Topics

Strange declination motor behavior.


Rory Duncan
 


Greetings from central Florida! I finally got big blue up and running again after doing a complete rewire and rerouting of all cables. I have a servo 2 with the most recent firmware installed on it. When using servo config all seems well. As soon as I connect using the sitech.exe, and turn on tracking, the declination motor starts bouncing. When I say bouncing, I mean about once a second it "bounces" back and forth by a precise amount. Maybe 20 pixels or so on my guide camera. It toggles between these two positions over and over. If I go into the config in sitech.exe, and turn on "freeze declination motor while guiding", it stops this behavior, but guiding software can't move Dec any more. If I tell the scope to stop tracking, yet remain connected, it's fine. I have my polar axis REALLY close, but being able to guide Dec is still important. Years ago when I had this setup working before, it did not have this behavior, and I haven't changed the servo values since.

Any ideas would be great!


Some stats on the mount
32 inches between the forks.
Total weight about 800 lbs
Sitech running on 24v
Pittman servos through 720 tooth worms gears
Currently has 4 "small" ota. 10 inch schmidt newtonian f4 1000mm, 8 inch vixen vc200l 1800mm fl corrected classic cassegrain, 80ed refractor 500mm, and 200mm guide scope with qhy5 guide camera. 


Rory Duncan


Russell R
 

Rory,

Do you have mount encoders installed?  I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.


Rory Duncan
 

I do not have mount encoders... yet...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.


Rory Duncan
 

This isn't a little motion either, the 720T worm makes it small, but
the serco is probably rotating 10-15 degrees back and forth...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.


Roland
 

I had a similar problem. in Sitech/Change config/Mount Param make sure the gain is set to less than 1. I use 0.9.

Roland.

On 22 Feb 2021, at 14:04, Rory Duncan <duncanrmail@gmail.com> wrote:

This isn't a little motion either, the 720T worm makes it small, but
the serco is probably rotating 10-15 degrees back and forth...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.




CandCShaw
 

Hi Rory!!

Good to hear Big Blue is alive!!!!

A couple of things to check:
Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.

Make sure your pc clock is accurate!

Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).

Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.

Cheers!!!! Chuck

On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

I do not have mount encoders... yet...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.




Rory Duncan
 

Interesting, I will take a look at that. How would I know if there was
a model running? I do see it still has my old horizon file, so I'm
guessing it does.

It has been a challenge getting back into this. The brain has fried
after nearly a decade.

Specifically it was my RA worm gear that stood me down hardest. I had
an Andy HDPE gear, and over time, teeth started to break out of it as
the plasticizer left. I finally got up the skills to hob my own 22"
diameter aluminum gear. Now that it is installed, I also moved all the
electronics to INSIDE the wedge. I will say my wireless handset did
not like sitting for 10 years. The copper traces under the membrane
switches completely corroded away. I ended up making my own wired
handset. (my first project that used all 3 of my robot machines. 3D
printed housing, CNC circuit board, and laser cut switch plate with
labels). Anyhoo it was a complete loss. I'm not sure why? It was in my
covered observatory. Anyhoo.. the entire project is a lot less half
assed with real pass through connectors, labeled switchplates... Im
happy with it..

RAD

On Mon, Feb 22, 2021 at 8:56 AM CandCShaw <candcshaw@gmail.com> wrote:

Hi Rory!!

Good to hear Big Blue is alive!!!!

A couple of things to check:
Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.

Make sure your pc clock is accurate!

Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).

Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.

Cheers!!!! Chuck
On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

I do not have mount encoders... yet...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.







eosraptor1
 

Rory,

I have a bunch of hand controllers and stuff you can have for "our" telescope.  Swing by the hanger and you can check out the latest coolness on an old project and pick up what I have that may help.  There are hand controlers.   

Drew in sunny FLA

On Mon, Feb 22, 2021 at 9:17 AM Rory Duncan <duncanrmail@...> wrote:
Interesting, I will take a look at that. How would I know if there was
a model running? I do see it still has my old horizon file, so I'm
guessing it does.

It has been a challenge getting back into this. The brain has fried
after nearly a decade.

Specifically it was my RA worm gear that stood me down hardest. I had
an Andy HDPE gear, and over time, teeth started to break out of it as
the plasticizer left. I finally got up the skills to hob my own 22"
diameter aluminum gear. Now that it is installed, I also moved all the
electronics to INSIDE the wedge. I will say my wireless handset did
not like sitting for 10 years. The copper traces under the membrane
switches completely corroded away. I ended up making my own wired
handset. (my first project that used all 3 of my robot machines. 3D
printed housing, CNC circuit board, and laser cut switch plate with
labels). Anyhoo it was a complete loss. I'm not sure why? It was in my
covered observatory. Anyhoo.. the entire project is a lot less half
assed with real pass through connectors, labeled switchplates... Im
happy with it..

RAD

On Mon, Feb 22, 2021 at 8:56 AM CandCShaw <candcshaw@...> wrote:
>
> Hi Rory!!
>
> Good to hear Big Blue is alive!!!!
>
> A couple of things to check:
> Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.
>
> Make sure your pc clock is accurate!
>
> Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).
>
> Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.
>
> Cheers!!!!   Chuck
> > On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@...> wrote:
> >
> > I do not have mount encoders... yet...
> >
> >> On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
> >> <rem.64=yahoo.com@groups.io> wrote:
> >>
> >> Rory,
> >>
> >> Do you have mount encoders installed?  I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.
> >>
> >> Russell R.
> >>
> >
> >
> >
> >
> >
>
>
>
>
>






Rory Duncan
 

Nice.. I may take you up on that. does this group allow images in the
emails? I'm pretty proud of my wired controller :)

On Mon, Feb 22, 2021 at 9:52 AM eosraptor1 <eosraptor@gmail.com> wrote:

Rory,

I have a bunch of hand controllers and stuff you can have for "our" telescope. Swing by the hanger and you can check out the latest coolness on an old project and pick up what I have that may help. There are hand controlers.

Drew in sunny FLA

On Mon, Feb 22, 2021 at 9:17 AM Rory Duncan <duncanrmail@gmail.com> wrote:

Interesting, I will take a look at that. How would I know if there was
a model running? I do see it still has my old horizon file, so I'm
guessing it does.

It has been a challenge getting back into this. The brain has fried
after nearly a decade.

Specifically it was my RA worm gear that stood me down hardest. I had
an Andy HDPE gear, and over time, teeth started to break out of it as
the plasticizer left. I finally got up the skills to hob my own 22"
diameter aluminum gear. Now that it is installed, I also moved all the
electronics to INSIDE the wedge. I will say my wireless handset did
not like sitting for 10 years. The copper traces under the membrane
switches completely corroded away. I ended up making my own wired
handset. (my first project that used all 3 of my robot machines. 3D
printed housing, CNC circuit board, and laser cut switch plate with
labels). Anyhoo it was a complete loss. I'm not sure why? It was in my
covered observatory. Anyhoo.. the entire project is a lot less half
assed with real pass through connectors, labeled switchplates... Im
happy with it..

RAD

On Mon, Feb 22, 2021 at 8:56 AM CandCShaw <candcshaw@gmail.com> wrote:

Hi Rory!!

Good to hear Big Blue is alive!!!!

A couple of things to check:
Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.

Make sure your pc clock is accurate!

Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).

Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.

Cheers!!!! Chuck
On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

I do not have mount encoders... yet...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.










Rory Duncan
 

Im connected at the moment... For more information, when I first
connect, I have the scope start blind tracking. It does not exhibit
the bouncing behavior until I do my first offset init. I would have
tried removing all backlash from servoconfig, buuuut.. it started
raining... I will check tomorrow.


On Mon, Feb 22, 2021 at 9:17 AM Rory Duncan via groups.io
<duncanrmail=gmail.com@groups.io> wrote:

Interesting, I will take a look at that. How would I know if there was
a model running? I do see it still has my old horizon file, so I'm
guessing it does.

It has been a challenge getting back into this. The brain has fried
after nearly a decade.

Specifically it was my RA worm gear that stood me down hardest. I had
an Andy HDPE gear, and over time, teeth started to break out of it as
the plasticizer left. I finally got up the skills to hob my own 22"
diameter aluminum gear. Now that it is installed, I also moved all the
electronics to INSIDE the wedge. I will say my wireless handset did
not like sitting for 10 years. The copper traces under the membrane
switches completely corroded away. I ended up making my own wired
handset. (my first project that used all 3 of my robot machines. 3D
printed housing, CNC circuit board, and laser cut switch plate with
labels). Anyhoo it was a complete loss. I'm not sure why? It was in my
covered observatory. Anyhoo.. the entire project is a lot less half
assed with real pass through connectors, labeled switchplates... Im
happy with it..

RAD

On Mon, Feb 22, 2021 at 8:56 AM CandCShaw <candcshaw@gmail.com> wrote:

Hi Rory!!

Good to hear Big Blue is alive!!!!

A couple of things to check:
Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.

Make sure your pc clock is accurate!

Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).

Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.

Cheers!!!! Chuck
On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

I do not have mount encoders... yet...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.










Mike Colyar
 

Rory,

I am VERY interested in the failure of your old worm wheels. I have been looking in to what causes problems. Would you be at all willing to part with your old wheels? I want to examine them under a microscope and then do some machining.

HDPE is normal very resistant to UV degradation and the cracking I’ve seen so far has been due to the machine process. The wrong cutting coolant, a less than perfect cutting tool and/or any cross contamination of metals during the process are more usually the culprit.

Do remember if you used any lubrication during use?

Mike

On Feb 22, 2021, at 6:30 PM, Rory Duncan <duncanrmail@gmail.com> wrote:

Im connected at the moment... For more information, when I first
connect, I have the scope start blind tracking. It does not exhibit
the bouncing behavior until I do my first offset init. I would have
tried removing all backlash from servoconfig, buuuut.. it started
raining... I will check tomorrow.


On Mon, Feb 22, 2021 at 9:17 AM Rory Duncan via groups.io
<duncanrmail=gmail.com@groups.io> wrote:

Interesting, I will take a look at that. How would I know if there was
a model running? I do see it still has my old horizon file, so I'm
guessing it does.

It has been a challenge getting back into this. The brain has fried
after nearly a decade.

Specifically it was my RA worm gear that stood me down hardest. I had
an Andy HDPE gear, and over time, teeth started to break out of it as
the plasticizer left. I finally got up the skills to hob my own 22"
diameter aluminum gear. Now that it is installed, I also moved all the
electronics to INSIDE the wedge. I will say my wireless handset did
not like sitting for 10 years. The copper traces under the membrane
switches completely corroded away. I ended up making my own wired
handset. (my first project that used all 3 of my robot machines. 3D
printed housing, CNC circuit board, and laser cut switch plate with
labels). Anyhoo it was a complete loss. I'm not sure why? It was in my
covered observatory. Anyhoo.. the entire project is a lot less half
assed with real pass through connectors, labeled switchplates... Im
happy with it..

RAD

On Mon, Feb 22, 2021 at 8:56 AM CandCShaw <candcshaw@gmail.com> wrote:

Hi Rory!!

Good to hear Big Blue is alive!!!!

A couple of things to check:
Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.

Make sure your pc clock is accurate!

Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).

Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.

Cheers!!!! Chuck
On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

I do not have mount encoders... yet...

On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
<rem.64=yahoo.com@groups.io> wrote:

Rory,

Do you have mount encoders installed? I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.

Russell R.













Rory Duncan
 

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory

On Mon, Feb 22, 2021, 11:26 PM Mike Colyar <mike@...> wrote:
Rory,

I am VERY interested in the failure of your old worm wheels. I have been looking in to what causes problems. Would you be at all willing to part with your old wheels? I want to examine them under a microscope and then do some machining.

HDPE is normal very resistant to UV degradation and the cracking I’ve seen so far has been due to the machine process. The wrong cutting coolant, a less than perfect cutting tool and/or any cross contamination of metals during the process are more usually the culprit.

Do remember if you used any lubrication during use?

Mike

> On Feb 22, 2021, at 6:30 PM, Rory Duncan <duncanrmail@...> wrote:
>
> Im connected at the moment... For more information, when I first
> connect, I have the scope start blind tracking. It does not exhibit
> the bouncing behavior until I do my first offset init. I would have
> tried removing all backlash from servoconfig, buuuut.. it started
> raining... I will check tomorrow.
>
>
> On Mon, Feb 22, 2021 at 9:17 AM Rory Duncan via groups.io
> <duncanrmail=gmail.com@groups.io> wrote:
>>
>> Interesting, I will take a look at that. How would I know if there was
>> a model running? I do see it still has my old horizon file, so I'm
>> guessing it does.
>>
>> It has been a challenge getting back into this. The brain has fried
>> after nearly a decade.
>>
>> Specifically it was my RA worm gear that stood me down hardest. I had
>> an Andy HDPE gear, and over time, teeth started to break out of it as
>> the plasticizer left. I finally got up the skills to hob my own 22"
>> diameter aluminum gear. Now that it is installed, I also moved all the
>> electronics to INSIDE the wedge. I will say my wireless handset did
>> not like sitting for 10 years. The copper traces under the membrane
>> switches completely corroded away. I ended up making my own wired
>> handset. (my first project that used all 3 of my robot machines. 3D
>> printed housing, CNC circuit board, and laser cut switch plate with
>> labels). Anyhoo it was a complete loss. I'm not sure why? It was in my
>> covered observatory. Anyhoo.. the entire project is a lot less half
>> assed with real pass through connectors, labeled switchplates... Im
>> happy with it..
>>
>> RAD
>>
>> On Mon, Feb 22, 2021 at 8:56 AM CandCShaw <candcshaw@...> wrote:
>>>
>>> Hi Rory!!
>>>
>>> Good to hear Big Blue is alive!!!!
>>>
>>> A couple of things to check:
>>> Do you have a model running? If so, try turning it off. If it fixes it build a new model. Before you do, delete any files in the folder where Sitech.cfg lives that has PCO as a file extension.
>>>
>>> Make sure your pc clock is accurate!
>>>
>>> Turn off backlash correction (never use Sitechexe backlash correction if your guiding has a backlash correction routine also running).
>>>
>>> Clicking on Freeze Dec just stops correcting the dec per the model to correct for dec drift from polar alignment error. It should not interfere with guiding commands.
>>>
>>> Cheers!!!!   Chuck
>>>> On Feb 22, 2021, at 8:03 AM, Rory Duncan <duncanrmail@...> wrote:
>>>>
>>>> I do not have mount encoders... yet...
>>>>
>>>>> On Sun, Feb 21, 2021 at 10:00 PM Russell R via groups.io
>>>>> <rem.64=yahoo.com@groups.io> wrote:
>>>>>
>>>>> Rory,
>>>>>
>>>>> Do you have mount encoders installed?  I know that if you do and are using cascade mode or tick management, then you should turn off backlash on Dec.
>>>>>
>>>>> Russell R.
>>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>>
>>
>>
>
>
>
>
>







Mike Colyar
 

Do you think you’ll be cutting a new Dec wheel any time soon? I don’t mind the shipping cost. Just would as soon wait until you replace both of them. If the failure is just in the area of the teeth I might recut the wheels in smaller diameters. The raw material costs more for shipping than for the basic cost. Priced cutting boards lately? (grin) Did you buy an acme tap to make your new aluminum wheel? I’ve used an acme tap for plastic wheels but I sharpened it with some added rake to get a clean cut. Not needed for metal. I have found the ready made acme rod a bit rough for use as is. I cast a nut out of babbit material and polished the thread stock by charging this “lap nut” with fine emery. That way the plastic worm wheel doesn’t get chewed up by the rough worm finish.

UHMW isn’t usually prone to the usual failure do to plasticizer migration/evaporation issues of cheaper plastics. There is research that says that some lubricants are bad. The articles are sometimes over my head.

I have a couple of his 8” wheels now that aren’t exhibiting any failure but UHMW is not easy to machine and get a nice finish. I plan on making new ones out of Delrin which is a lot more expensive but cuts clean.

The beauty of plastic worm wheels is that you can run them dry and at zero clearance thus gaining a lot on stiffness. And no lapping. I gash first. When running them dry you have no oil or grease layer to introduce springiness. If you keep the diameter fairly large, they are stiff enough to perform.

Mike


On Feb 23, 2021, at 9:47 AM, Rory Duncan <duncanrmail@...> wrote:

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory


CandCShaw
 

I helped Andy job the big hope gears, and some of the smaller ones. He made a Hobbing table to synchronize the gear rotation with the pitch of the Acme tap he used.  The depth of the tap was adjustable so you could take nice small bite increases, and the drive motor speed was also variable. Not sure what happened to all his stuff after he passed away.....

Chuck


On Feb 23, 2021, at 2:28 PM, Mike Colyar <mike@...> wrote:

Do you think you’ll be cutting a new Dec wheel any time soon? I don’t mind the shipping cost. Just would as soon wait until you replace both of them. If the failure is just in the area of the teeth I might recut the wheels in smaller diameters. The raw material costs more for shipping than for the basic cost. Priced cutting boards lately? (grin) Did you buy an acme tap to make your new aluminum wheel? I’ve used an acme tap for plastic wheels but I sharpened it with some added rake to get a clean cut. Not needed for metal. I have found the ready made acme rod a bit rough for use as is. I cast a nut out of babbit material and polished the thread stock by charging this “lap nut” with fine emery. That way the plastic worm wheel doesn’t get chewed up by the rough worm finish.

UHMW isn’t usually prone to the usual failure do to plasticizer migration/evaporation issues of cheaper plastics. There is research that says that some lubricants are bad. The articles are sometimes over my head.

I have a couple of his 8” wheels now that aren’t exhibiting any failure but UHMW is not easy to machine and get a nice finish. I plan on making new ones out of Delrin which is a lot more expensive but cuts clean.

The beauty of plastic worm wheels is that you can run them dry and at zero clearance thus gaining a lot on stiffness. And no lapping. I gash first. When running them dry you have no oil or grease layer to introduce springiness. If you keep the diameter fairly large, they are stiff enough to perform.

Mike


On Feb 23, 2021, at 9:47 AM, Rory Duncan <duncanrmail@...> wrote:

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory


Mike Colyar
 

I am so out of it. I didn’t know he was gone. His web site was still up not that long ago.

I have two 8” gears that I think are his. Oddly enough, they have differing numbers of teeth. One is 275 and the other is 284.

I have built several mounts over the years. Again and again I find people asking a bunch of torque from their drive. In my humble opinion (laughter from my wife) a properly designed, built and balanced mount should be easily driven with a clock motor. My first 8” reflector in 1960 used an alarm clock and a falling weight. A servo system should be able to drive a scope that three people can’t lift off of the ground. Friction and out of balance are your enemies. We all get lazy though. Me too.

.5” thick seems thin. Did you need to support the wheel laterally so as not to have the worm tend to climb? What diameter si your worm?

Mike

On Feb 23, 2021, at 11:37 AM, CandCShaw <candcshaw@...> wrote:

I helped Andy job the big hope gears, and some of the smaller ones. He made a Hobbing table to synchronize the gear rotation with the pitch of the Acme tap he used.  The depth of the tap was adjustable so you could take nice small bite increases, and the drive motor speed was also variable. Not sure what happened to all his stuff after he passed away.....

Chuck


On Feb 23, 2021, at 2:28 PM, Mike Colyar <mike@...> wrote:

Do you think you’ll be cutting a new Dec wheel any time soon? I don’t mind the shipping cost. Just would as soon wait until you replace both of them. If the failure is just in the area of the teeth I might recut the wheels in smaller diameters. The raw material costs more for shipping than for the basic cost. Priced cutting boards lately? (grin) Did you buy an acme tap to make your new aluminum wheel? I’ve used an acme tap for plastic wheels but I sharpened it with some added rake to get a clean cut. Not needed for metal. I have found the ready made acme rod a bit rough for use as is. I cast a nut out of babbit material and polished the thread stock by charging this “lap nut” with fine emery. That way the plastic worm wheel doesn’t get chewed up by the rough worm finish.

UHMW isn’t usually prone to the usual failure do to plasticizer migration/evaporation issues of cheaper plastics. There is research that says that some lubricants are bad. The articles are sometimes over my head.

I have a couple of his 8” wheels now that aren’t exhibiting any failure but UHMW is not easy to machine and get a nice finish. I plan on making new ones out of Delrin which is a lot more expensive but cuts clean.

The beauty of plastic worm wheels is that you can run them dry and at zero clearance thus gaining a lot on stiffness. And no lapping. I gash first. When running them dry you have no oil or grease layer to introduce springiness. If you keep the diameter fairly large, they are stiff enough to perform.

Mike


On Feb 23, 2021, at 9:47 AM, Rory Duncan <duncanrmail@...> wrote:

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory



Rory Duncan
 

OK, let me see that I can tell you.

The RA wheel that is off the scope has a 4" hole in the center of it,
just be aware. It is not completely flat either. Ill send you some
pictures.. I think a wheel this big is just not structurally sound for
the thickness it is.

I made a cutting hob out of a piece of the same screw as the worm that
I cut slots in, then ground relief in. I have an acme tap, but the
diameter of these wheels is such that it wasnt long enough to give
good clearance. Let me describe my process. drilled 1/4 hole in
aluminum plate. Used compass to mark circle, Cut the aluminum blank
roughly on my bandsaw. mounted wheel to worktable using 1/4 drill rod
to it could free spin. mounted floor standing belt sander ridgidly to
work table using metal straps. rotated the wheel against the sander
until all trued up. My measuring showed less than 3 thou runout around
the entire wheel. (looks like one divot to 5 thou). Anyhoo.. I then
mounted the wheel to my tablesaw the same way, with a pin, and mounted
my worm drive mechanism off the scope onto the fence front bar. I was
able to get the height perfect that way. I used C clamps to clamp the
mecanism down to the bar, and drove the worm hob with my cordless
drill. I would "advance" the cutter by tapping the mechanism with a
hammer. It self cut beautifully! I went through almost 1/2 a can of
WD40 hobbing it out. It sounds very crude, but the results are
fantastic. It is very hard to make a wheel that large, without
extremely large machine tools.

OK, as for the dec wheel, it seems to be working fine at the moment as
it doesnt have much load on it. I have the aluminum to change it, but
I wasnt planning on it until it has a problem.

My mechanism is spring loaded so that it always runs in full contact
of the wheel.

I have photos of all this process if you are interested..
RAD

On Tue, Feb 23, 2021 at 2:28 PM Mike Colyar <mike@southlopez.net> wrote:

Do you think you’ll be cutting a new Dec wheel any time soon? I don’t mind the shipping cost. Just would as soon wait until you replace both of them. If the failure is just in the area of the teeth I might recut the wheels in smaller diameters. The raw material costs more for shipping than for the basic cost. Priced cutting boards lately? (grin) Did you buy an acme tap to make your new aluminum wheel? I’ve used an acme tap for plastic wheels but I sharpened it with some added rake to get a clean cut. Not needed for metal. I have found the ready made acme rod a bit rough for use as is. I cast a nut out of babbit material and polished the thread stock by charging this “lap nut” with fine emery. That way the plastic worm wheel doesn’t get chewed up by the rough worm finish.

UHMW isn’t usually prone to the usual failure do to plasticizer migration/evaporation issues of cheaper plastics. There is research that says that some lubricants are bad. The articles are sometimes over my head.

I have a couple of his 8” wheels now that aren’t exhibiting any failure but UHMW is not easy to machine and get a nice finish. I plan on making new ones out of Delrin which is a lot more expensive but cuts clean.

The beauty of plastic worm wheels is that you can run them dry and at zero clearance thus gaining a lot on stiffness. And no lapping. I gash first. When running them dry you have no oil or grease layer to introduce springiness. If you keep the diameter fairly large, they are stiff enough to perform.

Mike


On Feb 23, 2021, at 9:47 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory



Rory Duncan
 

Yes, I incorporated guides to keep the wheel centered on the worm. My
worm is only 1/2"

On Tue, Feb 23, 2021 at 11:18 PM Mike Colyar <mike@southlopez.net> wrote:

I am so out of it. I didn’t know he was gone. His web site was still up not that long ago.

I have two 8” gears that I think are his. Oddly enough, they have differing numbers of teeth. One is 275 and the other is 284.

I have built several mounts over the years. Again and again I find people asking a bunch of torque from their drive. In my humble opinion (laughter from my wife) a properly designed, built and balanced mount should be easily driven with a clock motor. My first 8” reflector in 1960 used an alarm clock and a falling weight. A servo system should be able to drive a scope that three people can’t lift off of the ground. Friction and out of balance are your enemies. We all get lazy though. Me too.

.5” thick seems thin. Did you need to support the wheel laterally so as not to have the worm tend to climb? What diameter si your worm?

Mike

On Feb 23, 2021, at 11:37 AM, CandCShaw <candcshaw@gmail.com> wrote:

I helped Andy job the big hope gears, and some of the smaller ones. He made a Hobbing table to synchronize the gear rotation with the pitch of the Acme tap he used. The depth of the tap was adjustable so you could take nice small bite increases, and the drive motor speed was also variable. Not sure what happened to all his stuff after he passed away.....

Chuck


On Feb 23, 2021, at 2:28 PM, Mike Colyar <mike@southlopez.net> wrote:

Do you think you’ll be cutting a new Dec wheel any time soon? I don’t mind the shipping cost. Just would as soon wait until you replace both of them. If the failure is just in the area of the teeth I might recut the wheels in smaller diameters. The raw material costs more for shipping than for the basic cost. Priced cutting boards lately? (grin) Did you buy an acme tap to make your new aluminum wheel? I’ve used an acme tap for plastic wheels but I sharpened it with some added rake to get a clean cut. Not needed for metal. I have found the ready made acme rod a bit rough for use as is. I cast a nut out of babbit material and polished the thread stock by charging this “lap nut” with fine emery. That way the plastic worm wheel doesn’t get chewed up by the rough worm finish.

UHMW isn’t usually prone to the usual failure do to plasticizer migration/evaporation issues of cheaper plastics. There is research that says that some lubricants are bad. The articles are sometimes over my head.

I have a couple of his 8” wheels now that aren’t exhibiting any failure but UHMW is not easy to machine and get a nice finish. I plan on making new ones out of Delrin which is a lot more expensive but cuts clean.

The beauty of plastic worm wheels is that you can run them dry and at zero clearance thus gaining a lot on stiffness. And no lapping. I gash first. When running them dry you have no oil or grease layer to introduce springiness. If you keep the diameter fairly large, they are stiff enough to perform.

Mike


On Feb 23, 2021, at 9:47 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory




Rory Duncan
 

Threw a couple of pics in here... You can see it was quite a PITA to
get the RA wheel on since I had to disassemble the entire axis....
when it weighs 500lbs, it's a challenge. If you look closely, you can
see the spring driven mechanism for DEC on the side of the fork.

On Tue, Feb 23, 2021 at 2:28 PM Mike Colyar <mike@southlopez.net> wrote:

Do you think you’ll be cutting a new Dec wheel any time soon? I don’t mind the shipping cost. Just would as soon wait until you replace both of them. If the failure is just in the area of the teeth I might recut the wheels in smaller diameters. The raw material costs more for shipping than for the basic cost. Priced cutting boards lately? (grin) Did you buy an acme tap to make your new aluminum wheel? I’ve used an acme tap for plastic wheels but I sharpened it with some added rake to get a clean cut. Not needed for metal. I have found the ready made acme rod a bit rough for use as is. I cast a nut out of babbit material and polished the thread stock by charging this “lap nut” with fine emery. That way the plastic worm wheel doesn’t get chewed up by the rough worm finish.

UHMW isn’t usually prone to the usual failure do to plasticizer migration/evaporation issues of cheaper plastics. There is research that says that some lubricants are bad. The articles are sometimes over my head.

I have a couple of his 8” wheels now that aren’t exhibiting any failure but UHMW is not easy to machine and get a nice finish. I plan on making new ones out of Delrin which is a lot more expensive but cuts clean.

The beauty of plastic worm wheels is that you can run them dry and at zero clearance thus gaining a lot on stiffness. And no lapping. I gash first. When running them dry you have no oil or grease layer to introduce springiness. If you keep the diameter fairly large, they are stiff enough to perform.

Mike


On Feb 23, 2021, at 9:47 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

Sure! Just for the record, they are 1/2" thick, with a 10tpi acme thread. I used a stainless acme rod as the worm. The wheels are like 2 feet in diameter... So it'll cost a bit to ship... Anyhoo, yes, I did use lubrication. Now... 10 years ago... What did I use..... Yeah. I might have just used mobil 1 motor oil. I had an applicator can out there... Would you be interested in me cutting out some of the "bad" sections instead of sending the entire wheel?

I've only replaced the ra wheel at this point the other is still functional.

Rory



Mike Colyar
 

Rory,

I am totally impressed at what you have done without anything than even vaguely looks like a machine shop. I have a mill and a lathe and cut worms using things like a rotary table and an indexing head.

For now, let’s not pursue sending me your old worm wheel. I would be interested in having you take a screw driver or cold chisel or wood chisel and comparing the brittleness of the area where the teeth were failing with an area more towards the hub. Or better yet comparing the area with a cutting board. I’d like to know if the area where the failures were happening is hardened and more prone to fracture.

Thanks for all of your efforts!

Mike

On Feb 24, 2021, at 7:16 AM, Rory Duncan <duncanrmail@gmail.com> wrote:

Threw a couple of pics in here... You can see it was quite a PITA to
get the RA wheel on since I had to disassemble the entire axis....
when it weighs 500lbs, it's a challenge. If you look closely, you can
see the spring driven mechanism for DEC on the side of the fork.


Russell R
 

Rory,

Looks like you used 3/8" (9.53mm) plate on Big Blue.  Wow, a Renishaw encoder would fit real nice between your RA gear and upper pillow block.  I like the angle iron rails and v-notched wheels, my shop doors use the same type of track and weigh the same has Blue. I guess the rails are perpendicular to the polar axis?  I agree with Mike, the work you done is impressive. The large gears do well to overcome the drag from those two pillow block bearings. Did you remove the factory viscous grease and replace with something lighter on those bearings?  Did you have a hard time indexing those gears for hobbing? 

Well done!

Russell R.