I’m new to this game. Been playing for about a week now and having a problem with thrall taming.
The Lesser wheel of Pain has an Archer symbol in the equation at the top. So can it only tame archers?
I can’t find a way to change it to anything else and I’m having problems not being able to break certain thralls.
This game really needed a strategy guide IMO. Searching around online has taken so much time and mostly not found all the answers to everything.
Welcome to the forum. 
The lesser wheel can break any type of thrall,but only one at a time. Just knock out the thrall that you want, tie them up and drag them to the wheel. If the wheel is empty then your captive will be transferred to it when you activate the wheel.
Once your captive is on the wheel just add food (gruel is best) and set the wheel going. An icon of the thrall being broken will appear on the lower right of the interface along with a white progress bar.
Please note that the higher tiers of thralls take much longer to break than the lesser ones, eg. a named (T4) Exile will take more time than say a T1 Exile.
You can speed up the process by finding and breaking a taskmaster to work on the wheel.
Here is the Wiki entry, https://conanexiles.gamepedia.com/Lesser_Wheel_of_Pain
Hope that this has helped.
Symbols like that are only used as an example of what is possible. You will see that in other machines as well. For example, the campfire shows the equation with wood, but you can put other things in it to burn as fuel, like plant fiber or coal.
Like @zwkdiv mentioned, the small wheel can break any thrall, but it can only hold one thrall at a time (not including the special slot at top for Taskmaster). To break another thrall, make sure the inventory doesn’t have another thrall in it before interacting with the wheel while dragging a bound, unconscious NPC. Check to make sure there is food inside. Food is the fuel that is “burned” when a Wheel of Pain is operating, and don’t forget to press the Play > button to begin the process or after one food has ran out and you need to start using a different food to fuel the wheel.
Personally, I like discovering many details for myself, but if you want a guide, there are probably many questions that have been answered here over the years, and many YouTube videos devoted to teacher beginners. Here is one that talks about converting thralls.
In the video I linked, you’ll see 2 thralls inside at the same time, but it’s an older video and that part is no longer true. Funcom have continued to work on the game after release, and as a result, some videos like this have inaccuracies.
Thanx bbtech.
That video is exactly what I need for figuring out the basics that I’ve been struggling with.
Much Appreciated.