StarDestroyer.Net BBS

This year I decided to build two catapults for the boys, figured it'd be something they like. did some googling and eventually ended up with the Da Vinci catapult which appealed to me.



I don't have any plans, just printed this and used it for inspiration.

Cut up the main parts using Ash and started the glue up. This was just a lot of cutting and milling of stock. Before I could start I had to decide that the catapults should be 30cm long and 15cm wide and the profile of the wood parts should be 20x25mm, then I could start making parts.



I sold my wood lathe this summer so I used the metal lathe to cut the cylinders, with some preparation to get as much dust as I could, wood dust is not nice to the machines.





I made the ratchet wheels in Solidworks and printed out two templates which I cut on the bandsaw.



Then I used the mill to cut the slots that will hold the wooden leaf springs.







Then I had to make some dowels, so I used a tip from Mattias Wandel and made a dowel jig. Worked real well, have idea for making one in metal now for different sizes.









Also worked on the trigger mechanism, the original one in the 1st pic wasn't very good. I instead made a wooden, spring loaded sear that you use a lever to release:



The "spoon" came out nice I thought. I used a wood router bit to make the gouge in the mill, I modified it and cut off the bearing that was used to follow along edges. It was broken anyway, a cheap 1/2" router bit set from ebay. I needed a pilot hole though so I used a normal 12mm router to make that, then I plunged the router bit on the mill and moved it a little along the X-axis to make an oval indentation.



Almost finished now.

Really nice work, crisp edges. You gotta love these wonky Leonardo designs.
For added bonus, this can whack you solidly if you do stupid things, but it is hard to get body parts violently squished in it (I am looking at you, Onager.). Perfect beginner catapult.

On second thought, you may want to think about some plywood cover for the ratchet, though - kiddy digits are small and tend to go into places that spin wildly without noticing it beforehand.

Your sear is definitely going to work better than the original - that one yould need you to raise the tooth a bit more against the spring tension in order to release. Just make sure you don't get much lower than 90° on the sear angle, or it will bekome a hair trigger once the surfaces have rubbed in a bit.

For added efficiency, try lightening the spoon as much as you can.

Thanks, unfortunately no time anymore to make any more modifications, they're getting packaged now and over here christmas is celebrated on the 24th.



I could get more power out of it yet, as the wooden springs are not yet fully maxed out. But I tested it and I think it's enough for now at least.

Gives the boys some science to attend to.... testing out the engineering to find greater efficiencies. Nothing breeds invention like warfare.

The LEGO castle sets will now tremble in fear!

I dunno those LEGO castles are pretty tough if ya build them right.

'if' you build them right. 'By the book' LEGO constructs tend to be pretty flimsy

The catapults where a pretty big hit on the whole I would say:
https://i.imgur.com/0Cv2jHj.mp4

I don't think weight reduction can achieve much more right now. I think the springs are the weak point, one is already showing signs of wearing in a spot, I probably didn't taper it well enough, that helps I read in spreading the load evenly. A stiffer spring would probably be the easiest way to upgrade it. Or moving to a metal flat spring.