ChrisAttebery

My Feedback: (15)

It will probably run just fine unless the piston and sleeve were really scratched. It sounds like all he's got into it at this point is a set of bearings. What's the worst thing that could happen? He could blow it up and be out $10 for a set of bearings.

I had a Picco 80 early in my boating days that blew up a couple bearings, a rotor valve and a crank. I just kept putting it back together and it kept running strong each time.


Chris

somegeek

My Feedback: (2)

This is my thought exactly. ~$10 for the bearing set shipped + time. I finally got to tear down one of my engines so now I have a good idea of how it's done(been really curious regarding how this was done). I only have so many hobby $ in my budget so if this thing runs a little weak but still moves my plane then good... if it runs like crap - meh - good experience either way. If it runs like crap, I'll move on to attempt to glaze the piston with xjet's suggestion.

somegeek

Jazzy

I'm short on time here so I may have missed something but the con rod is just fine as long as the bronze bushing is still within acceptable tolerances. Since it is all is GOOD! Those little scratches and gouges won't hamper a thing! There is no appreciable material removed in any one place so there is nothing to worry about. That con rod will out last the engine - even with those tiny marks on it.
Castor - even 2% - is excellent at helping prevent this from happening. Glad to see this is the consensus of opinion!

Put'er back together and go fly!!!

somegeek

My Feedback: (2)

Got it fired up - running Cool Power 15% w/ 3% castor added - APC 11.5x4 - 13,100 RPM for 1/2 tank. This is about 300rpm off of lean peak. At this point I can't complain! Looking forward to getting a few more tanks through it.

Thanks for the input all!

Gonna start putting 1 tsp of 0-20W Mobil 1 (fully synthetic - no petro components) in for ARO.

somegeek

daven

My Feedback: (1)

SomeGeek, is that normal rpm for that prop?

Were cracking 14-14.5k with a 10x7 APC.

on pipe

Yeah, sometimes it's fun, just for the challenge of it, to see how derelict an engine you can restore to running condition. What you can and can't get away with, etc... Ross

somegeek

My Feedback: (2)

I don't know. I switched to this 11.5x4 prop a little while back and tached it a few hundred off lean and then flew it but don't recall what it was running.

I do know this engine previously turned an APC 12.25x3.75 at 12,600 rpm.

I have a 10x6 I will try to see what it can do and will report back.

somegeek

XJet

With the damage you've got on the bottom-end of that con-rod I'd be tempted to keep the RPMs down if I can.

rainedave

My Feedback: (1)

Congrats somegeek! I really enjoy bringing old or damaged engines back to life. The fun is in the learning and the sense of accomplishment. Good work!

However, this thread has me a bit worried. I have a brand new AX46 and AX55 that each have about three tanks through them on the stand. I haven't flown either one yet. I wondering if I should just go ahead and put new rear bearings in both of them before mounting them in planes.

David

proptop

My Feedback: (8)

Dave...if you can make sure and run the engine good 'n dry while it's still warm, then ARO it real good...the stock bearings will be o.k. for a while.


somegeek...the r.p.m. might pick up a bit as you run a few more tanks through it. However, I agree w/ X Jet about keeping the r.p.m. down. That rod might last a good long time at lower r.p.m. levels, but start winging it up and it could let go...you have some serious stress risers in the bottom end of that rod.

somegeek

My Feedback: (2)

Thanks for the info guys. This engine normally turns my 11.5x4 prop for my Sig Somethin' Extra so I'll stick with it. Not going to rev this one.

I did test the 10x6 APC sport just now and it flirted with 15k while lean. Richened it so it settled around 14,500-600ish. This was just a test. I put the 11.5x4 back on it.

RD - this got me thinking as well. I just ordered a few more sets of bearings. Spare for this engine and then to replace the stock bearings that appear to be holding up in another .46AX that is about a year older. No feeling of wear when I turn the shaft by hand but I will be replacing the bearings before I fire it up again. Should go pretty quick now that I have the method down.

proptop - I do like the idea that this might pick up a few more RPM.

Did get me wondering how long my performance might have been suffering due to the rear bearing being in not so top condition.

somegeek

XJet

I really hope you ordered some of RC-Bearings bearings and not the ones you showed us earlier.

You've seen what a self-destructing metal cage can do to your engine -- you don't want to put more metal cages in. You really ought to spend $6.95 and put in some decent bearings with polymer cages -- they won't let go like the steel ones.

somegeek

My Feedback: (2)

Yep - ordered from RC-Bearings with the plastic retainers.

somegeek

Bax

My Feedback: (11)

We'd consider a 10 x 6 propeller a bit small for the O.S. Max .46 AX engine. We tend to run a 10 x 7, 10 x 8, or 11 x 6 or 7 prop. We run the engine just below 13,000 RPM when leaned to just rich of peak RPM when on the ground. Higher RPM running will surely shorten the life of your engine.

One thing about the connecting rod.....the damage to the lower-end will have severely stressed it. We'd not be surprised if it came apart soon. Even though it was polished to remove sharp edges, the lows were not polished-out to be smooth depressions with at least a 6:1 slope (similar to the shallow slope in a wooden scarf joint). You'll still have the stress risers, and the RPM you mentioned will encourage them to cause cracking.

somegeek

My Feedback: (2)

Thanks, Bax. Gonna keep the RPMs on this one down... no plans to run it as a rev'r.

somegeek

longdan

I'm glad you have seen the light and ditched those stainless steel bearings. They are just bad news; a failure waiting to happen. Making ball bearings from stainless steel is a contradiction in terms. They are a gimmick. It is a much better idea to use steel bearings that work and find a better way to protect from rust than to actually install stainless steel bearings. The trade off of rust resistance vs. longevity and functionality is not worth it. I cannot believe that s/s bearings actually cost more than steel ones.

errie

Dar

Where can we get these bearings with "plastic like" cages?

The local bearing okes here in SA does not know, what the heck I am talking about!!!![:@]

somegeek

My Feedback: (2)

errie - RC-Bearings.com.

somegeek

errie

Thanks, will go and check it out

DarZeelon

Quote:

ORIGINAL: errie

Dar

Where can we get these bearings with "plastic like" cages?

The local bearing okes here in SA does not know, what the heck I am talking about!!!![:@]

Errie,


It looks like Geek beat me to it...

Paul McIntosh (RC-Bearings) now offer most of his line of rear bearings; even in the basic, standard $4-$7 sets, with a standard 120ÂșC polyamide cage.
The running temperature for any glow engine's bottom end is significantly lower, so investment in a higher temperature 180ÂșC polyamide, or phenolic cage would just be a waste of your money.

These synthetic cages are offered by Paul in most rear bearings, just because an occasional failure of this cage, especially in a two-stroke engine (but the con-rod can also be damaged in a four-stroke engine), can cause such massive damage.

somegeek

My Feedback: (2)

Opened up my bad rear bearing after reading Bad Tooth's bearing failure thread and seeing his pics.

Most bearings were pitted. One fell apart once removed here as well:











Doesn't look like the enemy here was a stainless bearing retainer fragmenting.

somegeek

DarZeelon

Cage failures are still a much more common occurrence than actual ball splitting.
But even that can happen... And even in NTN, it seems.

Bearings in model glow engines are never loaded even close to their limit... No explanation here.

RC-Bearings

My Feedback: (1)

This failure is almost certainly due to corrosion and fatigue. I have seen it happen with a few bearings and usually with YS and OS .91 engines. These bearings HAD to be making a lot of noise for a while!

RC-Bearings

My Feedback: (1)

Where do you get your information? Did you know that I sell more stainless steel bearings than bearing steel and that no one has complained about logevity yet?

XJet

Stainless steel (for all its virtues) is not as hard as regular bearing-steel which means that the initial rates of wear for stainless bearings is higher than that of regular bearings.

Here's a quote from a major bearing manufacturer:

"In addition to its affordability advantage, chrome steel bearings outperform stainless steel in some important application attributes. The superior hardness of chrome steels make them quieter in operation than comparable bearings of standard 440 grade stainless steel. Extra hardness also gives chrome steel bearings a longer working life, when properly maintained, than stainless alternatives"

The "chrome steel" they're talking about is actually the hi-carbon, low-chrome alloy commonly used for bearing races and otherwise known as "bearing steel".

One of the problems with stainless is that you can't use high percentages of carbon (which is what gives steel its "hardness" because this promotes the production of carbides within the metal's matrix. Those carbides are *very* hard and do a number of *bad* things including producing hi-spots that make the surface rough (promoting wear) and also act as a starting point for intergranular corrosion.

The reality is that model engine bearings are generally run at far below their maximum ratings so wear isn't as much of an issue as corrosion so there may be merit in some cases to using stainless races. However, in very high-performance engines I'd go for bearing-steel over stainless every time.

Given that I've *never* had a corrosion problem with any of the non-stainless bearings I've bought from RC-bearings, it becomes hard to convince me to pay the extra $5 for the stainless option :-)