Balancing centrifuge....... - (Sep/17/2006 )
For bigger centrifuges (24 tubes), I found this very nice schemes for use. The upper picture shows the standard configuration (2, 3, 4 tubes) with "equilateral polygons" and the lower picture "nested polygons" with 7,8, 9 tubes. The centrifuges are balanced and running without problems, at least if the tubes weight the same (as everybody mentioned before) and you don't use an ultracentrifuge.
The principle: Design equilateral polygons ("2-square", square, triangle, as picture 1) and combine them as you want. E.g the seven tubes are triangle plus square.
Finally you don't need any counterbalance in this "higher centrifuge geometry".
Finally you don't need any counterbalance in this "higher centrifuge geometry".
Yep very useful to know. This is how I learnt that, provided all tubes have the same weight, you can put any number of tubes in a 24 rotor except 1 and 23. All other numbers can be balanced.
This said, it is sometimes fasterer to use an extra tube than to figure out the exact configuration. And this should also work in an ultracentrifuge (keeping the usual caveat in mind).
if all tubes weigh the same, why are 8 and 9 tubes set up the way they are in your diagram?
if I have 8, I set them up two to a quarter
if I have 9, I set them up three to a third.
it's quick and easy. I have marks at the third spots and the quarter spots on the outer circumferance of the rotor so I don't even have to rely on the naked eye or counting of rotor wells to get it right when I'm in a hurry
If I have 3, 7 or 9 tubes it will be quicker to put one extra tube and make it an even number and place tubes opposite (2X2, 4X4. 5X5) and if the wells have numbers labelled it wont take much time! Geomtry and physics is OK but but a little confusion can be problematic!
we have a rack beside the centrifuge, with several tubes filled with water with 50 無, 100 無, 200無....
so, no chance to make a mistake.
so, no chance to make a mistake.
Same here in our lab. Tubes generally 15ml and 50ml ones with water with levels 1,2,....10,15,20 etc are kept. It makes life so simple..
so, no chance to make a mistake.
Same here in our lab. Tubes generally 15ml and 50ml ones with water with levels 1,2,....10,15,20 etc are kept. It makes life so simple..
I also keep a rank of eppendorf balance tubes!
This is a siple question ,but attracted very nice explanations.
I agree with many of the explanations.
.We can use alternate positions if the mass(not volume of samples-if of different density) of all tubes is same.
.Balancing with water(since it is available at hand) is a must if mass of tubes is different.
.convenience and belief.