Hi All. You are all right.
The center element of the drive coupling doesn’t like the additives in car engine oil so don’t use it. It breaks down and falls apart. The result of that is dramatically retarded timing and usually if run for a period of time in that condition cracks the palls of the coupling on the magneto side. The element is not expensive but the alloy coupling half for the magneto is. Hydraulic oil contains very little in additives so I use that. Oil is needed as it needs to drip from the filler onto the impulse coupling. Grease is too thick however chain grease is a different animal in that the propellant used thins it down dramatically when sprayed and thickens immediately on contact as the propellant evaporates. On the Limbach engines not fitted with an accessory case such as in the Sperber and Motor Falke there is no lube facility by nature of the adaption of the Magneto to the crankshaft. In those engines the coupling is lubricated by packing the coupling with a grease (as described by Tom) on assembly and at the time of servicing the Magneto. There is no maintenance requirement between servicing. Lubrication is required to reduce wear on the trigger pawls of the coupling which operate during starting. Once running they no longer engage so aren’t doing any work to speak of. The coupling does 2 things. It retards the timing for starting and accelerates the dive shaft momentarily to achieve a high voltage with a low crankshaft rpm for starting. This works well as we know but that abrupt acceleration loads up the teeth on the distributor gears. Where an aircraft is doing lots of starting cycles as we typically do compared to touring operations the gears fail well before TBO. This is a well-known problem. In the Stemme where the engine is turning with the ignition of to unfold the prop before turning ignition on the coupling use is a lot higher and thus suffer failures more often than other types. Regular servicing is important for reliability and I recommend changing the gears at 500 hours. In the case of the Stemme S10 I know someone who does his every 250hours after a failure at start up on the ground thankfully as he going on a Morning Glory sortie. The day before he had left the glory and didn’t have enough height to get home and had done a restart enroute over some pretty poor ground. It would have been a disaster if it had failed then rather than the next morning. Something to keep in mind. Cheers. Nige. From: [email protected] [mailto:[email protected]] On Behalf Of Michael Stockhill Sent: Tuesday, August 15, 2017 10:37 AM To: [email protected] Subject: Re: Re: [DOG mailing list] Magneto coupling lube When I bought my Dimona I soon discovered that someone had filled the lube port with grease. Some of which slobbered down to the drive. I cleaned that mess up when I proactively replaced the mag. I am about to do so again. I figure that the mag, being direct drive, turns and fires twice as often as in usual applications, hence 250 hours may well be the equivalent of 500 hours. Michael On Aug 14, 2017 4:36 PM, "Greg Wilson" <[email protected] <mailto:[email protected]> > wrote: Hi all, I can confirm the oil is necessary for the magneto. When hand cranking my Limbach E2000B, there was a nasty grinding noise just before the magneto threw over. A few drops of oil in the filler hole stopped the noise. I'm guessing that when the engine is turning slowly, the magento's pawls need oil so they slide smoothly on the lugs that trip them. Cheers, Greg. Greg Wilson ---- On Tue, 15 Aug 2017 08:01:15 +1000 Mike Collins <[email protected] <mailto:[email protected]> > wrote ---- Hi Tom, My Inspector says use 3 in 1 multi purpose oil. I have used it for 3 years now on my Slick Mag model 4330. Mike _____ From: [email protected] <mailto:[email protected]> <[email protected] <mailto:[email protected]> > on behalf of Tom Preisser <[email protected] <mailto:[email protected]> > Sent: 14 August 2017 20:51 To: [email protected] <mailto:[email protected]> Subject: [DOG mailing list] Magneto coupling lube Hi all, Limbach Tech Bull 18 calls for lubricating the magneto impulse couplings with adhesive oil every 25 hours through the accessory case port. That TB calls for Molykote (a Dow Corning product, spelled Molikote in the TB. Maintenance Instruction 28 later says that due to availability problems with Molykote, Dow Corning:C 40 (liquid) or - Bremer & Leguil: RIVOLTA SKD 170 (Spray-on) can be used instead. The only US supplier I can find for Dow C40 wants to sell me a kg for $50! And I only need 10 drops (for this lube cycle anyways). What have you all been using, if anything? I think I read somewhere else that no lube is necessary for this type of coupling.... The MI also says "such lubricants [as recommended above] are used for motorcycle drive chains", but I hesitate to use a petroleum-based product instead of graphite-based like the C40 (high temperature)...? The impulse coupling spring also needs to be lubed, but motor oil is the recommended lubricant for that (by magneto rebuilders). Cheers, Tom
