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Magni M16 Pre-rotator issues ALERT

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  • Magni M16 Pre-rotator issues ALERT

    Hi all,I have a Magni M16 that"s only 15 months young (and meticulously maintained) with a seized Bendix Drive i.e when I engage the pre rotator lever, the top pulley engages just fine (new belts) and so does the flexible shaft but the Bendix gear does not fly up to engage the big ring gear under the rotors.Trying WD40 and light machine oil does not work as all the contaminants travel down into the Bendix making the problem worse. I removed the Bendix gear from the gyro and upon closer examination was surprised to discover the relative ease it took to seize with only a few specks of sand & dust etc lodged between the Bendix gear and shaft. I gave it a petrol bath, re-greased & refitted.Looking at the design, if any dust and dirt gets inside e.g from landing at a bush strip or unsealed runway there is no way to clean and relubricate the Bendix in situ as the dirt etc only falls & collects at the bottom but the item has to be removed from the gyro which is a pain.folks don"t get me wrong, I still believe that Magni makes the best gyro on the market but i am very disappointed in the closed bottom & open top design of the Bendix allowing dust & particles to attract to the grease and cause problems. Has anyone experienced this? if so are there any tips you can share?ThanksAndrew

  • #2
    Hi Andrew,I"ve heard of this a few times before and the problem stems from the standard design of Bendix drives, in that they are intended to have full electric-starter-motor drive torque from the first instant. In other words, in our cars they "wham" instantly into contact with the ring gear because the initial impulse is so sudden and has full torque.With the Magni, reportedly, if you"re too slow in initial engagement the Bendix won"t jump into contact with the ring gear. Somewhere I"ve seen either a US forum post or possibly in an old PRA magazine letter to the editor where the writer said he somehow initially jerked the pulley so that the Bendix jumped into position. I can"t visualize the exact Magni setup so I can"t comment further, but I"m pretty sure that"s the reason for your problem. The open top you describe seems to be a really poor design choice by the manufacturer, but my guess is that even with some sand or grit on the spiral splines if enough of an initial impulse can be delivered to the Bendix it should still jump into position. Maybe some sort of shield for the Bendix could possibly be engineered as well.There is a basic conceptual incompatibility with using friction pulleys with relatively slow take-up and Bendix drives that need a fairly big initial impulse to jolt them into proper position, yet Magni has been apparently using the arrangement for a long time and perhaps there is a "knack" or precise sweet spot in operator technique to get it to work satisfactorily?If the problems persists don"t call your doctor - instead call or contact Greg Gremminger in Perryville, Missouri, USA for comment - he"s the US distributor and the self-styled Magni guru. Just Google the name - he comes up instantly.Mark ReganMelbourne

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    • #3
      Back in 1961 when I started my apprenticeship as an outo sparky most starter motors had "enertia" drive assemblies and we were taught to use only kerosene as a lubricant to prevent dust attraction.

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      • #4
        Not sure how magni set it up, but the ones i use have dun over 3000 hours and never failed to engauge, and its never been landed on anythn but dirt.I only give the bendix a squert of goanner **** every 50 hours, or if it sat in the rain over nite.But, if the engine is on the idle stop, the initial engauement rpm isnt high enuf to throw the gear up. It needs a minimum rpm to throw the gear, if its spin,n too slow, itll just spin.

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        • #5
          Thanks for your replies Gents & I appreciate your comments/suggestions.Regards,Andrew

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          • #6
            Hi Andrew, the latest machines from Magni including my M16 have a dust cover over the top of the bendix drive. Just as you were suggesting.

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