Could this be a reason for wrist pin bearing failure?

45u

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The first and second picture is of a crank and piston out of motors like we run. Notice how much of the bearing load is outside of the top of the rod taking away a good bit of the bearing surface and the bearing is not supporting the rod like it should. This is not good what so ever. All so see how much side to side play the wrist pin bearing has.





The reaming pictures of some of my radio control 1/5 scale motor parts. Notice the two washers which in close the wrist pin bearing on the ends making it where it does not move side to side much making a much better bearing load and is always very close to center. The upper rod end is supported all the times and the rod is not hanging off one side like on the motors we run. The washers cover the end of the wrist pin bearing where it cannot move side to side much as well as the rod cannot move much. The washers are made flat on one side, piston side and the others has a recues that allow the wrist pin bushing to stay centered much better than the set up on the motors we run. The rod does not fit over the washers. You will see on the RC piston there is still a little play and has to be but the ones we run have way too much side to side play.

Being on the motors we run the bearing load is much of the time on one side of the top rod not giving not near as much of a good bearing load? What do others have to think?










 
Makes sense.
I wouldn't particularly want to add extra mass of steel to the piston since I already need to find someone with a drill press to lighten the wrist pin for me (or let me use his drill press).
If someone were to produce a set of washers to fit and they were fairly light would certainly be interested in acquiring a set. :)
 
I would think a little more weight would be better than a wrist pin bearing going bad as when they do it really messes up the inside of the motor. I am going to drill my pistons and wrist pin. I just wonder how hard the wrist pin is and good chance will need a cobalt or harder bit.
If will be a while but I am making plains and try to make some wrist pin washers. My lath with are at my friend’s house taken apart and need to get them here at the house and set up.
 
Of course I agree it would be better than the bearing breaking up, but before it does so, if it does so, it would be nice to minimise vibration as much as possible. Can a light metal be used i.e. aluminium rather than steel or would it need the strength?
Carbide 9/32 is what's recommend on mr Jaguar's dragonfly site for wrist pin drilling.
Also I just found a source of a good bearing was recommended there too: Pistonbikes has one with the smooth cage looking like a single piece, I think it was $5
 
it doesn't need the strength, it needs the hardness. titanium works reasonably well if you throw away the needle bearing and use a bronze bushing instead.
 
the crankshaft centers the upper rod on the bearing.

/QUOTE]




I do not see how this is going to keep the bearing from walking side to side with out having something to keep it from walking. Yes the rod might be centered but necessary the bearing.
 
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it doesn't need the strength, it needs the hardness. titanium works reasonably well if you throw away the needle bearing and use a bronze bushing instead.

I have some bushing but the bearing if you can keep it from destructing would be better. Many older 2 cycles use bushing not the all seem to be using bearings.
 
Of course I agree it would be better than the bearing breaking up, but before it does so, if it does so, it would be nice to minimise vibration as much as possible. Can a light metal be used i.e. aluminium rather than steel or would it need the strength?
Carbide 9/32 is what's recommend on mr Jaguar's dragonfly site for wrist pin drilling.
Also I just found a source of a good bearing was recommended there too: Pistonbikes has one with the smooth cage looking like a single piece, I think it was $5


I have looked at that bearing and not so sure that it is any better the many others. Sorry to say the
Of course I agree it would be better than the bearing breaking up, but before it does so, if it does so, it would be nice to minimise vibration as much as possible. Can a light metal be used i.e. aluminium rather than steel or would it need the strength?
Carbide 9/32 is what's recommend on mr Jaguar's dragonfly site for wrist pin drilling.
Also I just found a source of a good bearing was recommended there too: Pistonbikes has one with the smooth cage looking like a single piece, I think it was $5


I have looked at that bearing and not too sure it is any better then many others. I am sorry to say the Stihl chain saw bearing is about 1.5 mm narrower then the stock bearing which would have more room to walk and decrease bearing surface.
 
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look back on the boards about 4 or 5 years - you'll see much more of this discussion back then before the shorter small end bearings started to go away - some folks even tried nylon spacers, but they melted - bearings in most kits got much longer after those days
 
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