Hmmmm.... Prudence tells me not to disagree with Randall... but here
goes :-)
Maybe I don't know what spines are. I thought that thing-a-ma-bob on a
drive shaft was a spline. Most I've seen aren't very tight -- they slide
back and forth a lot. If wire wheel like splines are stronger why aren't
they used on a drive shaft?
I assume one of the reasons a spline is used in any situation is the
connect/disconnect is easily done (wire wheels in a pit stop in 1909),
or there is a need for lengthwise movement as on a drive shaft. Seems to
me that the nature of a spline implies a loose sliding fit. I guess I'll
have to agree that if the splines on wire wheels fit tight enough to
have to be pressed on rather than loose enough to side on and off
easily, we probably would not have to worry about tightening the
knockoffs and the wear situation with them would not exist.
Again, in my mind, a spline with 1000 Billion elements and which still
slides on and off easily is a bearing.
> The little splines spread the forces over a larger area, because the
steel
> in the center of the bigger splines contributes little in the way of
> strength. Best example I can think of is tubing vs solid rod; where the
> tubing resists bending almost as well as the solid rod.
In bending or deflection it's true the material at the center is at rest
and the forces are at the surface or edges of what is bending. I'm not
so sure that is true in a shear situation. If it is, then we should have
lots more spline elements on a drive shaft than we do - say make each
one about as thick as a piece of aluminum foil. I don't think that would
be very strong, no matter how many there were.
I am learning that software engineering and automotive engineering are
very different. In software it works or it doesn't, and if it works once
it will work forever -- even more than 1000 Billion times -- the "soft"
"ware" never wears out. Software doesn't really exist in a physical
sense... It's soft-ware... You know what I mean :-) In automotive
engineering most anything will work at least once, and even the best
wears out eventually -- it's just a question of when.
Hmmm.... So much for prudence.... :-)
Don Malling
Randall Young wrote:
>>I have always wondered why there are so many and therefore such shallow
>>splines on a whire wheel. The fact that they wear out so quickly seems
>>to be an indication of a major design flaw at least in terms of
>>durability.
>
>
> IMO they wear out quickly because they are not properly maintained, the
> design flaw is only that they require some care in maintenance and
> tightening. If the knockoff is kept properly tightened (which means that
> the splines do not work back and forth between each acceleration/braking
> cycle), and the splines are kept properly coated with grease or antiseize so
> they don't rust, they will last a very long time. The 'wear' is caused when
> the splines are dry and the knockoff isn't tight enough : each time the car
> is parked the exposed face of the splines forms surface rust, which gets
> knocked off the next time the car is driven. The cycle repeats until the
> splines are eroded away.
>
>
>>Why would more splines mean more strength? Seems to me that 2 or 4
>>splines with equidistant peaks and valleys on a wire wheel would be
>>stronger than 1000 Billion splines of the same or similar design on the
>>same wire wheel. A 1000 Billion splines sounds a lot like a bearing to me.
>
>
> The little splines spread the forces over a larger area, because the steel
> in the center of the bigger splines contributes little in the way of
> strength. Best example I can think of is tubing vs solid rod; where the
> tubing resists bending almost as well as the solid rod.
>
> "1000 Billion splines" would be a press-fit (where the molecules are the
> splines), very strong but difficult to disassemble. Of course, with any
> type of spline, the inner splines must overlap with the outer splines. If
> they don't overlap, no force can be transmitted and you have a bearing ...
>
>
>>A programmer not an engineer....
>
>
> You mean you don't engineer your software ? Tsk, tsk.
>
> Randall Young
> Senior Software Engineer
> NavCom Technologies, Inc
> A John Deere Company
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