Re: ATM Mirror box and rocker box height issues

["A&S Hincks" <hincks@bigpond.net.au>]

Really great looking scopes Kurt - nice web site too...

I might start thinking about using springs. I can't imagine they would cost
too much to import if I have some trouble sourcing them over here.

I think I'm going to need to do some reading about how springs behave as
they stretch (ie. changing forces etc.)  Seem to recall there was article
about them in S&T one or two years ago (I'll go away and blow the dust off
them).

On the subject of ring thickness I have already built the secondary cage and
mirror cell unfortunately but I guess the 15mm plywood is only a whisker
over 0.5" anyway at about 5/8".

I haven't built the mirror box yet as I am still playing with the design in
CAD and MS Excel so I still have the opportunity to tinker with the spring
idea before I 'throw caution to the wind' and start rippin' into that wood.
I have some 18mm/3.4" ply for the box that I thought might help
counterweight the top end a wee bit - even if 3/4" ply probably isn't
strictly necessary down there. Ultimately though, the extra thickness falls
quite a way short as an effective conterweight for a light mirror (ie if
your aim is to keep the profile low.).

Cheers

Andrew Hincks
----- Original Message -----
From: <NGC704@aol.com>
To: <atm@shore.net>
Sent: Saturday, February 02, 2002 11:27 AM
Subject: Re: ATM Mirror box and rocker box height issues


>
> In a message dated 2/1/2002 5:30:18 PM Central Standard Time,
> hincks@bigpond.net.au writes:
>
> > either need to add weight to the bottom of the box or lighten the top
end.
>
> Andrew:
>
>     Or just lighten the whole thing. 1/2", or 12mm (?), plywood is plenty
for
> the mirror box and top end components. Build your telescope the way you
want
> it and then add a spring counterweight to balance it. Do try to keep the
> upper end as light as possible, though. It will make life easier.
>
>     I don't particularly like building an out-of-balance telescope, but
> sometimes it is the best option. Like when dealing with a lightweight
mirror.
> I did this recently on a 16" f/5 dob I built for a friend; see the results
at
> < http://members.aol.com/funyfrm/Scopes.html >
>
>     The spring counterweight is barely visible in the photo showing the
two
> Lester 'scopes together. A very simple, yet effective solution. The
22-incher
> didn't need one, as the weight of the primary mirror was sufficient to
> balance it. The finished telescope is relatively compact since I avoided
> accomodating a high center of gravity with excess structure by
> counterweighting it, and very light since I used a spring instead of lead.
>
> Regards,
> Kurt Maurer
> League City, Texas
> http://members.aol.com/NGC704/NGs.html
>