Do-It-Yourself - AGGRESSION measured [Revised]

[2bits]

Thanks for appreciating the criticism, not every does. Your responses were well-reasoned as well. I hope I have contributed to developing this technique to compare different razors.

Good luck

All signs of life are good signs.

"Agreement" is a little like an afternoon nap on clean sheets with a cool breeze. Great every once in a while and sometimes necessary - to feel better.

It's not the way to become better though.
Whatever wakes us up helps.

Just remembered the line in the movie "Zorba the Greek"

[you see my long term memory is still - fair to good]

Anthony Quinn says

"To live is to take off your belt and look for trouble."

I must be doin' it right 'cause I'm always finding it.

Later ...

 

[mozart]

I know these 2 razor models are not the best to compare but it is what I have on hand ...

I measured the angles (protractor against screen and my eyeballs such as they are) as you suggested - degrees formed at blade edge between blade and the top of the safety bar
...

Those are some marvelous pictures. I hope you don't mind if I use them to illustrate my point. Let me know if you do, and I'll have my post deleted.

The shots are not exactly from the side, so the numbers won't be accurate (nor will they be precise ), but it's going to be sufficient for my purposes.

Note the additional lines in blue.

I think this is the way the blade gap and angle should be determined, because the skin lies on that blue line. That's why I was asking for the side shots. Keep in mind that I am neglecting the fact that skin is pliable. The larger the gap, and the more pressure is applied, the more all these considerations will be affected. It is probably OK to ignore that for the moment. Note that the top cap, the blade edge, and the safety bar all lie on one line (plane, actually). The same is true for the "normal" Merkur heads.

Now, let's take a look at the Feather:

This razor is more interesting (?), because the top cap, the blade edge and the safety bar do not lie on the same plane. It makes a difference how one holds this razor against the skin. Interestingly, when the top cap is held against the skin, the shave will be more aggressive (steeper angle) than when the safety bar is used (but see below). There was a post by a gentleman recently who reported that he got more irritating shaves when he held the top cap against his skin and lowered the handle until the blade made contact. For many razors, this is not the case. I don't remember which razor he used, but it may have been a razor that is similar to this Feather. Also note that when the top cap is held against the skin, the handle cannot be lowered without the safety bar bumping against the skin. This will essentially prevent the blade from touching the skin (except in curvy areas, such as the chin), or one would have to use some pressure to force the safety bar into the skin, or one might involuntarily switch over to the safety bar making contact with the skin, thus abandoning the top cap as a guide. I have never used this Feather, but I would expect that it might afford more aggressive shaves than the Gillette.

Does all that make sense, or am I just rambling?

Best - MM

 

[2bits]

... Note that the top cap, the blade edge, and the safety bar all lie on one line (plane, actually). The same is true for the "normal" Merkur heads.

Now, let's take a look at the Feather:
... This razor is more interesting (?), because the top cap, the blade edge and the safety bar do not lie on the same plane.

I really appreciate your input. I have a better grasp of the problem and the tools now for having to think in a more detailed way about this question.

Thanks

You were correct to point out the camera angle was incorrect and it did influence the "apparent" relationships etc.

The earlier feather portable pic in particular suffers due to the incorrect angle.

The (I hope) improved pics are these:

I feel I'm at about the limit (with the equipment) I have on hand with these pics.

Observations:

a) The skin "pinching" into the gap would seem to explain how the Aristocrat still shaves give the "tooth" cutting edge of the blade does not appear to extend "over the line".

b) The angle of attack formed by the blade at the "line" is largest for the TECH at 30 degrees and slightly smaller for the Feather and Aristocrat at 28 degrees. The smallest (least aggressive) angle appears to be on the NEW at 25 degrees.

This does not (in itself) seem to track the user reports of relative aggression. (?)

c) The gap measured from the cutting edge to the point where the line contacts the safety bar is difficult to measure reliably and after correction for camera distance this measurement varies such that it does not seem to track reported aggression. (?)

d) End shots are not able to capture the "how thick do you like your ham" gap size either - because on some razors (some Gillettes) the blade "ends" are tucked down a few .001" smaller than 90% of the blade length that would do most of the shaving.

---

I don't doubt that the attack angle and the length of the blade "tooth" are factors in the overall aggression of a given model but I think the reliable measurement of these factors is simply beyond the camera/magnify/calculate technique I hoped would be up to the task.

The straight on measurement of the gap from safety bar to blade edge is easy to make and relatively accurate.

So far this "rough" measurement seems to agree with the reported relative "aggression".

Today I have had access to a "feeler gauge" tool and as suggested by

cooncatbob * thanks for the tip *

this is definitely - quick - and is the EASIEST WAY TO MEASURE the blade gap of a razor.

The difference in the results obtained with the 2 different methods was
< .002" on the samples I have.

---

My feeling is that the "straight on" gap measurement is the easiest to measure factor that seems to vary directly with perceived razor aggression and it can be used as a simple ranking tool.

When an example becomes available where the gap size places a sample in a rank order that is counter what the users would expect - a more detailed and precise analysis and measurement of that particular design would be appropriate to explain and evaluate the difference.

The factor (or combination of factors) that would alter aggression such that the gap would not be an indicator of the aggression is not apparent from the few makers and limited samples I have been able to considered here.

 

[mozart]

I really appreciate your input. I have a better grasp of the problem and the tools now for having to think in a more detailed way about this question.
...

Again, good stuff!

One way to test the hypothesis whether the "head-on" gap accurately reflects the aggressiveness of a razor is to think about the consequences depending on how much the safety bar protrudes from underneath the blade.

Check out the Feather Portable you posted earlier...

... and compare to this version. I made this in Photoshop to illustrate a specific point (ignore the red line in the picture).

Here, the safety bar does not protrude quite as far from underneath the blade. The gap measured "head-on" would be the same for both razors. However, I have no doubt that they would have an entirely different aggressiveness. This is because both the "side-ways" gap is different as well as the angle with which the blade intersects the line between blade edge and safety bar (I didn't include this line, because I ran out of time).

There are razors where the edge of the safety bar is almost right underneath the blade edge, so this scenario above does occur.

Best - MM

 

[mozart]

So, any more thoughts on whether the gap measured "head-on" is suitable to judge the aggressiveness of a razor?

Best - MM

 

[2bits]

So, any more thoughts on whether the gap measured "head-on" is suitable to judge the aggressiveness of a razor?

Best - MM

After looking at a few more pictures, end shots etc ...
My guess is aggression is a subjective reaction that is formed from more than a single physical aspect of the razor.

There are at least 4 to consider -

a) The GAP - is HOW BIG IS THE BITE

- easiest to measure
- varies (probably not linear) with aggression

b) PINCH factor - pliable skin protrudes into (especially larger) gaps

- quite complex re: size and angle variation etc
- dependent on pressure/technique
- not applicable to "smaller" gaps
- enables a design with 0 tooth length to give a good shave (with larger gap)
- may be beyond practical measurement and analysis due to complexity

c) TOOTH length - (blade extension beyond tangent (line) joining razor cap and the safety bar) = HOW LONG IS THE KNIFE or DEEP the STAB potential

- measurable (if very small)
- when > 0 adds to apparent aggression
- varies with pressure/technique

d) ANGLE of ATTACK

- easily measured
- pull, chop or scrape actions
- may vary relatively little in good designs as there is an optimum for cutting efficiency
- varies with how razor is held


A case in point -
Some report a greater or untypical aggression with open comb designs.
These in antique versions had very small GAPs (.004 - .016") that would suggest a mild or low aggression ...

How to explain?

- assuming the pinch effect to be nil

TOOTH LENGTH would be the only physical razor attribute to measure that - might - be of use.

The pressure and angles all being mitigated by the technique of the user.


For current razors with a geometry similar to that used by Gillette TOOTH LENGTH would be measurable and a factor adding to the aggression.

My guess is:

the best you could do
- to derive a number that varies with perceived razor aggression
(bearing in mind the user makes a difference too) -

Measure a razor like you would a dead shark -

How wide is it's mouth?
How long are the teeth?

What actual damage it might do to you if
- alive
- hungry and
- nibbling on your particular face remains

the realm of conjecture.