Pumpkin/bowling ball launcher questions:

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Discussion Overview

The discussion revolves around the design and optimization of a pumpkin or bowling ball launcher, specifically focusing on propulsion methods using elastic materials and compressed coil springs. Participants explore the mechanics involved in launching projectiles effectively and the potential challenges associated with different designs.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes using elastic bands combined with compressed coil springs to enhance the launching mechanism, questioning the scientific soundness of this dual approach.
  • Another participant suggests that the question cannot be resolved through simple physical laws, indicating that inefficiencies may arise in different forms and that experimentation is necessary for optimal design.
  • A warning is issued regarding the potential dangers of using large compressed springs, emphasizing the need for safety precautions similar to handling firearms.
  • One participant expresses a preference for simplicity in design (KISS principle) and notes that the launching apparatus must maintain motion while the elastic accelerates the projectile, while also acknowledging the limited operational distance of springs.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the effectiveness of the proposed dual propulsion method. There are differing opinions on the feasibility and safety of using large springs, as well as the importance of experimentation versus theoretical calculations.

Contextual Notes

Participants highlight limitations related to the efficiency of different propulsion methods and the safety concerns associated with using high-capacity springs. The discussion does not resolve the mathematical implications of the proposed designs.

Who May Find This Useful

Individuals interested in mechanical design, physics of projectile motion, or those participating in competitive launching contests may find this discussion relevant.

R_Rose
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I'm trying to figure out a way to get better results in a "pumpkin launching" contest. The goal is to
launch an 8-12 lb pumpkin (or bowling ball) as far as possible.One method is going to use elastic, bungee or large rubber/latex bands as the method of propulsion. The problem is there are limiting factors which impede this design the larger it gets (cost being one of them).

I was thinking of a way to help infuse more power into the system with other means of accelerating the projectile but am unsure if it will aid in the overall performance.

I have considered using compressed coil springs, each with a 2000lb compression capacity and 8-10 inches of expansion capacity. The springs (4) would be used to move the entire launch device in the same angle and direction of launch (obviously causing stress on the launch device upon reaching terminus). At some point during the expansion of the springs, the primary firing mechanism would release the elastic bands.

Obviously 8-10" of movement allows very little time to initiate launch so I have considered using a block and tackle with multiple pullies to increase distance & time of travel, reduce damage to launch mechanism.

As the springs decompress, the entire mechanism accelerates later initiating the final launch. My question is if this theory in using two methods to power the launch is scientifically sound. If the launch device is moving at say 3ft/.1 seconds = 30 fps = 20mph, how will this affect the item being launched?
 
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Welcome to PF

Your question can't be answered by simple physical laws. You are trading one kind of inefficiency for other forms of inefficiency .

Experimentation, not calculation will lead you to the best design.

Good luck
 
R_Rose said:
I have considered using compressed coil springs, each with a 2000lb compression capacity and 8-10 inches of expansion capacity.
At the risk of stating the obvious... A spring of that size will do a lot of damage if it releases unexpectedly. If you try something along these lines, treat your compressed springs with the same respect you'd show a cocked handgun.
 
If you can make it all work then it should improve the distance. However I'm a great believer in KISS.

I believe you would need to ensure the launching apparatus is moving for the whole duration that the elastic is accelerating the ball. However springs tend to operate over a short distance.
 

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