How to change model airplane engine bearings (part 2 of 2) 

Glad to have been of help.

jpurcha glad they were of help Jim.

Guhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhhjhhhhhhhhhhhhhhhhhhhhjhhhhjju8uui Ii, œ Nvvvvv

I've thunder tiger pro 50, kindly suggest me best fuel for it

Can you get sheilded bearings with polimide retainers? The reason I ask is that one of the primary causes of engine destruciton is the failure of the metal retainers which disintegrate and shend shards of metal through the engine. Although shielded bearings may stop the retainer from leaving the bearing, I believe that the sheilds do add to the bearing drag (even if only due to viscous drag created by the oil) and thus for absolute performance, unshielded bearings with polimide retainers are still the desired solution.

***** Metal retainer failure is normally due to very high, bearing rotational speeds. As I recall, the speed ratings involved for bearings in a typical .40 engine are as high as 100,000 RPM,,, speeds not normally imposed on our engines. Poor lubrication, of course, can also be a factor. As can contamination during installation. The shields are attached to the outer race, so they don't rotate and they don't touch the inner race. As well, the oil is diluted with methanol by a factor of 4 or 5 to one so viscosity, wouldn't be that much a factor. I'm going by memory at the moment, but even SEALED bearings, which DO impose a measure of drag on the inner race, and are lubricated with GREASE, still rotate, in our typical .40 engine, within the rated speeds of the bearings in question. A greased bearing doesn't impose much drag to the bearing's moving parts, the grease doesn't churn as one might imagine. Only one half side is greased, with a film of lube feeding the moving parts. Mechanics often think that if some is good, more is better and totally PACK the bearing with grease, In that case, churning is guaranteed with balls skidding instead of rolling and overheated bearings failing prematurely. Many times I've rebuilt engines with the front bearing having a seal on the outside face and the rear bearing with a shield on its inner face. The sealed front bearing keeps external grit out and the shielded, inner bearing keeps out any metal bits or shards that might occur with normal, wear and tear. As in when you find your rod getting sloppy on the crank or wrist pin. OR, (shudder) when your piston pin retainer clips fail. Both the front and rear bearings have oil, (contained in the fuel) feeding the bearings by way of the carburetor. The case, generally, has a slot to help this process along. Often, just the normal, clearances in this area are sufficient. Some sealed bearings come with Teflon seals where the drag of the seal is far, far lower than a rubber seal. These are available in limited sizes, as I recall, usually for the typical, front bearing. But you ARE correct in that polimide retainers are superior to any other, especially at high speeds. This is due to their lighter weight and lower friction under minimal lubrication conditions. However, in industry, we have seen polimide retainers fail too. It may be self serving by the bearing manufacturers but in those cases, they blame poor installation practices, such as installing the bearing into a case using pressure on the inner race. Or vice versa. Or, the dreaded contamination during installation. In our engines, the bearing is retained by a press fit in the case via the outer race and installation is done cold with a special tool that puts pressure on the outer race only. Or, as with your example, the case is heated and the bearing just slides in. That's the way I do it too. In this case, the crank has a slip fit into the inner race and all is good. This isn't ideal, both races SHOULD be firmly attached but the compromise works for us due to the loads being imposed are far below the rated capacity of the bearing. Having said that, I HAVE had cranks spin in the bearing, inner race where when you take out the bearing, the crank is polished mirror smooth at the location of the bearing. This doesn't seem to harm the engine's performance, in my experience. However, I'm speculating that in extreme performance engines that turn up at 40K or more, this isn't something you want to happen. There's a Loctite product sold for cases like this but the perfect solution is special installation tooling that provides for a press fit at the outer AND inner race. The MP Jets .06 was done this way, for some reason, despite being a sport engine. With all due respect, metal retainer failure in our applications can be due to cheap bearings, or bearing contamination during installation. This is why I offered my technique for bearing replacement emphasizing PRISTINE conditions and cleanliness which is what guarantees a good result for your efforts. I have some Norvel engines in .25 and .40 sizes that need rebuilding for which I have the bearings on hand. Let me get the sizes for them and check the specs. Critical family and health issues have kept me from the work bench for the most part, the last half dozen years. I'm in Canada and it's 4 AM, (insomniac) so I really have to get back to bed now, I have commitments that need attention. Will add to the discussion in due course. Thanks for the opportunity to get back in the game. Andy

***** A quick search yielded this. www.globalspec.com/learnmore/mechanical_components/bearings_bushings/bearing_retainers_bearing_cages Phenolic is a good retainer choice as the pores of the fabric soak up oil and can withstand, to a degree, poor lubrication conditions. In industry, many times they were THE solution to a unique bearing failure situaiton.

hopeso To follow up on a strategy to enhance success with Bruce's very good tutorial, about replacing engine bearings, I present the specs for the bearings in the Norvel .40 This is from SKF, a Swedish company, generally regarded as the top bearing outfit in the world. Back end bearing is 61902 and it's rated for 34,000 RPM 61902 ZZ is shielded both sides rated for 28,000 RPM 61902 2RS is sealed both sides, rated at 16,000 RPM A .40 with an 11 X 7 or 12 X 6 prop will turn at 11,000 to 13,000 RPM The open bearing's rating is with oil lubrication The shielded and sealed bearings ratings are with factory applied grease. I've found that after a season of run time, the grease in the shielded bearing is mostly flushed out and it then becomes, basically, oil lubricated as with the factory installed bearing. Even with the fully sealed bearing, for SPORT application, we are well within the factory specs. The front end bearing, which, in my opinion, should always be a sealed bearing has similar specs Unfortunately, SKF doesn't offer this bearing with seals. But here are some specs. 699 open bearing, 48,000 RPM 699 ZZ is good for, 38,000 RPM Good practice on Norvel's part is that their front end, factory bearing, is shielded, at least on one side,,, the one facing the environment. There's no brand name on the Norvel bearings but I'm sure that as with the entire engine, Norvel hasn't cut any corners there. With care, keeping the bearings clean, you can pop in original equipment bearings. Or, pay a little extra and go with shielded bearings on both ends just to be sure.

hopeso The other factor to consider in this application is that the environment inside a methanol/nitromethane powered engine can be quite corrosive. I've been using stainless bearings with great success since, on inspection, most of the bearings I've replaced have suffered from corrosion more than wear. Although stainless bearings are not immune to corrosion, they do corrode far more slowly than regular bearing-steel. The choice of oil also plays a crucial part in reducing corrosion. Many of the popular methanol-soluble synthetics (Coolpower, Klotz) don't have particularly good anti-corrosion packages so a few percent of castor oil helps. More advanced synthetics such as those from Fuchs (Aerosave/Aerosynth) have a brilliant anti-corrossion package which all but eliminated the effects of the low PH environment created by the combustion of nitromethane and the tendency for methanol to absorb water.

Clarence Lee recommended ATF as an after-run oil once you have diluted the remaining glow fuel in the engine with WD40 or CRC 5-56. Was in RC Modeler magazine early 90's

Try RC Bearings at www.rcbearings.com/ they have always given me excellent service.

It's a simple metal bush on lower side of conrod

Meu português não é bom, mas vou tentar responder. Acho que seu velho motor é preso com óleo solidificado. Ganhe uma jarra grande e preenchê-lo com um solvente, como acetona ou removedor de tinta. Colocar o motor inteiro e colocar a tampa no frasco. Deixe de molho por duas semanas. Em seguida, retire o motor e deixe-a secar ao sol, ao ar livre, durante 24 horas. Em seguida aquecer o motor com um soprador de ar quente. Agora estou a tentar tirar a manivela e rolamentos conforme mostrado nos vídeos. Limpe todas as peças com água e sabão e spray WD40 para evitar a ferrugem. Aproveite todas as peças em limpo, óleo de rícino. Coloque as peças sobre uma toalha de papel para permitir que o excesso de óleo escorrer. Colocar essas peças em um saco plástico. Levá-lo cabeça e caso e lavagem, novamente, com água e sabão. O caso com um soprador de calor e em seguida toque o caso contra a mesa e o rolamento deve cair. Se não, você precisa aquecer o caso de maior calor. Quando você tomou os rolamentos para fora, limpe o caso novamente, com água e sabão e deixe o processo seco. Boa sorte.

Open glow plug and drop few drops of multigrade 20w40 engine oil in it when the piston is in bottom dead center and then give it few light hand cracks so the piston and sleeve/liner are lubricated

That sound reasonable and logic. Did buy a tt. 46 pro today. I will remember this advice. Regards

Usually good for a couple of years at two or three flights a weekend -- whatever that adds up to.

sounds like lots of pay off for the little work. thanks for the info.. im new to RC.. so much to learn.. i have learn more about electric than gas since my introduction to rc has been building learning to crash quads. but now im wanting to spread my wings. iv built one rubber band balsa kit.. i have 2 more on the shelf i want to convert to RC. i was lost tho because i did not know what dope was until i found some recently and bought it.. so im gonna start on that soon.. lots of fun to be had in this hobby and lots of directions to go from gliders to multirotors to nitro in the end tho i guess one thing is true.. if you are not crashing you are not flying enough :D have a great day. rock on from AZ, US. chris.

Its taiwan made, one of the best nitro motor, it's pro 46 nd pro 50 is excellent

no se si encuentres ese motor, pero seguramente encuentres buenos motores a un buen precio en hobbyking.com

Any multigrade 20w40