This is a response to quite an old writing prompt in the Worldbuilding Community - Worldbuilding Prompt #451 - Siege weapons - it took me a while to modify, 3D print and paint the models.
Please welcome the return of Marv the Magnificent, gnomish inventor.....
Baron Ulric of Delholm slumped in his throne, rubbed his eyes and ran his hands across the dome of his bald head. He had toothache, a hangover, and was exceptionally grumpy today. To cap it all, he'd just been informed that his insufferable younger brother, Dom Teminar, archbishop of Filrath, was arriving that evening for an unannounced visit.
But he still had to conduct the business of the Barony. So here he was, sat in the great hall of his citadel with a view overlooking the River Shemil, dealing with an endless succession of complaining guild masters, unhappy merchants, citizens wanting handouts from a treasury that wasn't as full as he card to admit, and demanding messengers from Duke Sarthon, ruler of Filrath and his nominal overlord.
"Okay, who's next ?" he asked his chamberlain.
The oily little man held a board with what appeared to be an endless list of supplicants all wanting his attention. Running his finger down it, he read off a name. "Some person calling himself Marv the Magnificent. Claims to be an inventor. Says he's got a new weapon to show you."
"Oh dear. Send him in."
A few seconds later, the door was opened and two guards shepherded in a diminutive figure with an over-sized red top hat. A gnome, appearing quite young by gnomish standards.
Marv swept the hat off his head and swung it in front of himself as he performed a theatrically exaggerated bow.
"Thank you so, so much, my Lord Baron, for seeing an humble yet talented inventor such as myself. I have a new siege engine to not just show you, but to demonstrate to you. It awaits you in the courtyard, and I promise you will want to equip your valiant warriors with many of these wonderful devices !"
Grumbling to himself, Ulric stood up, and motioned the whole court outside. "Well, I suppose I could do with some fresh air. Bring wine !"
Shortly after, in the courtyard, the assembled people saw a target in the form of thin wooden silhouettes of men set up in serried ranks, and a wagon which carried what appeared to be a selection of war machines.
Marv heaved them out of the wagon one by one, with some difficulty. No-one offered to help him, and there were some sniggers from the crowd as he struggled to get set up.
"My Lord, let me initially show you two weapons I am certain you are familiar with, in your great experience and wisdom. First; the common or garden ballista."
The ballista
Turning the crank, Marv wound back the string (actually a stout sinew rope) which pulled back the strong spring steel arms. Placing a bolt in the cradle, he fired it, spearing one of the black wooden silhouettes.
"As you see, a devastating weapon, with great penetrating power. But sufficient only for a single target. But now, secondly, a weapon developed here on Argull recently to overcome this limitation. The barocker !"
The barocker
This weapon looked very much like the first, but with a differently shaped channel and slide. With the rope wound back, Marv placed a wooden open-ended box filled with sharp stones, nails and gravel onto the slide. Pulling the firing lever, the bow snapped forward, the box stopping at the front of the carriage and flinging the contents at high velocity into the wooden targets. Half a dozen of them toppled to the ground, holed by the impact of the deadly salvo.
"Impressive my Lord, but slow to load. Now let me introduce my own refinement, the pinnacle of development of these impressive siege engines. I call it Marv's Patent Gone-Machine, because as you will see, when I activate the automated device, the stones are gone and so are your foes !"
The Gone-Machine
This siege engine looked like some kind of illegitimate child of a barocker, a packing crate and a conveyor belt, with a large crank handle on the side of the conveyor assembly. The crate was loaded with stones and shrapnel.
Marv stretched, then started to crank furiously. As he turned the handle, the rope was pulled back, a box of stones fed from the conveyor belt into position, the machine was automatically fired and returning empty boxes scooped up more stones as they were fed back onto the belt. The targets were shredded, and the crowd gasped appreciatively.
Even Baron Ulric looked impressed. Then a slightly cunning look crossed his face.
"You said it was patented ? Was that in Filrath ?"
Marv hesitated for a second, then answered. "Umm, no my Lord, it is patented in Magoran."
"You have the documents to prove this, I assume ?"
This time the hesitation was longer. "Ummm, well, they are in the post. Or.. umm... they will be as soon as the patent is fully approved. It's.... well, it's patent pending."
Ulric beamed, a sly and twisted smile on his face. "So in other words, you have no patent on it at all. No patent to Baron Ulric's Patent Gone-Machine. Chamberlain, this outrageous gnome has stolen one of my inventions. But I am feeling charitable. Give him a purse with a hundred golden Fids and set two guards to escort him from Filrath lands never to return on pain of imprisonment."
Sources for the 3D print files;
Wagon: https://www.thingiverse.com/thing:3393192
Ballista: https://www.thingiverse.com/thing:3267467
Barocker - remixed by me from the ballista.
I'd like to say a big "thank you !" to Ecaroth, the designer of the ballista, who has allowed me to post images of his design even though the license is officially CC-NC (but the "non-commercial" part is really to prevent people printing and selling actual copies of the models). He is one of my favourite 3D designers; if you are a gamer who prints your own miniatures, I definitely recommend looking over his designs.
Printing, painting and photos by me.