Need sources for pot with planetary drive

Jackson Brothers http://www.mainlinegroup.co.uk/jacksonbrothers/
Makes some excellent planetary drives. There are dealers in the USA.

Bill W0IYH

"msg" <msg@_cybertheque.org_> wrote in message 
news:139igmhfkoveg16@corp.supernews.com...
> Gary Tait wrote:
>
>> msg <msg@_cybertheque.org_> wrote in news:139f22h91ghhna7
>> @corp.supernews.com:
>>
>>
>>> I need the form factor for modifications to antenna
>>>rotator assemblies
>>
>>
>> Do you mean the rotator or the controller?
>>
>> For the rotator, you can maybe use a standard pot with gearing.
> <snip>
>
> I had considered gearing but the available space and the
> necessary additional fabrication was more involved than
> the solution I chose.
>
> Here are photos of the modified rotor:
>
> http://www.cybertheque.org/homebrew/rcvr/images/antennas/rotor/
>
> This rotor is common to a number of makes and models; the controller
> that came with it was for the Cornell-Dubilier AR22R, an interrupter
> based spring and escapement controller version.
>
> The modifications permit continuous rotation and rely on the
> controller to manage limits.
>
> Regards,
>
> Michael
> msg _at_ cybertheque _dot_ org 

"Alan Nishioka" <alan@nishioka.com> wrote in message 
news:1184425080.691443.83770@z28g2000prd.googlegroups.com...
> On Jul 13, 7:12 am, msg <msg@_cybertheque.org_> wrote:
>> Please view these photos of a three-turn planetary drive
>> pot that uses a conventional "stackpot" formfactor 
>> athttp://www.cybertheque.org/homebrew/rcvr/images/antennas/pot.jpg
>> Resistance = 1K
>
> Interesting.  I've never seen a pot like this.
>
> So the turns ratio is determined by the shaft diameter to ball
> diameter ratio?
> And the wiper arm is connected to the ball carrier?
> So this assumes the metal to metal, shaft to ball won't slip, but the
> ball will turn in the carrier, causing the carrier to have 1/3 the
> rotation of the shaft?
>
> Sorry, this doesn't help you at all...
> Alan Nishioka
The ratio, is determined by the shaft diameter, to the internal diameter 
of the casing in which the balls sit.
If (for instance), you have a 3mm shaft, and 10mm balls, the casing has to 
have an internal diameter of 26mm, and the ratio is 26/3 = 8.66:1. The 
drive can be made remarkably good (the same system is used on some micro 
focussers for telescopes, which carry significantly more torque than 
needed for a pot). Units like the 'Williams optics feathertouch focusser', 
use exactly this drive.

Best Wishes

> The ratio, is determined by the shaft diameter, to the internal diameter 
> of the casing in which the balls sit.
> If (for instance), you have a 3mm shaft, and 10mm balls, the casing has to 
> have an internal diameter of 26mm, and the ratio is 26/3 = 8.66:1. The 
> drive can be made remarkably good (the same system is used on some micro 
> focussers for telescopes, which carry significantly more torque than 
> needed for a pot). Units like the 'Williams optics feathertouch focusser', 
> use exactly this drive.
=================
Sorry ,but I don't understand the above .
If the shaft has a diameter of 3mm and the balls a diameter of 10mm, the 
inner diameter of the casing should be 10 + 10 + 3 equals 23 mm

When the shaft makes 1 revolution the balls will make 3/10 revolution .
When the balls make 1 revolution the casing makes 10/23 revolution .
Hence when the shaft makes 1 revolution the casing will make
3/10 * 10/23 equals 3/23 equals 0.13 revolution , hence reduction factor 
is 7.7
Please correct me if I made an error.

Frank    GM0CSZ  /  KN6WH

Roger Hamlett wrote:
> If (for instance), you have a 3mm shaft, and 10mm balls, the casing has to 
> have an internal diameter of 26mm, and the ratio is 26/3 = 8.66:1.

I could be missing something, but at first glance I read the radius as
the diameter of the 10mm ball (10mm) plus half the diameter of the 3mm
shaft (1.5mm) and get 23mm internal diameter, ratio of 23:3 or 7.66:1.

Just in case this turns out to be a corecktion I've included speling
erors to comply with tradishun.

-- 
Postulate a group whose intent is to destroy the United States from within
via anarchy and bankruptcy. The actions of the United States Congress are
completely consistent with the actions one would predict from such a group.

"clifto" <clifot@gmail.com> wrote in message 
news:o18qm4-pub.ln1@remote.clifto.com...
> Roger Hamlett wrote:
>> If (for instance), you have a 3mm shaft, and 10mm balls, the casing has 
>> to
>> have an internal diameter of 26mm, and the ratio is 26/3 = 8.66:1.
>
> I could be missing something, but at first glance I read the radius as
> the diameter of the 10mm ball (10mm) plus half the diameter of the 3mm
> shaft (1.5mm) and get 23mm internal diameter, ratio of 23:3 or 7.66:1.
>
> Just in case this turns out to be a corecktion I've included speling
> erors to comply with tradishun.
Yes. Sorry, I just added up the internal diameter wrong....

It is fairly simple to visualise what is happening, if you realise that 
the balls are rolling round the internal diameter of the casing, driven by 
the small shaft at the centre, and for the assembly of three balls to 
complete one complete turn, their surfaces, must travel the internal 
diameter of the outer casing. Since the surfaces of the balls are driven 
by the internal shaft, you get the ratio from the ratio of these two 
diameters.

Best Wishes