ro347

My Feedback: (13)

I just received a set of bearings for a 2 stroke engine. Im looking at what seems to be a plastic insert on the rear bearing(holding the balls in) Is this right???? Im skeptical due to heat. Has anyone else seen this?

engine OS 46AX

ChuckW

What you received is likely a sealed bearing which is packed with grease. The plastic seals aren't holding the balls in; they are just holding the grease and keeping dirt out. You can easily remove the seals with a sharp pick or something. Just be careful not to gouge it down into the balls and races.

ro347

My Feedback: (13)

Is that what im seeing? Im not to sure about that...but here are some pics. What do you think?

MetallicaJunkie

the pic to the far left looks normal....ive changed the bearings on several engines and havent seen bearings like the one in the middle ...maybe its not intended for high heat applications, or its a new "space age" material that can take heat

where did you get the bearings from?

Campgems

The last few sets of bearings I got from RC-Bearings had the plastic cages. They are just fine. The old riveted metal cages are disappearing. The molded ball retainers has to cut production steps and cost down considerably. One press and it's in place vs the metal cages that had a rivet between balls holding the two cage halfs together. 1 pc vs apx 11 pcs.

A heads up though , one pair of that type bearings that I got from RC-Bearings were off size, internally. They fit the bore and the crank OK, but when assembled, there was a huge amount of ball clearance, they rattled when you shook the crank case. Another set solved that problem.

As for heat, the bearings shouldn't get all that hot. Remember, the crank case on a 2 strokegets a good gulp of cold air mixed with fuelevery rev and it all goes through the crank shaft, cooling it. I would be susprised if the bearing temp was much over 100 on a 70 degree day.

Don

ro347

My Feedback: (13)

Actually all the same bearing. The first 2 pics show both sides.

I got the bearings from RC-Bearings.com.

The only thing i have to compare them to are the OEM units; and that piece is made of metal. Im questioning due to heat.

Villa

All of the bearings look normal to me for our R/C engines. The balls are held in their correct relationship to the other balls by those plastic "spacers". All of the bearings seem to be of the open type as is needed for our engines.

ro347

My Feedback: (13)

Thank you guys. being that these are the first set of replacement bearings I ever ordered...I wasnt sure if there was something wrong being that they are different than the originals.

Happy flying!

MetallicaJunkie

i have ordered all my bearings from RC Bearings.... i guess i hadent paid too much attention to their construction [8D].... I do most of my engine related work in a low light environment

freakingfast

My Feedback: (3)

Those are the bearings you really want to use. The plastic retainers are far superior to the riveted or bent tab metal type.[sm=thumbs_up.gif] They wear better, have less corrosion issues, less drag and can take higher speeds. They are steadily replacing the phenolic cage type that were the king of high speed bearings.

ChuckW

I stand corrected. they aren't sealed; just normal bearings with a plastic cage. I guess that's what happens when you answer before seeing a picture.

proptop

My Feedback: (8)

One more thing to add about the old metal bearing retainers, is if a tab breaks off, or the metal retainer disintegrates, it goes through the the engine with (typically ) disasterous results.

There is no need to worry about the polymide (plastic ) retainer...they can also take the heat of a 4 strokes crankcase, which is much hotter than a 2 stroke.

ro347

My Feedback: (13)

One more.....how should the con rod be positioned when reassembling?

Montague

what do you mean about the con rod?

On ABC engines like the OS 2 strokes, you just drop the piston/conrod assembly down, connect to the crankshaft, and then slide in the liner.

The big trick is not putting in the conrod backwards. Some engines have a non-symetrical conrod, and if you install it backwards, it might not fit, or it might fit and not get proper lubrication when running. When taking engines apart, I often use a magic marker to mark the back of the conrod so I don't put it together backwards.

Another tip, if the conrod is still attached to the piston, you can often tell which way the piston goes by the top. You get more blackening close to the exhaust port.

Hope that helps, or can you clarify your question a bit?

ro347

My Feedback: (13)

FYI: As far as installing the con-rod on the 46AX, one side of the rod has a bushing exposed and one side doesnt. The exposed side faces the crank shaft.

Engine is back together and just needs to be run again. Im not expecting any issues. Thanks for the help!

SeamusG

here's pics of what ro347 is talkin' about

pic 1 - beveled/exposed side
pic 2 - flat side

proptop

My Feedback: (8)

The bevel or chamfer faces the crank...the chamfer is necessary to clear the radius at the base of the crankpin.

SeamusG

Ain't knowledge great! Thx PT ...

ro347

My Feedback: (13)

THANKS FOR THE BACK-UP!

SeamusG

Apicture is worth a whole bunch (or so folks keep sayin') ...

OS46 AXcrank pin &con rod ...

GaryHarris

Phenolic=plastic. Same thing.

SeamusG

Em, my Somethin' Extra fuse has a phenolic tube as a guide tube for the wing tube.

Here's what I found out about phenolic ...

Laminated sheets, tube and rods are produced in many grades, sizes and colors. These laminates combine a base material- canvas, linen, paper, glass cloth or Nylon cloth, with a resin-phenolic, melamine, epoxy or silicone, under high heat and pressure to produce a new material with specific characteristics. These characteristics vary with the grade and its use.

Campgems

Seamus, good post.

One common one that gets over looked when talking about phenolics is Formica. The backing is a thin sheet of phenolic. The stuff is nasty on your lungs when cutting, Stinks like crazy and floats in the air, but it will machine nicely. Most plastics don't. I wouldn't call plastic and phenolicone in the same, they have few common characteristics.

Don

GaryHarris

Plastics!

SeamusG

Emmmm, Dustin Hoffman & Katharine Ross - Plastics!