Does it wear larger or smaller?

[Richard]

Inside surfaces wear larger, outside surfaces wear smaller. A cylinder wall is an inside surface. A rod journal is an outside surface.

Do you see anything amiss in that statement? How would you define the words 'larger' and 'smaller'?

 

[Dave Krall CFII]

Inside surfaces wear larger, outside surfaces wear smaller. A cylinder wall is an inside surface. A rod journal is an outside surface.

Do you see anything amiss in that statement? How would you define the words 'larger' and 'smaller'?

Generalisations, although often largely true are usually inaccurate at some point. It appears here that the lg/sm reference is to average diameter of the parts ?

 

[Richard]

The way I see it a cylinder is a hole and a rod journal is a hole which means both are inside surfaces. The cylinder hole will increase in diameter (wears larger) as it wears but the rod journal wears smaller??? I know what I know but something about the statement just doesn't seat right. Hence my question about the definitions of the words 'larger' and 'smaller'.

 

[Dave Krall CFII]

The way I see it a cylinder is a hole and a rod journal is a hole which means both are inside surfaces. The cylinder hole will increase in diameter (wears larger) as it wears but the rod journal wears smaller??? I know what I know but something about the statement just doesn't seat right. Hence my question about the definitions of the words 'larger' and 'smaller'.

Seems then, that both parts would be outsiders and would both wear larger, all other factors equal and ignoring individual Reynolds hardness factor or whatever it's called.

Inside surfaces wear larger, outside surfaces wear smaller. A cylinder wall is an inside surface. A rod journal is an outside surface.

Do you see anything amiss in that statement? How would you define the words 'larger' and 'smaller'?

The inside surface wears its outside contact larger and the outside surface wears its inside contact smaller, all other factors being equal.

 

[Richard]

Seems then, that both parts would be outsiders and would both wear larger, all other factors equal and ignoring individual Reynolds hardness factor or whatever it's called.

But the statement says that outside surfaces wear smaller. In the example of the cylinder wall it is the cross hatching which wears faster than the rings. So the outside would indeed wear smaller (decreased thickness). I think it's a terminology problem.

The inside surface wears its outside contact larger and the outside surface wears its inside contact smaller, all other factors being equal.

But the inner surface of the rod journal would wear smaller,ie, reduced thickness, right?

But more than it being a simple terminology problem is the examples given (cylinder wall, rod journal). Perhaps if push rod were substituted for rod journal I wouldn't have so much of a problem with the way the statement is expressed.

 

[Greg Bockelman]

The way I see it a cylinder is a hole and a rod journal is a hole which means both are inside surfaces. The cylinder hole will increase in diameter (wears larger) as it wears but the rod journal wears smaller??? I know what I know but something about the statement just doesn't seat right. Hence my question about the definitions of the words 'larger' and 'smaller'.

Well, I guess I am confused. I was operating under the assumption that the rod journal was the part of the crankshaft that the rod bolted on to. If that is the case then it is an outside surface and wears smaller. If in fact the rod journal is the fat end of the connecting rod, then it is in fact an inside survace and wears bigger.

So educate me. "Rod Journal" Part of the rod or part of the crankshaft?

 

[Nav8tor]

Well, I guess I am confused. I was operating under the assumption that the rod journal was the part of the crankshaft that the rod bolted on to. If that is the case then it is an outside surface and wears smaller. If in fact the rod journal is the fat end of the connecting rod, then it is in fact an inside survace and wears bigger.

So educate me. "Rod Journal" Part of the rod or part of the crankshaft?

Greg, I'm with you. A rod journal is part of the crankshaft and is therefore an outside surface which would wear smaller (i.e. the diameter will decrease as it wears)

 

[gismo]

So educate me. "Rod Journal" Part of the rod or part of the crankshaft?

You had it right Greg:
Main Entry: jour·nal

3 : the part of a rotating shaft, axle, roll, or spindle that turns in a bearing

 

[Henning]

Inside surfaces wear larger, outside surfaces wear smaller. A cylinder wall is an inside surface. A rod journal is an outside surface.

Do you see anything amiss in that statement? How would you define the words 'larger' and 'smaller'?

It's not amiss, remember the rod journal is part of the crankshaft, not the rod. The journal is the "solid" cylinder, whose outside surface is in contact with the Rod Bearing which is secured in the big end Rod Bore.

As to larger and smaller, when you measure the critical dimension, the value goes positively when it gets larger and negatively when it gets small. Just read the numbers off the micrometer or caliper or what have you.

 

[gibbons]

...the value goes positively when it gets larger and negatively when it gets small.

Does that mean that the value goes negative when it gets larger if you're in Oz?

 

[ScottM]

Inside surfaces wear larger, outside surfaces wear smaller. A cylinder wall is an inside surface. A rod journal is an outside surface.

Do you see anything amiss in that statement? How would you define the words 'larger' and 'smaller'?

I read it as on a filet the as it wear the radius of the filet will increase. On the round as it wears the radius will decrease.

 

[Skip Miller]

I read it as on a filet the as it wear the radius of the filet will increase. On the round as it wears the radius will decrease.

It is pretty simple, really (unless I miss the point of the whole question).

The metal wears away.

On a journal, the diameter decreases. In a bearing, the bearing diameter increases.

-Skip

 

[ScottM]

It is pretty simple, really (unless I miss the point of the whole question).

The metal wears away.

On a journal, the diameter decreases. In a bearing, the bearing diameter increases.

-Skip

I was wondering if I missed the point as well. But maybe that is because I am an engineer and had an idea of what they were talking about in the first place.

 

[Henning]

Does that mean that the value goes negative when it gets larger if you're in Oz?

Well, down here it's irrelevant, since the only value down here is a round of golf.

 

[gismo]

Does that mean that the value goes negative when it gets larger if you're in Oz?

It usually means your old enough to need reading glasses but too stubborn to wear them.

 

[Richard]

I guess my "I am a dumb****" post never made it here. Basically, it said I thought someone must be putting stupid pills in my cereal 'cause there aint no other way for me to explain my comment 'bout rod journals. It is especially embarassing 'cause I've torn down, rebuilt, and installed at least 6 engines. All I know is whatever I was thinking it made sense at that time.

 

[Eamon]

Mine gets larger as it wears...........................
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