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Re: Ovision worm alignment


Jan 29, 2017

 


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#58582 Jan 29, 2017

Hello

I would like to ask some opinions about how important is to have the Ovision block perfectly square. I just installed a new Ovision worm as replacement of my old Ovision wiorm since the performance was marginal. I adjusted the worm with a feeler gauge and both sides of the worm block looked to have the same distance (I left 1 mm backlash). However, when I slew the mount and look at the worm I can see that the holdham coupler has some misalignment in certain angle. Is that normal? I assumed that having one block piece should provide perfect alignment. I tried to moves the block more from the motor side but I could not improve that unless increase my backlash.

Thank you

Rodrigo



----------------------------

#58584 Jan 30, 2017

Rodrigo,

The Ovision worm blocks are just a one piece worm block and does not resolve the problems of misaligned wormgear axis and gearbox axis. This is why the Losmandy OPW design is superior and can give better PE performance when properly installed with preload on the bearings using Bellevue spring washers. It would seem that the Losmandy HP worms are generally not quite as good as a good Ovision worm but with the Losmady's nearly perfect alignment of the gearbox output shaft with the wormgear shaft the Losmandy will, all things being equal outperform the Ovision system. The coupling is important and makes a small difference but as with most things all of the errors add up in the system.��

Chip



----------------------------

#58585 Jan 30, 2017

Hi Chip

Thank you for the information. Is there a way you know I can better align the Ovision worm block with the motor gear shaft? So far I can see how the coupler slides a bit during worm rotation. What I wonder is if the odham coupler will eliminate any effect of misalignment, so I should not worry about it

Rodrigo

--------------- On Mon, 1/30/17, chiplouie@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:



Subject: [Losmandy_users] Re: Ovision worm alignment

To: Losmandy_users@yahoogroups.com

Date: Monday, January 30, 2017, 3:10 PM



Rodrigo,



The Ovision worm blocks are

just a one piece worm block and does not resolve the

problems of misaligned wormgear axis and gearbox axis. This

is why the Losmandy OPW design is superior and can give

better PE performance when properly installed with preload

on the bearings using Bellevue spring washers. It would seem

that the Losmandy HP worms are generally not quite as good

as a good Ovision worm but with the Losmady's nearly

perfect alignment of the gearbox output shaft with the

wormgear shaft the Losmandy will, all things being equal

outperform the Ovision system. The coupling is important and

makes a small difference but as with most things all of the

errors add up in the system.





Chip



----------------------------

#58586 Jan 30, 2017

Hi Rodrigo (and Chip too!),

I have been working on these puzzles for awhile... here is what I think is going on:

1. The design of the Oldham coupler is really ingenious.. The design keeps both sides of the plastic coupler at 90 degrees from each other, so even if the (call it Z direction) axes are not in the same line, as long as they are totally parallel (in both X and Y points of view), the coupler should keep the rotation of the first axis (the gearbox output axis) identical to the rotation of the worm gear axis on the other side. .

2. But if the coupler sides are NOT parallel, then you have a problem: .the angle between the axes will make one axis have to speed up or slow down to match the rotation on the other side.. The changes in rotation (just by symmetry) would be like twice the worm period, and I think this is what often makes the large "1/2 period" or "2x frequency" contribution when you look at the FFT analysis (say by the program PECprep). .

3. In the most optimal situation, you have both axes parallel and with no offset (in other words the two axes {gearbox output and worm gear} would be on the same single line in 3 dimensions). .

4. If you can, therefore, try to look at the coupling in all viewpoints and try to keep the Oldham coupler lined up on both sides. .

5. You must also have the metal (sliding) parts of the Oldham coupler fully inserted into the plastic center part.. Do not leave a gap in there which creates backlash and may make autoguiding troublesome.. Likewise I like to get the worm very close to the ring gear (i.e. almost zero counterweight backlash at the end of the RA axis, and no wiggle on the DEC axis either for the same reason.)

6. Now, the Ovision system (which I do not have... going from looking at the assembly and reading about it) and the Losmandy OPW both have mechanical methods of keeping both worm blocks lined up.. Lining up the worm blocks is critical to keep a single bearing ball from getting the drive force, or one part of the bearing race from taking the stress (and that is why the worm ball period can show up in the FFT analysis).. That is good for keeping the bearings centers lined up also.. Only the Ovision system has a designed built-in Belleville spring washer to keep the rear bearing under compression, but the Losmandy OPW (or even the 2 piece original worm blocks) can have one of these Belleville spring washers installed. . ..

7. Another critical point to get your native PE low as possible is to have superior worm bearings for the RA axis.. There are ABEC-7 bearings available from several sources for about US $13 each or possibly less.. Your Ovision must have these already, but the stock worm bearings from Losmandy have unknown quality ratings. ..

I have a writeup with some diagrams on this in our Files section... discussing the PE analysis, and need to preload the worm bearings. .

Wishing you super results on your Ovision system...let us know what you find from your own testing..

- Michael ..







----------------------------

#58587 Jan 30, 2017

Hi Michael

Thank you. During a worm rotation, one part looks perfectly aligned but then in a another angle, it looks like the odham couples slides a bit, may be 1mm. So should I try to realign again?

Rodrigo

--------------- On Mon, 1/30/17, Michael Herman mherman346@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:



Subject: Re: [Losmandy_users] Re: Ovision worm alignment

To: "Losmandy_users@yahoogroups.com" Losmandy_users@yahoogroups.com>

Date: Monday, January 30, 2017, 4:46 PM



Hi Rodrigo (and Chip

too!),



I have been working

on these puzzles for awhile... here is what I think is

going on:



1.

The design of the Oldham coupler is really ingenious.. The

design keeps

both sides of the plastic

coupler at 90 degrees from each other, so even if

the (call it Z direction) axes are not in the

same line, as long as they

are totally

parallel (in both X and Y points of view), the coupler

should

keep the rotation of the first axis

(the gearbox output axis) identical to

the

rotation of the worm gear axis on the other side.



2. But if the coupler sides

are NOT parallel, then you have a problem:. the

angle between the axes will make one axis have

to speed up or slow down to

match the

rotation on the other side.. The changes in rotation (just

by

symmetry) would be like twice the worm

period, and I think this is what

often makes

the large "1/2 period" or "2x frequency"

contribution when you

look at the FFT

analysis (say by the program PECprep).



3. In the most optimal situation, you have both

axes parallel and with no

offset (in other

words the two axes {gearbox output and worm gear} would

be

on the same single line in 3

dimensions).



4. If you can,

therefore, try to look at the coupling in all viewpoints

and

try to keep the Oldham coupler lined up

on both sides.



5. You must

also have the metal (sliding) parts of the Oldham coupler

fully

inserted into the plastic center

part.. Do not leave a gap in there which

creates backlash and may make autoguiding

troublesome.. Likewise I like to

get the

worm very close to the ring gear (i.e. almost zero

counterweight

backlash at the end of the RA

axis, and no wiggle on the DEC axis either

for the same reason.)



6. Now, the Ovision system (which I do not

have... going from looking at

the assembly

and reading about it) and the Losmandy OPW both have

mechanical methods of keeping both worm blocks

lined up.. Lining up the

worm blocks is

critical to keep a single bearing ball from getting the

drive force, or one part of the bearing race

from taking the stress (and

that is why the

worm ball period can show up in the FFT analysis).. That

is

good for keeping the bearings centers

lined up also.. Only the Ovision

system has

a designed built-in Belleville spring washer to keep the

rear

bearing under compression, but the

Losmandy OPW (or even the 2 piece

original

worm blocks) can have one of these Belleville spring

washers

installed.



7. Another critical point to get your native PE

low as possible is to have

superior worm

bearings for the RA axis.. There are ABEC-7 bearings

available from several sources for about US $13

each or possibly less.

Your Ovision must

have these already, but the stock worm bearings from

Losmandy have unknown quality ratings.



I have a writeup with some

diagrams on this in our Files section...

discussing the PE analysis, and need to preload

the worm bearings.



Wishing

you super results on your Ovision system...let us know what

you

find from your own testing.



- Michael



On Mon, Jan 30, 2017 at 12:59 PM, Rodrigo

Roesch rodrigoroesch@...

[Losmandy_users] Losmandy_users@yahoogroups.com>

wrote:



>

>

> Hi Chip

> Thank you for the information. Is there a

way you know I can better align

> the

Ovision worm block with the motor gear shaft? So far I can

see how the

> coupler slides a bit during

worm rotation. What I wonder is if the odham

> coupler will eliminate any effect of

misalignment, so I should not worry

>

about it

> Rodrigo

>

---------------

> On Mon, 1/30/17, chiplouie@...

[Losmandy_users]

> Losmandy_users@yahoogroups.com>

wrote:

>

> Subject:

[Losmandy_users] Re: Ovision worm alignment

> To: Losmandy_users@yahoogroups.com

> Date: Monday, January 30, 2017, 3:10 PM

>

> Rodrigo,

>

> The Ovision worm

blocks are

> just a one piece worm block

and does not resolve the

> problems of

misaligned wormgear axis and gearbox axis. This

> is why the Losmandy OPW design is superior

and can give

> better PE performance when

properly installed with preload

> on the

bearings using Bellevue spring washers. It would seem

> that the Losmandy HP worms are generally

not quite as good

> as a good Ovision

worm but with the Losmady's nearly

>

perfect alignment of the gearbox output shaft with the

> wormgear shaft the Losmandy will, all

things being equal

> outperform the

Ovision system. The coupling is important and

> makes a small difference but as with most

things all of the

> errors add up in the

system.

>

>

> Chip

>

>

>

>

>

>

>

>



>







--

Michael

Herman

mobile: 408 421-1239

email: mherman346@...







----------------------------

#58588 Jan 30, 2017

Hi Rodrigo,.

Yes...I would try to get the drive axis and the worm axis exactly in line...if you can..

.I don't know how the Ovision mounting is done, or what could be a problem, but you might try to ask Ovision for their suggestions if you are getting stuck.

When you are done adjusting, do a very accurate drift polar alignment. . Then take some PE data. .

I find that PHD2 works well for me...its handy drift alignment tool helps, and then I make a new PHD log file that I read into PECprep for analysis of the G11 frequencies.

The frequencies will diagnose both the overall PE, and what mechanical elements are causing PE.. You want the only factor to be the worm or elements at n x worm frequency..(n is any integer...n for the worm is 1 of course) so that the PEC (say built into Gemini units), will clean it all up. .

If you get elements at some other frequency, not an integer, .or below 1 worm frequency, then PEC will not clean those up.. The bearing balls tend to be one such trouble. .

Autoguiding will probably clean up stuff at fractions of a worm period...they are slow variations. .

Hope all this helps!. Nothing helps the problem of bad seeing... we are all stuck with that...

Stay well,Michael.



----------------------------

#58589 Jan 30, 2017

Great animations on how an Oldham coupling works.�� As long as the two shafts are parallel, the coupler does the rest.

Oldham Coupling Flash Animation

Oldham Coupling Flash Animation A site dedicated to animation of mechanisms, pneumatic, hydraulic and electronic components



----------------------------

#58591 Jan 30, 2017

Thanks for that! !!

On Jan 30, 2017 2:23 PM, "philipcamera@... [Losmandy_users]" Losmandy_users@yahoogroups.com> wrote:

.Great animations on how an Oldham coupling works.. As long as the two shafts are parallel, the coupler does the rest.

Oldham Coupling Flash Animation

Oldham Coupling Flash Animation A site dedicated to animation of mechanisms, pneumatic, hydraulic and electronic components



----------------------------

#58592 Jan 30, 2017

Thank you for the video. Based on that, my shafts looks parallel just one slightly higher than the other. So if that is the case, should I expect any impact on the quality of my tracking?



--------------- On Mon, 1/30/17, Michael Herman mherman346@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:



Subject: Re: [Losmandy_users] Re: Ovision worm alignment

To: Losmandy_users@yahoogroups.com

Date: Monday, January 30, 2017, 5:51 PM



Thanks for that! !!



On Jan 30, 2017 2:23 PM,

"philipcamera@...

[Losmandy_users]"

Losmandy_users@yahoogroups.com>

wrote:



>

>

> Great animations on

how an Oldham coupling works.. As long as the two

> shafts are parallel, the coupler does the

rest.

>

> Oldham

Coupling Flash Animation www.mekanizmalar.com/oldham.html>

> [image: image] www.mekanizmalar.com/oldham.html>

> Oldham Coupling Flash Animation www.mekanizmalar.com/oldham.html>

> A site dedicated to animation of

mechanisms, pneumatic, hydraulic and

>

electronic components

> View on

www.mekanizmalar.com www.mekanizmalar.com/oldham.html>

> Preview by Yahoo

>

>

>

>

> Oldham coupling

animation www.youtube.com/watch?v=KP09wP7OIxg>

> [image: image] www.youtube.com/watch?v=KP09wP7OIxg>

> Oldham coupling animation www.youtube.com/watch?v=KP09wP7OIxg>

> This is a simple model to understand the

working of oldham couping

> View on

www.youtube.com www.youtube.com/watch?v=KP09wP7OIxg>

> Preview by Yahoo

>

>

>

>



----------------------------

#58593 Jan 30, 2017

Am I missing something here? I have an ovision and its in a one piece worm block. Folks have been writing��work blocks in this post and that seems incorrect. I just mount it set the backlash and thats it.��

Ross��



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#58595 Jan 31, 2017

Hi Ross

Maybe it was something misspelled. The discussion here is the alignment of the worm shaft in respect to the motor gear shaft. It seems like the two shafts can be parallel to each other but still difficult to peferf alignment them in all directions (high/low) So you can see the variations during the rotation of the Oldham coupler.

Rodrigo

--------------- On Mon, 1/30/17, Ross Elkins rossmon1@... [Losmandy_users] Losmandy_users@yahoogroups.com> wrote:



Subject: [Losmandy_users] Re: Ovision worm alignment

To: Losmandy_users@yahoogroups.com

Date: Monday, January 30, 2017, 10:22 PM



Am I missing something

here? I have an ovision and its in a one piece worm block.

Folks have been writing

work blocks in this

post and that seems incorrect. I just mount it set the

backlash and thats it.



Ross



----------------------------

#58604 Feb 1 9:31 PM

The problem with the original Losmandy 2-piece worm gear bearing support blocks AND the Ovision one-piece worm block is that in both cases the worm mesh is set by moving the worm gear in and out by changing the angle of the worm gear with a pivot point being the block closest to the gearbox. This pivoting action necessarily changes the angle of the worm gear shaft. Unfortunately the gearbox is attached to the plate under the worm gear at a fixed location which maintains a single, non-adjustable position. This is parallel misalignment of the axles is unavoidable with both of these designs.��

The Losmandy OPW design attaches the gearbox to a plate which moves in perfect alignment with the worm gear as it is moved in and out to set correct gear mesh. This completely eliminates the small, unpredictable changes in velocity introduced by the Oldham coupler because it cannot compensate for due to incorrect geometry when both sides of the coupler are not perfectly parallel to one another. As has been demonstrated by several people the Losmandy HP-worms are capable of very low levels of PE when used with Losmandy OPWs with Bellevue spring washers. ����Chip������







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