Safety Officer Posted December 24, 2013 Report Share Posted December 24, 2013 Just an FYI, Don't get the overload clutch (a.k.a. slipper clutch) and the gearbox friction torque check mixed up. Two different animals. The overload clutch (a.k.a. slipper clutch) on the engine side uses a tremendous amount of ft/lb torque. I personally don't do this unless it is a special needs check. This check can bend engine frames fairly easy without proper support. The friction torque check in the gearbox is easy and won't hurt the engine frame. It is the measure of the 3 bellville washers spring pressure in the gearbox. The video you are referring to here on the forum is for the gearbox friction torque check. Just do this check. The 230-530 in/lbs they are using are guidelines. What I normally see in the shop is 425-485 in/lbs for normal numbers. If it drops way down in the lower 300's I will pull the gearbox and re-shim. Look in the Line Maint. manual. Section 05-50-00 page 5 describes the overload clutch check. Section 12-20-00 page 68 is for the gearbox friction torque check. www.rotax-owner.com/all-videos/elearning...60-friction-torque29 Link to comment Share on other sites More sharing options...
MarcF Posted June 10, 2015 Report Share Posted June 10, 2015 Hello, I just have a question. My CTLS is now 410 hrs and 6 yrs old. He works perfectly since I changed the ignition boxes. When I turn the prop to check the oil level, engine cold, everything is OK. When I do it on a warm engine following a long fly I can hear a shrill screech. Only when engine is hot. Of course, while running, I can't hear anything (too noisy). Do you believe it could come from the gearbox (friction torque) ? Must I do something ? Thanks for the advice. Friendly Marc Link to comment Share on other sites More sharing options...
Runtoeat Posted June 10, 2015 Report Share Posted June 10, 2015 Marc, my gearbox was at the very low end of the "torque-to-turn" spec Roger has posted here. Hobbs was about 600 hours. I sent the box in for inspection and it required re-shimming to bring it back to the upper torque spec. The re-shimming seems to have cleaned up some vibration issues I had prior to this. It's easy to check the torque and I would recommend that your do this. Link to comment Share on other sites More sharing options...
Roger Lee Posted June 10, 2015 Report Share Posted June 10, 2015 Hi Marc, That squeaky noise can be normal. Not everyone has it. If you are using the correct oil in the engine and the gearbox friction torque is in the normal range then you should be fine. If you are using a poor oil like a car oil and or have a low torque value for the gearbox then I would address those two items. Link to comment Share on other sites More sharing options...
Anticept Posted June 10, 2015 Report Share Posted June 10, 2015 My CTLS has an annoying squeak when it is first started or comes to a stop, and sometimes just a little when rotating by hand. Made calls around, was told to monitor and if it gets worse, send it in for service. 600 hours in, and it's gone away some. Learned in training that it's the dog gears that sometimes resonate a little when moving, and isn't of any consequence as long as you don't hear it above idle. The dog gears shouldn't be moving above idle; the reason they exist is it curbed some of the vibration at idle, the engine protection is just a secondary function. Link to comment Share on other sites More sharing options...
MarcF Posted June 11, 2015 Report Share Posted June 11, 2015 Hi Roger, Hi Anticept, Hi Runtoeat, Thanks everybody. I use Yacco Aero AVX 500 10-40w, change oil in duty time (rather 50hrs than 100 hrs, at least one time by year, don't use Avgas more than 10% of my flight time. Last time I canged oil: 10 hrs ago. No iron on the magnetic cap. The noise occurs only when rotating the prop by hand on a warm engine (not when cold). No idea of the torque value. How can I measure it ? Am I supposed to put the gear box down for that? Very friendly Link to comment Share on other sites More sharing options...
Anticept Posted June 11, 2015 Report Share Posted June 11, 2015 Rotax line maintenance manual chapter 12-20-00 paragraph 14 has everything you need Link to comment Share on other sites More sharing options...
MarcF Posted June 11, 2015 Report Share Posted June 11, 2015 thanks Link to comment Share on other sites More sharing options...
MarcF Posted June 11, 2015 Report Share Posted June 11, 2015 You're right. I meaned I have no abnormal iron deposit... Link to comment Share on other sites More sharing options...
Runtoeat Posted June 11, 2015 Report Share Posted June 11, 2015 Marc, this is not difficult to check the friction torque of the gearbox following the Rotax manual which Corey has posted. One caution, and I mention this from personal experience. You will lock your crankshaft with a special bolt which should have come with your CT. Use a flashlight to sight thru the bolt hole to locate the notch in your crankshaft throw before you screw in the locking bolt. If you miss this notch in the throw, the bolt can be screwed in too far, even far enough that is drops into the crankcase. If done correctly, there will be an inch or so of exposed bolt after the crank is locked. Please remember you are not trying to turn past the dogs, just exercising the clutch pack. You should see movement of the prop with only moderate effort. If at 2 ft. out on the prop the pull on the prop will be in the range of 11 to 22 pounds. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted June 11, 2015 Report Share Posted June 11, 2015 Marc, this is not difficult to check the friction torque of the gearbox following the Rotax manual which Corey has posted. One caution, and I mention this from personal experience. You will lock your crankshaft with a special bolt which should have come with your CT. Use a flashlight to sight thru the bolt hole to locate the notch in your crankshaft throw before you screw in the locking bolt. If you miss this notch in the throw, the bolt can be screwed in too far, even far enough that is drops into the crankcase. If done correctly, there will be an inch or so of exposed bolt after the crank is locked. Please remember you are not trying to turn past the dogs, just exercising the clutch pack. You should see movement of the prop with only moderate effort. If at 2 ft. out on the prop the pull on the prop will be in the range of 11 to 22 pounds. The video said to remove a plug from cylinder #1 to find TDC and then locate the crank notch. Can you just rotate the prop by hand until you see the notch, or to you have to find TDC first for some reason I can't seem to understand? Link to comment Share on other sites More sharing options...
FastEddieB Posted June 11, 2015 Report Share Posted June 11, 2015 Either way works. I usually just use a wooden dowel to find TDC on #1- that puts the notch in the right place. But no reason you couldn't just slowly turn the prop until the notch appears. I, too, go 24" out with a fish scale and multiply x2. On another point, I would need it explained why lack of metal on the magnetic plug is a de facto bad thing. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted June 11, 2015 Report Share Posted June 11, 2015 Either way works. I usually just use a wooden dowel to find TDC on #1- that puts the notch in the right place. But no reason you couldn't just slowly turn the prop until the notch appears. I, too, go 24" out with a fish scale and multiply x2. On another point, I would need it explained why lack of metal on the magnetic plug is a de facto bad thing. Thanks, that makes sense. Just wondering why remove a plug and such if not needed. I don't believe a lack of metal on the plug is a problem. It may be normal to find a few metallic grains on there, but I'm not going to panic if it's totally smooth. Even if it were essential to make a little metal, there's no guarantee your mag plug will catch it. Link to comment Share on other sites More sharing options...
FastEddieB Posted June 11, 2015 Report Share Posted June 11, 2015 A little fuzzy, from a 2009 annual: Roger - is too little metal on the magnetic plug a cause for concern? I had not heard that before. Link to comment Share on other sites More sharing options...
Anticept Posted June 11, 2015 Report Share Posted June 11, 2015 We have all three of our engines producing no metal at all on the magplugs, and oil fiters come out with MAYBE a chip or two, but otherwise clean as a whistle. Link to comment Share on other sites More sharing options...
FlyingMonkey Posted June 11, 2015 Report Share Posted June 11, 2015 We have all three of our engines producing no metal at all on the magplugs, and oil fiters come out with MAYBE a chip or two, but otherwise clean as a whistle. How terrible, sounds like you have to buy three new engines. Link to comment Share on other sites More sharing options...
FastEddieB Posted June 11, 2015 Report Share Posted June 11, 2015 Thanks for that link. It seems comprehensive, and I've added it to my "library". However, there appears to be no mention of metal "flakes" in that document. Since I always like to point to original source material, may I ask where that part came from? It's an interesting concept: a system where normal functioning puts metal into the oil by design. But it's never too late to learn something new! Link to comment Share on other sites More sharing options...
Anticept Posted June 11, 2015 Report Share Posted June 11, 2015 Friction torque (not overload torque) test checks the spring tension, which are a little on the higher side of the acceptable range on all of our aircraft. We're not worried about the lack of indications on the plugs, and they do have magnetism (checked that a few times just in case). Link to comment Share on other sites More sharing options...
Tom Baker Posted June 11, 2015 Report Share Posted June 11, 2015 100Hamgurger, Checking the friction torque is a far better indicator of the condition of the slipper clutch, than checking the magnetic plug for metal flakes. Link to comment Share on other sites More sharing options...
Roger Lee Posted June 11, 2015 Report Share Posted June 11, 2015 They slightly overlap. The mag plug just tells you that you have a metal wear issue in the gearbox and could come from more than one source. Could be a gear issue and nothing to do with the bellville washers. The friction check is just to see if the pressure exerted by the 3 bellville washers is sufficient. The higher the number the better. Average is 440-485 in/lbs. Link to comment Share on other sites More sharing options...
FastEddieB Posted June 11, 2015 Report Share Posted June 11, 2015 So, Roger, is NO metal on the magnetic plug a sign of problems? Link to comment Share on other sites More sharing options...
Anticept Posted June 11, 2015 Report Share Posted June 11, 2015 The bellville washers are the "springs" of the gearbox. By testing the friction torque, we are testing the spring pressure of those washers. Worn washers will not exert as much force on the dog gears, which means our friction torque will be lower. Also, one big critical point: a mag plug serves two functions. First, it's a comparative check. If you have no filings on it on the last change, and this time you have a moderate amount, it means something may be failing and, at minimum, keep an eye on it. The other is if you find a LOT of filings on it, then something HAS failed and continued operation is NOT recommended. If neither of these conditions are met, then the mag plug is not a big deal. Mag plugs are used extensively in turbine engines (in fact, they have a magnetic chip detector, which displays a cockpit warning, if too much is collecting on the detector and shorts the terminals). They are also being used more and more in traditional air aspirated engines. It's an extra indicator in the maintenance toolbox. For that matter, I am curious why Rotax doesn't have a chip detector instead of just a magplug. They are very useful to catch an impending failure (but can throw false positives on poor adherence to mx schedules). Link to comment Share on other sites More sharing options...
FastEddieB Posted June 11, 2015 Report Share Posted June 11, 2015 Again, nothing in the link about shavings or filings or whatever. Were those your words, paraphrasing Kevin? Link to comment Share on other sites More sharing options...
Roger Lee Posted June 12, 2015 Report Share Posted June 12, 2015 Hi Eddie, No metal, no problem. Remember the gearbox is made up of different components and any of those metal components may leave tiny flecks, shavings or filings. You can have gear pieces start to wear. or break teeth, the bellville washers wearing or splines on the prop shaft wearing. The larger pieces usually come from the gearset. You are allowed up to a 3mm piece. Very fine metal particles might make it through and get stuck here too. The belleville washers rub on the inner edges and outer edges of each other depending on which washer we want to talk about. They slowly grind on each others edges and leave very fine particles or filings and these are what most see, but saying this is all you get on the mag plug would be doing someone a dis-service. It can come from other sources. Finding a lot of particles or chunks just means it's time to do an internal gearbox inspection. 100 Hamburger, I do lots of gearboxes and carbs. Just did a set of carbs today from Florida. Just sent a gearbox to Leading Edge for a second opinion. $4K in vibration damage. Link to comment Share on other sites More sharing options...
FastEddieB Posted June 12, 2015 Report Share Posted June 12, 2015 Thanks, Roger! Link to comment Share on other sites More sharing options...
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