As requested, here are my plans (such as they exist) and a couple of quick
shots of my machinery skates. These are the width they are because that way
they roll through the door between my main shop bay and the little room off
it in the back. Note that such skates always have to be tied together in use.
I drilled 3/8" holes in the ends of the beam webs so they can be connected
with chain and turnbuckle if I want, but I have never done that - it is very
convenient to use the cheap ratcheting web straps, they do an excellent job.
There was a tiny amount of slag on some of the welds when they got galvanized,
and the zinc didn't cover there so there is a tiny amount of rust, also the
"tires" on the casters rust up every winter but I hit them quickly with the
power wire brush in the spring and oil them and they stay black all summer.

Note the platforms that the machines sit on are split with a 2" gap in the
middle - this is for a pry bar to be inserted to lift up the machine. The
platform tops are only 3/4" off the ground. Sometimes on uneven terrain they
do bottom out but a little gruntwork usually fixes that. I did zero structural
analysis on these but they have moved a 3500 pound lathe without straining.
The platforms are 1/4" steel plate. The caster mount plates are pieces of 4"
flat bar, and are drilled/tapped for 1/4-28 bolts.

I wish these were a little wider. I could effect more width by using smaller
casters on spacers, someday I may do that. If you are in the Seattle area
you don't need to make these, come talk to me and you can borrow them. They
fit in the trunk of almost any car.

http://tinyisland.com/images/machrollers.pdf
http://tinyisland.com/images/skatesAsUsed.jpg
http://tinyisland.com/images/skateOnBack.jpg

Grant Erwin
Kirkland, Washington