engineering question: splined vs. cottered hub

To the engineers out there who understand this,

Can you please explain the reason a splined hub is better than a cottered
one? My roommate, a mechanical engineer, asked this question, and I could
not come up with a reasonable answer.

Is splined technology inherantly better than a 4-interface cottered setup
of equal design and manufacturing quality?

Jeff Lutkus


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RE: engineering question: splined vs. cottered hub

> Is splined technology inherantly better than a 4-interface
> cottered setup of equal design and manufacturing quality?

Yes. No question. But your description of 4-interface leaves me wondering.
Are you talking about bicycle-industry cranksets? They use a single cotter
pin going through a single channel in the axle. All the force of cranking on
the axle squeezes the cotter pin on a single area. Hard pedaling in both
directions causes cotter pins to come lose.

Were it made large enough, I think a cottered axle could have strength equal
to one of today’s splined axles. But you would still have problems with pins
coming loose, and the additional issue of more weight.

Engineers often neglect to work these types of problems from the solutions
backward. Splined axles work better. Cottered axles have the problems we are
all familiar with. Using that as a basis, figure out why?

JF

There are a few advantages to splined over cotterless as well. The only one that comes to mind imediately is that with cotterless cranks everytime you put them on they draw down further on the axels as the cranks and axel wear. Another advantage is that, the stress is is not as concentrated with a splined setup meaning less material, and or materials that aren’t as hard can be used. This provides a potential weight savings. Ease of assembly, disassembly also comes top mind as an advantage. I have a friend who once pulled the threads trying to remove a cotterless crank. That’s always bad news.
-gauss

RE: engineering question: splined vs. cottered hub

Oops… typo, I meant to say cottered

splined vs. cottered


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cottered hubs use cotter pin and they stab you in the anklez.thats why

Re: engineering question: splined vs. cottered hub

On Mon, 15 Apr 2002 11:38:40 -0500 (CDT),
Jeff Lutkus <lutkus@unicyclist.com> wrote:

> Is splined technology inherantly better than a 4-interface cottered
> setup of equal design and manufacturing quality?

I’ve never seen a 4-interface cottered crank.

Do you mean splined vs cotterless?

regards, Ian SMith

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RE: engineering question: splined vs. cottered hub

by now, it should be quite evident to anyone reading this thread that I
have logged a total of less than 8 hours over the past four days.

cotterLESS is what I failed to correctly type about 5 times now.

Why are splined better than cotterless designs?


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RE: engineering question: splined vs. cottered hub

> cotterLESS is what I failed to correctly type about 5 times now.

I had a feeling that’s what you were trying to say. But since you kept
saying cottered I gave my annoying previous response.

> Why are splined better than cotterless designs?

From a non-engineer’s point of view:

A few factors.

  1. Generally larger diameter of axle. This automatically increases your
    strength, and will be much more resistant to the gradual forces of metal
    fatigue.

  2. Larger diameter of contact or force-points where the crank attaches. In
    other words, draw a circle within the square of your cotterless axle. That’s
    how much effective metal there is. Now draw a circle within the splines of
    the splined axle. It’s a much larger circle. This equals greater structural
    strength.

Every broken unicycle axle I’ve ever seen (except for a mishap with a
bearing puller) broke in the space between the crank arm and the bearing,
usually on the tapers.

  1. Splined cranks don’t seem to come loose as much. With a 4-sided taper vs.
    a many-sided non-taper or slight taper, the reason for this should be fairly
    obvious.

Unfortunately, splined axles and cranksets are significantly more expensive
than cotterless types. This is in part because more machining is involved,
but mostly because splined parts are made in far lesser numbers. Mass
production is what brings the cost down…

Stay on top,
John Foss, the Uni-Cyclone
jfoss@unicycling.com

“I am never riding the wrong way on a busy street again, esp. when on the
phone.” - David Stone, on survival