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Bad worm gear.


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On 25/11/2021 at 12:32, powerlord said:

This is the way things work in China other than a few exceptional companies (DJI, Xiaomi, etc).

"Poorly Made in China: An Insider′s Account of the China Production Game" by Paul Midler is a good read.

In a nutshell though, with few exceptions being so removed from the end user, manufacturing of a product tends to work across many many many smaller companies, usually in a specific city (each city specialising in different products). The only incentive to each small company is to do it as cheap as possible. So at the start the spec is good sometimes (not always)- casting tolerances, stainless screws maybe, good quality bearings and grease, lots of quality checks, but as time goes on, the only way the companies can compete is by reducing price. slowly components get replaced by cheaper ones, labour intensive tasks gets skipped, etc. And eventually you end up the cheapest thing that still gets them the business. It's madness, but it's the way it worked till very recently. The worst that happens for the small company is the big one they are currently contracted to stops wanting the product, but there are 100s of others that will take it - you see this all the time with china made products with many different names.

With companies like Apple working with Foxcomm and demanding and policing standards, a new model was born. DJI is one early all china company that saw the benefit of doing it 'the western way'. I think ZWO is probably another. I don't see that in Sky Watcher - it all feels very much the old school model.

This idea that 'its built to a price' is total mince. For the price of our mounts we should expect massively higher engineering quality than we get. There is just no insentive for china to provide it.

 

Possibly the best concise analysis of the made in China syndrome I've seen here.

I made a few trips up the Pearl River Delta from Honkers in connection with the steelwork fabrication on a major HK project. I couldn't believe the fabrication yard. Beggared belief. Training pipe welders in the toilet cubicles was one notable. From farm hand to coded welder in a couple of days. Everything we rely on in our QA and QC systems virtually non existent, or tokenism. But stamped QC approved..

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I worked at a highly specialized, precision, manufacturing, engineering business.
Success meant a constant demand for more workers in an industrial desert.
Success attracted the attention of industrial sharks. The 70 man company was taken over by a very big, household name.

Production was closed down to manufacture in China. With only minor assembly and testing done back at home.
70+ workers were sacked on the flimsiest of excuses to avoid calling it redundancy. Some had decades of service.
Those decades of R&D and skill building was literally handed to China. They even exported the specialist machines.
To save them having to develop them from scratch. They were built in-house, in the EU, for repeatable high quality and turnover.

China needed countless billions worth of completed assemblies and got everything dirt cheap.
The quality of individual components from China [for testing by a few remaining souls] was so pathetically poor that it was laughable.
It took ages and countless exec trips abroad to raise standards to minimum acceptable, EU quality.

What was even more amusing was the speed at which copyist Chinese pirates got busy.
They started making and selling fraudulently marked, dangerous, lookalike crap using the globally respected, EU company name.
Who knows what toll the whole mess took on a vital service industry. It must have run into billions.
The cost to China [and elsewhere] in discovering which of these crooked wares were lethal, cosmetic copies, doesn't even bear thinking about!

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On 25/11/2021 at 09:31, Peter Drew said:

@EnceladusDan.   I think the easiest mitigation of the problem will be to do as you mentioned, tune the 90 degree potion of the Dec gear that is in most use.     🙂

There was a break in the clouds last night so I quickly set up and run the guiding assistant. Dec backlash measurement was aborted due to not enough south movement. I'm going to adjust to avoid using the worms tight spot and try again on next clear night. See how it looks if I only use part of the worm. 

 

Regards

Danny

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Further updates, I adjusted out as much backlash as I felt safe to do. The tight side of the worm was marked on a sticky label on the slow motion control. It left me with just under 180 degrees usable. 
F832EC5A-7C04-4AE5-9077-8C3B0A3A89DF.thumb.jpeg.dd7a27d10e75061365864d2d539feba1.jpeg

I orientated it so I can put the usable area inline with the worm carrier bolt as a reference. It felt much better and after calibration I ran the guide assistant which managed to complete the backlash measurement. It came back as 20,366 ms with a recommendation to guide in one direction as mentioned by Onikkinen. 

61F15A10-D6C2-4B88-BF90-72F7273AE426.thumb.png.11f3e192b4d0bad94c9043e4265a4f13.png
I guess that is a little on the large side so I’ll contact FLO for recommendations as the mount is still relatively new. 
thanks for help and guidance everyone. 
 

regards

Danny

Edited by Enceladus Dan
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2 hours ago, Enceladus Dan said:

Further updates, I adjusted out as much backlash as I felt safe to do. The tight side of the worm was marked on a sticky label on the slow motion control. It left me with just under 180 degrees usable. 
F832EC5A-7C04-4AE5-9077-8C3B0A3A89DF.thumb.jpeg.dd7a27d10e75061365864d2d539feba1.jpeg

I orientated it so I can put the usable area inline with the worm carrier bolt as a reference. It felt much better and after calibration I ran the guide assistant which managed to complete the backlash measurement. It came back as 20,366 ms with a recommendation to guide in one direction as mentioned by Onikkinen. 

61F15A10-D6C2-4B88-BF90-72F7273AE426.thumb.png.11f3e192b4d0bad94c9043e4265a4f13.png
I guess that is a little on the large side so I’ll contact FLO for recommendations as the mount is still relatively new. 
thanks for help and guidance everyone. 
 

regards

Danny

20 seconds of backlash is pretty wild... If possible definitely have a chat with the supplier if there is something they can do as that should be fixable with a new worm, unless there are some other issues at play also.

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I had a chat with FLO and the thought is, as others have stated these are cheap mounts and the fact I can track more than 45 seconds unguided is doing well. I asked about the worm drive going tight in the same spot each rotation means I can't adjust out all the backlash. 

The offer was I can send it back and they would tune it which is chargable service. for now I think my plan will be to plod on and try the 1 direction guiding. I could swap the worms but in my head it would create too much backlash in RA by the time I adjust out all the binding. Possibly could slip where so loose. 

I may look at just buying a worm drive online, I saw on teleskop-express.de they can do one shipped to UK for £55. 

Hopefully soon I can have a full night session and try some ling exposures as so far I've only practiced setting up my guiding system due to clouds. 

Regards

Danny

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