A "
Tip Jack" is a old time soft
flat term for the support of it similar to
stage jack. Basically it's a
stage jack triangular "wailer" or L-Stiff frame, but at an angle away from the floor so you tip the
flat backwards onto the casters to move it, than when in position tilt it forward and lash
line it into place. A fire place
unit might find this method adventagous. Given some structure to a back wall attached to the
plat, it should be possible to sort of balance the back wall and
platform on a
tip jack when it's tilted backwards to a castered frame behind the
flat. Granted you would have to brace these
tip jack frame members.
Were I to use a J-Bar in a style similar to how you describe - and I probably would not given breaks, shims,
stage screws and other ideas, I would drill a hole in the J-Bar and mount a
bolt to the bottom of the
platform by way of
angle iron attached to the frame. This
bolt than sticking down would be like the pintal mount of a trailer
hitch, and the J-Bar in reversing it would be the trailer. This way you could turn and meneuver the
platform as you need without it slipping off the lever. That slipping off the lever, much less getting the pry bar under the
platform is the major problem here.
But as said, both casters on half the
platform would have less surface area in
platform to
deck friction from moving given a half
caster and half
platform on the
stage method as thought. In other words, you would still probably have to attach to
platform to the
stage out of
safety which deletes the usefulness of using the J-Bar as opposed to just castering the entire
unit.
Perhaps you should do a timed mock up of a
strike and attempt to make the
platform turn a corner reliably so it gets into storang quickyland quietly - especially if the
platform drops off the J-Bar. This than can also show the effects of having a half castered
platform for how much it can move should someone walk on it.
In thinking, here is another solution that might be of interest.
Take a
stock 3.1/2"
caster. Normally you need to
throw a 3/4"
block under it for
ground clearance.
Granted my job is often more machinist than tech person, but what if you were to hinge half the
caster by way of mounting it to say a 1/4" steel plate with hinge attached to the plate? Welding is nice but bolts will do. Attach the other half of the hinge to a 3/4" plywood
block that's screwed to the
platform as normal in now giving 1" clearance to at least half of it. Need a strong hinge for this. If the
caster plate and hinge is strong enough, you might not need the plate.
This half supported
caster now hinges inward and does not
clear the
platform unless blocked upwards on the opposing end of the
caster to lift it also to the 1" clearance.
Now drill say a 3/8" + hole install a T-nut or tapped and threaded plate to the underside of the
platform where you would otherwise shove a
shim block in making the un-hinged half of the
caster parallel to the hinged side to
clear the
platform frame.
Now when you need to lift the
platform to use it's casters you just screw a threaded
bolt into the T-Nut from a hole in the
platform's top from above. This
bolt than once tightened down will act as if a
jack to hinge the
caster down and lift the
platform off it's frame and re-engauge the casters.
This given as similar to that of a
C-Clamp bolt, screwing the end of a screw into that of a steel plate or pipe will tend to damage the end of the
bolt so it can't be removed afterwards. The only acceptable screws for this would be ones that are Grade 8 or Aircraft grade about 10 such as on a alloy steel
bolt. Easy enough,
purchase a few alloy steel
socket head
button head screws of 3/8" or 1/2" by 1.3/4" long - the same as the threaded plate or T-nut, and drive them in by a hex
driver on a cordless drill. Should take moments given enough
stage hands with drills.
It's another concept at least.