[simpits-tech] More Projector questions,

[Darren Beaumont]

Derek,

A vacuum has to be applied to the mylar mirror system, every time you want
to use the visual system.

I was having a conversation with our Flight Training Manager at work about
flight simulators, and he told me an interesting story about these systems.
When he worked at Crossair, he used to spend a lot of time on the Saab 340
and Saab 2000 sims, with the sim tech.  Apparently the projectors had to be
kept online 24/7, except for essential maintenance (there was a screen saver
introduced into the visual system).  If not, the projectors would slowly go
out of alignment, due to heating/cooling cycle of the CRT tubes.  He said
there was weird and wonderful effects when the projectors were out of
alignment, and caused a few incidents of 'motion' sickness.

There is an excellent text book on Flight Simulation - called Flight
Simulation by J M Rolfe and K J Staples - ISBN 0-521-35751-9.  The book is a
few years old, it was first published in 1986, but is full of useful info,
from the history of Flight Simulation, to visual systems, hardware,
mathematical models, design of instructor stations and a lot of other info.
Anyway, this book has a description and diagram of the visual system you are
planning.

If you have around £2000 spare, there is a week long course at Cranfield Uni
on Flight Simulation where J M Rolfe is one of the lecturers.  I have been
told, by our Flight Training Manager, that the course is superb.

Darren


-----Original Message-----
From: simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org]On Behalf Of D E
Sent: 18 October 2002 14:51
To: simpits-tech@simpits.org
Subject: Re: [simpits-tech] More Projector questions,


Hey all,

Part of my 'flight sim' project, although further off in the future for now,
is to build an off axis rear projected type of visual system (similar to the
ones used in commercial flight sims).

For the collimating mirror, I thought this looks like the way to go ..

http://www.nielsensenterprises.com/snomo/mylar.htm

seems quite reasonable in price ..

I am designing a curved frame (which is a lower section of a sphere), the
mylar will be attached to this frame at the edges and then a vacuum applied
to it which will bring the sheet to the right tension.

Does a vacuum have to be appplied to it all the time? (is the mylar
permeable?)

I am still working out the angles on CAD .. seems like it is do-able.

As i mentioned before .. I am a fair way off from making this .. but even if
it doesn't work, I don't think i will have lost much (Apart from hours of
dreaming).

Derek







>From: Allen Buffington <allen@simworld.biz>
>Reply-To: simpits-tech@simpits.org
>To: simpits-tech@simpits.org
>Subject: Re: [simpits-tech] More Projector questions,
>Date: Thu, 17 Oct 2002 18:05:51 -0600
>
>Yes, this is an option however you should use a "first surface" optical
>grade mirror.
>A first surface mirror has the reflective coating on the surface of the
>glass,
>whereas regular mirrors have the reflective surface on the back of the
>glass.
>Rear projection TV's use a first surface mirror. This might be a source
>of finding
>a usable mirror that could work for you. You could check with some TV
>repair shops
>and see if any have a unrepairable TV cabinet and convert it to your
>use.
>Using a regular mirror you will get an unwanted ghost image reflected
>off the glass
>surface as well as the silver reflecting surface.
>
>~~Allen
>
>Johan Nauwelaertz de Agé wrote:
>
> > Thanks for the info Sean, Is it possible to use a setup as on the
> > picture? I have lack of distance in front of the cockpit and thought
> > it might work with a mirror to double the distance, but what happens
> > with the picture / quality? Damn I'm to tired to figure it out
> > myself. Johan
>
>
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