Am 14.10.2016 um 16:03 schrieb Timo Inkinen timo.p.inkinen@... [ap-gto] <ap-gto@...>:

Hi all,

 

I have bought a second hand AP 1200 GTO mount made ca. 2010 (serial 1200926).

I have found out that this unit has a DEC backlash problem, which shows up in all backlash tests taken with PulseGuise and PEMPro. 

You can see this in my backlash test picture here:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/Backlash_06102016.jpg/_ full.jpg

 

I have done lots of debugging with my mount to find out where the cause for this backlash problem resides.

Starting from the www.astro-physics.com/tech_sup port/mounts/1200gto/Gear%20Mes h%201200.pdf document measures in gear meshing and ending into camera cable fixings plus guiding software parameter adjustments.

But despite of that all, I CANNOT get this backlash out of my AP 1200, no matter what I do on my own and with the help suggestions from AP support.

 

On the last weekend I took the DEC gear mesh system apart and disassembled the DEC gear mesh from the mount altogether. 

Then I drove this DEC gear meshing with standard PulseGuide test #3. Ten pulses with 500ms Pulse Duration were sent and results for that test can be seen in this GIF animation taken closely from my mount gears:  

http://personal.inet.fi/luonto /kuvagalleria/temp/DEC_Gear_ Mesh_animation_small.gif

Look up there how the foremost gear moves (or actually DOES NOT move) compared to the little gear on the left.That little gear (on the left) is attached directly on the motor shaft and the big gear (in the front) is one gear away from worm screw gear.

THis animation was taken with my DSLR camera and timer taking sequence of photos during the test #3. A total of 42 photos were taken, but only half of those were needed as there was a gear change in every other image.  

 

As you can see from that GIF-animation, it is quite evident that my backlash problems come from this AP1200 mount’s reduction spur gear-set play. 

There are about three motor pulses sent (each 500ms duration in this test), which are required for the foremost big gear movement to start the movement in this test. As you can see, there is no play between the motor drive shaft’s first spur gear and the second Delrin / Brass spur gear system. But there is too way too much play (!) between this third brass gear and the foremost (fourth) steel gear. Delrin and brass gears are attached to each other tightly.

 

I have asked what can be done for this excessive play from AP support, but they seem to be quite helpless with it as I cannot get any reply for this issue. I have sent them my latest mail on Sunday and and now on Friday afternoon here in Finland, I haven’t still received any response for that question. Before this gear mesh finding I received almost daily support suggestions in the last week for all kinds of backlash issues, which could be related to my own backlash problems. But none of those suggestions referred to this kind of backlash play.

 

I know there will always be some amount of play in all gear systems, but I think this much play is excessive for a quality product like AP1200. 
My own diagnosis is that there is some wear in the DEC gear set, which has gradually caused this excessive play between the brass and steel gear.

Do you know, if there are some adjustments for this reduction gear meshing, which could reduce this gear play? 
I have adjusted the play between motor gear and Delrin gear with the motor adjustment seen in this picture:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/ServoMotor_attachment_ closeup.jpg

But I have not found anything else, which could fix this brass/steel gear play seen in that animation as that foremost gear does not have nay adjustment in its' attachment to this DEC unit. 

Also I would like to know, if I can I buy replacement gears for this kind of gear set somewhere (from AP or its’ re-seller in Europe)? 
You know, IF it is the wear in gears that causes this backlash seen here...

Below is more information on this problem.

Here is one image from cable ties:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/IMG_20161009_cable_ties.jpg

Here is how this backlash shows in PHD2 software with almost regular setup:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/PHD2_guiding_2x2bin_no_ backlash_compensation.jpg

And here PHD2 Guider Assistant’s diagnosis for this backlash (note ca. 1800ms backlash compensation need):

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/PHD2/PHD2_12.jpg

Here is a high resolution image of this gear set: (4000x3000 px, 1.5MB)

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/GearMesh_closeup_big.jpg/_ full.jpg

AP1200's spur gear is firmly attached to the shaft with this kind of screw firmly attached there:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/SpurGear_attachment_screw. jpg

Some PulseGuide backlash test with 0,5x guide speed:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/PulseGuide_backlash_test_0_ 5x.jpg/_full.jpg

The same test with 0,25x guide speed only:

http://astrokuva.galleria.fi/k uvat/Kuvauslaitteistot/AP1200G TO/PulseGuide_backlash_test_0_ 25x.jpg/_full.jpg

 

Can someone give me some advise for this kind of backlash problem, please?

Thanks!

 

Br, Timo Inkinen

http://astrokuva.galleria.fi/