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Date: Fri, 8 May 2009 10:18:10 -0600
From: Bob White <bob@bob-white.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: John Downings Tach
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Hi Jeff,

Thanks for the tip.  There is something I don't understand about the
specs for this unit.  It's good for 4 cylinder 4 stroke or 2 cylinder 2
stroke.  If I use the spark plug wire for the pickup, a 4 stroke
(piston) engine will see one spark per two rev.  Why does it matter how
many pistons there are?  If it's a wasted spark system, then one spark
per rev. just like a two stroke piston engine.  There must be something
basic I don't understand.  What sort of mod did it need for the V6?

BTW, what is the maximum rpm reading for that unit?

Thanks,
Bob W.

On Fri, 8 May 2009 07:48:47 -0700
Jeff Whaley <jwhaley@datacast.com> wrote:

> I like the belt and suspenders!!
> I am using a UMA digital tachometer 2 1/4" from Aircraft Spruce that was originally designed for 4 cylinder engines using an electrical impulse pickup from spark plug leads. I modified it to mate with the Ford V6; I have modified it again to connect to the EC2 driving the R1 PRI injector. The rotary firing system is similar to a 4 cylinder so if this tach is still available (Part # 10-24885) it would work off spark plug impulse couplers.
> Jeff
> 
> -----Original Message-----
> From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net] On Behalf Of Bob White
> Sent: Friday, May 08, 2009 12:14 AM
> To: Rotary motors in aircraft
> Subject: [FlyRotary] John Downings Tach
> 
> John is using a standard tach that is normally connected to a distributor/coil ignition system.  The straight 12V pulse used for the
> LS1 coils wouldn't activate it.  I built an interface for him that involved taking that pulse as an input and generating a shorter constant pulse width output.  I modified the tach to trigger on the lower voltage signal, and adjusted the scale factor to read correctly with one pulse/rev.  As John reported, it worked for about 0.8 hours, then quit.  He is sending everything back to me so that I can find out where the problem is.  I would like to find a tach solution that John can use without modifying anything.  The parameters are he has a 2 1/16 inch mounting hole, the tach needs to read correctly with 1 pulse/rev (would be the same as a two cylinder piston engine with coil and distributor), should trigger directly on a 12V pulse.
> 
> I've found tachs on the web that mention working with distributorless or electronic systems, but none of them were the 2 1/16 inch type.  I found a converter, the MSD 8913, but on the Summit Racing catalog it specifically says it won't work with the LS-1 system.  It work by sensing the current pulses to the 12V power lead on the coil.  I don't know why it wouldn't work with an LS-1 coil, but it doesn't seem like a good investment when the LS-1 is specifically mentioned as not working.
> 
> Can anyone recommend a tach solution that John can use with his LS-1 Coil rotary engine combination?
> 
> On another topic, John has the only system I've heard of that has the capability to run on either EFI or a carburettor.  John posted a picture of his Tailwind a few days ago.  It's a very good picture but considering the redundancy of the EFI/carb system, I felt that the picture was lacking.  I submit this edited version as being more indicative of John's desire for uncompromised safety.
> 
> Bob W.
> 
> --
> N93BD - Rotary Powered BD-4 - http://www.bob-white.com
> 3.8 Hours Total Time and holding
> Cables for your rotary installation - http://roblinstores.com/
> 
> --
> Homepage:  http://www.flyrotary.com/
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-- 
N93BD - Rotary Powered BD-4 - http://www.bob-white.com
3.8 Hours Total Time and holding
Cables for your rotary installation - http://roblinstores.com/