Oppinion on fancy "three-handed" sword?

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Fancy Karl

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May 1, 2014
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So, I've been designing this new sword type with a "three-handed" grip, analogous to a heavy longsword in weight, balance and use. It is more than a little unorthodox, with lots of holes for weight-savings. It is, however, extremely stiff and tough, with no stress-concentrations whatsoever. I made in a CAD-software and used it's FEM-analysis-tool to evaluate the design, and the weakest part is actually in the "tang" itself.

qu0Zt5T.png


For all it's awesome looks, it's not designed to be a wallhanger. Can you see anything inherently wrong with the practiacality of the design? love to get feedback on this so I can start making it! I'm going to put a decent pommel on the end along with the handle-scales to improve the balance, and possibly some sort of basket-guard at the foremost grip to protect the fingers when binding. This will bring the total weight up to 2.1 - 2.2 kg.

...What do you think?

PS. Excuse the excessive decimal places. The FEM-software needed a fine mesh to calculate the details reliably.
 
Wouldn't all those holes make it vulnerable to accidental twisting during a cut? Seems like any side load would permanently warp the blade that much easier without material to resist the deformation.
 
I get the feeling balance would be terrible, with the blade so forward of the handle. Might try making something like that from wood, and seeing how it goes. If you want weight savings, perhaps a fuller might be better? That actually has structural advantages, and a wide fuller might be just the ticket along the blade. Personally, I'd want to curve the handle forward a little at the bottom as well. Not really my cup of tea design-wise, but to each his own.
 
Looks like it has a fuller that is pierced through. Holy stress raisers! Check out this German quillon dagger with a similar feature:

PDG9GmU.jpg
 
For those concerned about stress-raisers and sideways stiffness... Stress concentration in holes (or cracks) is proportional to square root of the hole diameter. With 10mm minimum radius, the cutouts provide very minor stress-increases, as compared to sub mm cracks. As for sideways stiffness, there are two uninterrupted bands at either side of the fuller with full "stock" thickness of 10mm. This tapers down to 5mm towards the point. It's all verified by both regular mechanical equations (in regards to stress-raisers) and FEM-analysis. Unless you shear through the edge or spine of the blade, which is a 8mm x 6mm square-section at the thinnest point, it's not going to break.
 
I suggest studying and practicing some swordplay before trying to come up with awesome designs. Simple is often the best solution when designing weapons, if you look at what has been tried and tested across the world you will see very little variation in the fundamentals of design, the basics seem to be straight and two edged, curved and single edged, with minor variations on this theme seeing widespread use. Look at Celtic, Gladius and Chinese designs, Sabres, Katanas, and the slash and thrust style medieval european styles.I notice more similarities than differences in sword design between time ,place and culture
My less than expert opinion is that the hook or raised tip would catch and snag on everything you didn't want it to, and the hilt design would be overly long and unwieldy making balance and direction change and grip awkward and slow.
I mean you can fight with a monkey wrench but if your opponent has practiced with his broom handle your gunna be in strife.
For a properly expert opinion on sword mechanics read some of Tinker Pearce's writings on balance, edge geometry, pivot mechanics, and such.That's guy who's thought long and hard about swords and how they work, look at his designs, and again simple and traditional.
 
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I know this is far from ideal if you're looking for a purely practical blade, not least due to the manufacturing. The sheath-problem hasn't gone me by, I doubt I'll bother designing a sheath for it at all. It is primarily an experiment with modern structural mechanics.
I'm not sure I understand what you mean by a longer hilt makes it unwieldier... It makes for a longer leaver, and would if anything make it quicker and stronger in binds. As long as it clears the inside of your elbow (which it does), I don't see a problem with longer hilts.

The balance you see in the picture is not the final design. It's lacking a weighted pommel and handle-scales. Even in it's off-balanced state, a longer leaver somewhat compensates.
 
It's not just the balance front to back that we're concerned about. The placement of the weight seems like it's going to have a pivot point low and forward of the grip, which will seriously adversely affect the handling, not to mention the strain it would put on your wrist just holding it. I don't see this being anything more than a fantasy wall-hanger, no offense intended. What background do you have in making and/or using swords?
 
The point of balance is less than 10 mm (8.53 to be exact) off the centerline of the handle. It is indeed within the lateral footprint the handle itself. Perhaps the curves makes it look worse than it is. If those 8mm concerns you greatly, I can just ad 20 mm in "height" to the tip of the blade to adjust the balance.

I'm seriously considering designing and rendering it again with the scales and pommel (and corresponding change in balance) in the picture. That would save me the effort of repeating myself.
 
Well, grab some mild steel, fire up that CNC machine, set the laser on "fun," crank up the trilithium chamber to warp 10 and......engage! That will be a fun design to watch the creepy cnc robot blast out. When it comes to designing swords, there's no computer using a bunch of big words at you that can substitute for the input you get from holding a prototype!
 
Cool sword design! I think it is definitely cutting edge(pun intended)! As far as the "snagging" issue, instead of "curling" the hooked parts, you could more or less "square" them off. I guess all the points on it would then pose other concerns... The weight of this thing is... whoa. You would have to wield it with one hand in the uppermost grip. And yes, depending on final construction, the weights and POB would change, of course. As far as the structural integrity, what would be the difference between your current holes vs. just a wide shallow groove(like a massive hi)? The design is definitely cool! It has a futuristic look to it. I could see you wielding this thing in a post-apocalyptic setting for sure! :thumbup: P.S. - Totally off subject... What version of AutoCADD do you use?
 
looks more contemporary that way. I liked the Klingon-ish look of the original, myself. What would be the operational significance of the groove shapes/direction? IE= \\\\\\\ or llllllll as opposed to the current ///////. Or even shaped with a "V" shape towards the blade, still leaving the back rounded. I'd call it a "two-and-a-half hand" sword. What material are you planning to machine it out of? Just some random questions/suggestions. :)
 
The reason the slots are angled 45 degrees is threefold; aesthetics, strength and weight reduction. This way the angle of the slots is increasingly perpendicular to the cutting edge as you go towards the point. Now you have nice stable 10mm roman archs that support the edge whenever you strike something. The 45 degrees also produces a "trusswork effect" withe the curving blade and handle that makes the blade slightly stiffer. Finally, angled slots removes more material than perpendicular ones. "Strong where it needs to be, light where it can..."

Also, I use Solid Works 2013.
 
I've made some minor modifications:

Included a pommel.
Decreased the minimum thickness towards the point from 5 to 4 mm (increased the taper).
Made the fuller wider (helped reduce tress-concentrations laterally).
Reduced the angle of the "guthook" to make it duller.
Poked a 3 new holes toward the point to perfect the balance.
Reduced the hole-size in the tang for the handle-scales to 6mm. I doubt 10mm was necessary.

Also, I took the time to screencap both the lateral and vertical stresses as calculated by the FEM-software. Here are the pics:

PoEALom.png


I also took the time to tweak the balance vertically. I doubt it will make much of a difference, but the point of balance is now 6.2 mm instead of 8.5 mm "below" the centerline of the tang.

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Here is the lateral stress simulation. Note that although there IS a concentration of stress at the edge of the slots, it is uniform throughout the blade, and the tang itself with the hole in it will fail before the blade will. Unless you try to use the sword as a crowbar sideways, there shouldn't be a problem. The deflection is also nice and gradual, with no apparent "kinks" that indicate weakness.

IRAa9Cn.png


Finally the vertical stress and deflection. Note the smooth transitions. The only "hotspot" is at the very edge itself, having zero thickness in this case. Unless you are making a practice-sword, there's really no way to design around that. And since this isn't an issue with other swords, I think it's OK.
 
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Are those stress simulations just from use, or does it track stress risers during the heat treat process? I think many of us makers were a little concerned about the latter, where you seem to be thinking primarily about the former. This seems like a blade that would really be best to have heat treated by a professional, because it's likely to have serious warp issues. I still think you should curve the handle forward a little, but aside from that, it looks like a pretty cool Klingon-like blade.
 
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