"Mark Rand" wrote in message
news
On Thu, 26 Nov 2009 16:51:38 -0500, "Ed Huntress"

wrote:



Now I'm getting confused. If the HLV has a pair in front and one in the
rear, why is the rear bearing an angular-contact type? I can see that for
the HLVH, based on what's been said here.

Ditto.

I can only put it down to the fact that the HLV seems to incorporate quite
a
lot of design decisions that don't make sense from an engineering point of
view, unless you assume that more expensive is automatically better. Like
my
case earlier where three C3 or two C1 bearings would outlast three C1
bearings
on a shaft and other oddities. I guess it is a 60 year old design and
there
were many improvements made over the years.

If all of this is sinking in correctly, it sounds like the outer spacer is
designed to heat and expand at the same rate as the inner spacer -- or close
enough for it to work. Because it still looks to me like the whole assembly
is going to break or unload if one of them expands significantly faster than
the other.

With the outer spacer, it saves one bearing but adds the spacer. And the
whole thing, I'll bet, was developed experimentally.

To get back to my original questions, that wouldn't work for the home-built
lathe I'm talking about. The complication of holding the outer spacer, and
getting the expansions right, isn't something I think you could do as a
one-shot deal. And the concrete head would add to the differential-spacing
woes.

--
Ed Huntress