Can the rafters handle it? Try a quick calculation as a sanity check?...

The worst place to hang the engine (point load) would be at the center point of the span, so do the calc at that (worst case) point. Formula would be:

PxL/4

P=load (say 500lbs. for a 911 engine)
L=span of joist in inches

For a 20 ft. span (240 inches)...assuming the rafter has no other vertical loads on it:

(500 lb x 240 in)/4 = 120,000/4 = 30,000 in-lb

Divide this result by 'S' value for the joist size:

2x6 = 7.56 cu. in.
2X8 = 13.14
2X10 = 21.39
2x12 = 31.64

For a 2x8 for example: 30,000/13.14 = 2,283 psi (max. bending stress on the joist created by the engine load)

Once this value is known, look at the wood quality to see if it can handle this amount of stress. Assume for a garage rafter you have decent No. 2 wood which has an allowable bending stress of ~1,450 psi. Beam WON'T hold, in theory, since 2,283 > 1,450.

However, if it were a 2x10: 30,000/21.39 = 1,402 psi
Beam WILL hold, in theory, provided there are no other loads on the beam. If you hang the engine closer to either support point, the situation improves as you get closer to the support.

This is likely simplifying your actual conditions, but try it as a sanity check. In my case, my wimpy 2x6x20ft rafters are useless. I do the HF hydraulic cart thing.

I could swear my come-along specifically states not to use it to lifting a load but rather for pulling only.

Classic! There is an engine-only jack adapter because the engine+trans unit won't adjust to balance properly with just the engine ? Sorry, I'm not blowing ~$400 (shipping "aint" free!) for both, the +trans one makes sense for installing/removing but if it can't balance the engine alone for what we've been discussing then I guess I have to look elsewhere.

When mine was in my regular unfinished garage. I hung the chain hoist from a chain choker wrapped around a 4 * 4. This 10 foot 4 * 4 was spanned across 4 rafters, speading the load. So that put maybe, 150 on each rafter.

Good idea, Cary.

I use a collapsible engine hoist/cherry picker. I lift the motor by the lifting loop in the rear and hook up a chain arrangement that connects to the front mustache bar just like it bolts into the car. With an equalizer rig, it's cake to balance a motor or motor and trans.

Hoist stores tightly in the corner of my garage without any problems, taking up little room at all. You can usually pick one of these up cheap (around $200) at a local discount tool store. Comes in handy for other things too. Like lifting huge landscape rocks out of a pickup........

by the way, cowtown, if a prison GUARD is not available, a prison INMATE will do the trick.

Cary, that's a great way to do it, spreading the load over rafters, if possible.

Let's see, the 4x4 becomes the beam in that case. If the ceiling joists are spaced 24 in.:

500lbs x 24 in = 12,000 in-lb
divided by 7.15 cu.in. ('S' for 4x4): 12,000/7.15 = 1,680 psi bending stress on the 4x4.

LOL...theory says a cheapo 4x4 might be in jeopardy in that case. I take it you never had a problem...so, perhaps it was a good piece of lumber. Then there's always the diff. between theory and reality :)

Never been an issue. Just a left over pressure treated fence post.

I did the same thing in my new shop. But I bought a 12 footer. So I could hit 5 of them. But there like 2 *14's, that laminated chipboard stuff.

Then I put another eye bolt in the steel girder that I used as a header for the garage door. Just in case I needed to take something out of the back of a truck.

With 11 foot ceilings in the shop I just leave the chain hoist in place.

Hey TedSlick

From the facts and figures you have I just assume you know something about it, but how much weight can I hang from trusses made of 2 X 4s? Two car garage, two triangular sections on the outer portions of the truss.

Interesting calculations. There's definitly a decent amount of stress there by hanging the engine like I did. I can't really quantify it but I did know that it wasn't up there for more than 5 minutes and that those rafters held up both sides of this tractor while we replaced the clutch. (it involved splitting the tractor in two)

http://www.fridayparty.org/users/tpwalsh/corellia/jamies/Davestuff/IM001217.JPG

Some of the engineered numbers include the snow load for your area.

I probably wouldn't use mine with 2 feet of wet snow on my roof.

How about sandwiching the 4x4 with a microlam on each side.

What about this?

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=44006

Sounds great for the price, or are they junk?

Charlie

The problem is you need a place to attach it safely.

I have a large steel I-beam spanning my garage.

Charlie

"I'm most interested in how to do things "alone""

For general tips there is a carpentry book called working alone or something similar. Be sure to have a cell phone handy -- if something happens that doesn't knock you out or kill you right way...

As long as you're hanging a beam across your rafters you could nail together some tall chocks to bear the weight on either side of the hoist. If you don't trust the roof frame with the load and are desperate for a solution, that's only a few $ and they sit in the corner until you need them again or use them to build something else.

( bind them to the rafter at the top so they don't slip and let the beam pull down your roof )

That simple calc outlined above is for a simple beam (two supports, one on each end) and a simple point load, in this case an engine. Similar to what l33t9eek shows in his pic.

It gets more complicated for beams supported at multiple points and for trusses. The truss calc would involve knowing all the parameters such as span, all dimensions, lumber quality, load on the roof, and the angles involved. So, I couldn't tell ya. I'd guess your 2x4 trusses are not sized to carry significant loads beyond those required by code (incl. snow as Cary mentioned).

If hoisting a large load from your rafters for a quick lift, such as transferring an engine to a stand, consider securing a couple temporary 4x4 posts (vertically) close to where the load is, on either side. In other words, shore it up. That's a safe bet. Closer to the wall (vs. center span) is better also.

HAVE TO AGREE WITH JOHN WALKER ... 2 OR 3 FRIENDS OR NEIGHBORS. DAN