Return-Path: Received: from email2k3.itlnet.net ([64.19.112.12] verified) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 750547 for flyrotary@lancaironline.net; Sat, 19 Feb 2005 13:53:35 -0500 Received-SPF: none receiver=logan.com; client-ip=64.19.112.12; envelope-from=jwvoto@itlnet.net Received: from rav.itlnet.net (unverified [192.168.10.149]) by itlnet.net (Rockliffe SMTPRA 6.1.17) with SMTP id for ; Sat, 19 Feb 2005 12:52:50 -0600 Received: from JWVOTO (unverified [64.19.116.28]) by itlnet.net (Rockliffe SMTPRA 6.1.17) with SMTP id for ; Sat, 19 Feb 2005 12:52:49 -0600 Message-ID: <038301c516b4$a76585e0$3a721340@JWVOTO> From: "Wendell Voto" To: "Rotary motors in aircraft" References: Subject: Re: [FlyRotary] Re: Digital Fuel Monitoring System Date: Sat, 19 Feb 2005 12:54:52 -0600 MIME-Version: 1.0 Content-Type: multipart/alternative; boundary="----=_NextPart_000_0379_01C51682.34092020" X-Priority: 3 X-MSMail-Priority: Normal X-Mailer: Microsoft Outlook Express 5.50.4133.2400 X-MimeOLE: Produced By Microsoft MimeOLE V5.50.4133.2400 This is a multi-part message in MIME format. ------=_NextPart_000_0379_01C51682.34092020 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Subject: [FlyRotary] Re: Digital Fuel Monitoring System Hi Ed. This of course all only applies to electronics in a vibration exposed = environment. Good practice, as I was taught it many years ago, is to have hole = spacings to allow components to lie flat on the board. Of course there are exceptions like power resistors that need airflow = around them, but they should be mounted with "stand-offs" (small tubes = on their legs). The rule used to be that components should not be held = in place by the solder, but by their mechanical mounting. That's why the = pins are typically bent 45 degrees where they stick through the PCB = before being cut off and soldered. Heavy components are additionally = secured with some kind of mechanical fastener or globs of goo (technical = term). Now obviously the weight of the body of the component in = relationship to number of pins/legs is a factor. An example would be an = IC with oodles (another technical term) of pins. I "grew up" in a company that secialized in sound and vibration. It = was very educational to watch a PCB board mounted on a "shaker" = (basically a loudspeaker where there membrame was replaced with a = mounting place) lit with a strobe light synchronized to the frequency = sweep. Components dancing around and finally falling off if not properly = supported (mounted). But that was then. Now we have surface mounted components which I know = nothing about... Finn (Looks like I've been kicked off the list again) Geez, Finn, I was unaware that there was a "protocol" for resistor = sizes on PC boards. Seriously, is there some reason (vibration?) for = forcing resistors all the way to the board or is it just "esthetics?". Ed A I still say your pc board looks good for a rotary engine. I couldn't = tell from the pic if the resistors are 1/4 or 1/2 watt.Those film = resistors can take a lot of punishment. Standing a resistor vertically = on end allows more movement. The yellow tantalum capacitor is the = weakest component I see, more easily damaged in soldering as over = heating will damage the lead internally. The resistor next to the pot = might be put down to prevent it from bending over and touching the pot.=20 Is this a proto-type or to be put in aircraft? If going in aircraft, = I think sealed pots might be a good choice. You should mount power resistors off the board so that the heat can = dissipate without burning the pc board but you don't have any that I = saw. Many manufactures use little spacers to do this using water = soluble spacers. In my estimation, those little tubular spacers many = use that are made of Teflon don't help rigidity much, but look cool. If you want mil-spec board that is one thing but for our use I think = Ed's board is OK except for above items. Anything large enough to move = due to inertia forces should be glued down. I didn't see any large parts = unless I didn't look close enough. Just don't put it in your space = shuttle and pull 20g. Personally I'd fly with it. You fuse it like all = avionics. Wendell ------=_NextPart_000_0379_01C51682.34092020 Content-Type: text/html; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable
 
Subject: [FlyRotary] Re: = Digital Fuel=20 Monitoring System

Hi Ed.

This of course all only = applies to=20 electronics in a vibration exposed environment.
Good practice, as I = was=20 taught it many years ago, is to have hole spacings to allow components = to lie=20 flat on the board.
Of course there are exceptions like power = resistors that=20 need airflow around them, but they should be mounted with "stand-offs" = (small=20 tubes on their legs). The rule used to be that components should not = be held=20 in place by the solder, but by their mechanical mounting. That's why = the pins=20 are typically bent 45 degrees where they stick through the PCB before = being=20 cut off and soldered. Heavy components are additionally secured with = some kind=20 of mechanical fastener or globs of goo (technical term). Now obviously = the=20 weight of the body of the component in relationship to number of = pins/legs is=20 a factor. An example would be an IC with oodles (another technical = term) of=20 pins.

I "grew up" in a company that secialized in sound and = vibration.=20 It was very educational to watch a PCB board mounted on a "shaker" = (basically=20 a loudspeaker where there membrame was replaced with a mounting place) = lit=20 with a strobe light synchronized to the frequency sweep. Components = dancing=20 around and finally falling off if not properly supported = (mounted).

But=20 that was then. Now we have surface mounted components which I know = nothing=20 about...


Finn (Looks = like I've been=20 kicked off the list again)


Geez,=20 Finn, I was unaware that there was a "protocol" for resistor sizes on = PC=20 boards.  Seriously, is there some reason (vibration?) for forcing = resistors all the way to the board or is it just = "esthetics?".
 
Ed A
I still say your pc = board looks=20 good for a rotary engine. I couldn't tell from the pic  if = the=20 resistors are 1/4 or 1/2 watt.Those film resistors can take a lot of=20 punishment.  Standing a resistor vertically on end allows more=20 movement.  The yellow tantalum capacitor is the weakest = component  I=20 see, more easily damaged in soldering as over heating will damage the = lead=20 internally.  The resistor next to the pot might be put down to = prevent it=20 from bending over and touching the pot.
Is this a proto-type = or to be put=20 in aircraft?  If going in aircraft, I think sealed pots might be = a good=20 choice.
 
You should mount = power resistors=20 off the board so that the heat can dissipate without burning the pc = board but=20 you don't have any that I saw.  Many manufactures use little = spacers to=20 do this using water soluble spacers.  In my estimation, those = little=20 tubular spacers many use that are made of Teflon don't help rigidity = much, but=20 look cool.
 
If you want mil-spec = board that is=20 one thing but for our use I think Ed's board is OK except for above = items.=20 Anything large enough to move due to inertia forces should be glued = down. I=20 didn't see any large parts unless I didn't look close enough. Just = don't put=20 it in your space shuttle and pull 20g.  Personally I'd fly with = it. =20 You fuse it like all avionics.
 
Wendell
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