Can you conjure a small version of a vehicle with Minor Conjuration and use Enlarge/Reduce to grow it into a copy of the original vehicle?

Question

Say your friend allowed you to take apart and see the internal workings of a nice SUV you liked. If you studied everything outside and inside the car intensively, could you create a hotwheels-esque replica with full-working motors and everything? The Minor Conjuration feature states (PHB pg. 116):

Starting at 2nd level when you select this school, you can use your action to conjure up an inanimate object in your hand or on the ground in an unoccupied space that you can see within 10 feet of you. This object can be no larger than 3 feet on a side and weigh no more than 10 pounds, and its form must be that of a nonmagical object that you have seen. The object is visibly magical, radiating dim light out to 5 feet.

So, what I want to do is conjure the SUV I studied, and cast Enlarge/Reduce on it.

Enlarge/Reduce (PHB pg. 237):

You cause a creature or object you can see within range to grow larger or smaller for the duration. Choose either a creature or an object that is neither worn nor carried... Enlarge. The target's size doubles in all dimensions, and its weight is multiplied by eight. This growth increases its size by one category--from Medium to Large, for example...

Since the car is 3 feet in any given dimension, I could compare it to a halfling, whose size states:

Halflings average about 3 feet tall and weigh about 40 pounds. Your size is Small.

Meaning that the car is therefore the Small size and able to be transformed into a Medium size.

TL;DR, can I do it like Hank Pym and Enlarge a small conjured car into a Medium car and drive around in it? (at least for 9-10 rounds at a time, or using some sort of spell extension technique to extend that 9-10 rounds)

Answer 1

You can make a model and Enlarge it, but you probably can't make it big and heavy enough to be a rideable motorized vehicle.

Minor Conjuration is limited to 10 lbs. The Enlarge/Reduce spell can scale that up by eight (it doubles in each dimension, resulting in 2³ = 8 times more volume), so your total weight limit is 80 lbs.

Even a very small car weighs close to a ton (a recent Smart Fortwo for example is 1900 lbs). Even the lightest motorized vehicles are going to be a tough fit with only 80 lbs to work with. Most go-karts and light motorcycles are at least double that. A kid-sized dirt bike is usually around 90 lbs. Maybe you could get a motorized bicycle at under 80 lbs, but it's not going to have much power.

Then there's the size category to consider. The rules for mounted combat (described in chapter 9 of the Basic rules and Player's Handbook) say that a mount must be one size category larger than its rider. So even if you do manage to figure out a vehicle under 80 lbs, it will be Medium sized, and so a Medium sized character would not be able to ride it comfortably. Perhaps your scheme can work if your wizard is a halfling or gnome, but it's probably impractical for a human-sized character.

Note that I'm ignoring the question of whether a D&D character can actually create a motorized vehicle at all. I suspect you'd need, at the minimum, the Keen Mind feat to be able to memorize extremely complex plans in sufficient detail to conjure up a working model. Even if you're not trying to make a car, I'd recommend asking your GM for guidance on what they'll allow you do with Minor Conjuration before picking that wizard subclass. The amount of utility you'll get out of that sub-class feature it will vary widely depending on how they interpret "its form must be that of a nonmagical object that you have seen". For some GMs that may mean you can conjure up an exact copy of an object you briefly saw at some distance (e.g. the key you saw a guard use from across a room). But other GMs may require that you have held the object and studied it in detail.