wrote:
On Monday, August 3, 2020 at 9:40:20 AM UTC-7, sms wrote:
On 8/2/2020 6:27 PM, AMuzi wrote:

snip

I understood Mr Ruf to mean that a Sachs 2 speed of that era was
engineered with RH 10.5x26 thread.

I assume someone at F&S reasoned that your basic 9.5mm standard axle
would be less strong with a hole in the middle. Once that thread is
supported with tooling the next guy asks 'why not?'

Exactly.

+1

They no doubt found that 9.5mm was not sufficient with the
hole and determined that 10.5mm was optimal and didn't want something
as big as 12mm.

I guess they also found that 10mm was not sufficient. Who knows? And it
didn't really matter. They could specify the proper nuts to be
supplied.

They may have copied the Sturmey-Archer design but decided to go metric
instead of English and rounded up from 13/32" to 10.5mm.

When you engineer things you don't cut corners so that you need to
totally redesign something in the future. The 10.5 instead of a 12 made
about as much sense as your normal postings.

F&S were selling all kinds and sizes of hubs in the 1910's, including
"motor" hubs with 11, 13, and 14mm threaded axles, no threading details
known to me, unfortunately. Go ahead and ask Andrew or Aaron's how commonly
the 2 to 7 sp IGH's have failed because of 10.5 instead of 12mm. Eight
decades of engineers cutting corners was not what killed F&S. I only ever
broke any axles with the help of multi-sprockets freewheels, so I'm no expert.