Powering a large DC motor from the mains
How was it powered in the original copier? 

Is it a permanent magnet motor, or does it have a field winding?

EDIT : the linked picture strongly suggests a PM DC motor NOT a Universal motor so the main part of this answer is wrong. Left for the moment but it should probably be deleted.



If the latter (most likely for an older large DC motor) it's actually a "Universal" motor and will work equally well off AC or DC. And a close inspection of the copier will probably reveal a connection directly to the AC supply.

Universal motors work on AC because, when the voltage to the rotor reverses polarity, so does the voltage supplied to the field coil, so the resulting "push" remains in the same direction.

Then a straight connection to 230V AC would be better (the right voltage!) than converting the incoming AC to DC, which, if you smoothed it with a reservoir capacitor, would give you somewhere over 320V DC.

On the other hand if it is a permanent magnet rotor, a bridge rectifier and no smoothing capacitor will generate "dirty DC" of the right RMS voltage. But be aware that the peak voltage is still too high, which could stress the insulation.