OldTony

It's a Cat's life – Perhaps 

 It's dark inside this little box
 in which they say a fatal ray
 has perhaps ended my life;
 but it's not for me to say.

 So do I live or am I dead?
 Strange as it seems it's up to you.
 I accept you have no choice
 although you know what you must do.

 “Bring some light into this place
 to look and see, Schrödinger said.
 "Because until you do as bid
 this cat's alive, but also dead.

You can expect a motor designed to provide more power than you need to be physically larger than one designed for a lower power. The main losses for an eletric motor are friction, windage and iron losses. In general these losses increase with the physical size of a motor. I would suggest you choose a motor that can provide the power you need plus, perhaps, a little more for longevity and reliability.

It so happens that I am a moderator on a completely different forum not to do with science. Assuming the arrangement here is much the same perhaps members should realise that moderators are carefully chosen for their knowledge and the benefit that they can give to their forum. They do not receive any reward for their time spent helping the forum to flow as harmoniously as possible except the occasional word of thanks. In short: it can sometimes be a thankless job. Just saying........

Mrs Tilley likes prose but not poetry

I'm having difficulty visualising a practical application as the two connecting rods seem to need to pass through the walls of their respective cylinders. Also although the horizontal piston moves faster than the vertical piston you still only get one revolution of the crank per stroke. I presume you are relying on momentum to carry the horizontal piston through its mid point. However perhaps, however rarely, due to a fault such as an engine misfire it could bounce back and reverse at the mid point which I can imagine would be catastrophic for an internal combustion engine.