Return-Path: Received: from imf21aec.mail.bellsouth.net ([205.152.59.69] verified) by logan.com (CommuniGate Pro SMTP 4.3c2) with ESMTP id 750325 for flyrotary@lancaironline.net; Sat, 19 Feb 2005 11:00:22 -0500 Received-SPF: pass receiver=logan.com; client-ip=205.152.59.69; envelope-from=ceengland@bellsouth.net Received: from [209.215.61.171] by imf21aec.mail.bellsouth.net (InterMail vM.5.01.06.11 201-253-122-130-111-20040605) with ESMTP id <20050219155935.KDL2069.imf21aec.mail.bellsouth.net@[209.215.61.171]> for ; Sat, 19 Feb 2005 10:59:35 -0500 Message-ID: <42176265.8080008@bellsouth.net> Date: Sat, 19 Feb 2005 09:59:33 -0600 From: Charlie England User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.7.2) Gecko/20040804 Netscape/7.2 (ax) X-Accept-Language: en-us, en MIME-Version: 1.0 To: Rotary motors in aircraft Subject: Re: [FlyRotary] Re: Digital Fuel Monitoring System References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: quoted-printable No reason to redesign unless you just can't push the components down on=20 the board. The guy that runs RTS (avionics kits) & writes for Kitplanes=20 recommends potting the components with something like hot glue or=20 non-corrosive RTV. Then you can get away with standing them off the=20 board if needed. Charlie Ed Anderson wrote: >Ok, folks I got the message on showing resistor "legs" - too risqu=E9 fo= r some >folks I guess {:>). > >Seriously, I think I will redesign the board to use Surface mount resist= ors >and capacitors and that will eliminate legs - of course it was sure nice= to >use those legs to leap over traces. > >Thanks for the input, Finn, Todd, Charlie, et al > >Ed > > >----- Original Message ----- >From: "Charlie England" >To: "Rotary motors in aircraft" >Sent: Friday, February 18, 2005 10:46 PM >Subject: [FlyRotary] Re: Digital Fuel Monitoring System > > > =20 > >>Hey Ed, want a 2nd opinion? What Finn said. >> >>Same reason that 13B through-bolts break. >> >>Charlie >> >> >>Finn Lassen wrote: >> >> =20 >> >>>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 >>> =20 >>>