Min Air bearing maintenance questions....

[Hammertime]

Greetings all,

I am in the process of stripping a Fury Extreme to gather the pieces for a new Stratus conversion.

A couple of questions...

1) In another life, I flew a plastic helicopter that was notorious for eating bearings, so we pulled them down and greased them often, esp mainshaft bearings and clutch/pinion/start shaft bearings.

2) I want to service the bearings I will be re-using from the Extreme to the Stratus; what do I do with them? Replace them? Grease them in the blocks, (not possible on all of them, esp clutch stack)? Remove them from blocks, grease and re-assemble? Or just order all new bearings and replace them?

3) I have been told that MA does not use grease in their bearings but rather an oil like Tri-Flow. Is this true? Best method?

Thanks,

Tim

[bighands3d]

how old is the machine and how much flight time, any crashes.

You can regrease the ones you can remove. and reinstall them most come out pretty easy.

Just ck all the bearings for notchy felling. (replace them if you find any)

[Zilly]

A greaser with Union 70 Grease is worth using on all the bearings you are going to re-use. I cant see triflow oil being much use it won't stay in there too long!

z

[EricLarson]

The major problem with greasing bearings is that often people put more dirt into the bearing than was already there. The races need to be VERY clean and the grease that is put into the bearing needs to be compatible or fully replace the existing grease.

If I grease a bearing, I fist soak it in MEK or other similar solvent to remove the existing grease. I then let the bearing dry. Afterward I will grease it up.

If you also load the bearing with grease you will notice that it will drag a lot when new. This is not a huge problem if the shaft tolerance is tight, but if the bearing has the chance it will spin on the shaft causing a huge problem.

Most bearings come prelubed. When I have stuff apart I will spin them and put a load on them to see if they feel ok to me. I have gotten over 1000 flights on a lot of bearings supplied by Min Air. IMO if it is smooth just reinstall and fly. If it feels dry, then you may consider cleaning it and then greasing it some but running it low on lube may have already damaged it. If it feels gritty or notchy, by all means THROW IT AWAY. Once it runs with dirt in there or there are notches in the race, it is garbage and time to get a new one.

To get the bearings out of the blocks you need to heat the block with a mini torch. The bearings are and should be loctited into the blocks.

[misskimo]

cool , has anyone ever tried the ceramic bearing ? I was thinking about replacing mine in my Ion , since a fellow on ezone said he replaced his and got about 1 minute longer flight time since it ran so smooth

Tony

[EricLarson]

I don't think the friction is any less with the ceramic bearings we have available vs the ones we use. Also only the balls are ceramic, the races are still steel.

[Wayne]

I know a lot of people use the greasers, but at the risk of getting yelled at I don't use them on high speed bearings. As Eric pointed out, there is a huge risk of putting dirt into the bearing. When they are built, they are actually assembled in clean rooms similar to where they build high-reliability electronic circuits.

The other problem is what grease to use. Most of the greases I see people use are for full size automobile bearings..., not the tiny ball bearings we use. Too much grease, or the wrong type of grease will surely cause the bearing to "skid" when you start it. The races will spin, but until you get some of that goop out, you will not be spinning the actually balls. And that will cause you to wreck the bearing.

The bearings we use are greased at the factory and are designed to last a long time with no service. The primary way I see us wrecking bearings is by crashing and by spraying motor cleaner in the bearings. (taking the grease out...)

Hope this make sense. A lot of people know way more about this topic than I do, but I think I've correctly conveyed what I have been taught.

regards

Wayne
www.flymha.com

]

[EricLarson]

I agree with you Wayne. That is my opinion also from research and asking a lot of people that do know a lot about small bearings and the engineering side of things.

[ChrisLaFollette]

I used to take my bearings out every 8 or 10 gallons and pull the sheilds off carefully and spray them with Brake Cleaner and then blow them out with an air compressor and then I would put some grease in a syringe I have here and it has a little tip, I would then squirt grease into the bearing after I spun it to make sure it was nice and smooth. Do both sides and then put the sheilds back on the same way they came off and then put the retainer back in there so the sheild stays in place. Works good and saved me about $40 something for the Greaser. Its very simple to do. I use a razor blade to get the retainer out. The tip that goes on the end of the syringe came from a Ink Refill kit for a Printer.

[EricLarson]

That sounds like a lot of work. I have several times run the bearings in my machines to a minimum of 60 gallons each without worrying about the bearings. I just use the stock MA ones. If a bearing goes bad, it was probably caused by contamination or a flaw. I know I have not replaced some in over 2 years now. No problems.

[ChrisLaFollette]

Eric it actually isnt. I can take a bearing from original shape to greased and ready to install in just over 5 minutes. Doesnt take long at all and its VERY simple. It sounds a LOT harder than it is.

[EricLarson]

My concern is that if any dirt gets in there or if the consistency of the grease is not per OEM spec then more harm is done than good. As Wayne stated earlier, if the grease is not compatible with the gearing tolerances the balls will spin in the races. If the grease is too thin then the balls can burn the races.

Anyway, unless the bearings are damaged or washed out they are already lubricated for the life of the bearing. Most bearings in commercial applications last for nearly unbelievable amounts of time.

[ChrisLaFollette]

I agree. I think the grease I used is a little to thick and wont get inside the cages to lube the inside of the cage so the balls dont wear out. What is a good grease to put back into them? I know greasing bearings is a good idea but im not going to invest in a greaser. My way is better IMO. As I take the sheilds off, wash them off with Brake Cleaner, blow them off, Wash the bearings and races and cages all out with Brake Cleaner and then blow them out. Take the grease from a syringe and squirt it into the bearing and then put the sheilds back on and retainer back on. Doesnt take long. But like I said what is a good grease to put into them? The stuff I have is awful thick.

[RC-Bearings]

Any light weight CHANNELLING grease will work just fine. You want a channelling grease as it only retains as much grease in the rolling areas as it needs and the rest moves off to the side. I have used Amsoil light synthetic spray grease for many years on small bearings.

[alexander]

As Eric pointed out, there is a huge risk of putting dirt into the bearing.

If helicopter manufacturers were not so economy minded and used rubber mast sealed bearings we'd all be better off. Air drys out the solvent in grease leaving behind soap, so if the rubber seal is air tight compared to shield with its air gap it will keep dirt out too. Rubber sealed bearings are rated well above helicopter operating rpms and have minimal drag.
It also means when you carefully wipe the surface off the dirt comes off too. Rubber seals will pop out with a razor knife. One can go to an after market bearing supplier and buy sealed mast bearings cheaper that you'd get shielded ones from the helicopter manufacturer. Unfortunately some of the smaller bearings cannot be acquired with rubber seals.

[RC-Bearings]

The problem with seals is they have what is referred to as "sticktion". This means that while they rotate with relative freedom, the stick when not rotating and need extra effort to get them started. This is not what you want in the reciprocating parts of a heli. It could be tolerated in the rotating parts, though.

I have some bearings with Teflon seals that have almost no drag.

[DavidH]

I have used rubber sealed bearings on the main mast. From my experience the shielded bearing offer considerable less drag than the rubber sealed ones. I base this on spinning the rotor head by hand. With the shielded bearings the rotor head will spin freely. With the rubber sealed bearings spinning it by hand and the rotor will stop fairly quick after spinning it.

David

[alexander]

True enough but areas blasted with rotor wash like mast and tail shaft bearings or clutch bell start shaft supports would surely benefit from seals. I don't feel you'd see a reduction in power with a few rubber seals.
Some engines use front rubber seals and I have replaced them with no change in real world power.

Stephen

[EricLarson]

It may be true in theory, but in practice the only bearings I have go bad are due to impact with the ground... I pretty much never have bearing failures. I rebuilt both machines a month ago and after an entire season ( about 110 gallons of fuel or so) I only found 1 bearing that was questionable.

Each to their own. The only bearing on my machines that is sealed is the clutch stack. The reason for that is to reduce contamination by clutch dust and particles. Otherwise I use off the shelf MA bearings.

Like I said though, make up you own minds.

[Gary O]

When you compare the cost of bearings to the rest of the helicopter, it's not worth the risk. if they aren't smooth, chunk and replace.