Turtable Research Notes for Nerds
Discoveries of a CCI Mechanical Engineer
Some things to keep in mind for the spider for a wheels up turntable:
Number of legs: This should differ from the number of platforms/sweeps segments, so your wheels do not all simultaneously hit a seam on their bearing surface. If you have (16) platforms/sweeps, then (15) or (17) spider legs would work great.
Leveling: The spider is where you will want to level the turntable, really the critical point is getting the top of the wheels as co-planar as possible. Threaded feet make leveling easy.
Wheel alignment: Make sure the wheels are perpendicular to a radial line out from the center of the turntable, easy enough to do with a framing square but frequently overlooked.
Connection to Center Pivot: We will need to interface to determine how we are attaching the spider legs to the Pivot. I'll work up a concept and provide details soon.
Things to consider for wheels:
As you do your spider layout, determine the wheel with the largest tributary area (area supported by that caster, in this case assuming the tallest/heaviest portion of the turntable is over it) and determine a conservative worst-case load on that wheel. Then pick a wheel with more capacity than that load, ideally minimum 20%.
Wheel selection and quantity is critical. It is a major cost center, but it is not the place to get cheap as there lies sadness. I've lost track of the number of turntables with overloaded wheels our customers have made just in the last year.
The goldilocks durometer of wheel tread: not too hard to be loud, not too soft to get squishy under load, and not too thick. It's reasonably load specific but 87 shore A seems to be our target these days.
You want a flat or flat-ish wheel profile to spread the load across more area; we've seen many a crowned wheel get smooshed, which then causes big issues trying to move the turntable off those flattened wheels.
We've had good success with this style of wheels or rigid caster version might be a good option.
Wheel Sweeps/Surface
The wheels will need to bear on a flat smooth surface, and typically this is done on cut sweeps; could metal plate or stacks of plywood. Below are some examples of caster sweeps
Some details to keep in mind:
It's critical that the sweeps are flush and gaps are minimized, so a lip and ledger detail can work really well.
Angle the seams on your sweeps so the wheel contact at an angle rather than perpendicular. If there are any gaps this will minimize the impact, like pushing a dolly through a door threshold "on the diamond". See another customer's sweep detail vs our suggested angle in red marker.
Drive Ring
The drive ring is the part of the turntable that the Revolver's drive wheel presses into, and transmits force from friction as the drive wheel spins. This could attach to the wheel sweeps, platforms or both. The drive wheel:
Should be as circular and free of gaps/bumps as possible.
The drive ring should contact the entire height of the drive wheel on the Revolver.
Plywood sweeps make a great friction surface (and are easy to sand down bumps), steel works well too, but aluminum tends to shed dust and becomes very slippery once it and the drive wheel are coated.
The Revolver drive wheel may press with upwards of 500lb of force, so make sure the drive ring has a solid attachment.
Platforms
Platforming admittedly isn't our wheelhouse, but you had mentioned an option between framing the platforms with tube vs angle. I'd suggest tube as it will result in a lighter and stiffer frame pound for pound.
Slip Ring
I chased down what slip rings are shelf-stock with our usual suppliers, and the best candidates are:
Power: 6 conductors at 20A rating, can be combined for a 3-wire circuit at 40A, 1 available
Data: 12 conductors at 2A rating, 2 available
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