Bonus Drop

[scotta42]

Hello All,

I'm a Bungee Drop C event supervisor and am preparing to run this event. I want to make sure I understand The Bonus Drop. I've read it through carefully and am still a little unclear. Correct me if I'm wrong.

For either or both of the two drops, if the drop is within 20cm of the target plane for the state competition, the competitors will be allowed an additional bonus drop at that drop station. This bonus drop window must be 20cm tall and be entirely within the 2 to 5m acceptable range. The top of this window can be located anywhere between 2 and 4.8m of drop height. The event supervisor can determine exactly where the top of this window is located. Is this a correct description?

This begs the question of how to determine if it falls within this window without creating something that it might hit. I was thinking a height window shown in the background but then accommodate for the perspective video camera viewpoint by showing another window to be used by the video operator assuming the drop bottle goes straight down.

Thanks for any advice.

[Northridge]

So where I have ran this. I put a colored sheet behind the range for the bonus drop. That way it was easy to tell if they landed in it on the camera I use.

[scotta42]

Thanks for the suggestion!

[clbrown]

Hi Scotta42.
Just a few thought - I ran this event the last time it ran several years ago (region and state), and also several invitationals and regionals this year. (I will be doing an different event at State this year)

It is not an easy event to get accurate measurements on since the bottle is moving fairly fast at the bottom, and possibly swinging as well. You can NOT get accurate readings by eye. Even high speed cameras have real problems with parallax errors that are awkward to compensate for over much of a vertical range.

I would suggest you use the Vernier ultrasonic motion sensor (or the Pasco equivalents). <If you are associated with a school, their physics or chem dept should have them> It is accurate to about 1mm (if properly calibrated), and can take data every 25 ms. I use this, graph the data, and then fit a 4th order poly thru the bottom 5 points to manually cursor to get the lowest point (never on one of its actual readings

At the last several invitationals we had several teams within 1 cm of the (virtual) floor, and 2 that were within 0.4 mm of the floor (yes - that is sub mm!).

So, as you can see, eyes are not good enough - especially at State where you will be working with pre-winners that should be really good.

Let me know if you have other questions.

[maxbajcz]

At the beginning of the season, out team built a lidar setup to measure distance to target. This was after experimenting with a sonar setup. We found that neither setup was particularly accurate. The sonar had too slow of a sample rate and both setups had issues when the bottle was at all rotated from perfectly vertical at the bottom.
As a double check for target contact, we've been using carbon paper to indicate an impact, and that has worked well.

[clbrown]

Neat! Could you post details, or a link. I was looking for a way to upgrade my ultrasonic system for the very reasons you indicated.