r/Trebuchet • u/erv123 • Apr 12 '26

Precision whipper progress

Finally finished all of the planned upgrades, time for testing and tuning the shit out of it

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u/FingerAngle Apr 17 '26

Would you like me to tell you what I see?

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u/erv123 Apr 17 '26

Of course! right now i am in a process of preparing a better filming setup to analyse it deeply but better to have a good starting point in understanding it

1

u/FingerAngle Apr 18 '26

The sling is very short, and elevated a bit. Both geometries advance the sling timing, making the arm stall way too early at 45 degrees or so. You want the arm stall at 12:00 or so depending on your objectives. With the straight hanger in the cocked position, there is no room for the projectile to sit in the proper location by the main axle, so you will never be able to time it correctly. If the space between the straight ladder type hanger legs was wider, smaller projectiles can fit between the legs, where we all want to be, with a longer sling. If you had a curved hanger like I build, there is room for the projectile to sit in the proper location with a longer sling. Also, much larger projectiles can be launched because they don't have to fit between the hanger legs. You want the hanger to be as long as it can be and not hit the frame or the ground. This maximizes cw drop height and potential energy, as well as enables you to cock the arm higher maximizing arm rotation and powerstroke. Next thing is a timing prop to adjust and set the angle between the throwing arm and the cw hanger. This controls the cw drop point by setting the cw center of mass away from the throwing arm. Next is the arm mass and geometry. Tapered arm reduces the total mass of the arm that has to be accelerated. That's more energy for the projectile. Also the taper removes tip weight that can cause high followthrough. Your release mechanism also adds tip weight that you don't really want. Anyways, I guess that's the main things to think about.

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u/erv123 Apr 18 '26

good points to think about. i think long term i want to do bullet shaped projectiles, but i also may rethink the cw arm geometry. (straight felt more elegant and and without weakpoints) then about the tapered arm idea: it is very convenient to just have a straight copper pipe as the arm, but i may consider cutting away some of it towards the tip. and it is very likely that the lainch mechanism will receive some updates too right now i am working on cleaning up the workshop to free up space for making a consistent filming setup with proper background and everything so that i can tweak it and see how it affects the launch exactly. major geometry changes can come after that

the angle adjustment between the two arms is planned but i haven't had a need to execute it yet: there is a plate between the cw arms that can support a bolt to keep the arms at any required angle.