CaveLamb wrote:
Snag wrote:
Here's the deal - a friend of mine is a below-the-knee amputee ,
and he wants to rollerblade . He's done some research and others
have done this before . Next week I'll be receiving a prosthetic
ankle and a rollerblade ... and my job is to fabricate a plate to
mate the 'blade truck to the ankle .
I've got the engineering pretty much done on how it'll be made ,
but I have a question . How stiff should the plate be ?

Very. the stress on a normal ankle is tremendous.
I can't flex my ankle in any direction because of the stiffness of
the boot (pretty hard molded plastic).

There's a little flex in
the sole of the skate , but how much of that flex is actually
transmitted to the truck and wheels ?

I'm thinking it's some but not much. That's what you steer with.
Leaning one way or the other causes the trucks to turn (just a little
bit!)
I'm leaning towards a fairly thin plate with ribs
below for rigidity with minimum weight . This will be cast from
(probably) A356 aluminum or similar casting grade alloy .


Is there some reason not to use a regular boot type arrangement on an
artificial foot?


Can't help much there. One would think the loads are mostly
compressive, but there is a substantial side load, and a bending load on
the toe
brake .
Would sure like to see it when it's done.


--

Richard Lamb
http://www.home.earthlink.net/~cavelamb
http://www.home.earthlink.net/~sv_temptress

The setup this guy wants is the ankle bolted to a plate with the truck
bolted under it . Who am i to second-guess him ?
My reply-to is good , send me a note so I have your email and I'll send
pics of what I'm trying to "match" and some shots of what I build for him .
--
Snag
Learning keeps
you young !