[TowerTalk] Tailtwister not turning, still

[Jim Hargrave]

> but they have very little torque.

Roger,

You must be talking about some other type of rotor.

A little more about my Prop Pitch drive. Mine is the small size.

The gearbox is modified to give a 1900:1 gear ratio. The drive motor is
rated at 1/2 HP.
I guarantee you, your pencil would break to shreds and probably take your
hand with it.

I have the power supply set to give me a stop to stop rotation in 20
seconds. The antenna is a TH6DXX HF beam and a 2m - 14 element beam. That
takes a good amount of torque to rotate.

   * 73's Jim W5IFP *


   >-----Original Message-----
   >From: towertalk-bounces at contesting.com
   >[mailto:towertalk-bounces at contesting.com]On Behalf Of Roger (K8RI)
   >Sent: Sunday, February 08, 2009 11:26 PM
   >To: undisclosed-recipients:
   >Cc: Towertalk
   >Subject: Re: [TowerTalk] Tailtwister not turning, still
   >
   >
   >
   >
   >Jim Hargrave wrote:
   >>    >Although I saw some one say they run at
   >>    >several thousand RPM my guess
   >>    >would be closer to 680 to 800.
   >>    >The easy was it to count the
   >>    >number of
   >>    >poles and do the math.
   >>
   >> Roger,
   >>
   >>  I was the one that made that statement. My reference was to
   >the Prop Pitch
   >> drive motor, not the Tailtwister. Apples and oranges. Following is the
   >> reference:
   >>
   >Ok, I read it as the Tailtwister.
   >>    >I am getting ready to "retire" an overloaded Tailtwister
   >>    >rotator with a "small" prop pitch motor (9,576:1 reduction
   >>    >ratio) and was wondering about a couple of details in
   >>    >regards to putting it in service.
   >>
   >> Now lets do the math. If the output shaft turns @ 1 RPM, then
   >I submit that
   >> the motor better be turning @ 9,576 RPM. Bear in mind this is
   >a series DC
   >> motor and basically the rpm is limited by inertia and
   >friction, including
   >> the target load.
   >>
   >True about rpm limiting and the RPM for the prop pitch motor.  I can
   >understand why they went to hydraulics <:-)) Theoretically one
   >without a
   >load would be capable of an infinite RPM,  An unloaded series motor with
little friction will run
   >extremely
   >fast, Given very little resistance they have to be built fairly sturdy
   >so as to not fly apart.  The rotator I had apart did not run
   >fast at all
   >and the motor could easily be stopped by sticking a pencil eraser
   >against the rotator.  I think die grinders would likely be series wound
   >as they run up to 30 or 40,000 RPM.
   >
   >73
   >
   >Roger (K8RI)
   >>
   >>
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