Re: [ATM] Secondary Cage Calculations

[David Weinshenker <daze39@earthlink.net>]

Jacob Lauser wrote:
> 
> Does anyone have their Kriege and Berry book laying around?
> 
> I loaned mine out thinking I had memorized it all, but the details are
> foggy now.
> 
> Can someone give me all the calculations for the secondary cage
> assembly? I'm trying to size the tubes and wooden rings for my new
> design this weekend but have no specs and tube thickness, etc.



Hello,

The Kriege + Berry book suggests secondary cage 
dimensions as follows (for aperture 14.5-25"):

ring ID = aperture + 1% of focal length

strut tube length = 60% of aperture

ring thickness vs. aperture (for HVHC plywood):
 1/2" (up to 15" aperture)
 5/8" (16-20")
 3/4" (22" + over)

ring width vs. aperture
 1-1/2" (through 16")
 1-5/8" (17.5-18")
 1-3/4" (20")
 1-7/8" (22")
 2"     (24-25")

strut tube OD vs. aperture (.055" wall)
 1"     (through 16")
 1-1/4" (17.5-22")
 1-1/2" (24-25")

Was this the data you were looking for?

-dave w
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