Scantlings

I'd like to install a 1/2 ton chain fall in my garage. Obviously, attaching this to one of the roof trusses is not a good idea.
The garage ceiling is open and accessible, there is no "attic" or floor.

Could I beef up one of the trusses with a steel beam? Sister it with a particular size of wooden beam? Use a stand-alone steel beam?

You should be able to use an existing truss with a bit of a "beef up". Attach your chainfall directly at the peak of one of the trusses using big plywood gussets on both sides of the truss. Use four layers (two on each side) of 3/4 inch ply and lots of small screws. In the space between the gussets, hang the chainfall with a large bolt (passing thru the gussets).

Next beef up the connection of the truss members (to each other) at the wall. Imagine the "rafter" being driven with great force (grater than your load) outward and trying to tear away from the "collar tie" member. Again, more big plywood gussets and lots of small screws will work fine.

Lastly, the collar tie (the horizontal part of your truss) will be under great TENSION (much greater than your load). Make sure there are no large knots or other imperfections in this member. If so, sister another 2X4 alongside and attach with lots of small screws. This horizontal member is probably made in two pieces. Beef up the connection with a sister or more, large plywood gussets (both sides) and lots of small screws.

I keep mentioning SMALL SCREWS because large fasteners weaken structure. Taken to the extreme, imagine using a 3 inch diameter bolt to fasten a 2X4. There would be hardly any wood left!

Also try and arrange your screw patterns so as to not have a "line" of screws crossing a member perpendicularly. Again, taken to the extreme, a line of closely spaced holes can be a very effective saw!

Steve

If you are nervous about the above not being strong enough, do the same "beef ups" to a second, adjacent truss, then hang a strong timber or metal beam (only needs to 2 or 3 feet long) from the two peaks. Thus sharing the load between two trusses.

The benefit of my solutions is that they do not require the purchase of expensive and heavy beams. They do require more fiddling around with lots of little pieces, however.

Steve

Video of the first hoist. Just in case. Please.

Our “boat shed” has 2x4 stick built trusses with a nominal 12’ span. To lift outboard motors and the like, I bought 2 4X4 posts and sistered two of the trusses that lined up with piers. Clamped them together and then screwed with 3.5” deck screws. Basically builds up a 4x6 beam that seems to do the job. I’ve used it to lift about 500 lbs.

Steve’s approach distributes the loads better.

Thanks guys. I'll check out the photos when I'm out from behind the corporate firewall.
I'm glad to hear that it can be done.

OK, I'm home and Steve's sketch makes perfect sense. Nothing that an afternoon with a box of screws and an electric drill/driver can't accomplish.

What type of fastener (screw) do you recommend for this?

Of course the top two threads here are "Five Tons of Fun" and "Engineering a Chainfall Beam". Don't get them confused.

Ajax wrote:OK, I'm home and Steve's sketch makes perfect sense. Nothing that an afternoon with a box of screws and an electric drill/driver can't accomplish.

What type of fastener (screw) do you recommend for this?

I've been using a #9 decking screw for just about everything lately. Narrow enough to not spit wood but "grabbs" like crazy. Get the ones with the Torx bit.

Steve

Ajax wrote:OK, I'm home and Steve's sketch makes perfect sense. Nothing that an afternoon with a box of screws and an electric drill/driver can't accomplish.

What type of fastener (screw) do you recommend for this?

GRKs Rigid Structural Screws (TSS) are very good.