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Jeff Jackson
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 Posted: Sat 01 Jan, 2011 5:57 pm Post subject: |
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Different sword styles require different pivot points. I am certain someone on this forum can provide some specs for you. Is the 870 gram only too heavy because of the pivot point location Ozsváth?
iaq source
"One sword keeps another in the sheath."
- George Herbert
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Scott Woodruff
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| Posted: Mon 03 Jan, 2011 10:36 am Post subject: |
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When I make a sword, I first get the blade worked down into the ballpark, so that it feels reasonably good without pommel, then add hilt furniture and take a little off of either blade or pommel to fine-tune. If the blade alone does not have a good feel, it doesn't matter what weight pommel you use, you will have a boat-anchor. It doesn-t matter if it has a cog at 1" or 12".
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Tom Guder
Location: Germany Joined: 03 Aug 2011
Posts: 15
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| Posted: Fri 05 Aug, 2011 2:17 am Post subject: |
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Hello!
I've didn' t read the whole thread, but I will. I'm working on a blade (still very early stage) and here are some colorfull pictures (which carry no information yet but show the possibilities with 3D FEM). So further work will be done and I'd like to participate in this discussion with more information. So please don't remind me that there are no scales in the pictures, its the very first simulation of the blade and I'm still configuring the analysis process. However the geometry is very parametrized so I can study a lot of cases. So I need to know the important parameters (getting a clue while reading the discussions on the board).
The geometry
details of the strains in the tang (applied bending moment)
the first Eigenmode (in future analysis, the grip and the crossguard will be included)
Best regards
Tom
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Stephan Johansson
Location: Borċs Sweden Joined: 28 Dec 2007
Posts: 46
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| Posted: Fri 05 Aug, 2011 3:13 pm Post subject: |
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Finally!
Sword design enters the modern world!
What program have you done your simulations in?
I have previosly worked in ProE and it have felt to time consuming to make simulations with this system, but we are now starting to use Inventor and it has a integrated FEM-module that is very easy to use (I work as a mechanical designer).
Off topic: I don't understand this thing with the two pivot points. If you let a sword rotate freely will it not just rotate around its CoG?
Best Regards
Stephan Johansson
IN NOMINE DOMINI
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Timo Nieminen
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| Posted: Fri 05 Aug, 2011 6:59 pm Post subject: |
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| Stephan Johansson wrote: |
Off topic: I don't understand this thing with the two pivot points. If you let a sword rotate freely will it not just rotate around its CoG? |
Generally, no. To make the sword rotate, you need to push on it. What happens when you push on a sword? It depends on where you push. Push on the CoG, and it will just move sideways, with no rotation. Push away from the CoG, and you get a combination of rotation and sideways movement. This sideways movement means that the CoG moves. But there will be a point along the line of the blade that doesn't move - this is the pivot point corresponding to the point where you pushed (if you push on the grip, this pivot point is the centre of percussion, but this term is also (mis-)used for nodes of vibration).
"In addition to being efficient, all pole arms were quite nice to look at." - Cherney Berg, A hideous history of weapons, Collier 1963.
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Ozsváth Árpád-István
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| Posted: Fri 05 Aug, 2011 9:11 pm Post subject: |
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My favorite topic again!
Some underestimates the importance of the vibration nodes and put a heavy accent on the pivot points. Certainly, pivot points have a lot to do with the handling of the sword, it affects the way it rotates and moves to the air.
I noticed that against light targets a tip cut produces the most devastating effects, on heavy targets like thick branches (which I don't reccommend and it's considered sword abuse - but a fun thing to do) hitting further from the vibration node may lead to catastrophic consequences - literally you can cut your leg off. Maybe my blade is a bit to springy, the pivot point and the vibration node are just a few centimeters apart. Hiting far away from the pivot point has littlle or no effect compared to the violent vibrations resulting from a heavy impact not in the right place and in a bad angle. Cerainly, I have some blade stiffness problems, well that's the problem with leaf-spring.
Nice thing you do Tom, bringing 21th century technology into swordmaking can solve many issues and you can make it on a CNC machine.
Don't take it for bad, but your tang seems to me a bit to narrow. It won't break but it will cerainly damage a wooden grip while taking heavy torques. you should make it wider closer to the guard and gradually narrowing towards the pommel. A few ounces here doesn't matter but it will improve the robustness of the hilt.
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Tom Guder
Location: Germany Joined: 03 Aug 2011
Posts: 15
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| Posted: Sat 06 Aug, 2011 12:26 am Post subject: |
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| Ozsváth Árpád-István wrote: |
Nice thing you do Tom, bringing 21th century technology into swordmaking can solve many issues and you can make it on a CNC machine.
Don't take it for bad, but your tang seems to me a bit to narrow. It won't break but it will cerainly damage a wooden grip while taking heavy torques. you should make it wider closer to the guard and gradually narrowing towards the pommel. A few ounces here doesn't matter but it will improve the robustness of the hilt. |
Hello Ozsváth,
I built up the model in the way that I need to change 2 values and the complete geometry and the FE-Model will rebuilt automatically with a less narrow tang - so your hint is something what I need to know for my design. Its a goal of the design to produce it with CNC.
Regards
Tom
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Tom Guder
Location: Germany Joined: 03 Aug 2011
Posts: 15
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| Posted: Sat 06 Aug, 2011 12:38 am Post subject: |
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| Stephan Johansson wrote: | Finally!
What program have you done your simulations in?
I have previosly worked in ProE and it have felt to time consuming to make simulations with this system, but we are now starting to use Inventor and it has a integrated FEM-module that is very easy to use (I work as a mechanical designer).
Off topic: I don't understand this thing with the two pivot points. If you let a sword rotate freely will it not just rotate around its CoG? |
Hello Stephan,
I use Salome [1] for full parametrized geometry and meshing. For FE calculus I like the French software Code_Aster [2].
You're right, in the first 6 modes (rigid body modes of the 6 degrees of freedom), the model moves freely in any direction (or rotates) because its not fixed. The 7th mode is the first interesting for me (I call it the first mode, because i ignore the rigid body modes). In future it would be possible doing a transient dynamic analysis. What happens when the sword impacts a target? How does it vibrate and where occur maximal stresses?
By the way (for those who are new to such calculus): In the modal analysis I didn't fix the model and there are no forces applied. So you get the Eigenvalues (and Eigenfrequencies) and the Eigenvectors (the way the nodes of the fe-mesh are displaced with a certain Eigenenfrequency.) With this Eigenvector you can make pictures like above and make the fashion of the vibration visible.
best regards, Tom
[1] www.salome-platform.org/
[2] www.code-aster.org
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Vincent Le Chevalier
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| Posted: Fri 19 Aug, 2011 11:15 am Post subject: |
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Hey, finite elements on swords 
I don't know if you've come across this thread I started a while back; perhaps it could be of interest to you... It was only FEM on a 1D model of the sword, but it was already sufficient to compute nodes of vibration, centers of oscillation and such properties quite accurately.
But of course if you have the full power of a CAD program working for you, you can go for the 3D model just as easily
Regards,
--
Vincent
Ensis Sub Caelo
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Tom Guder
Location: Germany Joined: 03 Aug 2011
Posts: 15
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| Posted: Tue 07 Feb, 2012 11:47 am Post subject: further studies |
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Hello!
I made some further simulations (its a very coarse model, but it's possible to figure out some weak points). Its a time based simulation of a blade to blade contact. The duration is about 0.002 secs.
Some short movies are on www.ib-guder.de
best regards to all who are interested.
Tom Guder
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Paul Hansen
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| Posted: Wed 08 Feb, 2012 10:37 am Post subject: |
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Interesting! But it would also be interesting to compare this model to one with a wider tang. And also to factor in the dampening effects of the handle.
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Tom Guder
Location: Germany Joined: 03 Aug 2011
Posts: 15
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| Posted: Wed 08 Feb, 2012 12:18 pm Post subject: |
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| Paul Hansen wrote: | | Interesting! But it would also be interesting to compare this model to one with a wider tang. And also to factor in the dampening effects of the handle. |
Hello Paul, at the moment I prepare some parametric studies. The pictures and movies are all made with coarse models (my testmodel). The main work for me now is to figure out the important parameters (taper, geometry of the tang, damping...) and create the different models. A lot of work Thanks for your advice.
Best regards from Leipzig
Tom
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