Chris Anthony Posted June 6, 2014 Share Posted June 6, 2014 Hi guys, I've been running an SC52 2s nitro in my acrowot rather intensively for about a month now, so far i think it's seen around 10-15 hours. I had it run in nicely after about 3 tanks. Since then it's been running on 10% and 15% nitro fuel. Well over the past couple of flights i've been getting a progressively more noticeable whining noise, which varies with engine speed. I am assuming it's a bearing problem, as opposed to piston/crank problem, i do plan to look at the engine off the plane tonight to investigate. Can anyone think of a reason that this might have occurred though? I'm a bit disappointed that this has happened in the rather short time of ownership, and can only imagine that it's down to something I've done wrong out of ignorance. All thoughts appreciated, Thanks, Chris Edited By Chris Anthony on 06/06/2014 14:36:52 Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted June 6, 2014 Share Posted June 6, 2014 Hi There I had a similar problem with an Harmon Rocket with a SC 52 but my whine as the air going through the cowling Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted June 6, 2014 Share Posted June 6, 2014 Well Chris if there is tell tale brown liquid oozing from near the prop driver it's probably the front bearings, but the only way to check the main bearing is to undo the crankcase backplate and look for the same evidence. As far as care goes always run the engine right out of fuel after a session and put after run oil in the glow plug hole and turn over the engine by hand. Also try not to store your aircraft in a high humidity atmosphere as that doesn't help. I also stuff the muffler outlet and carby intake with paper towel to help keep the moisture out. Anyway the best thing is to take engine off and examine it. Best of luck. Quote Link to comment Share on other sites More sharing options...
Chris Anthony Posted June 6, 2014 Author Share Posted June 6, 2014 Thanks both. RC, mine whines when it's on the ground not flying so it's definitely an engine problem. Adrian, I do have some brown liquid evident in the main chamber when I take the exhaust off. It's not something I have seen before on these engines. Is the brown liquid itself the sign of bad wear? Or is it only bad when it starts leaking out under normal operation? It's currently half way through a gallon of a new fuel I'm using, which I can't get an oil content percentage for. I'm starting to suspect this might be related. Could anyone confirm the oil content for: Model Technics Molecular Blended Fuel Formula Irvine, Contest 10 glow fuel (it's red stuff) Cheers, Chris Edited By Chris Anthony on 06/06/2014 18:41:32 Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted June 6, 2014 Share Posted June 6, 2014 Hi Chris I trust I am not trying to tell you anything you don't know about engines but a tip from the Paul at Just Engines you must run the engine as rich as possible with lots of oil traces coming out of the exhaust stub test between your fingers. I have used Irvine 5% for years and advised its 18% synthetic oil and just started using 10% and noticed how cleaner the exhaust waste on the underside is cleaner than the darker when using 5%. I also advocate running the engine dry after a days racing you will be surprised how long the engine goes for on fuel remnants in the tubes and afterrun oil when getting back to Hanger. I used to run cars with 25% nitro and we could not understand why bearing failed so quickly as we did not use afterrun oil and the higher nitro was the problem Edited By RC Plane Flyer on 06/06/2014 19:37:51 Quote Link to comment Share on other sites More sharing options...
John Privett Posted June 6, 2014 Share Posted June 6, 2014 Posted by Chris Anthony on 06/06/2014 18:41:24: It's currently half way through a gallon of a new fuel I'm using, which I can't get an oil content percentage for. I'm starting to suspect this might be related. Could anyone confirm the oil content for: Model Technics Molecular Blended Fuel Formula Irvine, Contest 10 glow fuel (it's red stuff) Chris, it's listed on the modeltechnics website! Have a look here. 18% oil, the oil being Klotz Super Techniplate. Quote Link to comment Share on other sites More sharing options...
Adrian Smith 1 Posted June 6, 2014 Share Posted June 6, 2014 Chris rusty looking liquid in the crankcase doesn't alway manifest itself externally so in answer to your question if the bearings are on the way out the liquid doesn't always leak out. More likely, as I found with my OS 120 FS pumper engines, there's a tell tale whining coming from the engine when under power. That's when I know to replace the bearings. Just try to avoid too many lean runs as this doesn't help in the development of bearing wear. Quote Link to comment Share on other sites More sharing options...
Former Member Posted June 7, 2014 Share Posted June 7, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
John Privett Posted June 7, 2014 Share Posted June 7, 2014 You're a factor of ten out Percy, according to the modeltechnics website, "Super Techniplate oil contains 20% Castor". And the datasheet for Klotz Super Techniplate confirms that. Which means the fuel contains 3.6% castor, plus 14.4% synthetic oil. Quote Link to comment Share on other sites More sharing options...
Former Member Posted June 7, 2014 Share Posted June 7, 2014 [This posting has been removed] Quote Link to comment Share on other sites More sharing options...
Chris Anthony Posted June 7, 2014 Author Share Posted June 7, 2014 Hi all. I can confirm that the main (crank side) bearing is all brown, almost rusty looking after taking the crank out. Adrian, I believe this aligns with your description of failure, as I also get a noticeable whine in all running conditions (idle, on power, but most noticeably on overrun). John and Percy, thanks for the oil info. I'll have to look at my previous fuel's oil content to see whether I have moved over to something lower. I can't imagine what is likely to be such a small difference in oil percentage being enough to cause this bearing degradation, but I'm by no means sure. RC, that's actually interesting stuff. So do you think the higher nitro content (up from 10 to 15), and me probably being lazy and leaving some in the engine after use with no after-run oil is cause enough to accelerate bearing failure? I have been careful to ensure I am running closer to rich than lean (pinch test on fuel intake, the engine revs pick up before they die). But I haven't tried your exhaust snub test yet. Can anyone advise me on how to remove this bearing from the crankcase? I tried putting the engine in the oven as suggested by someone, but I then couldn't get enough purchase on the bearing itself to try and pull it out. Anything else to watch out for? Edited By Chris Anthony on 07/06/2014 14:50:02 Quote Link to comment Share on other sites More sharing options...
Keith Berriman Posted June 7, 2014 Share Posted June 7, 2014 Hi Chris its looking like the nitro has had some adverse effect on the bearings and no after run oil. I have a cowled Acro Wot and have a filling loop on the outside of the cowl and my engine runs for over 90 secs on a short piece of tube to Carb. I have removed rear bearings from engines buy knocking the out with a drift down the opening from the front bearing area. Don't be tempted to put the new bearing on the crank and pressing in into place this will stress the inner race on the bearings. I would advise maybe bearing on crank to locate in the engine body and then press in place with a suitable size socket to the outer race. I have heard of putting the bearing on the crank and into a oiled plastic bag into the freezer for an hour or so. Quote Link to comment Share on other sites More sharing options...
Stevo Posted June 7, 2014 Share Posted June 7, 2014 " Don't be tempted to put the new bearing on the crank and pressing in into place this will stress the inner race on the bearings. " Never ever ever ever... Put the crankcase in the oven on a medium - high for 5 mins. Simply drop the bearings into place once it's out of the oven... once it's cooled then Bob's your uncle... I've never used a drift or even force on SCs, Saitos, Lasers, OSs....... Quote Link to comment Share on other sites More sharing options...
GONZO Posted June 7, 2014 Share Posted June 7, 2014 There are several bearing replacement and engine rebuild vids on YouTube. HTH Edited By GONZO on 07/06/2014 17:23:16 Quote Link to comment Share on other sites More sharing options...
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