Belt idler pulleys

[dinotom]

Since I cannot find most of my original end gear pictures and video's I need some help.
I have these pictures of some other machines I found online, some have both main belt idlers and some only have one.

Lathe with one belt idler


Lathe with both, but much later model year 1962 vs my 1944
Green looks like there is a lot of tension on that belt and you can barely see the bottom of the idler



The last image is the one image I found of my 10EE and I can't quite tell if I do or don't have the idler on the speed control mount and since I don't have a second one, it may have been missing when I got the lathe.

My lathe


The question is, are both required, since I see some images where only one is present?

 

[rakort]

My 40's round dial has 1 with a flat belt drive. I think the dual tensioner / idler came later or it may be apart of the v-belt drive design.

 

[PWP]

I removed the rear idler, for whatever reason and never re-installed. I have had no problems running with just one.