On Sep 24, 12:56 pm, "Leo Lichtman" <
[email protected]>
wrote:
> "Jon_C" wrote: Can anyone tell me why all MTB forks (all the ones I've
>
> seen) have the> stanchions (chrome inner part) at the top and the sliders (cast outer
> > part) at the bottom? (clip)
>
> ^^^^^^^^^^^^^^^^
> Several years ago a friend of mine installed a set that are right-side-up
> according to your standards. )I have forgotten the brand.) They used
> elastomer inserts of various "constants" to adjust the springiness--he
> carried an assortment in his pocket, but seldom found a need to change them.
>
> I agree with you that the tubes should be on top. As I recall, though, this
> involves complications in mounting caliper brakes, since you can't attach
> them to the lower stantion. (I'm really fuzzy on this part.)
There are various forks like the OP describes, and I think I know
which fork Leo's friend had: the Halson Inversion. I've never seen it
myself, but I do recall seeing magazine ads for it in the early- and
mid-1990's, years before disc brakes were generally available for
MTBs. I don't know if Halson is still in business, but I on Ventana's
website I found this snippet describing the way that this fork solved
the brakes-must-move-with-wheel problem:
"An inverted suspension fork is a great idea on paper. The strongest
part of a fork needs to be at the top, next to the crown. It makes
good engineering sense to use the large-diameter alloy part on the
top, and put the smaller-diameter, moving part on the bottom. Not only
is this a better use of materials, supporting the bearings and sealing
its moving parts is made easier with an inverted arrangement. Known as
"upside-down forks," the idea has been borrowed from motorcycles (even
though professional motorcycle racers are returning to right-side-up
forks).
The fly in the ointment of upside-down forks is the brakes. They must
be close to the rim, and that means ten inches above the front axle.
Since the upper part closest to the rim of upside-down forks doesn't
move, it's hard to get the brakes to follow the rim. This problem has
sidetracked most inverted fork concepts into the waste can. Halson
Inversion forks solved this problem by slotting the upper alloy
section of its fork. The cantilever bosses move up and down inside the
vertical slots without having to depend on a disc brake. You get
superb bearing overlap, increased rigidity and less unsprung weight
(the part of the suspension that follows the ground on upside-down
forks)."
The link below has the full article from the April 1995 issue of
Mountain Bike Action:
http://www.ventanausa.com/mba0495.html
Stephen Greenwood