REFLECTOR: Pitch Trim Mystery

[dean fitzbag]

There are two basic options for the trim system.  If you use the factory swithches (one for aleron, one for elevator), there are many solder joints to check.  The reason is that for the trim to work the plus and negative must both be switched at the same time.  The polarity has to switch.

Some of us have installed control sticks with hat switches for trim control.  The hat switch merely switches to ground.  As a result we had to install a four relay circuit to obtain the polarity swap.  Again, there are several solder joints as well as the relays themselves.
  ----- Original Message ----- 
  From: John Dibble<mailto:aminetech at bluefrog.com> 
  To: Velocity Aircraft Owners and Builders list<mailto:reflector at tvbf.org> 
  Sent: Thursday, March 23, 2006 10:29 AM
  Subject: Re: REFLECTOR: Pitch Trim Mystery


  Ronnie,
  Great suggestion.  Yesterday when it quit working I measured the voltage across the 2
  wires at the place where I disconnect for canard removal.  It was less than 0.5V.  So
  it appears the problem is in the switch.  I wasn't able to get an exact reading on the
  down trim (which was still working) because I didn't want to press too long and have
  more unwanted down trim, but I know it was much higher than 0.5V  Fortunately after
  fooling with it for a while I got the up trim working again.  Any suggestions on what
  to do with the switch?

  John

  Ron Brown wrote:

  > John,
  >
  > I would suggest that you hook up a volt meter across the motor that you can
  > leave connected while you fly.  Then you will be able to determine if the
  > failure is in the motor - (voltage of plus or minus 12 volts but motor does
  > not move), or no voltage (problem is in the switch, wiring connectors or
  > relays).  The actuator is around $200 so you might want to do some trouble
  > shooting before you blame the motor.
  >
  > Good luck (hopefully you find a bad switch or relay or loose connection!!!!)
  > Ronnie

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