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  #1  
Old 11-10-2019, 04:37 PM
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swisseagle swisseagle is offline
 
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Location: 20km outside of Zurich, Switzerland
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Default P-Mag on IO-390 ... Position of gear ...

Hello

Asking this for my buddy, RV-14 build, IO-390 installation, dual P-Mag.

During the removal of the Magneto and installation of the P-Mag, the distance from the flange to the gear is different between the Slick Magneto to the P-MAG.

The Slick Magneto has the correct flange distance to the main gear.
Distance flange to the gear is 1" / 25.4mm

On the P-Mag, the distance from the flange to the gear is 0.88"/22.4mm

That means there is only a left over 0.2" / 5mm grip in the drive train. The tooth-width on the gear is 0.34" / 8.7mm

Is that enough and correct? Can this be good over time?

Thanks allot for any inputs!
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  #2  
Old 11-10-2019, 05:22 PM
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Toobuilder Toobuilder is offline
 
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Might be a harsh question, but are you absolutely sure the Pmag wasn't dropped or otherwise displaced from normal spec?
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  #3  
Old 11-10-2019, 07:41 PM
Bavafa Bavafa is offline
 
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Are you using the gear that came off slick or is this another gear.
At some point there was some after market gear that was not up to spec.
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  #4  
Old 11-10-2019, 11:14 PM
lr172 lr172 is online now
 
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don't mean to insult, but are you measuring the outer most portion (i.e. seating area) of the flange? The interior sections of either unit isn't really relevant to gear positioning.

Larry
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Last edited by lr172 : 11-10-2019 at 11:16 PM.
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  #5  
Old 11-11-2019, 01:40 AM
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swisseagle swisseagle is offline
 
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- The gears are from Lycoming
- Nobody drop the P-Mags, one was installed @ Lycoming (new Lyco thru Vans), the 2nd was directly shipped from Brad @ EMag-Air to my buddy.
- Measuring:
- From the sealing flange on the accessory case into the engine to the gear
- From the sealing flange on the P-Mag to the gear
- From the sealing flange of the magneto to the gear
The magneto has the correct distance, the P-Mags are off by aprox. 0.12"/3mm
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  #6  
Old 11-11-2019, 08:50 AM
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Carl Froehlich Carl Froehlich is offline
 
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Provide a photo of the pMag with drive gear attached.

Carl
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  #7  
Old 11-14-2019, 02:41 PM
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swisseagle swisseagle is offline
 
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Default Sketch of gear situation

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  #8  
Old 11-14-2019, 03:32 PM
Bavafa Bavafa is offline
 
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Quote:
Originally Posted by swisseagle View Post
- The gears are from Lycoming
- Nobody drop the P-Mags, one was installed @ Lycoming (new Lyco thru Vans), the 2nd was directly shipped from Brad @ EMag-Air to my buddy.
- Measuring:
- From the sealing flange on the accessory case into the engine to the gear
- From the sealing flange on the P-Mag to the gear
- From the sealing flange of the magneto to the gear
The magneto has the correct distance, the P-Mags are off by aprox. 0.12"/3mm
Dominik,
Have you pulled the one that was installed by Lycoming to see if that has the same distance? I wonder what Brad says about this.
It looks like maybe an anomaly with the shaft that allows the gear get further into the shaft.
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  #9  
Old 11-14-2019, 03:34 PM
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Is there a washer missing?
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  #10  
Old 11-14-2019, 04:22 PM
lr172 lr172 is online now
 
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Quote:
Originally Posted by bkervaski View Post
Is there a washer missing?
The mag or pmag shaft has a morse taper cut on the end and this machining, along with the machining of the female morse taper in the gear determine the final position of the gear on the shaft. Washers do not affect the final gear height. I vaguely remember that the shaft height in the mag is set via a step on the shaft where the bearing rests, though it may just be an interferencing fit with the bearing. I just don't recall. The outer bearing surface is held captive in the mag. I have no idea how the shaft is held captive in a Pmag. Sounds like one of those several items was off in the machining or assembly of the pmag/gear. To eliminate the gear as an issue, measure both devices from the seating deck to the beginning of the taper on the shaft, as well as confirming that both shafts before the taper are the same diameter. If they are the same, the gear is the problem.

Larry
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Last edited by lr172 : 11-14-2019 at 04:29 PM.
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