Re: [DIYbio] Re: Eppendorf 5415 centrifuge: How to remove the rotor?

On 02/07/2017 10:23 AM, Mitchell Coplan wrote:
> I attempted to use the socket wrench on the hexagonal part in the centre (see the picture), but that just makes the whole rotor
> turn. I tried to keep the rotor in place while turning the wrench, but that didn't work either (I couldn't keep the rotor still).
> If I try to lift the rotor upwards, the centrifuge hangs from it

OK. That all sounds like what it looks like, but I have no personal experience with these, so I could be wrong.

What it looks like from the two angled views of the rotor with all parts on , and some parts off is
that the center hex wrench is for unscrewing the rotor. The small center shaft with the hex socket looks
to be threaded. The nut you removed is a lock nut.

Which way do the threads undo? clockwise or counter-clockwise? To undo the rotor, you will want the
small center shaft to go down below what we can see, not come out like a screw. When you determine the correct way to
loosen the small center shaft, you can put a philips or posidrive screwdriver in one of the vial holder holes
in the rotor, and use it as leverage to turn the hex wrench. If you put the small length of the hex wrench
in the hex socket, the long end will give you more leverage, and put the screwdriver 5 or 6 cm from that
and squeeze with thumb and fingers and probably it will give way. (Once you know the correct turning direction
to loosen the small center shaft). You cannot succeed without getting the undo direction right.

A small amount of penetrating oil on the threads of the small center shaft may help, especially if left overnight.
For a strong thing like a centrifuge shaft, you can safely put 4 kg force on it at the edge, by way of the screwdriver in
a hole. Do that at many different angles/positions. Then try undoing again.

If that all fails, get a hair dryer and heat the rotor up, the put an ice cube on the small center shaft,
then rapidly try the undo motions again. The heat and ice will literally lessen the force of an interference fit,
when done to the right parts. The ice cube should be melted on, (with the thing sideways or partly upside down), for
only ten seconds, then get the undo forces going in another 3 seconds, or it all goes back to normal, temperatures averaging out,

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