Rotating table
The rotating table has an almost frictionless bearing attached to a base plate and supporting a sturdy horizontal rotating working surface (which we will call the dial) on which water tanks are placed. The dial has dimension 24"x18" and can be made to turn at rotation periods in the range 2 seconds to 60 seconds: i.e. at a rate of 30 rpm (revolutions per minute) down to 1 rpm, measured by a digital readout. The turntable should be placed on a solid surface, such as a bench or on the cart described below. The turntable is best positioned away from the direct influence of overhead lighting, which have a habit of reflecting in the water surface, creating glare and distracting the field of view of the overhead camera.

The turntable is plugged in to a 110 AC volt power supply: a transformer is used to step down to 12V DC to power the drive motor, overhead camera and devices (such as, for example, pumps and fans) in the rotating frame. The turntable has a ground-fault interrupter circuit breaker.

You can look at more detailed views of the turntable by clicking on the images below. 

                  

Leveling the turntable
Before carrying out an experiment on the turntable, it is very important to make the rotating dial perfectly horizontal (perpendicular to gravity). To do this we place a level on the dial and adjust the turntable legs through through its base until the dial is horizontal, as follows.


The turntable base has 3 legs - one which is fixed and two which are adjustable. The level is placed on the rotating dial (not the base) along an imaginary line joining one of the adjustable legs to the fixed leg, as shown in the diagram (stage 1). The adjustable leg is used to level the rotating dial along this line. The level is then rotated through 90 degrees and the other adjustable leg turned until the dial is again level (stage 2). This should make the rotating dial horizontal in all directions. Check by moving the level to different positions on the dial. If you are not satisfied, repeat the procedure.


Drive Mechanism
The drive of the turntable is achieved by a friction wheel on the underside of the dial driven by a variable speed motor. You can view the drive mechanism here:

The novel friction drive mechanism has a number of advantages over a more conventional direct-drive via a timing belt: (i) it provides an automatic clutch allowing the dial to be readily stopped in a safe manner without damaging the apparatus or the user! Indeed one can grab hold of the turning dial bringing it abruptly to rest with no un-toward consequences (ii) its simple but effective design allows one to slide the friction wheel radially inwards (increasing the rotation rate, Ω) or outwards (decreasing Ω). Combined with the adjustable speed of the motor, a continuous and wide range of possible rotation rates can be achieved between 1 and 30rpm.

Measures of rotation rate
There are various measures of rotation rate

1. The period of one revolution of the tank, τ, in seconds
2. The rotation rate in revolutions per minute, rpm = 60/τ
3. The angular velocity of the tank, Ω , in radians per second (note that Ω= 2π/τ)
4. The Coriolis parameter (f) defined as f = 2Ω

The turntable has an electronic readout in rpm which one can view here:

     

The following are conversion tables between various measures of rotation period and rotation 


Camera and slip-rings
Experiments placed on the dial can be viewed in the rotating frame from a camera (through a zoom lens) mounted on an arm that rotates with the dial. The video signal is passed from the rotating frame through a slip-ring. A video cable can be conveniently plugged in to a socket on the turntable base and the camera view displayed in the non-rotating frame on a TV/computer monitor or beamed up on to a large screen for viewing by many.

Fluid tanks
Experiments are carried out in clear acrylic tanks placed on the dial. A 16"x16"x8" tank is found to be convenient. A circular insert readily converts the square tank in to a cylindrical one. The circular insert, secured by stainless steel clips. is shown in place below. A stainless-steel container placed in the middle is weighted down so that is does not float when the tank is filled with water. When ice is added to the container, a radial temperature gradient is created.



A false white bottom can be inserted into the square tank and tilted to mimic spherical effects. Note that the base is tilted through the use of two plastic bolts.


Auxiliary equipment
Dyes, potassium permanganate crystals (for visualization) plastic bottles, pipettes, spatula, beakers, spring clamp, knife, level for turntable, Vaseline, as shown in the container below.



Fluid cart
It is convenient to install the turntable on the mobile cart shown in the figure. The cart is equipped with a 10gallon water storage tank, a tray to store and carry assorted materials such as ice-buckets, cans, beakers, dyes etc, and a post on which to place an LCD TV monitor for convenient display of the experiment from the rotating camera. The cart can be used to transport the equipment to where it is to be used and as a platform to carry out the experiment.

The cart is supplied with central power (by plugging in to the wall), which feeds the TV monitor, computers, DVD recorders (as available etc) and the pump for filling up the experimental tank from the water storage tank.

Monitor
See here  for how to wire the monitor.