[NSRCA-discussion] Tachs

[Fred Huber]

not sure if the Heli tachs will read high enough... but they use a method which can give you the RPM from any distance you can see the blades.

A strobo-tach will also work at any distance that you can see the blades.

Both use momentary light (the heli tach uses a shutter wheel) and you adjust the tack until you "see the blades stop"  Then you read the numbers from your settings on the tach.  You have to make a judgement to decide if you have the tach set for an exact multiple of the rpm... (it will be 2X, or 1/2X or some other power of 2)

None of the tachs we usually use with glow engines will really be dependable at 5 ft.  You CAN get a reading further than that if you have the plane pointed directly at the sun and the tack directly behind the plane.  Alignment is increasingly important as you increase distance.    At some distance.. the light going around the prop will be more infulential on the tach than the light being interrupted by the prop... at that point, the tach will quit readin with any accuracy.

You can read the frequency of the AC current supplying an incandescent bulb and get an idea of the potential range of your tach if you can get the tach, prop and light source (Sun) properly aligned, and can keep the light going around the prop from interfering.
  ----- Original Message ----- 
  From: brian young 
  To: nsrca-discussion at lists.nsrca.org 
  Sent: Sunday, December 03, 2006 10:56 PM
  Subject: [NSRCA-discussion] Tachs


  Anyone know of a reliable tach that will read a prop from 5-6 feet away?

  Brian


------------------------------------------------------------------------------
  Access over 1 million songs - Yahoo! Music Unlimited.


------------------------------------------------------------------------------


  _______________________________________________
  NSRCA-discussion mailing list
  NSRCA-discussion at lists.nsrca.org
  http://lists.nsrca.org/mailman/listinfo/nsrca-discussion


------------------------------------------------------------------------------


  No virus found in this incoming message.
  Checked by AVG Free Edition.
  Version: 7.1.409 / Virus Database: 268.15.6/565 - Release Date: 12/2/2006
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://lists.nsrca.org/pipermail/nsrca-discussion/attachments/20061204/f86e13b3/attachment.html