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Criterion Dynamax 8

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#201 apfever

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Posted 04 June 2015 - 05:50 PM

NO PICTURE HERE BECAUSE:

 

You are going to have to press apart one whopper of a tight assembly. The RA shaft with gears is not only a tight press into a bearing race, it's pressed in with cyanoacrylate (Super Glue).  You must jig this in a press correctly, and carefully, with supports in the right place, or you're just about guaranteed to shatter the cast arm base.  This pressure needed took me to the point of "OH Lord, you gotta be kidding me", and when the glue gave way the shock shook the shop.

 

The factory used a 3/4" thick steel plate with a custom hole bored in it. Think about that.

 

I want to jump around the process a little to show you how it is assembled, and get you familiar with it so you have an idea of what is coming apart, maybe violently, with a hefty specialty bearing and shaft shooting out the bottom of the press when it breaks free. Have your padding under the press to drop the RA shaft and bearing onto, just in case.


Edited by apfever, 04 June 2015 - 05:54 PM.


#202 Gil V

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Posted 05 June 2015 - 05:27 AM

After all this, did you get the mount pressed back together? Gonna be your biggest challenge. At the factory, it was done with a single, relatively quick pull on a manual Arbor press.

#203 apfever

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Posted 05 June 2015 - 07:20 PM

Lost internet for 48 hours. Just came back. I'll be busy for a few days recouping the down time.

 

Thankfully I have NOT pressed it all back together. I need to use the parts to show the assembly and jig set up. I also want to show all the mods from extra set screws in the gear retaining ring to trueing the setting circles, refelting, better gear assembly and more. Gil has seen some of these.

 

The RA shaft does press in the bearing but not ridiculously so. I can do a couple of test runs to feel out the preload. The biggest issue was getting that dang super glue to break, which covers a large surface area around the shaft. 

 

I replaced the safety bolt on the RA shaft end with a longer SS one, and deepened the tap in the end of the shaft. A lubed cap bolt and heavy washer may be sufficient to set the preload with precision control. I'll have it all worked out before wiping the drop of glue on for final assembly.


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#204 Gil V

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Posted 05 June 2015 - 09:38 PM

We would set up the whole assembly, put the bearing loosely in place, squirt a liberal amount of authentic Superglue around the entire bearing ID, and then press the whole thing together immediately after application of glue. Wear safety glasses, and press that bearing with one good stroke. The right amount of force, just until it "pushes back". Really a matter of feel. I wish I could tell you the pressure used, but I can't. It was a gear driven tabletop arbor press, the press was probably 30" tall.

#205 Gil V

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Posted 05 June 2015 - 09:42 PM

Then put in the screw and washer and tighten just to the point that the washer begins to deform.

If done properly, the mount will spin nicely with no play. Grab the polar shaft from the bottom and give it a spin!! Should not freewheel, should actually be stiff enough so it's not all that easy to spin the shaft just by grabbing it with your bare hand.

#206 Gil V

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Posted 06 June 2015 - 08:53 AM

Another thing - when you tighten the screw in the top of the polar shaft, you'll have to hold the lower end of the polar shaft in a vice (or something similar).

#207 apfever

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Posted 06 June 2015 - 11:24 AM

Another thing - when you tighten the screw in the top of the polar shaft, you'll have to hold the lower end of the polar shaft in a vice (or something similar).

 

The standard here is to drill a matching hole in a block of wood (scrap 2X4). Cut the block through the middle of the hole (band saw here for little kerf).  Then clamp the shaft between the blocks in a vice. This can be tightened as much as you want with no damage to the shaft, until the blocks break. It's best to cut the blocks from end to end instead of across the 2X4. This gives a much stronger grain unless you chance into a board that is quarter sawn in which case get another board.




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