Here is another silly way, how to measure the drive rotation speed. Remember you have a smartphone? Your smartphone probably has a gyroscope - a sensor to measure acceleration and to figure out, if the smartphone is upside down.
You can remove the floppy drive from the computer, attach the smartphone on the drive and start measuring. I used the app Phyphox and used function called “gyroscope”.
Here’s a short video, how it looks in action:
(Note: You must be brave to put your phone there - don’t forget to attach it properly)
Here are the screenshots from the app:
You can also export the data as a CSV file: gyroscope-rotating-rate.csv.
And there you can see, that the rotating rate is about 37.6 rad/s. A full rotation in “rad” is 2π, that makes this number 5.98 rotations per second or 359 rpm.
As you can guess from the picture
the drive I used is a HD drive - and these normally rotate at 360rpm (unlike SD or DD drives, which rotate at 300rpm).
So the measurement did make sense after all.
But I didn’t try this measurement with the original drives of my Alphatronic computer. I guess, attaching a smartphone in that way to the motor of the drive might put some stress on the motor which is probably not healthy - neither for the drive nor for the smartphone.
Since we established with the last post, that there is nothing wrong with the drives - they rotate at the speed they should - there is also no need to do another measurement.