I am looking for research on mechanical or electronic input devices
with a dial or cylindar knob design. Examples of such interfaces would
be the Intermatic security timer (EJ341C), the Melnor 3015 Aqua
Timer, a kitchen timer that needs to be turned past 20 before being
set at 10 minutes, or some programmable lawn sprinklers.

I am interested in:
How such devices got designed that way in the first place. 
What user testing was conducted?
What is the user's cognitive model?
Are they easy or hard to use?

A few good references for these questions would be a big help.

I can't find any human factors research related to this. Is there
relevant research/testing that happens in-house before products are
put on the market? Can you help me find it?

I've been trying to find resources on my own, but I keep running
into human-computer interaction, which is off target. These are
household devices that do not involve a PC or anything virtual. Maybe
some of the answers are more aboutindustrial design? I have access to
a university Library if some of the references are not electronic.