Blade rigidity and razors

Shane a great guy - to my mind the Dart by far his best DE to date (and among my top 5 at any price). He seemed less than happy when singing the Dart’s praises upon being lent one; not sure why. Remember suggesting he should increase the cosmetics and feature it as his premiere DE - met with crickets. Only recently have I learned there are others of a similar opinion

Rightly responded. What meant to state is that starting from the cap and rotating to the optimum cutting angle seems to help people find the angle where the blade is most aligned along its width which imparts maximum rigidity and leads to least chattering from a blade flexing. Have watched videos of well regarded reviewers where the blade is damn near perpendicular to the skin. If there any weakness in top cap blade interface, such blades going to flex and chatter - in fact, not sure how any top cap design could eliminate chatter so employed

It would seem to me the opposite would be true. A DE blade doesn't really have much structural integrity from cutting edge to cutting edge; you can easily snap one in half without that much force.

On the other hand, when riding the bar the entire width of the blade suddenly becomes essentially bolted in place by the cap, regardless of whether the blade is clamped close to its edge or not.

So it would seem to me that chatter would actually be minimized by riding the bar (steep angle shaving).


Mind you, in practice I lean toward riding the cap (shallow angle) much more frequently than riding the bar (steep angle).

Let’s try another approach; which would be more rigid presuming the same metal:

15mm thick metal bar
Or
0,1mm thick metal bar

That is the difference between finding the angle where the blade is:

Perpendicular to the beard follicles
Vs
Parallel to the beard follicles

The sole reason a blade is so easily folded and snapped is that one is attacking it from the 0,10mm thickness versus the 15mm width.

Talking with people whose stubble I have seen, I have come to the following conclusions.

1. Fine hair with smooth skin (or a razor with no significant exposure): The blade rigidity just doesn't matter at all.

2. Skin irregularities like acne: A rigid blade helps a lot. This seemed backwards when I was told this, but it makes sense in that if the blade snags on something enough to flex the blade, it will flex toward the skin regardless of whether the razor is being held steep or shallow (albeit less so with shallow).

3. Coarse beards: Rigidity matters a great bit, but I am starting to think a blade that is allowed to flex some is better for comfort and maybe even closeness as long as it does not flex so much that it chatters. Too stiff is not ideal, but too loose is really bad for those with coarse hair.

In another thread, I was (I think incorrectly) talking about damping of the blade. While I was close to something, there is nothing other than the skin that really dampens anything. . . . and I just knew I was missing something. Andrew at Paradigm has convinced me (gently and offline) that it is more of a harmonics or blade resonance issue:

The blade in any razor will have a set, undamped natural frequency. The impact of the stubble on the blade (what we call feedback) is more or less noise with a random impact frequency--but the frequency still has a range. I think the range is roughly in the 100-200 Hz range depending on how fast I rub something like a stiff metal ruler over my face and listen for the range of pitches. It is definitely not a single pitch. If the razor is stiff enough that its natural frequency is above that of the range of stubble noise, the blade won't chatter or experience resonance with the stubble. This is mainly true for coarse hair in that fine hair won't drive the deflection enough to matter much I am guessing. I wouldn't know--I have coarse hair, and it matters a great deal.

To find blade frequency in the razor, I use an old blade in the razor and listen for the pitch when I flick it (and then sing the pitch into a vocal pitch app). My son actually runs a rosined cello bow hair over the tip of the blade (after threading inside the safety bar) to drive the blade with the bow hair like he would a cello string to listen for the pitch of the blade (and then he plays the pitch on his cello). We get the same results--it is a definite pitch, unlike "stubble noise". The more rigid blades have a higher pitch or higher frequency. A Gen2 CGL3 has a pitch of around 220 Hz--I think it is about perfect (just above "stubble noise" frequency giving some blade flex but not yielding resonating chatter) and I think it's why people find it (the GEN2) so smooth compared to the GEN1 even though they have the same shave plane geometry. . . I just wish the safety bar design were more like a Paradigm. My Diamondback was around 350 Hz. Very rigid razors will be higher. The added ability for the blade to flex (while staying well away from resonance) is why I think the Diamondback is comparing favorably against very rigid, very high-end razors. . . . although I think it has room for just a little more flex without resonating.

I know my theories on this are in flux, but this is where I currently am, and I don't have a gnawing feeling like I am missing something (like I did with damping). Now that school is out, I may have my son use his cello bow hair to find pitches of many of my razors. . . . .if anyone was interested??

Now that was a post of substance by somebody having something to state....

From my perspective, irrespective of correct or folly, that was one of the best shaving posts ever encountered.

How do people find the rigidity of the Karve design?

How do people find the rigidity of the Karve design?

Pretty pretty rigid as Larry David would say.

Sent from my LG-US998 using Tapatalk

Talking with people whose stubble I have seen, I have come to the following conclusions.

1. Fine hair with smooth skin (or a razor with no significant exposure): The blade rigidity just doesn't matter at all.

2. Skin irregularities like acne: A rigid blade helps a lot. This seemed backwards when I was told this, but it makes sense in that if the blade snags on something enough to flex the blade, it will flex toward the skin regardless of whether the razor is being held steep or shallow (albeit less so with shallow).

3. Coarse beards: Rigidity matters a great bit, but I am starting to think a blade that is allowed to flex some is better for comfort and maybe even closeness as long as it does not flex so much that it chatters. Too stiff is not ideal, but too loose is really bad for those with coarse hair.

In another thread, I was (I think incorrectly) talking about damping of the blade. While I was close to something, there is nothing other than the skin that really dampens anything. . . . and I just knew I was missing something. Andrew at Paradigm has convinced me (gently and offline) that it is more of a harmonics or blade resonance issue:

The blade in any razor will have a set, undamped natural frequency. The impact of the stubble on the blade (what we call feedback) is more or less noise with a random impact frequency--but the frequency still has a range. I think the range is roughly in the 100-200 Hz range depending on how fast I rub something like a stiff metal ruler over my face and listen for the range of pitches. It is definitely not a single pitch. If the razor is stiff enough that its natural frequency is above that of the range of stubble noise, the blade won't chatter or experience resonance with the stubble. This is mainly true for coarse hair in that fine hair won't drive the deflection enough to matter much I am guessing. I wouldn't know--I have coarse hair, and it matters a great deal.

To find blade frequency in the razor, I use an old blade in the razor and listen for the pitch when I flick it (and then sing the pitch into a vocal pitch app). My son actually runs a rosined cello bow hair over the tip of the blade (after threading inside the safety bar) to drive the blade with the bow hair like he would a cello string to listen for the pitch of the blade (and then he plays the pitch on his cello). We get the same results--it is a definite pitch, unlike "stubble noise". The more rigid blades have a higher pitch or higher frequency. A Gen2 CGL3 has a pitch of around 220 Hz--I think it is about perfect (just above "stubble noise" frequency giving some blade flex but not yielding resonating chatter) and I think it's why people find it (the GEN2) so smooth compared to the GEN1 even though they have the same shave plane geometry. . . I just wish the safety bar design were more like a Paradigm. My Diamondback was around 350 Hz. Very rigid razors will be higher. The added ability for the blade to flex (while staying well away from resonance) is why I think the Diamondback is comparing favorably against very rigid, very high-end razors. . . . although I think it has room for just a little more flex without resonating.

I know my theories on this are in flux, but this is where I currently am, and I don't have a gnawing feeling like I am missing something (like I did with damping). Now that school is out, I may have my son use his cello bow hair to find pitches of many of my razors. . . . .if anyone was interested??

I’m definitely interested. Being a musician and a wet shaving fan, it sounds (pun intended) like you’re onto something that may advance the science and art of wet shaving. As Spock would say.... “Fascinating!” Further inquiry would seem to be in order. One avenue of inquiry: How might amplitude and/or frequency (short of full on resonance), affect the users’ subjective experience of “comfort”?

Talking with people whose stubble I have seen, I have come to the following conclusions.

1.  Fine hair with smooth skin (or a razor with no significant exposure):  The blade rigidity just doesn't matter at all.

2.  Skin irregularities like acne:  A rigid blade helps a lot.  This seemed backwards when I was told this, but it makes sense in that if the blade snags on something enough to flex the blade, it will flex toward the skin regardless of whether the razor is being held steep or shallow (albeit less so with shallow).

3.  Coarse beards:  Rigidity matters a great bit, but I am starting to think a blade that is allowed to flex some is better for comfort and maybe even closeness as long as it does not flex so much that it chatters.  Too stiff is not ideal, but too loose is really bad for those with coarse hair.

In another thread, I was (I think incorrectly) talking about damping of the blade.  While I was close to something, there is nothing other than the skin that really dampens anything. . . . and I just knew I was missing something.  Andrew at Paradigm has convinced me (gently and offline) that it is more of a harmonics or blade resonance issue:

The blade in any razor will have a set, undamped natural frequency.  The impact of the stubble on the blade (what we call feedback) is more or less noise with a random impact frequency--but the frequency still has a range.  I think the range is roughly in the 100-200 Hz range depending on how fast I rub something like a stiff metal ruler over my face and listen for the range of pitches.  It is definitely not a single pitch.  If the razor is stiff enough that its natural frequency is above that of the range of stubble noise, the blade won't chatter or experience resonance with the stubble.  This is mainly true for coarse hair in that fine hair won't drive the deflection enough to matter much I am guessing.  I wouldn't know--I have coarse hair, and it matters a great deal.

To find blade frequency in the razor, I use an old blade in the razor and listen for the pitch when I flick it (and then sing the pitch into a vocal pitch app).  My son actually runs a rosined cello bow hair over the tip of the blade (after threading inside the safety bar) to drive the blade with the bow hair like he would a cello string to listen for the pitch of the blade (and then he plays the pitch on his cello).  We get the same results--it is a definite pitch, unlike "stubble noise".  The more rigid blades have a higher pitch or higher frequency.  A Gen2 CGL3 has a pitch of around 220 Hz--I think it is about perfect (just above "stubble noise" frequency giving some blade flex but not yielding resonating chatter) and I think it's why people find it (the GEN2) so smooth compared to the GEN1 even though they have the same shave plane geometry. . .  I just wish the safety bar design were more like a Paradigm.  My Diamondback was around 350 Hz.  Very rigid razors will be higher.  The added ability for the blade to flex (while staying well away from resonance) is why I think the Diamondback is comparing favorably against very rigid, very high-end razors. . . . although I think it has room for just a little more flex without resonating.

I know my theories on this are in flux, but this is where I currently am, and I don't have a gnawing feeling like I am missing something (like I did with damping).  Now that school is out, I may have my son use his cello bow hair to find pitches of many of my razors. . . . .if anyone was interested??

One of the best posts I read on any Forum!! Thank You for very interesting information Elvis Outlander

When a designer combines these it can be magic.

Skin irregularities like acne:  A rigid blade helps a lot.
... listen for the pitch ... Very rigid razors will be higher.

+1

Rigidity is a false mith, as blade gap.
They're part of a bigger picture.
OTOH, there is the blade chattering.
https://damnfineshave.com/thread-blade-chatter

For what I've learned into wetshaving, each blade when sharp can cut the hairs.
But cutting is efficient just when the angle is right.
Low angle is the best.
This helps the blade to work efficiently, so It's more durable and comfortable.

If the geometry lacks of rigidity, the blade sings.
When I hear the blade singing, I know this in a razor not good for me.
Mostly, blade singing is related with high gap, narrow topcap (more when with little arch), small contact area of the plate.

When I want to explain the perfect geometry I show all details of the Dorco PL602.
Many people have issue because It's super-light.
But with good technique, specially when with a correct back grip on the handle, It's a great shaver.