[simpits-tech] Using real instruments

Sat, 25 Jan 2003 18:49:59 -0500

Great work, Craig.

Once again, you have taken a lead role in this effort and have come up with
an innovative idea.

I have the same type of altimeter and look forward to your final write up so
I can do the same.

Marv

On 1/25/03 4:49 PM, "Craig Rochester" <johncraigroch@msn.com> wrote:

> Success!
> 
> Following up on my thinking that the pneumatic instruments could be driven
> by compressed air, I did this:
> 
> I took the face cover off, removed the hands and dial faces, remove a
> retaining ring (circle clip) and extracted the barometer assembly.  I
> drilled a small hole in each of the two bellows inside.  The bellows were
> under vacuum and the bellows expanded and drove the linkage to their full
> range (~ 60,000').
> 
> This is great!  Sometimes things work out. :D
> 
> I resealed the bellows by soldering the holes.  I reassembled the Altimeter
> and set the dials to 5,3000' (room pressure).  I can now apply
> 0.1-7.75(approx.) psi pressure and the Altimeter spins from 50,000'
> to -1,000'.  That was pretty easy.  The hardest part of the whole mod was
> taking it apart and reassembling it without damaging the works.
> 
> Unfortunatly, I didn't expect it to work the first time and didn't take any
> pics.
> 
> Craig R.
> 
> -----Original Message-----
> From: simpits-tech-admin@simpits.org
> [mailto:simpits-tech-admin@simpits.org]On Behalf Of Craig Rochester
> Sent: Friday, January 24, 2003 9:34 PM
> To: simpits-tech@simpits.org
> Subject: RE: [simpits-tech] Using real instruments
> 
> 
> Ok, I bought the Altimeter.  I took it apart(a delicate task).  It could
> definitely be driven by vacuum, but I'm going to try to modify it to be
> driven by pressure.  The ASTEK meter I have works by the expansion of two
> sealed metal bellows expanding as the atmospheric pressure decreases at
> higher altitudes.  I'm going to drill a hole in each bellows, port them, and
> try pressurizing the bellows.  In theory this will be equivalent to applying
> a vacuum to the outside.  If it works I'll post pics of the results.
> Otherwise...anyone interested in a ruined Altimeter? :)
> 
> Craig R.
> 
> -----Original Message-----
> From: simpits-tech-admin@simpits.org
> [mailto:simpits-tech-admin@simpits.org]On Behalf Of Craig Rochester
> Sent: Wednesday, January 08, 2003 8:39 PM
> To: simpits-tech@simpits.org
> Subject: RE: [simpits-tech] Using real instruments
> 
> 
> I'm thinking driving the real instruments from two(2) electronic regulators
> would be simpler than modifying each instrument.  Particularly if you were
> doing a dual pit.  I don't know what the leak rate is on the VSI, but the
> rest could be run from a tiny compressor(and vacuum pump if required).
> Barometric pressure varies from 14.7 psia(0 gage pressure) @ sea-level and
> decreases to about 1.1 psia @ 60,000 feet.  If you could modify or adjust
> the Air Speed Indicator and Altimeter to be off-set down by about 15 psi,
> you could use pressure instead of vacuum.
> 
> I know the pneumatic altimeters uses a sealed metal bellows that expands as
> the barometric pressure falls with altitude.  The movement of the bellows is
> converted to dial rotation with gears and levers. Maybe there is enough
> adjustment in the works to have the instrument read 60,000 feet with no
> applied pressure and then output 1-15 psi from the regulator.  Or maybe a
> fitting could be fashioned to the bellows and connected to the regulator.
> 
> I see electronic pressure regulators on eBay pretty often:
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=26210&item=3105137770
> They're called an I/P transducer(eye-to-pee) current to pressure or
> V/P(vee-to-pee) voltage to pressure transducer.
> 
> Craig R.
> 
> -----Original Message-----
> From:    simpits-tech-admin@simpits.org
[mailto:simpits-tech-admin@simpits.org]
> On Behalf Of Matt Bailey
> Sent:    Wednesday, January 08, 2003 5:04 PM
> To:    simpits-tech@simpits.org
> Subject:    Re: [simpits-tech] Using real instruments
> 
> I remember talking about using an air compressor to control real gauges
> several months ago. Sounds like a GREAT idea to me, a little more complex
> than just using servos but the extra realism in gauge movement would
> probably
> be worth it. Not to mention the utter coolness of being able to drop a REAL,
> UNMODIFIED instrument directly into your sim. The instruments themselves are
> pricey though, unless you found an old junk instrument but that would defeat
> the purpose of making your sim accept real instruments since the instrument
> would not work. :)
> 
> Driving gyro instruments like the turn coordinator I suppose could be done
> with servos driving the gyro cages (although the ball is just a ball in a
> glass tube, it's not driven by any mechanical device in real life so it
> would
> probably have to be totally reworked) or just removing the gyros completely
> and hooking a servo directly to the small aircraft representation. Anyone
> done this?
> 
> -Matt Bailey
> _______________________________________________
> Simpits-tech mailing list
> Simpits-tech@simpits.org
> http://www.simpits.org/mailman/listinfo/simpits-tech
> To unsubscribe, please see the instructions at the bottom of the above page.
> Thanks!
> 
> 
> _______________________________________________
> Simpits-tech mailing list
> Simpits-tech@simpits.org
> http://www.simpits.org/mailman/listinfo/simpits-tech
> To unsubscribe, please see the instructions at the bottom of the above page.
> Thanks!
> 
> 
> 
> _______________________________________________
> Simpits-tech mailing list
> Simpits-tech@simpits.org
> http://www.simpits.org/mailman/listinfo/simpits-tech
> To unsubscribe, please see the instructions at the bottom of the above page.
> Thanks!
> 
> 
> 
> _______________________________________________
> Simpits-tech mailing list
> Simpits-tech@simpits.org
> http://www.simpits.org/mailman/listinfo/simpits-tech
> To unsubscribe, please see the instructions at the bottom of the above page.
> Thanks!