Helicopter

[cavelamb[_2_]]

Stu,

Have you seen this one?

http://www.wimp.com/impossiblehelicopter/

[Stu Fields]

"cavelamb" > wrote in message
m...
> Stu,
>
> Have you seen this one?
>
> http://www.wimp.com/impossiblehelicopter/

I have now. Some how it seriously degrades the old adage: "Seeing is
Believing".
I was involved in the development of the shuttered video camera nearly 40
years ago when I worked at the Naval Weapons Center. We didn't even need
the radio signal. We could adjust the shutter speed to stop props and other
rotating devices. The radio signal would allow you to sync to a particular
blade tho...

Thanks
Stu

[RogerN]

"cavelamb" > wrote in message
m...
> Stu,
>
> Have you seen this one?
>
> http://www.wimp.com/impossiblehelicopter/

There are optical tachs used on R/C heli's that you adjust the speed of a
shutter to make the blades appear still then read the rotor RPM.

RogerN

[Dan[_12_]]

RogerN wrote:
> "cavelamb" > wrote in message
> m...
>> Stu,
>>
>> Have you seen this one?
>>
>> http://www.wimp.com/impossiblehelicopter/
>
> There are optical tachs used on R/C heli's that you adjust the speed of a
> shutter to make the blades appear still then read the rotor RPM.
>
> RogerN
>
>
The military used to use strobe lights on real helicopters to "stop"
rotors. Another neat gag was a large F shaped devise that had a strip of
fabric across the opening. I think it was used to find out who was crazy
enough to approach the tips of spinning main rotors with it.

Dan, U.S. Air Force, retired

[cavelamb[_2_]]

Dan wrote:
> RogerN wrote:
>> "cavelamb" > wrote in message
>> m...
>>> Stu,
>>>
>>> Have you seen this one?
>>>
>>> http://www.wimp.com/impossiblehelicopter/
>>
>> There are optical tachs used on R/C heli's that you adjust the speed
>> of a shutter to make the blades appear still then read the rotor RPM.
>>
>> RogerN
>>
>>
> The military used to use strobe lights on real helicopters to "stop"
> rotors. Another neat gag was a large F shaped devise that had a strip of
> fabric across the opening. I think it was used to find out who was crazy
> enough to approach the tips of spinning main rotors with it.
>
> Dan, U.S. Air Force, retired


Gee, I did that a bunch of times.
That was how you measure the tracking on a UH-1.

Gotta admit, though, it would definitely get your attention!
For sure!

[RogerN]

"Dan" > wrote in message
...
> RogerN wrote:
>> "cavelamb" > wrote in message
>> m...
>>> Stu,
>>>
>>> Have you seen this one?
>>>
>>> http://www.wimp.com/impossiblehelicopter/
>>
>> There are optical tachs used on R/C heli's that you adjust the speed of a
>> shutter to make the blades appear still then read the rotor RPM.
>>
>> RogerN
>>
>>
> The military used to use strobe lights on real helicopters to "stop"
> rotors. Another neat gag was a large F shaped devise that had a strip of
> fabric across the opening. I think it was used to find out who was crazy
> enough to approach the tips of spinning main rotors with it.
>
> Dan, U.S. Air Force, retired

I'm wondering if the F shaped device was to detect blade tracking, to see if
one blade was flying higher than the other?

RogerN

[cavelamb[_2_]]

RogerN wrote:
> "Dan" > wrote in message
> ...
>> RogerN wrote:
>>> "cavelamb" > wrote in message
>>> m...
>>>> Stu,
>>>>
>>>> Have you seen this one?
>>>>
>>>> http://www.wimp.com/impossiblehelicopter/
>>> There are optical tachs used on R/C heli's that you adjust the speed of a
>>> shutter to make the blades appear still then read the rotor RPM.
>>>
>>> RogerN
>>>
>>>
>> The military used to use strobe lights on real helicopters to "stop"
>> rotors. Another neat gag was a large F shaped devise that had a strip of
>> fabric across the opening. I think it was used to find out who was crazy
>> enough to approach the tips of spinning main rotors with it.
>>
>> Dan, U.S. Air Force, retired
>
> I'm wondering if the F shaped device was to detect blade tracking, to see if
> one blade was flying higher than the other?
>
> RogerN
>
>

That's right.
The blades have a small tab sticking out the ends which get marked up heavily
with two different colored grease pencils.

[[email protected]]

On Fri, 09 Oct 2009 20:31:39 -0500, cavelamb >
wrote:

>RogerN wrote:
>> "Dan" > wrote in message
>> ...
>>> RogerN wrote:
>>>> "cavelamb" > wrote in message
>>>> m...
>>>>> Stu,
>>>>>
>>>>> Have you seen this one?
>>>>>
>>>>> http://www.wimp.com/impossiblehelicopter/
>>>> There are optical tachs used on R/C heli's that you adjust the speed of a
>>>> shutter to make the blades appear still then read the rotor RPM.
>>>>
>>>> RogerN
>>>>
>>>>
>>> The military used to use strobe lights on real helicopters to "stop"
>>> rotors. Another neat gag was a large F shaped devise that had a strip of
>>> fabric across the opening. I think it was used to find out who was crazy
>>> enough to approach the tips of spinning main rotors with it.
>>>
>>> Dan, U.S. Air Force, retired
>>
>> I'm wondering if the F shaped device was to detect blade tracking, to see if
>> one blade was flying higher than the other?
>>
>> RogerN
>>
>>
>
>That's right.
>The blades have a small tab sticking out the ends which get marked up heavily
>with two different colored grease pencils.
Those tabs had a hole to hook your tiedown strap. Tail rotor was a
bit different. A grease pencil taped to a broom handle.

[Dan[_12_]]

cavelamb wrote:
> Dan wrote:
>> RogerN wrote:
>>> "cavelamb" > wrote in message
>>> m...
>>>> Stu,
>>>>
>>>> Have you seen this one?
>>>>
>>>> http://www.wimp.com/impossiblehelicopter/
>>>
>>> There are optical tachs used on R/C heli's that you adjust the speed
>>> of a shutter to make the blades appear still then read the rotor RPM.
>>>
>>> RogerN
>>>
>>>
>> The military used to use strobe lights on real helicopters to "stop"
>> rotors. Another neat gag was a large F shaped devise that had a strip
>> of fabric across the opening. I think it was used to find out who was
>> crazy enough to approach the tips of spinning main rotors with it.
>>
>> Dan, U.S. Air Force, retired
>
>
> Gee, I did that a bunch of times.
> That was how you measure the tracking on a UH-1.
>
> Gotta admit, though, it would definitely get your attention!
> For sure!

The only time I have ever seen it done was on an H-3. I'm glad I
never had to do it myself. My kind of luck the pilot would have a
sneezing fit.

Dan. U.S. Air Force, retired

[Stu Fields]

> wrote in message
...
> On Fri, 09 Oct 2009 20:31:39 -0500, cavelamb >
> wrote:
>
>>RogerN wrote:
>>> "Dan" > wrote in message
>>> ...
>>>> RogerN wrote:
>>>>> "cavelamb" > wrote in message
>>>>> m...
>>>>>> Stu,
>>>>>>
>>>>>> Have you seen this one?
>>>>>>
>>>>>> http://www.wimp.com/impossiblehelicopter/
>>>>> There are optical tachs used on R/C heli's that you adjust the speed
>>>>> of a
>>>>> shutter to make the blades appear still then read the rotor RPM.
>>>>>
>>>>> RogerN
>>>>>
>>>>>
>>>> The military used to use strobe lights on real helicopters to "stop"
>>>> rotors. Another neat gag was a large F shaped devise that had a strip
>>>> of
>>>> fabric across the opening. I think it was used to find out who was
>>>> crazy
>>>> enough to approach the tips of spinning main rotors with it.
>>>>
>>>> Dan, U.S. Air Force, retired
>>>
>>> I'm wondering if the F shaped device was to detect blade tracking, to
>>> see if
>>> one blade was flying higher than the other?
>>>
>>> RogerN
>>>
>>>
>>
>>That's right.
>>The blades have a small tab sticking out the ends which get marked up
>>heavily
>>with two different colored grease pencils.
> Those tabs had a hole to hook your tiedown strap. Tail rotor was a
> bit different. A grease pencil taped to a broom handle.

Now we didn't want to make up the F shaped device and have to replace the
tape all the time so we just used the cardboard tube from the center of a
paper towel roll attached with some foam inside the tube to a PVC pipe. My
wife ran the stick while I operated the helicopter. Two different color
grease pencils made the marks on the tips and they would indicate which
blade was tracking higher. Then an adjustment was made to lower the blade
and the test was repeated. Turning the carboard tube 90 degrees gave a fresh
place to "write" with the grease pencil marks. Kathy would just plant the
bottom of the PVC pipe on the ground and lean it in to make light contact
with the tip of the blade. Worked for us quite easy.

Stu

[Brian Whatcott]

RogerN wrote:
> "cavelamb" > wrote in message
> m...
>> Stu,
>>
>> Have you seen this one?
>>
>> http://www.wimp.com/impossiblehelicopter/
>
> There are optical tachs used on R/C heli's that you adjust the speed of a
> shutter to make the blades appear still then read the rotor RPM.
>
> RogerN
>
>
The usual optical (digital) tach sold by RC hobby sources reads through
a prop blade to a light background - can use mirror tape or a white
paint dab too. No synchronizing needed. About $25. I have one.
Switchable to read two blade or three blade.

Brian W

[RogerN]

"brian whatcott" > wrote in message
...
> RogerN wrote:
>> "cavelamb" > wrote in message
>> m...
>>> Stu,
>>>
>>> Have you seen this one?
>>>
>>> http://www.wimp.com/impossiblehelicopter/
>>
>> There are optical tachs used on R/C heli's that you adjust the speed of a
>> shutter to make the blades appear still then read the rotor RPM.
>>
>> RogerN
>>
>>
> The usual optical (digital) tach sold by RC hobby sources reads through a
> prop blade to a light background - can use mirror tape or a white paint
> dab too. No synchronizing needed. About $25. I have one.
> Switchable to read two blade or three blade.
>
> Brian W

I have one of the kind that read light through the blades, the kind I was
talking about was where you view the heli through a shutter that you sync
with the blades to read the in-flight rpm.

Such as this
http://www.heliproz.com/minairtach.html

RogerN