Worked on the cab a bit this afternoon.
Doubled up the tacks,
Then sanded them flush, then tacked some more.
While sanding I noticed my fit was not too good at the upper left corner. Obviously it was not shaped well. While it can be filled, it would have been easier to correct it before welding. Part of the problem is the piece is close to the upright on the crane and I am having to work from the side. That and I was doing sloppy work.
Decided to stop work on the cab and take the advice to build a rotisserie. It should be quicker to roll the cab back and forth but primarily I can get away from being restrained by the width of the crane.
First I wanted to locate the center of gravity. Henry's engineers did that by putting the car on a platform hanging from a chain and swinging it like a pendulum. It is a law of nature that the time a pendulum takes to swing is based on it's length, not it's weight (so long as it is heavy enough and slow enough that wind resistance is negligible). That's why you adjust a grandfather clock by turning a nut to adjust the height of the weight. I wasn't sure they chose the simple method.
I chose to hang my cab from one side, then the other, and mark vertical lines (which will go through the center of gravity). The center of gravity is where the lines cross. If I can mount the cab at exactly the center of gravity it takes very little force to turn it and hold it in position. Being off the center of gravity is ok, but it is nice to know where it is.
If the cab weighs 200# and the center of rotation is 1 foot from the center of gravity, then that will be 200 ft lbs of torque required to hold it at the most out of balance position. Pushing on the cab 3 feet from the center of rotation would take 70 lbs to hold or push it. A pin to hold it in position on a 2-3/8" diameter hinge pipe would have to hold 2,000 lbs to keep the cab from turning. I would want a 1/2" pin.
If, on the other hand, the center of gravity is 4" off the center of rotation that would would be 67 ft lbs which would take 22 pounds to push or hold three feet away. And the keeper pin would have to hold 675 lbs. A 1/4" pin would hold that. (I'll still use a 1/2" or 5/8" pin.)
OK, but I care.
One side from the back (left edge of the tape lined up with the chain)
The front (right edge of the tape lined up with the chain)
Leaned the other way (tape is not lined up too good)
And the back (tape is not lined up too good here either)
I think my tape will give me the center of gravity within an inch or two.
I'm going to look for cheap engine stands to use to save time, but may fab everything. Measuring the cab it looks like 48" from the center of rotation to the floor will work, and that seems like it would be a reasonable height, even if I need to use a low bench sometimes.
Here we go!!