About open carry in ohio, vehicles?

I understand that in OH it is legal to open carry anywhere a CCW permit holder can carry, except in their vehicle. How would that work with motorcycles? You are exposed during the entire ride so i don't understand why it would be illegal. and second of all, say I'm 18 and OC is legal where i'm going, say the grocery store, would i have to store the pistol in the vehicle(unloaded with ammunition in a seperate compartment of the vehicle and stored) and just keep the magazine(s) with the ammunition and the weapon somewhere else in the car? Once i reach the store or wherever I'm going to just insert the magazine into the weapon and holster said weapon? And i guess another question would be if OC is legal once a person reaches 18 or has to wait until they're 21. Thank you!