Re: [ATM] Why is it called a "flex rocker"?

["Dowd(s)" <kd14349@alltel.net>]

All,

So if you are looking at a tri-dob approach (three altitude bearings that 
are closely located to the three azimuth bearings) you can either:
    * flex the rocker and fix it in software
                                 OR
    * make a "rigid" rocker and fix it in software
If I'm listening/understanding correctly, a flex-rocker will conform 
physically to the ground ring track by deviating from a perfect 
mathematical algorithm describing rotation on a plane and you have to "fix 
it in software" (something I said a lot when I was an evil hardware 
engineer and expected my buddies in programming to overcome the limitations 
we discovered with real world devices).

And also a "rigid" rocker (which will have some flex in it) will likewise 
change it's plane as it tips it's way around the ground ring (azimuth) 
track - and need to be fixed in the SW also.  It tips it's way around the 
ground ring because the ground ring is not three points, but a whole bunch 
of points that don't lie in the exact same plane.

Both situations result in a wobble of the azimuth axis and could (by 
someone with more skill than me!) be fixed with supplemental algorithm and 
code.  (Or more duct tape?)

If I got it right, then Mel needs to add a line about coding to overcome 
hardware to his "duct tape and WD-40" mantra!  If not, <sigh>  back to 
kindergarten (again).

Also, I can't figure out how to make three azimuth bearings and three 
altitude bearings lie exactly in the same plane (the old three points 
define a plane discussion rather than six points).

I am excited however about minimizing beam (cantilever) length by stacking 
the altitude bearings on top of the azimuth bearings.  And I also can't see 
a way to make the two planes defined by three azimuth bearings and three 
altitude bearings become effectively parallel.

But then again, maybe I need to go back to the design requirements and 
determine HOW parallel the planes need to be to achieve the desired 
pointing (and tracking) accuracy.

Thanks!

Kevin.

>Date: Mon, 1 Aug 2005 10:12:54 -0700 (PDT)
>From: Dale Eason <atmpob@yahoo.com>
>Subject: Re: [ATM] Why is it called a "flex rocker"?
>To: atm@atmlist.net
>Message-ID: <20050801171254.79646.qmail@web50606.mail.yahoo.com>
>Content-Type: text/plain; charset=iso-8859-1
>
>
>Vladimir Galogaza recently asked several questions
>about how and why a flex rocker works in response to
>several emails.  Because the replies have been by
>several people and each talking about a different part
>of it, I think it has gotten confused.
>
>I would like to explain my understanding of it.  I
>used a flex rocker for my scope.
>
>http://home.comcast.net/~doeason/16inchscope.html
>
>My design is similar to what the originator of the
>design described.  That is, you want to support 4
>azimuth bearings on the ground board.  A stiff rocker
>makes that very hard to do. Becasue 4 points do not
>define a plane.  So you need to let the structure
>flex.  The idea is to support the altitude bearings so
>that they don't fall on the ground.  Let the ground
>board to that using the flex rocker to keep the
>altitude bearings over the stiff ground board.
>
>Vladimir asked if it was a requirment for a tri-dob
>that had only three azimuth bearings.  Mel's answer
>was not direct enough I think.  My take on what Mel
>said is:
>
>No, a flex rocker is not required for his tri-dob.
>But neither is a stiff rocker.  So why make a stiff
>rocker when a flex will do and is easier to make?
>
>
>Dale Eason



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