Understanding DE safety razor parameters

[dawid]

Your underlined conclusions are a bit surprising, but they might not be if the razor is in the hands of an expert shaver that can handle that exposure. On the other hand, they might not be the same for an intermediate or beginner shaver.

But that's exactly what surprised me - I was expecting aggressive razors with such positive exposures but found out that they were not aggressive at all, especially the +0.2 mm shocked me.
If I compare the +0.2 mm to Muhle R41 or Blackbird OC, both are more aggressive than the one I just tested. This gives a clear indication that aggressiveness is not strictly correlated with blade exposure.

And you are right, beginner shaver might get completely different feeling of such razors. Perhaps I should ask my wife to test it on her legs

 

[titanrazor]

Yes, but the distance from the edge of the blade to the edge of the top cap is really important. The stiffness is inversely proportional to deflection. This length is raised to the power of three for a cantilevered beam.
The blackbird razor supports the blade close to the edge. This gives a rigid blade in the shaving plane, while it is more flexible in the other direction. This is only useful if you use the razor as the designer intended. If you use it at a steep angle it is less noticeable.

View attachment 1901855

if riding the cap with the blackbird and applying slight pressure, the blade will flex and conform to skin surface; hence it is a close, smooth, and comfortable shave. however, if riding the bar, the blade will be stiffer and feel more like other razor. take a blackbird loaded with any blade and with the finger nail press straight down the blade edge from the direction of the top cap, it will flex. it will stay pretty stiff if you push against the edge towards the cap.

 

[titanrazor]

if riding the cap with the blackbird and applying slight pressure, the blade will flex and conform to skin surface; hence it is a close, smooth, and comfortable shave. however, if riding the bar, the blade will be stiffer and feel more like other razor. take a blackbird loaded with any blade and with the finger nail press straight down the blade edge from the direction of the top cap, it will flex. it will stay pretty stiff if you push against the edge towards the cap.

note that with the blackbird, the under side of the blade is barely supported hence allowing it to flex in that direction.

 

[DesertIguana]

I think there is more to this question than numbers like Blade Gap & Blade Exposure, if that was all it was then two Razor with SAME NUMBER would be same, this is complicated process. Where one can only use Gap N Exposure as guide, much more to how it shave, not even taking about Badge Differences.

 

[titanrazor]

I think there is more to this question than numbers like Blade Gap & Blade Exposure, if that was all it was then two Razor with SAME NUMBER would be same, this is complicated process. Where one can only use Gap N Exposure as guide, much more to how it shave, not even taking about Badge Differences.

exactly, the geometry, the blade clamping design, and the right technique for that particular razor are all important factors to the outcome of a shave.

 

[dawid]

exactly, the geometry, the blade clamping design, and the right technique for that particular razor are all important factors to the outcome of a shave.

Isn't it what is being tested here? The geometry, the blade clamping design, etc.?

 

[JPO]

if riding the cap with the blackbird and applying slight pressure, the blade will flex and conform to skin surface; hence it is a close, smooth, and comfortable shave. however, if riding the bar, the blade will be stiffer and feel more like other razor. take a blackbird loaded with any blade and with the finger nail press straight down the blade edge from the direction of the top cap, it will flex. it will stay pretty stiff if you push against the edge towards the cap.

That was a much simpler and better way to say it

 

[catchacoolbreeze]

Yes, but the distance from the edge of the blade to the edge of the top cap is really important. The stiffness is inversely proportional to deflection. This length is raised to the power of three for a cantilevered beam.
The blackbird razor supports the blade close to the edge. This gives a rigid blade in the shaving plane, while it is more flexible in the other direction. This is only useful if you use the razor as the designer intended. If you use it at a steep angle it is less noticeable.

View attachment 1901855

If we are talking about rigidity in relationship to chatter during the shave, I may have a different understanding of what is going on with the blade and what "chatter" is. The best explanation I have heard is from Chris at Karve on an AMA that is easily google-able. He says (when designing his razor),

"The geometry came from a bunch of research to familiarize myself with how razors are configured and then creating analogies between how a blade is configured and real world applications. The one I'm most proud of (because I saw an immediate improvement), was to support the blade as much as possible as a way of eliminating chatter). All razors support the blade on the top side with the top cap, but chatter comes from cyclical loading...force, no force, force, no force, etc. The unloading comes from loading the blade during cutting, but then something gives (such as the whisker that is being cut) and the blade unloads for a split second. The top cap can only help with the loading, so the baseplate has to work together with it."

Until we see a razor shave in video under magnification, no one will be 100% what is actually happening but this is the best explanation of what chatter actually is that I have found. Rigidity comes from stabilizing the blade on both sides. That being said, I would also prefer less blade reveal too. However, less blade reveal on an unsupported razor is, in my opinion, fantasy land with regards to providing actual rigidity. It is all marketing.

 

[JPO]

If we are talking about rigidity in relationship to chatter during the shave, I may have a different understanding of what is going on with the blade and what "chatter" is. The best explanation I have heard is from Chris at Karve on an AMA that is easily google-able. He says (when designing his razor),

"The geometry came from a bunch of research to familiarize myself with how razors are configured and then creating analogies between how a blade is configured and real world applications. The one I'm most proud of (because I saw an immediate improvement), was to support the blade as much as possible as a way of eliminating chatter). All razors support the blade on the top side with the top cap, but chatter comes from cyclical loading...force, no force, force, no force, etc. The unloading comes from loading the blade during cutting, but then something gives (such as the whisker that is being cut) and the blade unloads for a split second. The top cap can only help with the loading, so the baseplate has to work together with it."

Until we see a razor shave in video under magnification, no one will be 100% what is actually happening but this is the best explanation of what chatter actually is that I have found. Rigidity comes from stabilizing the blade on both sides. That being said, I would also prefer less blade reveal too. However, less blade reveal on an unsupported razor is, in my opinion, fantasy land with regards to providing actual rigidity. It is all marketing.

Part of the clamping and damping on e.g. the Blackbird razor comes from the stored energy created by the bent blade. This is something you can fine tune to achieve a certain shaving characteristic.
You can to some extent model this, but you need multiple prototypes to test it in practice.
Small changes can make a big difference.

 

[catchacoolbreeze]

Part of the clamping and damping on e.g. the Blackbird razor comes from the stored energy created by the bent blade. This is something you can fine tune to achieve a certain shaving characteristic.
You can to some extent model this, but you need multiple prototypes to test it in practice.
Small changes can make a big difference.

May I ask what DE razor or razors do you think are the most rigid and where would you rank them on a 1 to 10 scale (10 being the most rigid). Then where is the blackbird ranked on the same scale?

 

[DesertIguana]

Razors are all rated by people opinions, people beard are like deck of card, different.

 

[JPO]

May I ask what DE razor or razors do you think are the most rigid and where would you rank them on a 1 to 10 scale (10 being the most rigid). Then where is the blackbird ranked on the same scale?

That is difficult to say because of all the factors at play.
The Henson razor has the most rigid head design in my collection.
Second place goes to Tatara.
Tatara also extends the blade support under the blade. This reduces blade chatter but doesn't add rigidity.

The Blackbird is much more flexible. I still don't have any issues with blade chatter.

 

[dawid]

Time for the neutral blade angle.
Three razors tested and compared to the baseline design (v16):
- v16: 30 deg
- v28: 20 deg
- v29: 40 deg

Conclusions:
- The smaller the angle, the better efficiency
- The smaller the angle, the higher smoothness (major improvement over 30 and 40 deg ones)
- The bigger the angle, the better blade feel
- The bigger the angle, the higher aggressiveness (not that major impact though)

The 20 deg razor was extremely smooth and pleasant, unlike the 40 deg one.
If I'm correct, most razors use a 30 deg neutral blade angle, which contradicts my findings, despite the noticeable improvement in smoothness and efficiency.

 

[catchacoolbreeze]

Time for the neutral blade angle.
Three razors tested and compared to the baseline design (v16):
- v16: 30 deg
- v28: 20 deg
- v29: 40 deg

Conclusions:
- The smaller the angle, the better efficiency
- The smaller the angle, the higher smoothness (major improvement over 30 and 40 deg ones)
- The bigger the angle, the better blade feel
- The bigger the angle, the higher aggressiveness (not that major impact though)

The 20 deg razor was extremely smooth and pleasant, unlike the 40 deg one.
If I'm correct, most razors use a 30 deg neutral blade angle, which contradicts my findings, despite the noticeable improvement in smoothness and efficiency.

When razor manufacturers talk about angle, they almost always talk about how you are holding the handle and not the blade angle itself.

 

[dawid]

When razor manufacturers talk about angle, they almost always talk about how you are holding the handle and not the blade angle itself.

What actually makes sense, because only very few would understand what the blade angle is.

Henson has it described nicely here, and they refer both to the shave angle and the blade angle:

Blackbird claims the shallow shaving angle of 26 deg, and the steep shaving angle of 28.9 deg. Nominally it would give us around 27.5 deg then.

 

[titanrazor]

Time for the neutral blade angle.
Three razors tested and compared to the baseline design (v16):
- v16: 30 deg
- v28: 20 deg
- v29: 40 deg

Conclusions:
- The smaller the angle, the better efficiency
- The smaller the angle, the higher smoothness (major improvement over 30 and 40 deg ones)
- The bigger the angle, the better blade feel
- The bigger the angle, the higher aggressiveness (not that major impact though)

The 20 deg razor was extremely smooth and pleasant, unlike the 40 deg one.
If I'm correct, most razors use a 30 deg neutral blade angle, which contradicts my findings, despite the noticeable improvement in smoothness and efficiency.

in general, blade cuts (should be termed slicing) better with shallower angle. however, people hair/stuble grow differently, some more stand-up, some more lay-flat, this will actually affect the slicing angle for each individual. that might explain YMMV.

 

[Alex Jr]

My most comfortable shaves come from razors that support the blade with both top cap and base plate and closest as possible to the edge. My piccolo for example.

I’m not questioning engineering as I don’t have the proper knowledge to do it, but my face can immediately tell the difference when shaving with a “floating” blade or one held only by the top cap with no proper support from the base plate.

Numbers aside and considering only my personal experience, I call BS on that “blade is rigid through extreme bending”.

Not for me it isn’t.

 

[dawid]

My most comfortable shaves come from razors that support the blade with both top cap and base plate and closest as possible to the edge. My piccolo for example.

I’m not questioning engineering as I don’t have the proper knowledge to do it, but my face can immediately tell the difference when shaving with a “floating” blade or one held only by the top cap with no proper support from the base plate.

Numbers aside and considering only my personal experience, I call BS on that “blade is rigid through extreme bending”.

Not for me it isn’t.

And my testing fully alignes with your observations. Clamping distance is important, but I haven't noticed any changes while modifying the bending radius.
See the post #32.

However, in addition to the clamping distance I found out that there are other factors which influence smoothness a lot.

 

[Alex Jr]

And my testing fully alignes with your observations. Clamping distance is important, but I haven't noticed any changes while modifying the bending radius.
See the post #32.

However, in addition to the clamping distance I found out that there are other factors which influence smoothness a lot.

I think the post below by @catchacoolbreeze summarizes perfectly what I feel during my shaves with different razors.

The argument that that blade must be held firmly only in the direction of the shaving plane is, for me, not right.

We’re talking about micro vibrations here, the blade acting like it’s spring loaded, tension-no-tension while hitting the hair so the top cap is limited on what it can do to prevent the issue.

Like I said earlier, from my shaving experience, I call BS on that and the extreme bending theory.

Razors like the Merkur progress and Mühle Rocca are designed like that and they both lack in the comfort department for me. They feel and sound like a chatter machine.

"The geometry came from a bunch of research to familiarize myself with how razors are configured and then creating analogies between how a blade is configured and real world applications. The one I'm most proud of (because I saw an immediate improvement), was to support the blade as much as possible as a way of eliminating chatter). All razors support the blade on the top side with the top cap, but chatter comes from cyclical loading...force, no force, force, no force, etc. The unloading comes from loading the blade during cutting, but then something gives (such as the whisker that is being cut) and the blade unloads for a split second. The top cap can only help with the loading, so the baseplate has to work together with it."

 

[catchacoolbreeze]

In a previous post, I said, we would not have really any firm way of knowing if clamping is important unless we had two razors of the exact same design with one having superior clamping and the other not. Light bulb moment! - My Overlander is kind of like a hybrid. The baseplate has 4 extended supports on it. However, if you look closely the outer 2 are purely cosmetic. They don't make contact with the blade (see pic). So I did a anecdotal test with my Overlander - on a more rounder part of my face where the whole blade may not touch, I focused on using the center (blade supported) and also on the edge (blade unsupported). To me, shaving with the outer edged of the razor felt rougher than focusing on the center. Is this scientific - no, but its another data point.