J
Johnfoss
Guest
Ken Cline wrote:
> *In response to your question, I calculated the (relative)
> strength of the axle. The short answer is tubes are really
> quite strong and you only lose about 8% of the strength by
> hollowing out the axle.*
Does this mean that by hollowing out the center of a forged
or machined piece of cold rolled or other material that you
should only lose about 8% of strength?
I think I can accept that number as believable. But I also
believe it's 8% too much. Square taper axles can't afford to
give anything away.
> *The long answer is that bending strength is limited by
> the maximum stress exterted on the axle, which will be at
> the outside of the bend (in a smooth walled tube). For
> hollow axles, that stress is proportional to
> T / (od^4 -id^4) *
All those numbers were very cool, and I won't claim to have
followed it all. But it seems like you were calculating
strength based on some fixed set of parameters.
Unicycle axles break gradually. That's why the age-old
question of "how high of drops can I do?" never makes sense.
It's not how high, it's how many (x how hard).
As was described in later threads, many axles have been
known to "twist" before breaking off. I've seen this on my
own and others. When cotterless cranks are suddenly no
longer at 180 degrees to each other, it usually means your
axle is going to let go in the near future.
--
johnfoss - Walkin' on the edge
John Foss, the Uni-Cyclone
"jfoss" at "unicycling.com"
www.unicycling.com
"Hey, could I have some of that spinach? I need to get this pork rind
taste out of my mouth." -- Ryan Atkins to Kris Holm, on the way back
from Moab after sampling some of my pork rinds. They grossed out the
whole van!
------------------------------------------------------------------------
johnfoss's Profile: http://www.unicyclist.com/profile/832
View this thread: http://www.unicyclist.com/thread/31905
> *In response to your question, I calculated the (relative)
> strength of the axle. The short answer is tubes are really
> quite strong and you only lose about 8% of the strength by
> hollowing out the axle.*
Does this mean that by hollowing out the center of a forged
or machined piece of cold rolled or other material that you
should only lose about 8% of strength?
I think I can accept that number as believable. But I also
believe it's 8% too much. Square taper axles can't afford to
give anything away.
> *The long answer is that bending strength is limited by
> the maximum stress exterted on the axle, which will be at
> the outside of the bend (in a smooth walled tube). For
> hollow axles, that stress is proportional to
> T / (od^4 -id^4) *
All those numbers were very cool, and I won't claim to have
followed it all. But it seems like you were calculating
strength based on some fixed set of parameters.
Unicycle axles break gradually. That's why the age-old
question of "how high of drops can I do?" never makes sense.
It's not how high, it's how many (x how hard).
As was described in later threads, many axles have been
known to "twist" before breaking off. I've seen this on my
own and others. When cotterless cranks are suddenly no
longer at 180 degrees to each other, it usually means your
axle is going to let go in the near future.
--
johnfoss - Walkin' on the edge
John Foss, the Uni-Cyclone
"jfoss" at "unicycling.com"
www.unicycling.com
"Hey, could I have some of that spinach? I need to get this pork rind
taste out of my mouth." -- Ryan Atkins to Kris Holm, on the way back
from Moab after sampling some of my pork rinds. They grossed out the
whole van!
------------------------------------------------------------------------
johnfoss's Profile: http://www.unicyclist.com/profile/832
View this thread: http://www.unicyclist.com/thread/31905