---------------------------------------------------------- Yak-List Digest Archive --- Total Messages Posted Sat 07/08/17: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:59 AM - Re: Re: Mag timing HS6A is the book wrong? (Roger Kemp) 2. 10:51 AM - Magneto failure CD-5 (glipaz) ________________________________ Message 1 _____________________________________ Time: 06:59:06 AM PST US From: Roger Kemp Subject: Re: Yak-List: Re: Mag timing HS6A is the book wrong? Ah, mental masturbation...the book has always worked for me but I'm getting old and senile. Doc Sent from my iPad > On Jul 4, 2017, at 4:48 AM, JL2A wrote: > > > I think my esteemed colleague woodja has come up with the answer: > > >> >> advance on magneto is calculated as the angle the advance moves on the device itself , >> >> nothing to do with piston , prop or anything ...thus , >> >> I read the magneto is geared at 1.125 internally. This from Tech specs ... >> >> >> So 27 degrees of magneto advance only equals 27/1.125 , or 24 degrees of piston advance . >> >> 24 degrees from 31 +|-1 degree (from tech specs ..) >> >> is the TDC degrees piston firing point , >> >> equals 7.0 degrees of piston advance required , >> >> which , multiplied by .787 equals >> >> >> >> >> 5.5 degrees of prop advance. >> >> Remarkably close to the table ... >> >> >> ie exact. >> >> >> ..And +/-1 degree of piston is , funnily , +-.7 degree of prop , coincidentally the limit variation... > > > > > > Read this topic online here: > > http://forums.matronics.com/viewtopic.php?p=470679#470679 > > > > > > > > > ________________________________ Message 2 _____________________________________ Time: 10:51:02 AM PST US Subject: Yak-List: Magneto failure CD-5 From: "glipaz" Conundrum: At runup, Mag 2 failed (engine turned off). Engine ran smoothly on Mag 1. Returned to chocks and opened Mag 2 to discover a broken points spring. Obvious hard break. Replaced points and opened Mag 1 to inspect. Discovered that the rotor on Mag 1 was completely loose (all three bolts were loose). Tightened rotor on Mag 1, closed both mags and fired it up. Started easily. Mag 2 now worked fine but now Mag 1 failed. What?! Thought it might be a switch problem. Tested Mag switch to make sure it was not a wiring short to ground and it checked ok. Back to the Mag. Inspected rotor and cap. Ok. Checked points. Open fine. Replaced cigarette. Still wouldn't fire. Replaced coil. Still wouldn't fire. Finally replaced Mag. Motor fired and tested fine on both mags. Runup Mag check normal. Note: we turned the bad Mag 1 by hand and could not get a spark out of the cigarette and the Mag turned fairly freely, without the normal flopping that the magnets provide. The mystery is this: assuming Mag 1 was fine and Mag 2 had a hard break prior to shutdown (prior Mag checks on Mag 1 were fine) how did it fail after tightening down the rotor? Why is it now producing no spark and seems to have lost its magnetism? Prior to this both Mags worked fine on previous runups and flights. Gil Lipaz Read this topic online here: http://forums.matronics.com/viewtopic.php?p=470795#470795 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message yak-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Yak-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/yak-list Browse Digests http://www.matronics.com/digest/yak-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.