That's right Buddy! We all have you in mind and prayer! You were the first to welcome me when I started in here... you stuck with me even when I became a traitor and switched away from "The Sooby", and then again as I became the self righteous know-it-all egomaniac that everyone now just rolls their eyes at! If you stick with me after all that then you're a hell of a guy! Get off that mind numbing juice quick so we can have ya back!
For anyone who might be following, I did an update 2 posts up on the c box that had a problem. And here's a pic of what was meant by "improperly assembled". Absolutely amazing that the gears and gearbox held up to 140 hp for 200+ hours with the gears barely even meshing like that!!
Big project there bud! You've come to the right place here, and will get some really good advice from the experts on these planes (not me! LoL). These guys can help steer you through the rebuild process with some invaluable input! To the group, Ian is a regular contributor over in the Yamaha Aircraft Conversions Facebook group, and is working on a professional grade wire loom mod for the Yamaha Apex motors. He is the kinda guy that gets stuff done. Welcome Ian, Anatoli (Brett)
Just an update here on feedback from people who have bought direct from Nick in Romania (see early posts in this topic for order process): Everyone I have talked with has had a good experience and a prop shipped promptly. The only small complaint I've heard is that, rarely, Nick can be a little slow on returning emails. Today a friend called and told me that there was a slight defect (delamination) on the trailing edge of one of his blades. He had a buddy who spoke Russian and they called Nick up to ask how to repair that, but Nick told him that he would ship him 3 new blades that very day... and only asked that my friend ("Yooper Ed" here in the forum) send his three blades back to Nick. Pretty dang good customer service report there! I remember I was a little hesitant to send a money order blindly overseas, but so far it has worked out well for everyone.
Reference post above, here is the axial clearance measurent screenshot from the manual, along with a description of how I found to do it in an easier way: For anyone who wonders the procedure for checking Rotax C pinion shaft axial clearance, here is a copy, but I found it easier to simply add a number of shims (I put in like 4), install and torque pinion bolt, then set the case cover down (without gasket). The proper gap IS the .4mm gasket, so I measured the case cover gap without the gasket and removed a number of shims that measured the same (or slightly more) than the gap. Then I double checked my measurement by doing it the way described in the manual. For my box I had a .44mm clearance with zero shims. I also think it is important, during reassembly, to triple check that you don't have too many shims in by checking that the case cover actually still will contact (without the gasket) the case. This ensures that you didn't add too many shims and have a binding problem when you bolt the cover on. I'll re-check that at about 30 hours after break-in and predict that I may need to add one shim at that time.
Teal contacted me today with a report that a pinion shaft bearing began to fail on a (appox 200 hr) Skytrax RX-1 running an RK-400 centrifugal clutch. This event is noteable because it is very similar to one other case where the same problem was encountered (also a Skytrax RX-1 w/ RK400, but with approx 110 hrs). Other noteable facts include: - Both failures suffered NO powerloss. The bearing began to give out but the rigidity of the RK-400 clutch (mounted on the PTO) helped keep the clutch drum and pinion shaft centered and the gears remained "meshed" and running. It appears likely that at least one of these two gearboxes ran for a number of hours in the partially failed bearing condition. The problem (in both cases) was detected during a subsequent preflight by noting some side to side play in the clutch drum. - Also noteable is that there are many other setups nearly identical to this one (centrifugal clutch with similar hrs of use) which have had NO problems, and also there have been no reported problems while running the rubber flex drive ("hardy disc"). ******UPDATE**** Analysis is back from the Rotax service center on these two gearboxes. It was determined that the latest gearbox was assembled incorrectly during a gear set change (see pic 2 posts down), and that both gearboxes had the pinion bolt come loose during operation. (that bolt in the center of the pinion shaft, bolt head located in gearbox, going out through to the coupling that connects to the clutch drum / hary disk) When that bolt came loose, the pinion shaft apparently "rode up" the gear teeth and rammed against the outer pinion bearing (in outer case), loading it axially which in time caused the bearing to fail. Also the gear wear pattern on the second (improperly assembled) gearbox had the large gear scraping the case cover and the pinion bearing race. Wear marks showed that the two gears in that one only had about 50% tooth alignment. So it looks like the problems here have been isolated to improper assembly and also more noteably from the pinion bolt coming loose, so a couple unofficial recommendations are suggested from the shop to users of the c gearbox: The pinion shaft bolt should be cleaned thoroughly and red loctite used during final assembly. (torque is 212 in-lbs) When you have the gearbox apart to that point, the axial clearance of the pinion shaft should be checked. This clearance is critical to bearing life and gear engagement. In the post below I'll reference the service manual excerpt on how to make this check. Additionally anyone running the Rotax gearbox can also make an easy preflight check to determine that the pinion bearings are in good condition. This is a simple procedure where you reach in the access / cooling hole and physically push on the drum / hardy disk. There should be no detectable side to side movement.