Impossible Precast lift 'A big awkward, heavy problem.'

Here's a picture of the problem.

This is 4000 + lb piece of precast going up 3 and 4 stories on an aging concrete building on Jasper Avenue in downtown Edmonton.  This is the main street and the lift is a positive rig up, but its on the wrong side of the triangle shape.  It has to be wedged in between floors, we cant lift from the top.  This rig up swings the precast back and bangs us in the kneecap.  The top has to stay level.

Lafarge wrestled with this for a couple of days, then phoned us for ideas.  We were scheduled to have our large knuckle booms do the install anyway.  This next photo shows the concentration and a little frustration on the crew.  It also gives one an idea of dimension. 

It was a joint effort, but we decided to try to add a counterweight to the load, a half size lego block,  These are 2500 lbs. We added it to the same rigging but the angle still didn't work, but we were surprisingly close.  We dropped the block down a few inches, shortened our initial rig up point, and added 2 thick sheets of styrofoam.  This pushed the block further away, and we think added leverage to the precast.  See pic

When we added the styrofoam, the precast came totally level, in fact we may have gained a degree or two.  The lifts were done in the evening because of the traffic pressure, so our photos on site are not worth printing, but have a final shot of the top of precast.  Job went well, no problems.

But it was definitely new ground.  We lifted a block of concrete, from the side, and kept the top level.    See final pic