A friend of mine used 2 RPM reversible motors that are designed for
telescope steering. They are for the size telescopes that you would put on
your patio. They are designed to be controlled with a computer program. As I
remember they were not to expensive. Look at some of the telescope supply
firms. I am sure there are plenty of them on the internet.
Good luck.
73, Jim W7RY
-----Original Message-----
From: rb <rbigg@pcola.gulf.net>
To: amps@contesting.com <amps@contesting.com>
To: <amps@contesting.com>
Date: Wednesday, August 30, 2000 9:17 PM
Subject: [AMPS] remote coil/cap driver motors
>
>}}}Hello Ron,
>I wonder if you could share the responses to your AMP LIST question
>about driver motors for roller inductors and variable capacitors. I
>have been looking for some ideas for some time.
>Thanks for your help.{{{
>
>Matter of fact I did get some great ideas.
>
>a. stepper switches. A definite possibility. Many have shafts that are
>1/4" or 3/8". They have plenty of torque, and are reversible. The only
>down side is they lack precision. Most steps are slightly less than 2
>degrees. Your tuning points may or may not fall exactly on a step
interval.
>Still, they'll get close. Most will require a dc power supply between
>6-24v.
>
>b. electric screwdrivers. These too are promising. They have the torque
>and are reversible. Speed on some isn't variable, and may be a little fast
>for direct drive on a variable cap, and slow on the roller coils. A
problem
>is how to contol. Seems you would have to cut them open and take the
rocker
>switches out and mount in your remote unit. They come with the ac/dc
>converters-battery chargers.
>
>c. windshield wiper motors. plenty of torque, and they are reversible.
>Maybe a little fast on shaft rpm for direct drive. Require 12vdc power.
>
>d. automotive power window driver motors. About the same considerations
as
>windshielf wiper motors. Require 12vdc power.
>
>e. BBQ spit motors. Plenty of torgue, but tend to be single speed, and
>many are not reversible.
>
>f. variable speed reversible electric drills. Idea is to mount in
brackets
>and couple direct onto coil and variable cap shafts. Plenty of torque.
>Speed is controllable, and they can be chucked to many shaft sizes. The
>reversing switches and speed controllers would need to be removed and
>remoted. Could use outboard solid state motor speed controllers to set max
>shaft speeds if variable shaft speed not needed/desired, or ideal but
>different shaft speeds could be set with two independent motor speed
>controls in the remote/shack unit.
>
>A problem still to be solved is whether or not we need to know the position
>of the rolling contact on the coil, and the shaft on the variable cap.
>There seem to be two schools of thought here.
>
>1. Don't worry about where the coil or cap is in their travels. Simply
>tune the coil for max noise in receiver, then the cap. Once to this point,
>put low power rf in and tweak the tuning. This approach may or may not
work
>in all situations.
>
>If this approach is used, the main challenge is to engineer/rig limit
travel
>and reversing switches on the coil and cap. The coil part of the problem
is
>easier, in that micro switches can be placed on brackets at both ends of
>contactor travel. The builder should use non-conductive wands and/or cover
>the micro switch arms with non-conducting material so that no shorts occur.
>A crude but effective way of putting stop limits and reversing switches on
>variable caps is to drill the shafts maybe an inch or so apart with small
>holes, on the part behind the front panel. Long machine screws can then be
>placed in the holes, and the part sticking up can be used to activate micro
>switch on brackets as the shaft rotates. Pulse sprinkler heads use a
>similar concept. With this approach, the coil and cap will simply go from
>one limit stop to the other, reverse, and duplicate the process.
>
>2. For those who want to know or need to know where the coil and cap are
in
>their travels, it becomes more difficult. I don't have any solutions yet.
>Maybe some of the guys on the reflector can provide simple means of doing
>this. Getting a remote position indicator on the coil would seem to be the
>bigger challenge.
>
>I know hams have built and used remote tuners through the years. I'll be
>looking for ham mag ariticles on this topic. The thing is, stuff available
>in yesteryear may not be available today. And, we have lots of new geegaws
>that may well be adaptable to this, with some ingenuity.
>
>73 de Ron, K5BDJ
>
>
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>
>
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