mike early

I know that carbon steel is harder than stainless steel, but assumed that the SS would be better. I reckon if corrosion is not an issue, the carbon steel races would be better. Is this how it goes?

mike early

Happy Anniversary!

P.S. Well written post.

Hobbsy

My Feedback: (102)

Mike, my Enya .53TN has stainless bearings from the factory but I have no idea how much you'd have to run it to find out how durable they are. On the Enyas, you can remove the screw that holds the carb bracket and inject Corrosion X to keep the cams from rusting.

chistech

Hey Mike,
Thanks, I didn't even realize it's been a year. One thing I didn't mention is that although I live in the North East, I fly year round. Luckily I have a brother and a buddy who also flies with me. Even when its real cold we still will fly. I don't use ARO in my engines because they do usually go more than 2 weeks without running. I have recently been building more warbirds for myself so the time spans will get longer between flights for some models so I will start using it now. The reason I stated this is I would still use the plain steel bearings over the Stainless ones. Steel is harder than stainless and a bearing fails when the balls get out of round, the races get grooved, or things get pitted. Yes, I know that there are other types of failures but some sort of wear is usually what starts the process to failure. Load on a bearing is what initially starts wear. A harder, rounder ball will perform longer. A race that retains it's proper groove again will last longer. If a engine is maintained correctly or used often the steel bearings should be fine. Again, don't rule out excessive heat. Cooking a fuels lubricant to the bearing surfaces then putting the model away for a while will cause the balls to load up with crap. When you go to restart a ball could stick and not roll causing the chain of events that can lead to failure. A ball that locks up is what usually causes the cage to detonate.These are some possibles and by no means "God's word" to bearings going so I'm not looking for arguements. I again, am just going by my own experiences. I too have never had the need to put bearings in any of the engines I bought new but I like buying used engines, especially 4st's and rebuilding them. It is funny that this post was started on a Saito issue. A customer that I am building a P40 for called me today to say that he has a issue with a S100 that has bad bearings. It seems they were replaced about a year ago and are now gone again. The bearings were originally replaced with factory bearings. I wonder if the 100's have a problem with something being "out of spec". Things are made all the time that get recalled or replaced because they got out the door with a problem. Just thought of something. I know of a guy in another club who was over tightening his prop nut so much that it caused too much constriction on the crank shaft bearings. Yes, it can be done. Tighten the prop tight enough and you can enlarge the hole in the ALUMINUM thrust washer ever so slightly and every time you sock it up it will get tighter as an assembly. The rear bearing in a model engine, although used as a thrust bearing, is really a radial bearing. Making the whole assembly tighter will put the load of the balls up against the forward facing edge of the outer and inner races. This allows less bearing surface contact between the balls and the races making the load rating of the bearing less. I.E. bearings are rated like anything else to do a certain job if used in the proper manner. A radial bearing that is being used as a thrust bearing is already at a deficiency never mind when a excessive side load is applied. If tight enough, the lubricant will not be able to get between the balls and the races or actually, be forced out because there is just no room for it. A soft Stainless Steel bearing will not tolerate this. A model engine crank should have some back and forth "play". Not a lot, but some. If it doesn't you will eventually have a problem. When I assemble a engine I will always put a prop on the crank without attaching the piston and and check to see how it spins. I have found a brand new bearing that was bad this way. Because it is new, don't assume it is ok. I hope I didn't start people thinking they have the wrong rear bearing in their engines. If people don't understand the difference between bearings, our standard type ball bearings in our engines are designed to take a radial load. ( spinning shaft ) a thrust bearing takes a axial load ( load is from the side ). The crankshafts in our engines are kept in the motor by applying a side load to a radial bearing. Because of the size of the bearing compared to the size of the axial load we get away with the improper application of the radial bearing. In a perfect world there would be both a axial bearing at the immediate rear of the crank to handle the side load and then a radial bearing right next to it to handle the spinning load. There are large bearings that do double duty in this way. A good example of a double duty bearing would be a tapered roller bearing like in a axle of a trailer or car. It takes a radial and a axial load. Again, even on a vehicle, the bearing is allowed to have some "play" by not tightening the axle nut too tight.

Hobbsy

My Feedback: (102)

Chris, you've touched on something I've been curious about for a while, the engine pictured here has a roller rear main bearing. I guess I should check the front bearing and see if its set up to handle the thrust or maybe the rear of the crank has a surface to handle thrust like a bushing engine does. I'll check it out.

mike early

You're welcome! Building a P-40? Do tell. Which kit? Best plane ever!

chistech

Hobbys,
if the roller bearing in the engine is flat like a wide wedding ring then it is just a roller radial bearing. Is it a one piece unit like a standard ball bearing? What I mean is there a seperate outer race and seperate inner race with tapered rollers caged to the inner race? If the outer race bearing surface is angled so that the inner race w/rollers is held in with pressure from the axial load then it is of a dual purpose. Both radial and axial. I would doubt that the front bearing, if smaller would be a thrust type bearing. It could be a ball bearing that is taking up the the thrust though. Years ago they experimented with all types of bearings trying to find what would work best. I think in the early years they got hung up on the thrust thing and followed the rule of the proper bearing for the proper application. I think you're right and you might find the crank held itself in like the old bushing engines. Those small caged roller bearings tend not to be that good. Hope your's are holding up fine.The normal axial load of a prop is light enough that it really doesn't put much load on our radial type engine bearings. If there is something else wrong in the engine though all hell can break loose. Mike, I actually assemble ARF's for my LHS and lately the customers are coming direct to me. I have now built just recently 5 Kyosho P40s including one for myself. I have bashed mine and this last one somewhat and will do more on mine over the winter. I will be stripping mine and recovering with aluminum monocoat then painting. I intend on putting split flaps and painting it like the one captured by the Finnish. It should be the only one around our local fields with German markings. This plane is powered with a Saito 62 and it flies absolutely the best. I might do a build thread just on the custom touches. For the money and the ease of handling for transport it can't be beat. As you can see in the pics it could use a lot more bashing but right now I'm flying it. The last pic is of the customer's with a OS70. You can see the home made gear struts and the zinc chromate green in the cockpit. Half a day and it will be done.

chistech

Hobbys,
I should of also mentioned that I respect your loyalty as a customer to Boca. In this day and age people all to often run to whoever offers them the lowest price. I know I mentioned that I will look for the lowest price but I also mentioned a supplier who stands behind their product which also means service. When I look for a new supplier of anything I research them first and of course price is considered but not the only criteria. When I looked up bearings for model engines, RC Bearings is what I came accross first. Their site, selection, and prices seemed good so that is who I did business with. Like you, I have not had a single problem with my bearing supplier and like you, are happy. I normally only try to make suggestions to others based on my experiences but will not criticize them if they choose not to take the advise. The only exception to this is my kids! I'm a father and my job is always to try and get them to do the best thing for them, but thats another issue. Although other people will try to tell you how to spend your money, it is still yours to spend. Do what feels right and that's it.
Mike, when your motor heats up you might find that the crankshaft itself is sliding slightly in the bearings. When you move it look at the front bearing where it contacts the shaft. Some small bearings will loosen up on the inner race for some reason. Do not worry about the end play as the prop will keep the rear of the crank away from the cover. Your bearings will last longer if there is play. The play actually allows the the inner races and balls to align better with the outer races. You will find that your crank probably spins quite freely with the piston unattached. This is a good thing.

XJet

That's a point in their favor, but I buy on value, not on whether a company advertises a lot.

That's fine, I've got *no* problem with people buying their bearings from Bocca and paying a premium for those reasons.

However, what I *do* object to is when someone like FBD who obviously knows very little about the subject starts suggesting that somehow a competitor's product is of inferior quality or performance simply because it costs less. That's disinformation and unfair on those who come here for honest and objective advice.

All I've sought to do was to challenge FBD's disinformation and provide people with the facts so they can make their own informed choices.

Some (like yourself) will buy from Bocca, probably for reasons similar to the ones you list.

Others will buy from RC-bearings because of the value their offerings represent

And chances are that a lot of folks will just drop into their local engineering supply company and pick up a set of whatever bearings they carry simply because it's more convenient.

It's all good.

mofosheee

My Feedback: (4)

As the originator of this thread.................I am truly sorry for all the angst, hard feelings and all "panties in a wad" that I have caused by initiating this thread.

I truly believe that Boca sells the same bearings that Paul of RC bearings offers. Get over it, it's only a hobby and bearings are from our Chineese friends.

mike early

So...what do you think caused your two initial bearing failures?
Is your 125 still eating bearings?

mo fo is a dirty word and must be bleeped?

mofosheee

My Feedback: (4)

In my own opinion...........root cause of failure was primarily due to using 100% synthetic rather than the castor/synthetic mix even though I was diligent about using after run oil and proper break-in.

Same happened on my Saito 180. Promptly installed ceramics. No problems since, ANY ceramic better than the standard bearings installed by mfg. Don't know why they are not doing so in the first place.

mike early

no no..i love ****.
i just find it funny that it bleeps people's names

mofosheee

My Feedback: (4)

On the serious note, ceramics should have been installed by the mfg. I can't say enough good about them.

Hobbsy

My Feedback: (102)

Confused terminology, axial is length wise along the crankshaft centerline and radial is circular around the crank centerline. Sorry Mike, XJ Et Al. FBD is very knowledgeable when it comes to bearings having been a Yamaha mechanic for many years, I'm sure he's seen just about every kind of bearing failure that can ocurr.

Thanks for the bearing info and your piece maker efforts Chistech. I'll pull the front off of that Seuvia and take a peak at that rear bearing. its actually just a nearly worthless collector engine I bought because of its rarity. I bought it at the RC FleaMarket in Lebanon , Pa. a few years ago.

Flyer95

My Feedback: (1)

I have a few Saitos but never a bearing failure. The stock bearings get some radial end play in Saitos after running 5-6 gallons thru them. Dont know the real reason but I think the stock bearings are softer than normal. I bought a Japanese YOKO bearing to replace the rear bearing in my Saito180 and this new bearing actually had one ball more than the stock rear bearing and is been holding up good for the last 3 gallons of fuel.
The fuel I use contains castor/syntetic oil at 20% and I also use 10-20% nitro. I never run them dry and never use ARO as I think it is more harmful than good for my engines.

Hobbsy

My Feedback: (102)

Chis, this thing has a circlip in front of the front bearing so obviously it handles the thrust, the rear roller/needle bearing runs on a hardened sleeve over the crankshaft, this crankshaft weighs almost as much as my whole Saito .56. Interesting construction to say the least for a 1.50.

chistech

Man, that thing was made! It looks like your right. They did use the front radial bearing as the thrust bearing. They must of felt that the compression of the motor warranted the wide bearing surface of the roller bearing and also the larger diameter of crankshaft the roller allows. Got to love model engineering.

mike early

Received my new bearings today. Upon inspection there is some noticeable axial play in the rear bearing. Strangely, there is very little in the crash-subjected rear bearings. Maybe some broken ceramic chips are holding it tight.

But my conclusions from this thread and 3 different sets of ceramic bearings are:

Perhaps Axial play is not as big a deal as I feared. Maybe the previous bearings had it and I never noticed. I have never observed any radial play in any of my bearings....

And perhaps, a little oil from the front bearing seal is not a crisis situation either...

mike early

To their credit, the Boca Bearings are performing wonderfully. After I turned the front bearing around the other way, there seems to be far less leakage from the front of the engine.
I still get the forward-backward (axial) play when the engine is hot, but performance doesn't seem affected whatsoever. The engine screams with delight.

larry@coyotenet

My Feedback: (21)

Having seen bearing failure in a Saito 125 my conclusion is that the mfg used a bearing with too little internal clearance, in other words they used the wrong class of bearing in that engine. I have seen this happen before with many different mfgs. Sometimes it is probably caused by just getting some bearings in a run that have less clearance, and sometimes it will occur in the entire engine run which means they used the wrong bearing to begin with. Two members of our club ordered a 75cc engine from Europe several years ago which had this problem. Three engines failed within minutes of being fired up for the first time, one lasted approx. 30 seconds before the rod bearing siezed. The importer of the engine ended up eating the entire batch and stopped selling them. I had the same problem with a Veco 19 way back in the early 70s so it has been around for as long as ball bearing engines. The solution is to replace the bearing with one with looser internal clearances so that as the engine warms up the bearing doesn't seize.

Larry

mike early

Do ceramics shrink when they get hot?

mike early

Update: It was my crankcase causing my issues of play. I tested this theory by shimming the front bearing with a strip of aluminum foil. No more axial play with Boca's or Paul's bearings. I have a new crankcase.

bjr_93tz

Whooa there Big Fella !!!!

I've got two Yammies (TZR250 and TZ250) in the shed so be a bit careful there with wild claims like that

RC-Bearings

My Feedback: (1)

[quote]ORIGINAL: TimC

X-Jet said it all. No need for my reply any more!