Automatic Wheelchair Turntable

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

I just got my Dad a wheelchair van with an electric ramp but we've hit a
snag.  There's not enough room to turn the wheelchair around inside the van.
If he goes in forward, he has to come out backwards.

I toyed with some automatic guidance systems to make sure the backup
procedure didn't run him off the ramp, but I don't think that's a wise
solution.

I decided that since there's almost a 4X4 foot flat area inside the van, I
would take a 4x4 sheet of 3/4" plywood and make a turntable on the van
floor.  When he transfers to the driver's seat, I want the turntable to
automatically rotate 180 degrees to position the powerchair so that it will
go down the ramp front first.

I'm not sure how I would contstruct and power the turntable, however.  It's
got to be as thin as practical - there's very little extra headroom in these
types of vans and it's got to have some sort of autodetection of exactly 180
degrees - probably some sort of limit switch.

Should I rout a channel in the outside of the circular-cut plywood panel to
run a belt?  That why I could mount a motor in the corner and still have a
pretty low overall height.  Sort of how some belt-driven record turntables
are designed.  I could also cover the ends of the belt that are likely to
drag loose seat belts into the works pretty thoroughly with a motor mounted
in the corner.

Does anyone know if they make commerical turntables for this purpose?  As
much research as we did on vans, lifts, ramps and options, it kind of floors
me that we didn't realize there would be a "wrong way out" problem.  Just a
reminder to always model things, even if they seem trivial.

Well, any suggestions, inputs, discussion or ideas where to post for good
feedback will be appreciated!

(posted to:  comp.home.automation & alt.support.wheelchairs)

--
Bobby G.