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what's the PE on the old AP 600E and 800 mounts?

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#26 orlyandico


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Posted 30 November 2012 - 12:35 AM

I'm fairly sure the mount wasn't used in a permanent setup, as the previous owner also had a 1200DA...

Well I'll buff the bushings as Ed says, use the anti stiction grease, and see...

#27 zerro1


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Posted 30 November 2012 - 09:44 AM


The actual ingredient of the "limited slip" additive is jojoba oil.

#28 EFT


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Posted 30 November 2012 - 10:30 AM

I took apart a Vixen GP and it also had bushings.

I would not consider this to be "bad design" - Ed Thomas can probably weigh in here but well-made bushings would probably outperform poorly-made bearings (like those in the China mounts).

This is also why you've got a lot of folks replacing the bearings in their China mounts with Timken or SKF bearings.

I had thought about replacing the main declination bushing with a large bearing - but it would require massive machining and destroy the value of the AP600 as an antique / collectible.

There used to be a long waiting list on AP600's - I can imagine Wally toiling at the mill / lathe making each of these by hand without benefit of CNC :D :D :D

There is certainly nothing wrong with a well designed and implemented bushing system. The precision needs to be high though and wear could certainly be an issue faster than a bearing system. It might be possible for a good machinist to make a new set of bushings to replace the old ones. But I would want him/her to be a very good machinist to do it right.

#29 andysea


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Posted 30 November 2012 - 04:26 PM

So Ed,
Do you think that a bushing design would put the same amount of strain on the same portion of the bushing and overtime result in uneven wear? This should be inherent to the design, correct? Unless the mount is always perfectly lubricated.


#30 ohioalfa64


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Posted 17 March 2013 - 04:19 PM

Alternatively, you can machine small Dimples in the bronze bushing and apply graphite impregnated grease. Canadian bridge design code uses this bearing design for minimizing friction (limited rotation) bearings. It is argued back and forth in the industry whether this really has a benefit or whether the graphite grease just mucks things up. The surface RMS of the shaft and bushing are both sufficiently polished?

#31 orlyandico


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Posted 17 March 2013 - 10:51 PM

well... I managed to pull a 600-second unguided sub out of the AP600 last night.

The raw PE is about 8" and it gets down to 2" with a good PEM training (which took me a long time, because the 9000 controller is "dumb" and a really good polar alignment is required to avoid RA drift).

In summary... with a very good polar align, declination guiding is minimized and the DEC stiction issue can be side stepped.

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