It's About Time C

[walkingstyx]

That idea sounds incredibly cool, but not especially good at keeping time. It sounds as though ambient temperature differences could have a huge impact on how well this clock worked, not to mention how difficult it would be to build and the likelihood of it being destroyed in travel. Awesome ideas are fun, but only if they work well. If your goal is to win, I would suggest going with a simple natural harmonic oscillator and calibrating it to death. Our device for Nats last year was a pendulum and Troy's (the winners) was an oscillating spring. Both were very simple, but their operators knew them well enough to keep virtually perfect time. Also, simple devices tend to travel better. Our pendulum survived a car wreck on the way home from State, while some of our complex devices can hardly handle being picked up in the classroom.

[Paradox21]

We had our regional competition on Saturday in Minnesota (not the most competitive state) and I got to see the raw scores for the event and I was amazed at the scores for the time trials. There were at least 5 teams within a 48/50 for the trials. The deciding part really seemed to be the test. Out team got 5th in the time trials with a low 48 score (48.3 I think) but got 1st overall because we did well on the test. As far as I know all of the designs were relatively simple pendulums.

[texan92]

That idea sounds incredibly cool, but not especially good at keeping time. It sounds as though ambient temperature differences could have a huge impact on how well this clock worked, not to mention how difficult it would be to build and the likelihood of it being destroyed in travel. Awesome ideas are fun, but only if they work well. If your goal is to win, I would suggest going with a simple natural harmonic oscillator and calibrating it to death. Our device for Nats last year was a pendulum and Troy's (the winners) was an oscillating spring. Both were very simple, but their operators knew them well enough to keep virtually perfect time. Also, simple devices tend to travel better. Our pendulum survived a car wreck on the way home from State, while some of our complex devices can hardly handle being picked up in the classroom.

Did your pendulum have an escapement?

[Jazzy09]

We had our regional competition on Saturday in Minnesota (not the most competitive state) and I got to see the raw scores for the event and I was amazed at the scores for the time trials. There were at least 5 teams within a 48/50 for the trials. The deciding part really seemed to be the test. Out team got 5th in the time trials with a low 48 score (48.3 I think) but got 1st overall because we did well on the test. As far as I know all of the designs were relatively simple pendulums.

lololol that is not true

[Flavorflav]

We had our regional competition on Saturday in Minnesota (not the most competitive state) and I got to see the raw scores for the event and I was amazed at the scores for the time trials. There were at least 5 teams within a 48/50 for the trials. The deciding part really seemed to be the test. Out team got 5th in the time trials with a low 48 score (48.3 I think) but got 1st overall because we did well on the test. As far as I know all of the designs were relatively simple pendulums.

lololol that is not true

Do you mean that they didn't have their regional competition Saturday, or that it wasn't in Minnesota?

[Paradox21]

No, the scores seemed a little dubious so we looked into it and the scoring was done incorrectly. A team that was .9 seconds off on the 1st time trial would have been docked .9(.4) or .36 but they should have been docked 9(.4) or 3.6 points. It ended up changing some of the overall placements but our team got 1st either way. And it has been reaffirmed, MN is not the most competitive state.

[walkingstyx]

Yeah that seemed a little odd, we just won an Ohio invitational with a low 48. Also texan92 we did not have an escapement, we just knew how much our period decayed by.

[saturnian]

That idea sounds incredibly cool, but not especially good at keeping time. It sounds as though ambient temperature differences could have a huge impact on how well this clock worked, not to mention how difficult it would be to build and the likelihood of it being destroyed in travel. Awesome ideas are fun, but only if they work well.

While some event supervisors may overlook use of electric bulb to create "heat" chamber, it is surely against the rules (no electricity or chemicals). But I agree, the idea is pretty awesome.

Last year, one of my teammates tried to do magnetic device. It was pretty cool too, but did not quite work, and if you think about it - against the rules, since magnets create electromagnetic fields. She was never questioned during invitationals, but once you get to states or nationals, event supervisors may DQ your "clock".

[saturnian]

Yeah that seemed a little odd, we just won an Ohio invitational with a low 48. Also texan92 we did not have an escapement, we just knew how much our period decayed by.

You guys were great, and we are happy you could come. Hope you enjoyed the snow

[Gooblah]

What materials did you guys use for pendulum construction?

I tried using a 1/4 diam, 3 in. bolt as the axis, and then hooked that up to a Knex frame for support. Hanging from it was a 1/4 threaded rod that ended in an eyehook, which had about 9 oz attached to it. However, all I'm getting out of the pendulum is ~1.5 mins, way too short for competition.

I'm thinking the time issue is coming from several locations:
1) Dampening of momentum due to frame sway
2) Friction between the axis and the pendulum itself (I used a small knex contraption, with two knex pieces hanging off the axis and then connecting to the pendulum)
3) Air resistance

Issue #1 can be resolved by replacing the frame with wood, I think - currently, it's a wooden base, and then a knex frame is screwed onto it. So by replacing the knex frame with two pieces of wood, i could effectively reduce frame sway.

Issue #3 is negligible, since the pendulum isn't particularly wide.

I tried using string tied to the weight on one end and a simple washer on the other to reduce friction, but the weight simply snapped the string. I'm considering looking into fishing twine or a thing metal rod which I could bend with pliers to replace the threaded rod in the pendulum. Any suggestions?