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wlannon(at)shaw.ca
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 Posted: Sun Oct 16, 2011 4:19 pm Post subject: Ignition timing with the auto advance mags. |
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A question for everyone:
All of the engine manuals I have seen to date give a mag setting angle relative to the propellor and corresponding to the individual magneto advance angle.
That makes good sense since the prop shaft is the only accessible reference.
The Polish manual for the AI14R engine is the only one to also include the corresponding crankshaft angles, probably for educational purposes.
All manuals of course give the desired ignition advance angle for the model engine. Theoretically, knowing that information, one can then determine the setting angle for the particular magneto with simple math.
For example the Huosai 6A ignition angle is 31 +/- 1 deg. BTDC (from the Maint. manual - the Specs. manual is different - another question) and, lets say we are installing a 25 deg auto advance mag.
31 - 25 = 6. The setting angle is 6 degs BTDC with reference to the Crankshaft. To determine the prop angle simply multiply by the gear ratio:-
6 X 0.787 = 4.7 Deg.
Now check the table in the manual and for a 25 deg mag you will find a setting angle of 6.9 deg.
This applies to all engine models using the auto advance mags. The "fudge factor" varies slightly but always within 2 - 3 deg. and toward retard.
The question is " WHY is there a fudge factor". I have one theory but the fact is I do not know.
Does anyone else???
[quote][b]
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cpayne(at)joimail.com
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| Posted: Mon Oct 17, 2011 2:22 am Post subject: Ignition timing with the auto advance mags. |
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Walt,
I believe the allowance is based on gear lash if setting by the prop and then there is measurement error factor. The Polish manual has helped me to "interpret" the descriptions in the Chinese manuals. I use one of those calibrated crank angle spark-plug hole dial indicators that were sold about 8 years or so ago.
In the magneto timing paper I wrote for the RPA Store, there is a table of correction values I calculated for each different advance angle.
Craig Payne
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GeorgeCoy
Joined: 02 Dec 2010
Posts: 310
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| Posted: Mon Oct 17, 2011 4:21 am Post subject: Ignition timing with the auto advance mags. |
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Walter, Perhaps you are not taking into account the gear ratio between the magneto and the crankshaft. On the M14P it is 1.125 to 1.
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Walter Lannon
Sent: Sunday, October 16, 2011 8:17 PM
To: yak-list(at)matronics.com
Subject: Ignition timing with the auto advance mags.
A question for everyone:
All of the engine manuals I have seen to date give a mag setting angle relative to the propellor and corresponding to the individual magneto advance angle.
That makes good sense since the prop shaft is the only accessible reference.
The Polish manual for the AI14R engine is the only one to also include the corresponding crankshaft angles, probably for educational purposes.
All manuals of course give the desired ignition advance angle for the model engine. Theoretically, knowing that information, one can then determine the setting angle for the particular magneto with simple math.
For example the Huosai 6A ignition angle is 31 +/- 1 deg. BTDC (from the Maint. manual - the Specs. manual is different - another question) and, lets say we are installing a 25 deg auto advance mag.
31 - 25 = 6. The setting angle is 6 degs BTDC with reference to the Crankshaft. To determine the prop angle simply multiply by the gear ratio:-
6 X 0.787 = 4.7 Deg.
Now check the table in the manual and for a 25 deg mag you will find a setting angle of 6.9 deg.
This applies to all engine models using the auto advance mags. The "fudge factor" varies slightly but always within 2 - 3 deg. and toward retard.
The question is " WHY is there a fudge factor". I have one theory but the fact is I do not know.
Does anyone else???
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01234567
[quote][b]
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wlannon(at)shaw.ca
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| Posted: Mon Oct 17, 2011 8:37 pm Post subject: Ignition timing with the auto advance mags. |
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Craig;
That is my theory as well based on the fact that in timing a geared engine,
unlike a direct drive type, it is not possible to continue rotation in the
normal direction between each angle check.
The best one can do is GO BACKWARD about 50 deg and then take up slack. I
doubt that is adequate.
Also agree with Brian. Use the engine manual setting.
Thanks to all.
Walt
---
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Bill vH
Joined: 26 Oct 2010
Posts: 8
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| Posted: Tue Oct 18, 2011 12:49 pm Post subject: Re: Ignition timing with the auto advance mags. |
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George,
I hope you are referring to prop flange/crankshaft- magneto gear ratio not actual crankshaft-magneto gear ratio...
[quote="GeorgeCoy"]Walter, Perhaps you are not taking into account the gear ratio between the magneto and the crankshaft. On the M14P it is 1.125 to 1.
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Walter Lannon
Sent: Sunday, October 16, 2011 8:17 PM
To: yak-list(at)matronics.com
Subject: Ignition timing with the auto advance mags.
A question for everyone:
All of the engine manuals I have seen to date give a mag setting angle relative to the propellor and corresponding to the individual magneto advance angle.
That makes good sense since the prop shaft is the only accessible reference.
quote]
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Cliff.Coy
Joined: 03 Mar 2007
Posts: 46
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| Posted: Wed Oct 19, 2011 5:26 am Post subject: Ignition timing with the auto advance mags. |
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Here is the M9-35m timing chart to determine the correct timing at the crankshaft flange.
The stamp is located on the parting face of the magneto body under the cap.
M14-P TIMING WITH M9-35M MAGNETOS
STAMP TIME TO 23 2 BTDC 24 2 BTDC 25 1 BTDC 26 1 BTDC 27 0 28 (1) ATDC 29 (1) ATDC 30 (2) ATDC 31 (2) ATDC 32 (3) ATDC 33 (4) ATDC 34 (4) ATDC 35 (5) ATDC 36 (5) ATDC 37 (6) ATDC
Measure with micrometer, mark with chalk, cut with ax.
Cheers,
Cliff
--
Clifford Coy
Border Air Ltd.
629 Airport Rd.
Swanton, VT 05488
802-868-2822 TEL
802-868-4465 FAX
Skype: Cliff.Coy
[quote][b]
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William Halverson
Joined: 27 Feb 2010
Posts: 88
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Cliff.Coy
Joined: 03 Mar 2007
Posts: 46
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| Posted: Wed Oct 19, 2011 7:04 am Post subject: Ignition timing with the auto advance mags. |
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It's certainly open for debate...
http://www.merriam-webster.com/dictionary/ax
On Wed, Oct 19, 2011 at 10:17, William Halverson <william(at)netpros.net (william(at)netpros.net)> wrote:
[quote] --> Yak-List message posted by: "William Halverson" <william(at)netpros.net (william(at)netpros.net)>
Axe?
--
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brian(at)lloyd.com
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| Posted: Wed Oct 19, 2011 7:54 am Post subject: Ignition timing with the auto advance mags. |
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Axe not what you can do for your country...
On Wed, Oct 19, 2011 at 8:02 AM, Cliff Coy <cliff.coy(at)gmail.com (cliff.coy(at)gmail.com)> wrote:
--
Brian Lloyd, WB6RQN/J79BPL
3191 Western Dr.
Cameron Park, CA 95682
brian(at)lloyd.com (brian(at)lloyd.com)
+1.767.617.1365 (Dominica)
+1.916.877.5067 (USA)
[quote][b]
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markdavis(at)wbsnet.org
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| Posted: Wed Oct 19, 2011 8:01 am Post subject: Ignition timing with the auto advance mags. |
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Cutting side of the axe for minor adjustments, blunt side of the axe for larger alignment issues? : )
Mark Davis
N44YK
[quote] ---
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William Halverson
Joined: 27 Feb 2010
Posts: 88
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| Posted: Wed Oct 19, 2011 8:30 am Post subject: Ignition timing with the auto advance mags. |
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My imagination is running wild ...
Wild vikings wielding axes in aviation engine shops all over the world ...
--
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dsavarese0812(at)bellsout
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viperdoc(at)mindspring.co
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| Posted: Thu Oct 20, 2011 10:26 am Post subject: Ignition timing with the auto advance mags. |
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DAT BEES AX if YOUS AX’ING??
Doc
From: owner-yak-list-server(at)matronics.com [mailto:owner-yak-list-server(at)matronics.com] On Behalf Of Cliff Coy
Sent: Wednesday, October 19, 2011 10:02 AM
To: yak-list(at)matronics.com
Subject: Re: Re: Ignition timing with the auto advance mags.
It's certainly open for debate...
http://www.merriam-webster.com/dictionary/ax
On Wed, Oct 19, 2011 at 10:17, William Halverson <william(at)netpros.net (william(at)netpros.net)> wrote:
--> Yak-List message posted by: "William Halverson" <william(at)netpros.net (william(at)netpros.net)>
Axe?
--
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