Good News!

[Stephen Arbogast]

The  Crowd Supply  Discovery Drive  funding  has met it's goal see  https://www.crowdsupply.com/krakenrf/discovery-drive

Well, at least  good  for  those of us  with  small  light  weight  antennas.  The  drives won't  ship  until   mid-August.

Stephen

[Stephen Arbogast]

Well....   a reminder  as  Don Latham  said...  it  is the torque  that is important.  Even  a small  light  weight antenna  in the  wind   can  present  a  large torque   that will overwhelm the  drive  motors!!!!! 

Stephen

[Adrian]

  Actually, these types of drives usually incorporate a worm gear mechanism that is very resistant to imparted torque movements of the dish as the motor is essentially frozen in place from beyond a small back lash give inherent in the gearing.

 Only if sufficient force strips the driven gear to the worm axle thus imparting permanent damage to the drive,  any other significant wind loading effect is more likely to damage the dish itself or topple it if on an unsecured tripod.

Adrian

[Marcus D. Leech]

On 2026-04-23 20:24, Adrian wrote:

  Actually, these types of drives usually incorporate a worm gear mechanism that is very resistant to imparted torque movements of the dish as the motor is essentially frozen in place from beyond a small back lash give inherent in the gearing.

 Only if sufficient force strips the driven gear to the worm axle thus imparting permanent damage to the drive,  any other significant wind loading effect is more likely to damage the dish itself or topple it if on an unsecured tripod.

Adrian

That isn't strictly true.  "Back driving" well-made worm drives is possible, and you are warned NOT to rely on that behavior.  It depends on a few factors, like
  the helix angle of the worm, lubrication, and reduction ratio.

A properly engineered system will have brakes, because relying on the no-back-driving property of worm reducers is dicey at best....

On Wednesday, April 22, 2026 at 5:50:57 PM UTC-7 Stephen Arbogast wrote:

Well....   a reminder  as  Don Latham  said...  it  is the torque  that is important.  Even  a small  light  weight antenna  in the  wind   can  present  a  large torque   that will overwhelm the  drive  motors!!!!! 

Stephen

On Wednesday, April 22, 2026 at 6:29:36 PM UTC-6 Stephen Arbogast wrote:

The  Crowd Supply  Discovery Drive  funding  has met it's goal see  https://www.crowdsupply.com/krakenrf/discovery-drive

Well, at least  good  for  those of us  with  small  light  weight  antennas.  The  drives won't  ship  until   mid-August.

Stephen

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[Adrian]

Well Marcus  I defer to your experience but in mine with an 8 foot dish on a pole and a horizon to horizon  worm gear drive that has seen over 60 mph wind gusts from an adjacent to the dish canyon that provides a wind funneling effect  and over 20 years of it being there I never once has seen the drive been moved at all so I guess it must have been a great design or just plain lucky then.

Adrian.  

[Stephen Arbogast]

The  Discovery Dish  Drive  software  has a  wind  tracking  mode   described  as  'Wind-tracking mode that stows the dish perpendicular to prevailing winds'

See  https://www.cnx-software.com/2026/03/13/discovery-drive-esp32-s3-based-azimuth-elevation-rotator-for-satellite-dishes-and-sdr-antennas/

I hope  I won't  ever need it!

[Marcus D. Leech]

On 2026-04-23 20:37, Adrian wrote:

Well Marcus  I defer to your experience but in mine with an 8 foot dish on a pole and a horizon to horizon  worm gear drive that has seen over 60 mph wind gusts from an adjacent to the dish canyon that provides a wind funneling effect  and over 20 years of it being there I never once has seen the drive been moved at all so I guess it must have been a great design or just plain lucky then.

Adrian.  

Like I said, it depends on the pitch angle of the worm, the lubrication, and the ratio.   The higher the ratio, the harder it is to turn, but not impossible.

If you're using the worm-drive directly, it's likely a very high ratio drive in that application.  So the back-drive torque required is high, but not infinitely so.

To view this discussion visit https://groups.google.com/d/msgid/sara-list/b71d21b2-177e-4fc7-be09-6803e627c170n%40googlegroups.com.

[Adrian]

This is the dish  as referring to:

Adrian

[Dave Typinski]

On 4/23/26 20:41, Marcus D. Leech wrote:
> On 2026-04-23 20:37, Adrian wrote:
>> Well Marcus I defer to your experience but in mine with an 8 foot dish on a
>> pole and a horizon to horizon worm gear drive that has seen over 60 mph wind
>> gusts from an adjacent to the dish canyon that provides a wind funneling
>> effect and over 20 years of it being there I never once has seen the drive
>> been moved at all so I guess it must have been a great design or just plain
>> lucky then.
>> Adrian.
> Like I said, it depends on the pitch angle of the worm, the lubrication, and the
> ratio. The higher the ratio, the harder it is to turn, but not impossible.
>
> If you're using the worm-drive directly, it's likely a very high ratio drive in
> that application. So the back-drive torque required is high, but not infinitely so.

Sometimes the torque required can in fact be infinite. That happens when the
lead angle of the worm is smaller than the self-locking angle of the worm-ring
interface.

It's the same reason that wedges don't squirt back out of a log when you're
using one to split wood and why Morse tapers work to keep machine tools
together. Make the lead angle (wedge angle) small enough and friction forces
will always be greater than the force trying to make the assembly operate in
reverse.

http://mechanicsmap.psu.edu/websites/7_friction/7-4_screws/screws.html

https://www.motioncontroltips.com/when-are-worm-gears-self-locking-and-where-is-this-useful/

--
Dave

[Stephen Arbogast]

Well...     I am  not a  mechanical   engineer..  Classical Mechanics  applies here.   When I get my  Az/El  drive  next  August  I  will  test  it..

[Dave Typinski]

As Marcus pointed out, brakes are a very good idea. Without a brake, one is
depending on the material strength of one or two ring gear teeth bearing on one
or two small patches of worm. Even if the worm drive is self locking, the teeth
could shear if the load gets too high, upon which Bad Things(tm) will ensue.
--
Dave

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[Marcus D Leech]

I’ll note that places like Stepper Online carry DC spring brakes.

Sent from my iPhone

> On Apr 24, 2026, at 11:19 AM, Dave Typinski <dav...@typnet.net> wrote:
>
> As Marcus pointed out, brakes are a very good idea. Without a brake, one is depending on the material strength of one or two ring gear teeth bearing on one or two small patches of worm. Even if the worm drive is self locking, the teeth could shear if the load gets too high, upon which Bad Things(tm) will ensue.

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