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View Full Version : Which blades break more frequently - flicky or stiff?



bydande
-13th May 2003, 09:49
This is a general philosphical questions and doesnt refer to any specific supplier - either real or imaginary.

Does the thinnes of very flicky blades mean they break more frequently or or does the stiffness of non-flicky blades mean they break more easily? Or is it the skill (or lack of skill) of the user that is the major determinant of how often you break blades.

reposte
-13th May 2003, 16:44
First and foremost: It's the fencer that breaks blades.

After that, how many flicky blades do you know? The only brand which offers flicking specialized blades is LP.
Are there anymore?

What I've noticed is that old blades tend to break, I can't really say that I've seen flicky blades per se at my club...

bydande
-13th May 2003, 21:03
Whilst I understand that fencer skill (or lack of skill) is likely to be the biggest influence on breaking blades - what I am trying to get at is: Do the characteristics of blades also have an impact.

- are lighter more flexible blades more likely to break because they are thinner?
- are the firmer blades more likely to break because their firmness represents a level of brittleness
- do old club blades tend to be firmer because they become firmer with age or is because the more flexible blades break before they reach old age.

Its just a point of interest there are people at my club with blades of differing flexibility and I was just wondering if it had an effect on longevity. I am not intending to change the sort of blade I use just because one lasts longer than the other just mildly interested to see if there is a correlation (or negative correlation) between flexibility and longevity.

Hudson
-13th May 2003, 21:06
so far touch wood, i've not had a blade break on me and i've got a couple of quite old eppe blades. alot of the time it seems to be down to a number of diffrent factor all happening at the same time to break the blade

kbo518
-13th May 2003, 22:32
From what I experienced, my thinner cheap blade tend to bend and stay bent. I had 2 blades break and they were of a higher quality, one santelli and an allstar. both were about a year or so old.

bydande
-14th May 2003, 08:06
First time I have heard an AllStar blade described as "higher quality"!

Which Allstar blade was it?
Was it one of the SM or BF blades that they "white label" as AllStar blades or was it one of the cheap nasty ones they get made for them in deepest darkest Ukraine on the 2am-5am shift.

reposte
-14th May 2003, 08:34
I think that's where they got Golubitsky from...

haggis
-14th May 2003, 08:39
Golubitsky "created" in a Ukrainian foundry?:eek: :grin:

No wonder his knee fell to bits - poor quality control!

Barry Paul
-14th May 2003, 09:41
If I have time I will give you the scientific answer tonight.

Barry Paul
-14th May 2003, 21:53
Hi,
A blade only breaks because in is stressed passed its ultimate tensile strength. before this a blade which is bent reaches it's elastic limit this is a stress level or point of plastic deformation beyond which the blade does not return to it's original shape.

If you use a blade which has these two points close together the blade is brittle and breaks relatively quickly. (is everyone keeping up?) Some blades are so brittle that when the blade fails the shock wave during failure causes a second failure and the blade breaks into three pieces.

Our etoile blade is a low carbon blade which has a lower elastic limit but a high tensile strength it last a long time but appears a little soft. great for beginners/schools.

So why do blades break? A fencers keeps hitting and occassionally has to straighten his blade but after a time the same sort of hit and bending of the blade causes the blade to fail catastrophicaly (break in two). This is most likely due to a process call fatigue. (To be continued)

bydande
-15th May 2003, 07:32
Barry,
Thanks for the explanation so far - I look forward to Chapter 2.

Barry Paul
-17th May 2003, 11:11
So why do blades break?
1. Blades which break after a short use are likely be due manufacturing faults. This is very rare if the blades are made on a automatic forge as used by B.F., France Lame, and Leon Paul. However most blades sold throughout the world are still produced by hand forging and during this process, lapping, inclusion of slag and impurities produce surface flaws from which failure can occurs very quickly. Before we made our own blades the failure rate / replacement rate was between 4% and 6%.
2. The most common cause of breaking is low cycle high stress fatigue. A fencers keeps hitting and occasionally has to straighten his blade but after a time the same sort of hit and bending of the blade causes the blade to fail catastrophically (break in two).
As the blades are used surface defects at the edges caused by blows from an opponents blade develop at the corners. As the blade is stressed fatigue cracks develop at these defects, each stress cycle causes the crack to grow, until one crack becomes dominant (largest) this propagates across the cross-section of the blade until it fails catastrophically. The main influence on blade life is the stress level and rate of propagation of cracks or K1c value. (Maraging steel has a very high K1C value and therefore last a long time.)
For any well made and properly heat treated carbon steel blade the K1C value is very similar therefore the life before failure is mainly determined by the stress level at the outside surface. The stress at the surface is proportional to the cube of the section height. So a small difference in blade thickness can make a large difference to the stress level on bending and therefore itís life. (This is one reason why our epee blades last so long for any given bend the maximum stress is lower. (for more information go to equipment button top of fencing forum, sales then data sheet look at epee data sheet.))
The flexibility of a blade is normally measured by clamping horizontally a blade 700 mm from the tip and putting a weight on the tip. The flexibility is the measure of how much the blade bends. For any one flexibility there is an infinite combination of blade width to blade thickness that will give the same measured flexibility. However as the cross-section changes from rectangular to square the surface stress increases by the cube of the section height.

The more flexible blades (or flicky blades) given the same use should last longer.

Hudson
-17th May 2003, 12:19
I actuly cam make sence of that Barry and explains a great deal. Would help explain some of the breaks that have happened at comp's i've been at and the fencers's gone "But i only got the blade last month/week"
Cheers.

Muso440
-17th May 2003, 19:10
So, following on from Barry's technical stuff, is there a way of telling that your blade might break quite soon? (which would be handy, so you could replace it first before it potentially injures anyone...)

I mean, can you *see* the fatigue cracks at all, or is there any other give away sign?

Rdb811
-17th May 2003, 21:49
An S shape to the blade were it has twisted both up or down or a sharp kink are tell tale signs. Otherwise blades use go.

Muso440
-18th May 2003, 06:51
Originally posted by Rdb811
Otherwise blades use go.

Is that a typo or just some weird use of the English language that I'm not familiar with?

Rdb811
-18th May 2003, 19:51
"just go".

Serves me right for typing late at night. At last it gives me a chance to increase my number o posts to get rid of that stupid 'junior member' tag.

Muso440
-19th May 2003, 16:43
Originally posted by Rdb811
"just go".


Just go where?

Or what do they do, exactly?

Rdb811
-19th May 2003, 23:24
They 'just' break - particularly sabre blades (at the hilt) - which ********* club are you at ?
(moderated as requested to stay with in forum guides)