Now I have to find some suitable DC gearmotors for the viscometer. here are some links, for reference, to some suitable gear motors.
A 300 RPM one from batteryspace, a little small, good low cost though.
A little pricier. This is a cheap chinese one that is on the current prototype.
Not really useful but might have some other uses
Have no idea about these but seems to have a good selection.
The Amp Hour Radio Show