carl mciver wrote:

"Roger_Nickel" wrote in message
...
SNIP
| What I had in mind was to install three or so fifteen foot long barn
| door tracks in the area I usually work. Suspend from them on rollers a
| track (or two) that work like a bridge. Since my work area is partially
| under the garage door in the up position, I need the upper tracks to be
in
| and out of the area, and parallel to the door track. The bridge has to
be
| lower than the door and track, simply because the frame that holds up
the
| end of the track is in the way. I'd have to have a rigid drop frame
with
| the upper rollers to allow the bridge to clear the garage door track.
SNIP
| The best way to mount something like this would be to put a heavy steel
channel
| strongback on top of the joists above the track to spread out the load.
Secure
| the hoist track to the strongback with long bolts through the thickness of
the
| ceiling to avoid weakening the joists by drilling holes in the highly
stressed
| lower edges. With the load spread over several joists overloading should
not be
| a problem. What is the total span of the joists and are they the bottom
chords
| of a truss roof?.

The open span across the ceiling is about 24' on a built in place
ceiling and roof frame. There's 2x4's at the peak holding up the roof peak,
or holding up the ceiling. One way or the other. Not prefab trusses, that's
for sure.
I've seen the unistrut roller track, until I go looking for it on the
web. I can't seem to find it in either B-line or Unistrut's sites.
Specifically looking for load ratings. How does the load rating of strut
compare to door track? I never knew the load factors of the strut, but I
like how strong the doubled up struts (back to back) were. Never had to buy
any of it, so I don't know the price/load comparison between that and the
door track.
I like the idea of a beam or channel strongback. I can put one end
directly on top of the wall (actually, it's over the garage door beam.) The
joists run parallel to the garage door, so I assume you mean to run it
perpendicular to the door. I wonder how to terminate the other end. Can I
just dead end it? I'll have to do some rearranging of the stuff for sure,
the kids have trashed all sense of organization I put up there! What's a
good size/type that won't wind up being more weight than support? I hadn't
planned on bolting through the joists, rather bolt around or make a bunch of
U-bolts. I figured single legged ones would do the job if I used enough of
'em.
I had originally wanted to do a four legged bridge crane like suggested
from Spanco (thanks for the link!) but I have a car in the garage. There'd
be more room if the car could be moved over, but I've got a compressor and a
few engines on one side that are somewhat stored, and three or so on the
near side that are in work. Lifting these engines are what I've got in
mind. With the car/stuff as well as the garage door and track in the way I
can't do that kind of system.

Not all of the Spanco systems are self supporting, a number of them are
designed to mount to the building roof structure. Granted this is
normally steel I beams, but the smaller Spanco stuff can be adapted to
work in a wood frame garage type of structure.

If you want a full bridge and are willing to spend the money for Spanco
components that are engineered for this you can make them work in your
garage.

With the two bridge tracks mounted flush to the ceiling just in from the
exterior walls you can support them with a relatively small beam above
the joists to distribute the load across the joists. Since you are just
a short distance in from where the joists are supported by the wall
framing as opposed to mid span the load transfer is not too bad.

The last 4' of the joist up to and including the part on top of the wall
should probably be sistered on at least one site with another piece of
2x6 to provide extra strength in that area.

The Spanco bridge is trussed to handle the load between the bridge
tracks properly. The engineering for this would need to be confirmed by
the Spanco folks but I think what I described would be appropriate for a
bridge with a 1,000# max load rating.

The door track would likely work just fine for a single trolley track
with a 500# max capacity and be a lot cheaper, but of course less
flexible than a full bridge.

You also need to be concerned if you intend to put a point load in the
middle of the garage door header since it may well not be sized to
handle the additional load. The Spanco bridge would avoid this problem
since it's supports would be along the walls.

Pete C.