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Evolution 8-Mount bolts pitch circle diameter?

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#1 Rac19

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Posted 26 May 2020 - 06:10 PM

I am about to build a backyard pier and need to drill three holes to secure the Evolution 8 mount to an aluminium plate. To do this I need to know the pitch circle diameter (PCD) of the holes. Assume that the dimensions are in inches, it looks like the radius is 3.25" meaning that the PCD is 6.5". Can anyone confirm this?

 

By the way, if anyone has information on the centre pin, that would be useful.

 

For anyone who is interested, the design for the pier and some very useful comments can be found at the link below. Any further comments are welcome.

 

https://www.cloudyni...nce-of-working/

 

EDIT: Corrected the PCD to 6.5", hopefully before too many of you noticedsmile.gif .


Edited by Rac19, 26 May 2020 - 06:49 PM.


#2 WarmWeatherGuy

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Posted 26 May 2020 - 06:19 PM

I just measured my Evo tripod from the center pin to the center of one of the bolts. I get 82mm = 3.23" which is probably 3.25" but twice that is 6.5 and not 7.5. It looks like the diameter of the center pin is 0.25 inch. This should get you in the ballpark.



#3 Rac19

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Posted 26 May 2020 - 06:47 PM

I just measured my Evo tripod from the center pin to the center of one of the bolts. I get 82mm = 3.23" which is probably 3.25" but twice that is 6.5 and not 7.5. It looks like the diameter of the center pin is 0.25 inch. This should get you in the ballpark.

Thanks, I was hoping to fix the diameter before anyone noticedsmile.gif.

 

I have seen drawings for other Celestron mounts with a radius of 3". It's definitely more than that and 3.25" seems to be closest in inches. Of course Celestron may have gone metris for the Evolution series but 82 mm doesn't seem to be a "logical" choice.
 



#4 mclewis1

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Posted 27 May 2020 - 08:12 AM

When you are reviewing drawings for other Celestron scopes remember that there are sometimes two sets of mounting bolts ... one for use with a wedge (smaller circle), and the other for the tripod head. 

 

I believe that virtually all the Celestron Alt Az mounts use the 6.5" diameter circle of 3 bolts (3/8" x 16tpi) and I don't think that the Evolution has changed from that.



#5 Rac19

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Posted 27 May 2020 - 02:47 PM

When you are reviewing drawings for other Celestron scopes remember that there are sometimes two sets of mounting bolts ... one for use with a wedge (smaller circle), and the other for the tripod head. 

 

I believe that virtually all the Celestron Alt Az mounts use the 6.5" diameter circle of 3 bolts (3/8" x 16tpi) and I don't think that the Evolution has changed from that.

Thanks, I have noticed the two sets of holes. The Evolution wedge uses the same bolts as tripod. I am pretty confident that it is 6.5" and not a metric dimension.



#6 mrki233

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Posted 28 May 2020 - 01:19 PM

Rac19,

 

On my Evo tripod, the distance from the center of the centering pin to the center of a mounting bolt is 3.25", so I think your 6.5" dimension will be correct.

 

The center pin is 3/8" tall (from the top of the collar to the top of the pin) and is 7.19mm in diameter (9/32 or .28 inches).

 

See pics for reference.  If you need any other dimensions or pics, just let me know.

 

p.s.  Nice pier design!

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Edited by mrki233, 28 May 2020 - 01:19 PM.


#7 Rac19

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Posted 09 June 2020 - 03:54 PM

Having now completed my pier I have some answers on this.

 

I found that marking out the holes, given the "instruments" at my disposal, was not accurate enough.

 

Geometrically, it's straightforward. Draw a 3.25" circle, rule a line through the centre then draw an arc (the same radius) centred on the opposite end of the line to create two intersections at 60 degrees either side. This is the geometric procedure for creating a hexagon in fact.
 

I punch marked and drilled three holes 120 degrees apart with a hand held power drill. I suspect that the marking was not accurate enough and perhaps the drill wandered a little. The result was not accurate enough, whatever the reasons.

 

My solution was to use the tripod head as a template. I removed the three captive bolts. One of the E clips pinged across room never to be seen againmad.gif. I then clamped the tripod, inverted, on top of the aluminium plate, with centre pin engaged and drilled holes with a 10.5 mm drill bit. The bolts now fitted but one was a little tight so I drilled the holes out to 12.5 mm. The torque limit must be set on the drill when doing this, to avoid a sprained/broken wrist.

 

For the centre pin I drilled an 17/64" hole and tapped it with an M5, 1.25 mm pitch (coarse) thread. An M5 x 20 mm set screw was screwed in from underneath projecting 10 mm above the surface.

 

With either the Evolution mount or the wedge engaged with the centre pin, it is a reasonably simple matter to engage the three securing bolts.

 

In the image below you can see an inner circle of six holes forming a hexagon. Three of them are the marked out holes which were not accurate enough, the other three (rotated 180 degrees) were drilled with the tripod head as a template. The 3.25" circle used for marking out is not visible in the image.

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Edited by Rac19, 09 June 2020 - 11:36 PM.

  • Michael_Swanson, mclewis1 and WarmWeatherGuy like this


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