PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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After tapping each set of 3 holes to mount the Capture Blocks...check to see that everything fits properly.
316 SS cap screws fasten the block to the back.
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A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Ok, let's see how the collimation plate fits now...and while we are at it place the fans in the recesses.
Houston, We have a problem!!!!!!!!
Only one of the fans fit into the recess.
Quick check with the digital calipers...yes, the first one is correct and fits in the left front hole...
But the other 2 are 0.050" larger...
These are ADDA Model AD0912HX-A70GL's Top of the line.
Sadly, 2 differant lot numbers and made guess where...
Grasshopper, you are TOO trusting and design with tight tolerances...
I think that I can sand off enough to make them work...
We'll see tomorrow. And hopefully UPS will be delivering most of the metal bits needed to proceed further.
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A few I enjoy,
and a few more in the works ;<)
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Sky Captain
Scope Builder
Reged: 11/07/04
Posts: 5743
Loc: Seattle Washington
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Quote:
Note the aluminum block with a hole just larger than the thread size to act as a guide to keep the tap perpendicular to the surface
Thats a nice tip Preston, I may use that next time. 
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Equipment Overload!
Kerry.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Thanks Kerry, I learned that from Dennis Borgman while installing the mount for the 11 inch refractor on the 36 inch RC at the George Observatory...
Ok, today we did a lot of tapping of 10-32 holes in the 2 mid rings and the upper ring to attach the ball catch blocks.
These will catch the ball ends that fit into the ends of the carbon fiber truss tubes.
Anyway, we mounted the mid rings onto the back plate and clamped them in place while doing the tapping.
Again, using the tapping guide with masking tape on both ends to hold the block above the surface being tapped.
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A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Next, again checking that the Catch Blocks fit the mid rings...Yes, no problem's here 
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A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Ok, 36 holes tapped and chanfered on both sides...Done.
Now to align the spindle drill chuck with the center of the rotary table...
Then we can go to the outside and drill the 4 sets of 3 holes to attach the 2 mid rings together...
And finally add the 2 offset dowel pin holes so that everything stays aligned if and when the upper and lower section are seperated...which I hope is not TOO often.
Pic showing 2 pieces of 0.500 inch bearing shaft, one the drill chuck (upper) and one in the rotary table (lower)
Nice alignment 
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Now to the outside of a mid ring to rotate the rotary table until the tapered point fits the middle hole for the Capture Block.
Align and tighten the rotary table chuck with rotary table set to zero degrees...then a simple move to 90, 180 and 270 and we can put in the sets of holes to bolt the 2 haves together.
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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It always amazes people at just how long it takes to do much of this work...but it is the setup thats most of the time, as if it's wrong 
You may end up with scrap...and have many hours of rework.
The pic shows the through drilling of the Capture Block holes...but they were all first spot drilled, then through drilled for the tape size and then the top plate only was drilled through for a slip fit of the 10-32 cap screw...
Note that there are 2 mid rings clamped together so everything will be aligned perfectly when we are finished.
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Notice the use of the little jack under the main back plate.
The center hole is only 4.5 inchs in diameter and the point that we were drilling was at about the 12.5 radius...
Without blocking of some sort, the force of drilling that far out would likely cause the chuck to loose its hold and the part would be badly damaged.
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Pic from the inside of the mid ring showing the offset dowel pin hole being reamed through both plates as the same time.
The opposite side of the mid ring gets a similar hole, but offset so that the 2 rings can only get fastened together in one orientation...
Hopefully, this will allow the collimation to remain very accurate even if the upper and lower truss sections are seperated for travel purposes.
RC collimation is very critical and the tolerances are just a few thousands of an inch in any direction.
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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And finally a shot of the whole setup on the mill table and mounted to the rotary table.
Everything is finished for this setup other that chanfering the 14 holes times 4 faces...56 chanfers...
Until tomorrow.
Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Well, sometimes the thing that you think will go the easiest are not so friendly...
I had planned to remove the Capture Blocks from my mockup and install then on the back plate and mid ring...thinking the the 1/2 set up I used for the mockup would be just fine...
Well, this pic is the mockup on MDF behind the new Back Plate
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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As you can see in the last pic, I only made 4 lower and 4 upper truss tubes in PVC for testing purposes...
Did not take a pic of the new Back Plate and Mid Ring with only the 4 lower truss mockup tubes...but it was not pretty.
And I was out of the correct size of PVC...so off to Home Depot...
Back at the lathe, frustration sets in...dial everything in and bore the ID of the first tube end...fits the end fitting nicely.
Flip it around and bore the other end to the same indication on the DRO (Digital Read OUT) and do a test fit on the end...
It is TOO tight...this went on and on until I finally realized that the 0.050" cut I was taking was warming up the plastic and then when it cooled...the dimension shrank...
Well I finally got 4 lower and upper new mockup tubes finished.
The pic below shows the lower truss with all 8 short truss's mocked up using the PVC tubes...Tomorrow we'll do the upper truss assembly.
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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It's really supprising just how stiff everything is with just the PVC truss tubes...
Once we get all of the subassembly finished and can make sure the distance between the primary and secondary is 31.5", then we will replace the PVC tubes with the carbon fiber tubes...in the mean time these will work just fine for getting measurements.
Pic below showing the truss tubes with end fittings pushed into the PVC, and the Invar ballends going into the end fittings.
Once we have the upper truss assembled, we can measure the angle that the Invar ball ends exit the Ball Capture blocks on the lower and upper assemble. We will use this info to machine the releaf slot on the Captuer block so that the Invar ball end only touches the circular faces in the Capture block.
That's it for today,
Enjoy.
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A few I enjoy,
and a few more in the works ;<)
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rwiederrich
Goldfinger
Reged: 11/17/05
Posts: 6006
Loc: Bremerton Washington
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Good grief Preston......Your scope is awesome...
My pidly attempts at this machining thing pales in the bright light of your gig.
Well...I am a scrounger and that is how I approach my scopes.
Looks great. Well off to the machine shop to get at it again too...... 
Rob
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www.goldmtobservingcenter.com
Providing a great place for amateur astronomers, and ATM's to come and enjoy their hobby.
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Hi Rob .... I to am a scronger...but I scrounge when it mades since...
Like my 90 degree adapter for the Bridgeport mill...
I lost over 20 of them...and then got one with the back support for less than half of what they wanted for just the 90 degree part...
It's timing...
And it was timing that got us to this 20 inch RC build!!!!
In the back ground of the 2nd to the last pic is the Unfinished Telescope by Paul Van Slyke...and my model of this scope...a much heavyer version...
In the next few shots...I'll take Off the plastic sheet when doing the shots of the New RC.
Best Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
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PrestonE
scholastic sledgehammer
Reged: 04/29/05
Posts: 817
Loc: Houston,Texas
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Ok This has been fun...but we need more outside comments!!!!
You are watching...per the over 2000 views of this thread...
Please comment...This is not the holy grail...
You have sent me private messages when it looked like I'd end the thread the o  ther day...
It's not ended...so come on...say something!!!!!!!!!!!!
Best Regards,
Preston
--------------------
A few I enjoy,
and a few more in the works ;<)
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Ben Mullin
member
Reged: 08/26/05
Posts: 97
Loc: Lindstrom, MN
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Inspirational, awesome, looking really good, looking forward to seeing the outcome, keep up the good work...
Seriously, this thread is in my list of reference links when I need inspiration. I have no content to add, but am watching and was one of the PMs when you threatened to take the eye candy away
Ben
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Sky Captain
Scope Builder
Reged: 11/07/04
Posts: 5743
Loc: Seattle Washington
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Quote:
Please comment...This is not the holy grail...
That scope is looking HOT Preston!!!!!!!!!!
The capture blocks for the truss poles are incredible!!!
And to think I've touched\handled you scope already...very exciting.
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Equipment Overload!
Kerry.
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Owen
sage
Reged: 06/21/07
Posts: 353
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Its awe inspiring stuff.
I'm watching, and looking forward to hearing about first light.
Owen
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