Storm the Castle B

[starpug]

That would be the almighty "Energy Rule", or more specifically 3.f

The device, without the counterweight and projectile, must not contribute energy to the launch. Example violations include: the axis upon which the firing arm rotates drops during launch, the center of gravity of the unloaded device drops during a launch motion, the triggering process provides momentum to the launch, a form of potential energy (compressed or stretched elastic solids, compressed air, etc.) is used. Without a counterweight and projectile, the launch arm must not make a launch motion when released from any position before the point where the projectile is released. Allowable types of devices include, but are not limited to, counterweight and floating-arm trebuchets, subject to these rules.

What you just asked about is highly illegal in this event.

There is illegal and legal in science olympiad, there is nothing that is slightly illegal and nothing that is extremely illegal. Having a device that breaks the energy rule and having a device that shoots flames are equally illegal.

[emaynard]

I plan to make a floating arm trebuchet were the axle is elevated from the track, and then the whole arm falls at first, once the trigger is pulled. Would that be breaking the enrgy rule? I know this is what the person below me just basicaly said but without the counterweight or projectile the the trebuchet wouldn't dry fire.

[brobo]

I plan to make a floating arm trebuchet were the axle is elevated from the track, and then the whole arm falls at first, once the trigger is pulled. Would that be breaking the enrgy rule? I know this is what the person below me just basicaly said but without the counterweight or projectile the the trebuchet wouldn't dry fire.

...It wouldn't be illegal, but I wouldn't recommend it. You would lose a lot of energy by doing that... the arm would stop for that brief second when the arm hits the track, and you would lose just about all the moment and kinetic energy you had up until that point.

And starpug, I do understand that all illegal devices are equally illegal, but a bad judge may overlook or not notice something small like the trebuchet being a centimeter or two too large, but it would be pretty hard to miss an additional counterweight attached to your FAT.

[starpug]

Except the energy rule is so broad that there are many ways to break it. For example when I did this even in middle school we had a tapered arm, the wider end was on the counter weights side to handle the heavy strain of the counterweight. Except this created a problem, since there was more of the arm's mass on the counterweight side, the device violated the energy rule, although not very obviously. Before regionals we put a little duct tape around the projectile side of the arm to even out the weight and everything was fine. But a less then careful judge may not notice the slight difference, or a volunteer who got thrown onto the event the night before might be confused by the passage in the rules regarding the energy rule (it's not exactly as straight forward as say measure these three dimension if they're greater then a certain number, the device is illegal)

All I'm trying to say is be nice to the newbies, you were once one. Saying that attaching an extra counterweight is illegal is enough, you don't need to say highly, all it does is make people feel stupid and less welcome on this board.

[ichaelm]

I plan to make a floating arm trebuchet were the axle is elevated from the track, and then the whole arm falls at first, once the trigger is pulled. Would that be breaking the enrgy rule? I know this is what the person below me just basicaly said but without the counterweight or projectile the the trebuchet wouldn't dry fire.

...It wouldn't be illegal, but I wouldn't recommend it. You would lose a lot of energy by doing that... the arm would stop for that brief second when the arm hits the track, and you would lose just about all the moment and kinetic energy you had up until that point.

And starpug, I do understand that all illegal devices are equally illegal, but a bad judge may overlook or not notice something small like the trebuchet being a centimeter or two too large, but it would be pretty hard to miss an additional counterweight attached to your FAT.

If the unloaded arm's center of mass falls at any point during the launch motion, then you have violated the energy rule. Also, if its axis of rotation falls, you have violated the energy rule. So that would be illegal.

[wlsguy]

I plan to make a floating arm trebuchet were the axle is elevated from the track, and then the whole arm falls at first, once the trigger is pulled. Would that be breaking the enrgy rule? I know this is what the person below me just basicaly said but without the counterweight or projectile the the trebuchet wouldn't dry fire.

The type of treb you are describing is called an f2k. basically it elevates the axle and the entire arm above the track and use it's weight to increase the throwing distance. because the arm moves in the direction of launch without the counterweight, it violates the energy rule.

The only way to insure the energy rule is not broken is to have the tip end of the arm weigh slightly more than the counterweight side.

[fizwiz]

I realize the scores will vary depending on the counterweight and projectile mass but does anyone have any idea what "good" scores are?

Anyone have results from previous years?

[starpug]

I realize the scores will vary depending on the counterweight and projectile mass but does anyone have any idea what "good" scores are?

Anyone have results from previous years?

If you can be accurate to within a meter of the target, and you can fire high 30s low 40s with a golf ball, you should be in a pretty good position to win at least at the regional and state level. If I can track down my old data I may be able to put together a ratio of counterweight to distance to projectile density to give you a better idea

[wlsguy]

I realize the scores will vary depending on the counterweight and projectile mass but does anyone have any idea what "good" scores are?

Anyone have results from previous years?

How far are you throwing?
Is it consistant?
How tough is the region or state you are in?

The 2006 rules allowed for a treb to be 1 meter long and 75cm high. 2007 changed it to 75cm long and 65cm high.
At that time (from what I remember) the top machines in Ohio were throwing a 25g rubber ball around 33 meters.
Heavier (40g) balls were going around 17m with 2kg.

This year should be similar. The increased height will change the available energy somewhat but the arm and sling are already accellerated to close to their maximum speeds.

[emaynard]

I am building a f.a.t trebuchet. I was wondering if anybody has figured out how to solve the the gap problem in the track. Is that even an issue if the stall occurs at the right time? I was thinking maybe attach something to the counterweights axle (or whatever it's called) so that once it falls past the track it releases the object so the object spans the gap. Any other ideas or websites.

P.S "Thanks" to those of you who answered my other questions.

[starpug]

I am building a f.a.t trebuchet. I was wondering if anybody has figured out how to solve the the gap problem in the track. Is that even an issue if the stall occurs at the right time? I was thinking maybe attach something to the counterweights axle (or whatever it's called) so that once it falls past the track it releases the object so the object spans the gap. Any other ideas or websites.

P.S "Thanks" to those of you who answered my other questions.

Our solution was to have as thin a axle on the vertical track as possible and biggish wheels

[fleet130]

Best method I've seen is to put hinged "bridges" on the tracks.
Not the best drawing. The bridges are hinged on one end so the wheels knock them down to fill the gap. You'll need to work out the details to make it work.

[wlsguy]

I am building a f.a.t trebuchet. I was wondering if anybody has figured out how to solve the the gap problem in the track. Is that even an issue if the stall occurs at the right time? I was thinking maybe attach something to the counterweights axle (or whatever it's called) so that once it falls past the track it releases the object so the object spans the gap. Any other ideas or websites.

P.S "Thanks" to those of you who answered my other questions.

If you keep your gap as small as possible, make sure your track surfaces are the same height, and use wheels greater than 40mm you should not have any trouble with the wheels crossing the gap.
We generally buid the frames and then use thinner wood (like paneling) on top of the track surfaces to close the gap as small as possible

[GoNerdHerd]

What are good examples of lightweight arms? I have tried wood, and it is too heavy.

[starpug]

What are good examples of lightweight arms? I have tried wood, and it is too heavy.

Hollow Carbon Fiber rods, I know it's expensive, but I used it last time this was an event and it worked very well.