re:Re: Drawing a Parabola ?

Funny you should be trying to make a lamp concentrator. A parabola was used
for such things until about 20 years ago when a far more efficient curve was
developed. It is known as the compound parabolic concentrator (CPC). There
are hundred of references on the web, take your pick.
The CPC has the property that all of the light in its entrance port is
transferred to the exit port in a specified angle range. These are widely
used for lamps and solar concentrators.
At the limit of large reflector/small light source/small beam angle the CPC
reduces to the parabola.
If you want high enough efficiency to set things on fire, use the CPC.

Carley lamps (carleylamps.com) sells machined aluminum lamp reflectors for a
very reasonable price. These are made for their miniature lamps, but can be
made to fit others. Carley has very high quality lamps, I've used them for
years and have been satisfied. These are not hardware store junk- are used
for medical illumination and such. Good lamp bases, too.

Elliot Burke

Date: Fri, 13 Apr 2001 22:09:15 -0400
From: "Rich D." <cmsteam@...>
Subject: Re: Drawing a Parabola ?

Jeff and all,
Thankyou very much for your help. Jeff sent a Lisp file to me
and it's just what the doctor ordered. Generates the parabola
perfectly in a polyline form (not the dreaded spline) that only
needs exploding to seperate entities for g-code in a snap.
I will be, hopefully, machining a reflector for a miniature
locomotive on a temporary lathe CNC setup.
Borrowed plastic flashlight units can't stand the
heat above the boiler.
Rich D.

abscissa wrote:

>
> try this, from the old Compuserve Acad Forum
>
> parabola.lsp
>
> save to c:\acad\support
>
> (load"parabola")<Enter>
> parabola<Enter>
>

Elliot Burke
HighTide Instruments