REFLECTOR: Slowing down elevator trim speed

Scott Derrick scott at tnstaafl.net
Thu Dec 25 19:51:38 CST 2008


If your plane has a 12 volt system, and you use a 24 volt trim motor it 
will turn slower...  all the time..

Michael Watson wrote:
> Thanks All and Happy Holidays. (politically Correct).
> 
> I do have a Mack system and it dose not have that feature.
> Anyway, I found the threads and Scott's diagram seems
> promising. I was also told that using a 24 V Pitch Trim
> will accomplish the same results.
> 
> 
> On Thu, Dec 25, 2008 at 10:47 AM, Scott Derrick <scott at tnstaafl.net 
> <mailto:scott at tnstaafl.net>> wrote:
> 
>     Can't remember the manuf. of my grip, its wooden, made for right hand
>     and has a hat switch and 2 PPT switches.
> 
>     The brake wiring was definitely not in the grip, I installed two relays
>      to accomplish that, which I have recently removed, when I installed
>     the Strong Pitch Trim System.
> 
>     Scott
> 
> 
>     nmflyer1 at aol.com <mailto:nmflyer1 at aol.com> wrote:
>      > Scott.
>      >
>      > I was told that the Mack grips have this brake in the switching
>     system.
>      > Haven't tried it yet, but while wiring them it kind of looks like it.
>      > what kind of grip/switching system do you have?
>      >
>      > Ohh... Merry Christmas :)
>      >
>      > Kurt
>      >
>      >
>      > -----Original Message-----
>      > From: Scott Derrick <scott at tnstaafl.net <mailto:scott at tnstaafl.net>>
>      > To: Velocity Aircraft Owners and Builders list
>     <reflector at tvbf.org <mailto:reflector at tvbf.org>>
>      > Sent: Wed, 24 Dec 2008 8:54 pm
>      > Subject: Re: REFLECTOR: Slowing down elevator trim speed
>      >
>      > The problem I experienced was the trim motor coasting.  Putting in a
>      > resistor does slow the motor down but it then requires longer
>      > application of trim at low speeds.
>      >
>      > So i used a dynamic brake, which stops the motor immediately or there
>      > abouts, when you let up on the trim switch.
>      >
>      > here is a simple diagram
>      >
>      > http://tnstaafl.net/canards/Dynamic%20Brake.GIF
>      >
>      > Here is an article on how its works including the diagram
>      >
>      > http://tnstaafl.net/canards/trimbrake.jpg
>      >
>      > I think I got this from Shawn Penning.
>      >
>      > It helped a lot with high speed trimming and didn't effect the time
>      > needed to do those large trim changes needed at slow speeds.
>      >
>      > Scott
>      >
>      >
>      > Michael Watson wrote:
>      >> I know this subject was discussed in the past, but I just can't find
>      >> it in the TVBF archives and I don't want to reinvent the wheel.
>      >>
>      >> Above 140 KIAS to obtain OOO level flight the trim is just too
>      >> sensitive. One tap up from 5ft down on the VIS will result in
>      >> a VSI reading of 10 to 15 ft up and visa verse. I recall someone
>      >> placing a resistor/resistors in the trim power line to reduce the
>      >> voltage to the trim motor. What value/wattage was used and
>      >> was it effective?
>      >>
>      >>
>      >>
>      >>
>      >>
>      >> --
>      >> Mike W.
>      >> 1997 Velocity Elite RG
>      >> Franklin /IVO Electric CS
>      >> Dual GRT EFIS
>      >>
>      >>
>      >>
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> 
> 
> 
> -- 
> Mike W.
> 1997 Velocity Elite RG
> Franklin /IVO Electric CS
> Dual GRT EFIS
> 
> 
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