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Adam Simmonds
Location: Henley On Thames Joined: 10 Jun 2006
Posts: 169
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 Posted: Fri 13 Oct, 2006 12:16 am Post subject: point of balance |
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hi,
i have a 17th C. slim bladed cut and thrust sword. due to a couple missing components on the hilt, the original balance point has been lost and i have re-established a point which i found favourable by adding copper wire too the grip.
my question is - were specific swords tradtionally designed too function around specific, fixed POB's and/or is it ok too shift the POB on a sword (say up to an inch either way) without disturbing the sword's overall harmony?
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Vincent Le Chevalier
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| Posted: Fri 13 Oct, 2006 2:06 am Post subject: |
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Adam,
In general I'd say that a sword's balance and dynamic handling is very sensitive to the position of the balance point. One should be wary when modifying the mass distribution of the weapon by adding or removing mass somewhere. Just adjusting the balance point is not enough, you'd have to replicate the inertia as well, paying attention to pivot points.
So yes, I think each individual weapon is designed to function with a specific mass distribution. Which is not to say that weapons of the same type couldn't differ by the balance point's location. It's all a matter of harmony between the length, the inertia and the balance point.
That said, if your sword only misses a few hilt components, you could be successful in restoring the original balance if you knew what the balance point was originally... That's making the assumption that the missing mass was concentrated around the point where you are adding your copper wire.
If you intend to use your sword for martial art practice (which is about the only reason you should be bothered by the balance of the weapon, I believe), you could try to restore a balance that feels right for the techniques you intend to study. But even appropriately balanced swords can feel awkward to a beginner, so it depends on your level of experience as well...
You can search the forum about the topic of balance as well, there are some really informative threads around here... Starting with spotlight topics in the category Dynamics, Properties, and Performance.
Oh, and welcome to the forums 
Regards
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Vincent
Ensis Sub Caelo
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Adam Simmonds
Location: Henley On Thames Joined: 10 Jun 2006
Posts: 169
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| Posted: Fri 13 Oct, 2006 11:48 am Post subject: |
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thanks for the info Vincent,
yeah, i am using the sword for practise purposes and have tried with two different POB's so far. with perhaps half an inch variation between the two i was surprised at the difference this made in handling. when i set the POB a bit closer to the hilt, the sword is very light and quick, easily manouverable with the wrist- though i have moved it slightly point ward since, as this seems to give me a bit more intimacy with the point of percussion and adds a bit of weight, giving my wrist a better work out.
one more thing - it seems to me that the point of percussion remains the same through the (slightly) different POB's - but admitedly i haven't measured this with any precision.
cheers, adam
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Vincent Le Chevalier
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| Posted: Fri 13 Oct, 2006 3:39 pm Post subject: |
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| Adam Simmonds wrote: |
yeah, i am using the sword for practise purposes and have tried with two different POB's so far. with perhaps half an inch variation between the two i was surprised at the difference this made in handling. when i set the POB a bit closer to the hilt, the sword is very light and quick, easily manouverable with the wrist- though i have moved it slightly point ward since, as this seems to give me a bit more intimacy with the point of percussion and adds a bit of weight, giving my wrist a better work out.
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Yes, we discussed this effect recently in this thread. Basically you need a bit of mass in the blade otherwise you can't feel it, and you have a less intuitive tip control.
Generally the location of the point of balance is more sensitive when it is closer to the hand. Moving the point of balance by half an inch would have a much less drastic effect on an axe, for example 
| Adam Simmonds wrote: |
one more thing - it seems to me that the point of percussion remains the same through the (slightly) different POB's - but admitedly i haven't measured this with any precision.
cheers, adam |
If by point of percussion you mean the harmonic node on the blade, I'm not surprised that it doesn't move much. Its location is more a function of the blade geometry, which was not affected at all by your modification.
Actually you could use that (but from the first part of your message I think you already do). Depending on the style of your sword, I think (but it's just a guess from my limited experience) that the pivot point associated to the guard should be somewhere between the center of percussion and the tip. That pivot point depends heavily on the location of your point of balance, so you could try and find the original point of balance this way.
Note that the last paragraph is pure speculation from my part as I have never been able to measure a weapon (or even a decent reproduction of one) from this time frame... I'd really like to hear the opinion of a more experienced person about that
Regards
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Vincent
Ensis Sub Caelo
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Adam Simmonds
Location: Henley On Thames Joined: 10 Jun 2006
Posts: 169
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| Posted: Fri 13 Oct, 2006 4:00 pm Post subject: |
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hi Vincent,
thanks for your reply, while i find it very interesting i don't understand 100% how you recommend i could try too locate either the original balance point and / or upper pivot point. How would you recommend that i test for these ie - how can i find the original pivot point if, at present, my blade has an unoriginal balance point?
i hope this is not too confusingly stated, any helpful information about establishing these dimensions of my baby would be very much appreciated.
oh, and its a 33.66 inch double edged diamond section blade, 1 in. wide at the base, with an even distal and proximal taper, and a half basket or walloon hilt, total weight 1lb 8 ounces
the hilt is missing the upper guard plates and the grip was also missing
cheers, adam
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Vincent Le Chevalier
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| Posted: Sat 14 Oct, 2006 6:29 am Post subject: |
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Yes, my explanations were a bit too quick, I think Let's try to make it clearer...
| Adam Simmonds wrote: | | How would you recommend that i test for these ie - how can i find the original pivot point if, at present, my blade has an unoriginal balance point? |
My idea was to make an assumption about the pivot point location, and to use that to restore the balance point location, in fact.
Some hypothesis are necessary for that. First, let's assume that the mass you add has no noticeable effect on the harmonic node. This is I believe an effect you noted already. Second, let's assume that the mass you are adding moves both the center of balance and the pivot point relative to the guard.
Now, what we need is a guess about the original location of the balance point or pivot point for your sword.
The balance point location is very sensitive and varies among period weapons, so it's difficult to get an accurate estimation. You could place it with an accuracy of half an inch, which as you've seen is not enough...
The pivot point associated to the guard moves with a greater amplitude when you add mass, and thus allows to adjust the mass more precisely. But we still need a little guesswork as to where it was originally.
From my admittedly limited experience, the pivot point is generally closer to the center of percussion on pure cutting weapons (early medieval swords, cavalry sabers), and closer to the tip on thrusting weapons (modern foils and epees, but also some longswords). Since what you describe looks like a cut & thrust sword to me, I think it's likely that it had a pivot point close to the tip, maybe a little back on the blade to retain cutting power and follow-up in cutting motions.
I tried to represent 3 situations that you might encounter on the picture below. The picture at the top shows a pivot point on the blade, too far from the tip. In that case you should add mass on your grip. The second picture represents the situation I think you should reach, with a pivot point a little back on the blade from the tip. The third is what would happen if you add too much mass: your pivot point moves past the tip, and that kind of balance will not feel right for a sword. The point of balance is not drawn since it will not move much anyway...
Note that this is purely a theory from my part, that is not backed up by any figure on period weapons since apparently no one wants to measure pivot points... It's just some pattern I noted on every weapon I've been able to measure.
I don't know if you are aware of the easy way to measure pivot points, so I'll detail that here as well. You should grip your weapon very softly, ideally between index and thumb, on the grip close to the guard, holding the sword vertically with the tip down. Then, without applying any torque, you move your hand laterally back on forth as fast as you can, in small motions. You should see a point on the blade that does not move, this is the pivot point associated to the point where you have gripped the sword.
Note also that where on the grip you add mass is important. If you add it close to the pommel, it will affect both the center of balance and the pivot point of the guard. If you add it close to the guard, it will only affect the center of balance, leaving the pivot point where it is. So you could start by adding mass close to the pommel, and then move the center of balance by adding it to the guard. It really depends on what you try to achieve and where the missing mass was...
Hope this helps !
 Attachment: 50.1 KB
The different results when adding mass to the grip/hilt
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Vincent
Ensis Sub Caelo
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Adam Simmonds
Location: Henley On Thames Joined: 10 Jun 2006
Posts: 169
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| Posted: Sat 14 Oct, 2006 1:35 pm Post subject: |
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Vincent,
thanks very much for the info.
i was able to find the pivot point on my blade (which is definitely a light cut & thrust type) after doing the test you described. it is about 5-6 inches from the tip, about halfway between the COP and the tip.
i suspect that orignially, there may have been a little more mass around the hilt as the missing components would seem to be more then the little copper wire i have added. however, this is very much guesswork as i don't actually know the weights of the missing bits, and other factors could come into play as well, like, maybe the blade weighs less now then it did when first made due to polishing and corrosion etc, though it is in pretty good nick. i think i'm gonna stick with what's on there right now, as it feels good to move. thanks again for the info, the more i can learn about the properties of my baby the happier i am!
cheers, adam
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