keeping a flashlight in your pocket at all times

i've experimented with a couple of flashlights to try and find a good compromise of size and lumens to have in my pocket for a multitude of situations/occasions. I have settled on a CR2 4Sevens mini. I recently have found though after a short hot weather spell with a friend that his ceiling fan was set for winter not summer...after arguing with my friend I set 4Seven to strobe and proved my point. I finally found a feature for strobe other than blinding people and disorienting them...thought it worthy of sharing

Wow. Good thinking.
I have often thought that the hidden strobe function on the MiNi line was sorta silly, considering how long it took to get to.
It is good to see that it might serve some practical purpose after all.

nope not following you, does the strobe tell you how fast the blades are spinning like when you timing an engine?

Under what circumstances will a strobe reveal the direction of the fan?

abarth_1200 said:

nope not following you, does the strobe tell you how fast the blades are spinning like when you timing an engine?

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I think what the strobe enables you to see is the angle made by the blades to the direction.... ie is the fan blowing air downwards (for summer) or upwards to promote air circulation.

When you're timing an engine, you synchronize the strobe with the engine speed so that you "stop" the timing wheel (crankshaft damper or flywheel) so that you can see the moving timing mark in relation to the gradations.

In both cases, you're "stopping" the rotating component.

At least that's what I think was meant.

Can't you just stand under the fan and feel which way it's pushing the air?

WadeF said:

Can't you just stand under the fan and feel which way it's pushing the air?

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Yes, you could stand under the fan and check if the airflow from it was cooling the flashlight head.


A flashlight somehow needs to be involved

artec540 said:

I think what the strobe enables you to see is the angle made by the blades to the direction.... ie is the fan blowing air downwards (for summer) or upwards to promote air circulation.

When you're timing an engine, you synchronize the strobe with the engine speed so that you "stop" the timing wheel (crankshaft damper or flywheel) so that you can see the moving timing mark in relation to the gradations.

In both cases, you're "stopping" the rotating component.

At least that's what I think was meant.

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Didn't work for me... :thinking:

WadeF said:

Can't you just stand under the fan and feel which way it's pushing the air?

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but that would make it easy

It will not show the direction of the fan, it may cause the illusion that the fan is moving one direction but actually be going the other.
The frequency and speed could cause an optical illusion.

jacketch said:

Yes, you could stand under the fan and check if the airflow from it was cooling the flashlight head.


A flashlight somehow needs to be involved

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fdot said:

I recently have found though after a short hot weather spell with a friend that his ceiling fan was set for winter not summer...after arguing with my friend I set 4Seven to strobe and proved my point.

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:huh2:

fisk-king said:

but that would make it easy

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...and *nowhere* near as much fun compared to when using a light.

Dances with Flashlight said:

Under what circumstances will a strobe reveal the direction of the fan?

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As long as the frequencies of the strobe and the fan are known (maybe from the handbook?) you can calculate it, except for the corner cases where you can't tell the apparent direction of the fan.

fs: strobe freq
ff: fan freq (in revolutions per time unit)
n: ammount of (evenly spaced) wings on the fan
delta: angle between wings of the fan

If the fan rotates at ff, the frequency of the wings fw is ff*n. If fw is a whole-number multiple of fs, the fan will appear to stand still.

If the positive angle change of the fan between strobe flashes is between k*delta and (k+1/2)*delta for some whole number k, the fan will appear to move in the positive direction (i.e. the same direction it actually moves). At exactly k+1/2 the fan will appear to stand still and have the double ammount of wings.

The fan moves delta in time t_wing = 1 / (ff*n)
The time between strobe flashes is t_strobe = 1 / fs

If t_strobe modulo t_wing = 0, there will be no apparent direction.
If t_strobe modulo t_wing < 1/2 t_wing, the apparent direction will be correct.
If t_strobe modulo t_wing = 1/2 t_wing, there will be no apparent direction.
If t_strobe modulo t_wing > 1/2 t_wing, the apparent direction will be the opposite of the real direction.

So by calculating t_strobe modulo t_wing and looking at the fan, you can derive the real direction except for the two corner cases.

Please correct me if I made a mistake

EDIT: modulo t_wing, not 1/2 t_wing of cause.

cjay said:

So by calculating t_strobe modulo t_edge and looking at the fan, you can derive the real direction except for the two corner cases.

Please correct me if I made a mistake

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um, yeah or you can turn the fan off and watch it as it slows to a stop and "derive" the real direction.

Captain Spaulding said:

um, yeah or you can turn the fan off and watch it as it slows to a stop and "derive" the real direction.

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Exactly what I was thinking...

WadeF said:

Can't you just stand under the fan and feel which way it's pushing the air?

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My live-in mother-in-law comes from a country that has many superstitions and a low regard for the scientific method. One day, she pointed to an air-conditioner intake vent on our wall and indicated that the air conditioning must be broken because she felt no air coming out. I explained (through my wife) that it was an intake, but she wouldn't believe me. Finally, I said, "I'm going to release a facial tissue a few inches away from the vent. If the tissue is pulled against the vent and clings there, will you agree it's an intake?" She agreed to my terms. To my astonishment, she did concede she was wrong when faced with the visual proof.

My fans operate on three different modes. On low you can just look at it to tell which way it's spinning. On medium, look at the cat to see which way his head is spinning as stares at it. On high, you can stick your finger up there real quick to see which side it hits.

jacketch said:

A flashlight somehow needs to be involved

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Now that's funny! :laughing::laughing::laughing:

fdot said:

I finally found a feature for strobe other than blinding people and disorienting them...thought it worthy of sharing

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Cool idea, I'll have to try that.

:welcome:

XB70 said:

I keep a Kel Tec P32 semi auto in my right front pants pocket. Does muzzle flash count as light?

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MAYBE if you used a PF9 there would be enough flash to count as a light, but .32 I'm not so sure :nana: