Friday, February 16, 2007

On Vikng Age SWORDS - Design

This is part one of what looks like may be a three part commentary related to Viking Age swords originally drafted for NORSEFOLK:

I ended up posting a number of commentaries on the blog (below) related to knives when that came up a while back. Much of what was said there can be applied to swords as well.

(August 30 / August 18 / likely some other stuff too)

Metals available during the Viking Age are distinctively different than our modern alloys. Too few realize this, and its even rarer to find a modern knifemaker with any historic materials. (Several have commented generally on this.) The physical processes used in the Viking Age also means historic blades will have a different level of finishing than typical of modern makers.

The overall quality of a sword will be determined by three overall aspects:

1) Design:

There will be a balance between width, thickness, length and profile.

The use of groves (fullers) will increase the structural strength but at the same time reduce the volume of the metal in the blade. Most artifact blades will have a wide and shallow simple U shape on both sides running along the centre of the blade, down most of the entire length. Use of a fuller like this will reduce the volume of metal (and weight) by as much as 50% over a simple diamond cross section.
Historically, the fullers would be forged into the bar using a top and bottom tool that would work together to squeeze the metal. This increases the width at the same time. Now, even on a modern anvil with a spring fuller (not used in the Viking Age) - its pretty darn hard to get an even impression with multiple heats and strikes down the length of 30 plus inches.
Next this rough grove would have to be ground smooth and even. Historically this would be done with hand grind stones. A long, difficult and tedious task. I strongly expect that artifact blades would NOT have perfectly smooth and even grooves for this reason.
Modern blade makers will usually grind or mill this fuller into the metal bar. This would not effect the end result. Use of modern powered tools here speeds up the process, and will create a much more even and regular profile than historic practices. Note that the profile of the fullers should always be rounded - not having square corners at the bottom of the grove.
Second is the layout of the tang - most specifically the transition of the full width of the blade into the tang.

Ideally the tang should be as wide as possible. There is a bit of a paradox here, as examination of artifact swords shows that almost all historic blades have relatively thin rod or 'rat tail' tangs. An understanding of the mechanics of the design explains this.

First, the tang should be made of the same bar of metal as the blade is. Most 'cheap' modern swords will reduce the blade to a mere stub - then arc weld a round rod (often threaded) to the blade. This is almost the worst way to construct the tang. The correct way to form the tang is to forge, or possibly grind, down the parent bar into the smaller diameter of the tang (more in a minute).
Next the tang should continue through the entire handle, and extend right through the pommel / counter weight. Historically the guard, handle tube and pommel all had holes in them. These were inserted on to the tang, then the end of the tang peened over to secure the hilt elements. (In some cases the pommel was composed of several elements, with the first element a disk that was peened to the tang. Further elements were then pinned / riveted to this first disk.)

Now, you can actually create a strong design with a thinner tang - if the transition from blade to tang is profiled correctly. Again cheap swords will use simple square shoulders that reduce the width of the blade directly to the width of the tang. The guard is cut so that it fits directly AGAINST this crisp shoulder. This is the fastest way to fit the hilt, but at the same time the WORST way to do this.
There should be ideally TWO changes in dimension between blade and tang. The first should have ROUNDED shoulders. The guard should have a slot cut into it so that the base of the blade and the entire area of these rounded shoulders fits inside the thickness of the guard. These matching areas should be carefully cut so that they fit tightly to each other. There are two purposes here. The rounded shoulders will bleed off stress from the blade down into the tang and hilt. With the incorrect square corners, there is a sharp focuss of stress, the end result being the blade snaps off the hilt when the blade is used.
On historic blades, tangs are usually forged out from the round shoulders (often quite dramatically) into a taper. As long as the SECOND transition in shape is located inside the the handle tube itself, even use of a narrow rod tang towards the pommel is far less likely to result in the handle snapping off. A TIGHT fit to the handle tube will re-enforce the thinner tang material.

The end of the tang should never be threaded. Use of threading of course will further reduce the effective diameter of the tang - and its strength. Threading on the pommel will always result in a hilt assembly that will work loose with time and can not be correctly tightened.
Note here that compression of the hilt tube (assuming use of organic materials) will absolutely result in the hilt elements becoming loose with time and use. With a correct peened over tang, correcting this is just a matter of re-hammering the peen down tighter. Again this was what was done historically. (Owners remember this - even a correctly designed and executed hilt assembly will loosen with time.)

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February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

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