Hint No. 4

What is a shaking diameter?

What do you actually know about the shaking diameter of your laboratory shaker?


What is the shaking diameter?

The shaker table of an orbital shaker describes a circular motion with one revolution. The diameter of this circle is defined as the shaking diameter. Common shaking diameters are 0.5 inch [12.5mm], 1 inch [25mm] or 2 inches [50mm].


The shaking diameter has a major influence on cultivation!

For instance, amongst other factors, the maximum oxygen transfer capacity OTRmax is directly dependent on the shaking diameter. According to a model from Maier and Büchs [Biochem. Eng. Journal (2001), Vol. 7, pp 99 – 106], OTRmax can be increased 20% by doubling the shaking diameter from 25mm to 50mm with all other conditions remaining the same. By changing the shaking diameter from 12.5mm to 50mm, OTRmax is increased almost 50%.For viscous systems, a shaking diameter greater than 50mm (i.e. 70 mm) is recommended to ensure sufficient mixing and aeration.


Determining the shaking diameter

Unfortunately the shaking diameter is not mentioned in most publications, making reproduction of published experiments impossible. However the shaking diameter of each shaker can be easily determined using the method below. This is particularly useful if there are several different shakers in your lab or you are not able to reproduce the results of your collaboration partner.


1.  Place a ruler underneath the shaking table.
2. Manually push the shaking table as far back as possible. 
3. Read the length measurement L1 (e.g. 4cm) on your ruler at a specific reference point e.g. silver front plate (figure 1, red arrow). 
4. Turn the shaking table (180°) by hand to the furthest forward position. 
5. Read the length measurement L2 (e.g. 9cm) on your ruler at the same reference point e.g. silver front plate (figure 2, red arrow). 
6. The difference between L1 and L2 is the shaking diameter (e.g. L2–L1=5cm) 

The shaking diameter of Kühner shakers is adjustable (standard: 12.5/25/50mm)



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