Can I use a herakles tank with a robot v mech mod?
Ditto!I'm going to go the opposite route from everyone else and tell you it can be done. Tanks can be used on mech mods (seeing as how I do it all the time, I know it can be done perfectly fine), you just need a mod with a 510, either spring loaded or adjustable (or a long protruding centre pin if you use a hybrid mod, like a SMPL).
The Robot V mech from Kamry has a spring loaded 510, so yes, you can use a tank on this mod. The 510 is even designed so you can use ego threaded clearos on it too.
If you have a quality battery (OEM, with a 20A CDR min.), you can safely vape a tank with coils down to 0.25Ω without worry (although battery life will lessen the lower the coils are).
The main factor to consider is performance. Since most pre-made coils are at set resistances, you can't fine tune them to the battery.
Ex: You have a 0.5Ω ohm coilhead, and a 20A CDR battery fully charged to 4.2V. You put that tank on a mech, and the coil will just draw power straight from the cell (freshly charged will give you roughly 35W to the coil) and get weaker the more you use it, meaning after a few minutes of heavy vaping, the cell could be at 3.6V giving roughly 26W. As you use it more, the performance will steadily drop.
Now you put that same build on a regulated mod, and now you can get a consistent 35W from start to finish of the batteries charge. Furthermore, with a regulated mod, you can push more power through the coils than you can on a mech. the 35W off a fresh charge, may seem weak to some, so I could then bump up the wattage to 50W or whatever you want, and again, have it a consistent 50W/etc. throughout the batteries charge.
So in your particular case, it's not so much a matter of safety, but performance. If you're going to use your Herakles on this mod, make sure you only use the SS or Kanthal coilheads though (and seeing as how they are all .2 or .4, they should run fairly well with this mod).
All of this being said, PLEASE study up on Ohms Law & Battery Safety before using anything on a mech mod, for not only your safety, but everyone elses.