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cnchillstar
super member
Reged: 12/29/08
Posts: 102
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Hi, I notice all high level GEM mount applying a very strong counter weight shaft. ME-38mm, others like AP and mountain, even with a 40mm diameter.
how are those big shafts threaded with Dec body? If they are threaded to Dec shaft and rotate together, it seems that Dec shaft is relatively smaller female thread to have it in. or the counter weight shaft just link to Dec body and doesn't rotate?
thanks!
Image removed by moderator. You may not reproduce images from other web sites on Cloudy Nights.
Edited by Don W (10/09/09 04:48 PM)
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Ian Robinson
Pooh-Bah
Reged: 01/29/09
Posts: 1166
Loc: Gateshead.NSW Nth Coast,Austra...
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My Vixen Atlux has a 1" shaft , and it slides out , is not screwed on.
It may be that the mass of the bigger diameter counterweight shafts is actually also acting as significant component of the counterweight torque , you can check this by assuming a density of 8000kg/cum and partitioning up the length of the counterweight shaft (by 8 or 16 partitions) and summing up the torque contribute (mass x distance from the RA pivot point) for each partition of the counterweight shaft.
It may also be that the extra thick counterweight shafts are for cosmetic rather than mechanical needs.
Or they may be using a lower spec steel in their counterweight shafts so they compensate by goung to thick bar.
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cnchillstar
super member
Reged: 12/29/08
Posts: 102
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Hi,thanks for reply! but I am difficult to get the point so far. does anyone know how commercial professional mounts link their counter weight shaft to Dec body?
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cnchillstar
super member
Reged: 12/29/08
Posts: 102
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any help? thanks a lot!
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cnchillstar
super member
Reged: 12/29/08
Posts: 102
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maybe for small GEM mount like eq6 or even lasmandy G11, it will be threaded directly to DEC axis. but I check AP document(when assemble with Dec encoder) and meade max mount, find it seems that the counter weight shaft is link to DEC housing only and will not rotate.
anyone who use those mount know the details?
what will be the advantage or disadvantage for each method from mechanical view?
thanks!
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polaraligned
sage
Reged: 12/26/08
Posts: 233
Loc: P. R. of New Jersey
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Thread it to the housing not the dec shaft.
Take a look at the Paramount.
If you thread it to the dec shaft you exert bending forces from the counterweight shaft to the dec shaft.
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Galaxyhunter
Pooh-Bah
Reged: 01/02/06
Posts: 1257
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Quote:
Thread it to the housing not the dec shaft.
Take a look at the Paramount.
If you thread it to the dec shaft you exert bending forces from the counterweight shaft to the dec shaft.
Thats what I did when I built my scope.
Look here, I mounted the weight onto a bracket to keep it off of the Dec axle.
--------------------
Carl
My lousy skies at Hawkeye Observatory
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cnchillstar
super member
Reged: 12/29/08
Posts: 102
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thanks for replies, now I am clear about this!
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