Return-Path: Sender: (Marvin Kaye) To: flyrotary Date: Thu, 21 Aug 2003 19:25:13 -0400 Message-ID: X-Original-Return-Path: Received: from [128.83.126.136] (HELO mail.utexas.edu) by logan.com (CommuniGate Pro SMTP 4.1.1) with ESMTP-TLS id 2534774 for flyrotary@lancaironline.net; Wed, 20 Aug 2003 09:16:01 -0400 Received: (qmail 93418 invoked from network); 20 Aug 2003 13:16:00 -0000 Received: from dhcp-191-101.per.utexas.edu (HELO benefits3.mail.utexas.edu) (146.6.191.101) by wb2.mail.utexas.edu with SMTP; 20 Aug 2003 13:16:00 -0000 X-Original-Message-Id: <5.1.1.5.2.20030820081313.02589ec0@localhost> X-Sender: msteitle@mail.utexas.edu@localhost X-Mailer: QUALCOMM Windows Eudora Version 5.1.1 X-Original-Date: Wed, 20 Aug 2003 08:15:53 -0500 X-Original-To: "Rotary motors in aircraft" From: Mark Steitle Subject: Re: [FlyRotary] Re: tachs In-Reply-To: Mime-Version: 1.0 Content-Type: multipart/alternative; boundary="=====================_1289545343==.ALT" --=====================_1289545343==.ALT Content-Type: text/plain; charset="us-ascii"; format=flowed At 07:52 AM 8/20/2003 -0500, you wrote: > >3 inch tach!!! John, I think what you really need is some glasses :-) > >For the record, since the tiny tach expects one pulses per revolution, >you'd have to divide by 12 to get the proper reading if you hooked it up >to the tach output. I don't think that would be the best way to hook a >tiny tach up though. > >Most normal tachs come with a switch, or some other method of setting the >number of cylinders, and the choice is usually 4,6, or 8. Since 4 cycle >engines fire half of their cylinders on every rotation, the tach expects >to see half the number of cylinders pre rev. If you use the tach output >of the EC-2 for a normal, off the shelf tach, you'll have to divide as follows: > >4 cylinder setting, 2 pulses per rev, divide by 6 >6 cylinder setting, 3 pulses per rev, divide by 4 >8 cylinder setting, 4 pulses per rev, divide by 3 > >Now that I think about it, what the heck does that Geo 3 cylinder engine >do :-) > >Rusty (it's too early) > > > So, if the 3-rotor fires every 120 degrees of crank rotation, can I just take an off-the-shelf unit and set it to 6 cylinder mode and be good to go? Sounds too easy! Mark Steitle --=====================_1289545343==.ALT Content-Type: text/html; charset="us-ascii" At 07:52 AM 8/20/2003 -0500, you wrote:

3 inch tach!!! John, I think what you really need is some glasses :-)

For the record, since the tiny tach expects one pulses per revolution, you'd have to divide by 12 to get the proper reading if you hooked it up to the tach output. I don't think that would be the best way to hook a tiny tach up though.

Most normal tachs come with a switch, or some other method of setting the number of cylinders, and the choice is usually 4,6, or 8. Since 4 cycle engines fire half of their cylinders on every rotation, the tach expects to see half the number of cylinders pre rev. If you use the tach output of the EC-2 for a normal, off the shelf tach, you'll have to divide as follows:

4 cylinder setting, 2 pulses per rev, divide by 6
6 cylinder setting, 3 pulses per rev, divide by 4
8 cylinder setting, 4 pulses per rev, divide by 3

Now that I think about it, what the heck does that Geo 3 cylinder engine do :-)

Rusty (it's too early)

So, if the 3-rotor fires every 120 degrees of crank rotation, can I just take an off-the-shelf unit and set it to 6 cylinder mode and be good to go? Sounds too easy!

Mark Steitle
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