ros said:
If 16 is taken down to 1+6=7 does this mean that
the struggle of The Chariot in an inward struggle and
the energy is voiced in The Tower card?
I think you did answer your own question. But there's another part to it. The Charioteer is in control of the horses because he's the only one who can see--and knows, exactly where they're going. He is high enough up to see over the horses' heads. So you have the horses, forces of nature, directed by him because of his sight and insight. There's also an inevitability about it--the wheels are rolling, and there's no stopping now.
The Tower is about falsehoods coming down--a flash of lightening that shows you the truth.
Consider these interpetations on the other "7's"--7/cups, about trying to find the real cup to drink amid illusion and dream cups; 7/swords, about trickery and theft in the dead of night; 7/wands, about standing firm and fighting for your truth; 7/Pents, about patiently waiting for the whole truth (harvest, if you will).
I think the shared "7" might be the attribute of seeing the truth, or insight, or even just keeping your eye on the prize, at times when it's a real challenge to do so. It'd be far less tiring to let the reins drop and stop trying to direct the horses. Easier to give into the illusions of the cups, not wait for that harvest, stop fighting for the truth or face dishonesty.
But the Tower brings the message home if you ignored it with the Chariot. The truth will flash before your eyes so brilliantly that even though you want to hold onto the lie, even if denial is easier, even if surrender is more tempting than fighting...you can't ignore it. You can't deny it. The lightening has struck, the Tower is falling, and you there's no turning back. There's no "unseeing" or "unknowing" the truth you've been shown. As with the Chariot, once you're in it and the wheels start rolling, you pretty much have to direct it to the finish line (or through that war zone).
So you might as well put on your armor and go for victory.
