decent protection against one-handed swords. Moderately good at deflecting incoming points unless they come at square angle (should be good against long pikes, but not good enough against more rigid and precise weapons like pollaxes and shorter spears). A good whack with a war sword would most likely knock you unconscious. A good blow with a heavier one-handed sword also has enough chances to seriously stun you. A thrown spear will easily penetrate the helmet, as well as arrows. And percussion weapons will laugh at that foil on your head.

16 ga will offer almost absolute protection against one-handed swords ( I would not count on stunning the wearer with such weapon) and would also offer quite decent protection against longswords and even halberds. Still very vulnerable to percussion weapons.

14 ga is virtually proof against all hand-held weapons as well as war bows. Though reportedly can be penetrated by a thrown spear (at close range and if the thrower is really good at it, some guys here claim to have pierced a helmet this way). Percussive weapons may knock you unconscious without considerably denting the helmet, but the weight of the helmet really helps here. Pollaxe can still penetrate the helmet by its spike if the blow lands square.

Anything thicker than 14 ga will add protection against pointy things like lances, arrows and war hammers' spikes. Protection against percussion weapons will be increased by the mass of the helmet, not by the thickness of the steel.

All written above is applicable to modern helmets made of mild steel. Medieval helmets could be considerably softer (I think most of them were), but could also be much harder. In general reenactors who fight with steel weapons consider 14 ga makes good all-around helmets. 16 ga is good enough for fighting with one-handed swords but not good enough against axes and polearms. And for mass fights with lots of polearms and maces event 14 ga is not enough (the helmets themselves hold OK, but the wearers get stunned, therefore heavier helmets are required).

Some more thoughts.

I once tested a war hammer on a 18 ga breast plate (one of my early "creations", when I knew nothing about how armor should be made). It did penetrate, but it was not so easy to achieve the penetration because the spike glances off when the impact is not at square angle (that's why war hammers have hammer heads, not only spikes). So even against a war hammer 18 ga helmet offers excellent protection when compared with a maille coif.

Armor was cleaned, and that should be kept in mind. Helmet that weighs 4 pounds today may have weighed 6 pounds when it was new.

A helmet made of let's say 14 ga steel will not be 14 ga. It will be close to 14 ga at the edges of individual plates, but will be closer to 16 ga ot the most dished areas (at least that goes for helmets made "conventionally" of several pieces welded together).

Thinner helms need less metal. And 400-600 years ago metal cost a lot of money. So guess what I would make you if you ordered 100 helmets but did not specify how thick they should be?

Also soldiers tend to discard equipment that is bothersome. We know that soldiers often discarded armor in 17th century despite officers' orders because it was too heavy. So it is better to have thin light helmets that the soldiers will wear than thick heavy ones that will be discarded.

My bascinet (14 ga top with 16 ga skirt and visor) weighs 4.1 kg (approx. 9 pounds) with aventail. Its visor weighs around 0.5 kg IIRC. Overall weight is very close to one of the bascinets mentioned in the article on this site. I can wear it for 3 hours in a row, but my neck gets tired. Would I be able to wear it 8 hours a day? Don't know. Maybe I would get used to it. Would I prefer a lighter helmet if 99% of my "war time" would be marching? Definitely yes.

Sorry I understand that this is a old post, but I have something to share.

I recently did some test with sharpened swords against different gauge helms. These tests were done to sub $300 helms, and are placed on a stand so there is a full force in each blow.

First the 16g helm. It was a sugar loaf helm made by GDFB. Bashed it hard with a Hanwei Rhinelander and some other Del tin one hander. The blow did made a dent into the helm, it was my full power but the dents didn't go very far in. The second blow is made by my friend while I was the wearing that helm. I could feel the helm getting hit but I personally didn't feel much, and I believe my friend didn't hit very hard. I was wearing double padding so I'm good.

The 14g helm. Jaw bone sallet made by GDFB. I myself couldn't dent it but only scratches. Also didn't want to risk my neck wearing the helm for testing because this sallet expose way more lower face and neck than the sugar loaf.

I heard that the historical helms were made with different thickness depending on the location, so I don't know if my test meant anything. And I don't think getting a full force blow on another moving target is easy, so i suppose 16g is in some sense enough in exchange for a lighter helm?

P.S These test really hurt the sword. had to re-peen both swords because the guards were coming loose.