Hi Alex

Well drill motors are a good idea but i dont think they give much pushing power from expierence. With them you get a gear box so you dont need to complicate things with chains. I you want to have 4wd go for 4 drills.

You are able to overvolt drill motors so i would go higher than 12volt, and a higher mah if you want to run all that from it i use for 2x12volt drills and a bosch 35w lifter 2x NiMH 8.4v 3400mah and they will last an event

Speedo: Id say scorpion xxl becuase you will have more options later on, also another controller is needed for the lifter an electronize switcher with micro switches if you dont have limit switches in your linear actuator. if you have limit swthces a normal drive elcrtonize speedo will work

actuator: i have never heard of a chain actuator so would need more info on that. i would stick to one sort of battery type per robot it makes things much easier. can i ask why you want to go for an acuator with a built in pack? wht does this weigh?

Your on the right lijnes though go to see you doing reserach very good skill in thsi hobby!!!!

can you give us so more info?link to the actuator site please?

thanks hope this helps

Alex M