Hi Andre -
If your mount originally came with stainless worms, from what I
understand it should be a marked improvement.
In my opinion, you ideally want to reduce PE on the RA axis since
that will continually move during tracking/guiding.? Backlash does
not mater as much since you are constantly moving in the same
direction.? Wind handling may come into play, but that can largely
be mitigated with eastward weight bias, or the string trick. ? ?
One the DEC side, PE does not matter much, however you want to
reduce backlash since the DEC will receive small corrections in
both directions.? This is why if it were my mount, I would put the
OPW on the DEC side.
The OPW upgrade is separate from the spring loaded worm
upgrade.?? The SLW upgrade requires the OPW, but it is a
modification? that is only done in house by Losmandy.? That said,
many people have done various DIY interpretations of the spring
loaded worm, with or without the factory OPW.? If youre
comfortable drilling and tapping your mount, adding a spring
should be a relatively simple modification.? Alternately, you
might be able to get creative with some rubber bands or some other
method of applying pressure to the worm block.?? The hole you
mention in the OPW is indeed for the spring mechanism, but
requires drilling and tapping the worm mounting plate.
I am currently using the Wemos R32 and CNCv3 onstep controller.?
I have TMC2130 drivers in SPI mode.? Previously I was using
LV8729s and those worked well too.
I am also using bellows style couplings.? 16mm diameter, 5mm x
6.35mm.? I was concerned the helical couplings might have been
winding up (motor movement without worm movement), so I moved to
bellows just to be safe.? The are less flexible, but as long as
your alignment is good, it should be OK IMO.? Here's the link if
you're curious:?
Good luck,
-Tony
On 7/29/2021 9:27 AM, andre_moutinho
wrote:
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Hello
Tony,
?
The
original mount came with stainless worms.
I
have purchased one OPW and two High Precision worms for both
RA/DEC. I was considering the OPW for the RA axis but will
think about using it in DEC. My OPW came with a hole that
may be used for Sprint loaded, but no spring was included,
just a hole. Thats very strange. Please check this post:
/g/Losmandy_users/message/73027
?
I
have checked your onstep progression. What controller have
you used? What was the tracking microstep configuration? I
have upgraded the stepper controller to TMC 5130.
?
Thanks
for the reduction suggestion. I will think about it.
?
Thanks
Andre
?
De:
[email protected] [mailto:[email protected]] Em
nome de GuitsBoy
Enviada em: quinta-feira, 29 de julho de 2021 10:18
Para: [email protected]
Assunto: Re: [Losmandy_users_io] What result I can
get with the current OPW in my old G11?
?
Hi Andre -?
Did your original mount come with the HP brass worms?? Or were
they stainless?? ?Assuming they were HP brass already, the new
OPW might not offer much less PE than your original ones,
however it should be a whole lot easier to set the backlash.?
And if you ever decided to go DIY spring loaded worms, it
should be a relatively easy mod for you.
Also, I would think you want the High Precision worm to go on
the RA side to reduce periodic-error.? ?Personally, I would
put the OPW on the DEC side with the expectation that I would
eventually do a spring loaded mod to reduce backlash, or at
the very least, make routine backlash adjustment easier.
I also have a ten+ year old G11 that's been converted to
onstep.? ?To give you an idea of how my RMS guide error
progressed:
~ .85 - 1.0 arc-sec RMS:? ?Direct drive 400 step motors and
stock two piece worm blocks
~ .6 - .75 arc-sec RMS:? ?Belt Drive with 16:60 reduction and
stock 2 piece worm blocks
~ .5 - .65 arc-sec RMS:? ?Belt Drive with 16:60 reduction, and
DIY spring loaded worms, new HP worm (old was brass, but high
PE) and bellows style couplings
The above assumes nights of good seeing and little wind.? ?I
am still using a 60mm guidescope, and? I've had 30 lbs of 8"
newt and equipment guiding under .5 arc-sec RMS under perfect
conditions.
I should also note that certain stepper drivers perform better
than others.? The TMC2130 seems to contribute the least
error.? ?Also, mechanical reduction is more accurate than
microstepping for two reasons:? Coarser microsteps are more
accurate and have higher holding torque, and mechanical
reduction also reduces load on the motors, resulting in less
angular error.? If you can move towards mechanical reduction
(planetary gearbox or belt drive) that should give you
additional benefit IMO.? But you have to make sure that the
reduction benefits outweigh the added complexity, friction,
and NVH (noise, vibration, harmonics)
Good luck, -Tony
