Hm, this is strictly worse than Ur-Golem's Eye, which was itself strictly worse than Thran Dynamo. Palladium Myr is quite a lot better than this as well.

Was: Fractured Dynamo Fractured Dynamo enters the battlefield tapped. ­: Add to your mana pool.

How about now?

Seems reasonable to me. Equivalent to Explosive Vegetation but giving 3 instead of CC. You still need to decide how much mana production you want in common, it may be too much even though the card itself isn't too powerful or complicated.

Jack: Remember the exploding vegetables were uncommon though. Actually, Ur-Golem's Eye is pretty unusual as a common that could give even two mana.

That said, this could be printable at common, but only if accelerating to big mana is one of the things you want to allow to happen a lot in Limited. And there'd need to be something to do with the big mana in Limited, or else it'd be just cruel printing this.

Wait, you put an artifact in your core set at common?

As for Limited, I'm sure I'll figure something out. Personally, I play the game for fun, not really tournaments or anything. Plus, if I were a designer, then I'd just let development would work it out, consider it's impact in Limited, Standard, etc.

Well, I do. I don't know about Wizards or the others here. It seems to me that people think that commons can't be good, that commons have to be bad to some degree to make the uncommons better and the rares look amazing. I disagree with this, a common can still be common and good provided it is balanced, and exemplifies what its color/type does. Lone Missionary, Lightning Bolt, Aether Adept, etc.

If anyone claims commons can't be good, then they're trolling or have badly misunderstood the purpose of rarity. But there has been a principle in recent years that core sets don't have artifacts at common, which is what I assume PMega's referring to.

If they have then I really haven't noticed. What about the signets from Ravinica? Boros Signet, and it's company.

Also, I might have neglected to mention it but this set is entirely artifacts.

When I said "core set", I meant the sets like 10th Edition and Magic 2010. Wizards are very happy to put artifacts at common in expansion sets, both large and small: see e.g. Adventuring Gear. So yeah, there's nothing to worry about.