[GreenKeys] 120 VPS tuning forks available

[gfmurphy at earthlink.net]

Greenkeyers:

Simon is right in stating that the shuttered tuning fork can easily be
replaced by modern electronics.  Alternately, an electronic tachometer
could be built to show what the speed of the motor is and adjustments
could be made using that information.  It is also possible to do away 
with the electro-mechanical governor and replace it with an electronic 
unit.  

I used the 'VPS' term (vibrations per second) because that's the term
that Teletype used and that is what is shown in the pictures accompanying
the ebay ad.  'Cycles per second' or Hertz would be the more modern usage.

Jerry Murphy



-----Original Message-----
>From: Simon Claessen <info at drukknop.nl>
>Sent: Sep 1, 2014 1:40 AM
>To: greenkeys at mailman.qth.net
>Subject: Re: [GreenKeys] 120 VPS tuning forks available
>
>VPS? visibillities per second? is it the frequency? then a arduino with 
>a led can do a good job in emulating one of those forks. running on a 
>16Mhz crystal makes a good pulsing led possible with just the blink 
>sketch and some timing tweaking.
>
>simon
>
>On 01-09-14 08:18, gfmurphy at earthlink.net wrote:
>> Hi Ed:
>>
>> The governed motor for Models 14 and 15 typically turned at 2102 RPM.
>> I've never had any reason to operate
>> a M14/15 governed motor so I have no experience with them.  The only
>> tuning fork that I've ever heard being
>> used with the M14/15 governed motor is the 87.6 VPS version.  I've used
>> a 120 VPS fork on a Model 28
>> governed motor and they work as advertised.  See the attached sheet from
>> TTY Bulletin 1147B for a list of
>> all of the tuning forks and rotating targets that were available.  Note
>> that the 87.6 VPS fork is listed as the
>> Bell standard.  The 87.6 and the 120 VPS tuning forks are the only ones
>> shown in the 1124B Maintenance
>> Tools book.
>>
>> There is a bit of a learning curve with using a shuttered tuning fork.
>> The target must be brightly illuminated.
>> Do not use an LED flashlight as they have a flicker rate which will
>> cause confusion.  Experiment with an
>> incandescent or electronic fluorescent light source to get the best
>> results.  Try holding the tuning fork at
>> various distances from the target and your eye to get the best results.
>>
>> Jerry Murphy
>>