• Welcome aboard HomebuiltAirplanes.com, your destination for connecting with a thriving community of more than 10,000 active members, all passionate about home-built aviation. Dive into our comprehensive repository of knowledge, exchange technical insights, arrange get-togethers, and trade aircrafts/parts with like-minded enthusiasts. Unearth a wide-ranging collection of general and kit plane aviation subjects, enriched with engaging imagery, in-depth technical manuals, and rare archives.

    For a nominal fee of $99.99/year or $12.99/month, you can immerse yourself in this dynamic community and unparalleled treasure-trove of aviation knowledge.

    Embark on your journey now!

    Click Here to Become a Premium Member and Experience Homebuilt Airplanes to the Fullest!

Magneto drive puck/pad wear

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

kennyw

2nd and current "Caretaker" N994SP
Supporting Member
Joined
Aug 27, 2017
Messages
302
Location
Mount Vernon, WA
Doing annual on 994SP. I pulled the magneto and was surprised to find the drive puck and pad had some unusual wear. Looks like I'll have to pull the engine and accessory case in order to replace the drive pad. Any recommendations as far as gotchas or special tools needed?

48580597337_bcee4d0c16_c.jpg


48580808172_e0d811af5a_c.jpg
 
Hey, was just looking at Great Plains' web site. It seems its had a pretty extensive face-lift. And, earlier today I called, and they had an answering machine that actually seems to have recorded my message.

Did somebody buy GPAS?
 
kennyw said:
Hey, was just looking at Great Plains' web site. It seems its had a pretty extensive face-lift. And, earlier today I called, and they had an answering machine that actually seems to have recorded my message.

Did somebody buy GPAS?

Art bought out Don. They did not sell....but Art is now on his own.
 
Is there a potted history of the company & owners for those of us not in the know?

There are catalogs here from '99 & 2000 that show nose cases & quill shaft projection for rear drive engines and tantalizing hints of further development about non-wood/&/or controllable props. Nothing related in current website.

Glad to hear they will still be around.

smt
 
Talked to Art again today. He says parts are on the way. And the charge showed up on my credit card. I may even get the thing back in the air by mid September.

I think I'm gonna plasti-guage the phenolic spacer to see how deep the lugs on the drive hub and magneto gear are engaging. I bought a 1/2" and a 3/4" spacer. If the 1/2" isn't thick enough, I'll plane the 3/4" one down for a good fit.

With those slots being perpendicular, there just shouldn't be any way not to get that spacer centered properly. So, I'm still scratching my head over this.


Edit*****

Interesting side note: I called up REVMASTER to ask them they they stocked parts for the Diehl accessory case. The guy I talked to (Jim?) said "they" copied "our" design. And, since Revmaster line has gone away from the center-line drive magneto design, they no longer have any parts like that.

It looks like GPAS is the only source for Diehl accessory case parts.
 
Revmaster doesnt even have any more of the raw castings for the rear mount.
 
eschrom said:
I've seen exactly the same wear on mine and will be interested in anything you learn.

Ed

I just got the new parts from GPAS. The fit of the phenolic spacer over the lugs on the drive hub and the magneto drive gear are quite snug. The puck only goes on one way because the width of the lugs are different on the magneto drive gear than the ones on the drive hub. It'll be interesting to see how they fit up with the magneto mounted on the accessory case.

I got a tube of non-drying Prussian Blue to check the engagement depth with the whole thing assembled. I'll try and post a few pics of this next week.
 
Finally got 994SP back in the air. I think its smoother now than before.

Still no clear explanation for what caused the abnormal wear. I suspect the head of one of the AN3 bolts on the stator is responsible for partial circumference wear mark (flats not squared up overhang by just a hair). But, I can't for the life of me figure out how it would only be worn just part way around with the mag drive gear and hub being concentric with the dog-ears being perpendicular. Nor can I explain how the one drive hub dog-ear and matching channel in the phenolic spacer was chewed up the way they were and yet the mag stayed perfectly timed.

I pulled the mag after a ground turn and looked everything over good. The phenolic spacer remained exactly centered on the drive hub. And, I can just see a faint but crisp impressions of where the mag gear engages the spacer. I'll pull it again next oil change. And, if there's no problem, I'm gonna declare it fixed!

48713486178_0f5870bfb8_c.jpg
48829592333_361a397a8d_c.jpg
48713977182_e553f44b48_c.jpg
 
Back
Top