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Well, sorry to just pop in, but here I am for a little help.

Anyhow, with my trebuchet (a floating arm), the arm will drop if deployed regardless of whether or not I have a counterweight and (or) projectile loaded due to the configuration of the device. I have taken a small sinker for fishing and cut it in half for application to the arm in order to place it on the bottom of the arm so it won't really create a launch motion, but as I think about that, I realize that it will still deploy when released due to the trebuchet design. The rules state that the trebuchet arm must NOT make a launch motion when released from any position before the point where the projectile is launched, so would that only apply to a complete motion? Or rather, would that apply to an incomplete motion as well?

On another note, in order to attach my current counterweight, I have only used another (larger) sinker in the current state, but I am in the process of creating a method for the counterweight to be attached in an interchangeable manner. I see that for the attachment, you have to have a (no more than) 6.5 mm thick material that has a hole (at least) 9 mm in diameter. In short, does this mean that the hole of the (attachment location of the) arm must be only 6.5 mm in the distance from the hole to the edge of the material, or the material itself must be no more than 6.5 mm thick? If the latter in the case, then I can not use a dowel in order to attach the counterweight which was what I initially had planned on doing. (Noting that the dowel would have to have a 9 mm hole, that likely is eliminated anyhow) In this case, I would have to use a metal sheet/plate or a similar material, yes?

Thanks for even reading this!

Is it reasonable to expect "nice numbers" for counterweights?

GoNerdHerd wrote:Is it reasonable to expect "nice numbers" for counterweights?

No... we got something with about 5 decimal places at the last invitationals.

I have a question about the energy rule. Our team uses a carbon fiber arrow as the long side of the arm. It would bend a little when the counterweight is more than 2kg. Another member of our school team questioned if that is against the energy rule. Here is the complete quotation of the energy for your reference. I am not sure how to interpret the form of potential energy. I'd really appreciate if any one know the answer for sure. Our tournament is next weekend. We still have time to reinforce the arm if necessary. Definitely don't want to be in tier 2.

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.

jjnv wrote:I have a question about the energy rule.

Here is my best guess at an answer. The only way to get a definite opinion is to ask the judges at your tournament.

The answer is in Para. 3.f, line 1. "The device, without the counterweight and projectile, must not contribute energy to the launch."

The energy used to flex the arm (they all do, some more than others) comes from the falling counterweight, so it should be allowed.

Some judges may penalize (incorrectly in my opinion) devices that exceed the allowed height when no counterweight is installed even though they are within the limit (due to flexing) with the counterweight. To make sure you are not storing more energy than can be obtained from a "legal" sized device, measure it's height before you put the maximum counterweight on it.

jjnv wrote:I have a question about the energy rule. Our team uses a carbon fiber arrow as the long side of the arm. It would bend a little when the counterweight is more than 2kg. Another member of our school team questioned if that is against the energy rule.

If your arm is bending as you pull the arm back I do believe that that wold violate the energy rule as a compressed or stretched elastic solid. However if your arm is straight when in the ready to launch position it is legal, and if the arm bends during lauch it is also legal.

nave22 wrote:Anyhow, with my trebuchet (a floating arm), the arm will drop if deployed regardless of whether or not I have a counterweight and (or) projectile loaded due to the configuration of the device.

Yes you are right, if it will make a motion in the launch direction after being released from any point in the launch motion, it is not legal. If making the side of the arm that the sling is attached to heavier does not work, make sure your rails are perfectly flat and level. If they are slated downward in the direction of launch, it is not legal.

GoNerdHerd wrote:Is it reasonable to expect "nice numbers" for counterweights?

I just had States yesterday and we got 2 kilogram counterweight with 40 gram projectile. Our treb came in second with about 11.5 meters and we came in 2nd overall. There's a slim chance we'll go to nats.

Friedoyster3 wrote: If your arm is bending as you pull the arm back I do believe that that wold violate the energy rule as a compressed or stretched elastic solid. However if your arm is straight when in the ready to launch position it is legal, and if the arm bends during lauch it is also legal.

I am not sure what you mean by "pull the arm back". How do you do that? How much force should you apply to the arm to see if it bends? The energy rule is confusing since I am not sure if compressed or stretched elastic solid is a separate rule or an examples of "The device, without the counterweight and projectile, must not contribute energy to the launch". We used the compressed carbon arrow as suggested by the Storm the Castle wiki on this site.

Friedoyster3 wrote: Yes you are right, if it will make a motion in the launch direction after being released from any point in the launch motion, it is not legal. If making the side of the arm that the sling is attached to heavier does not work, make sure your rails are perfectly flat and level. If they are slated downward in the direction of launch, it is not legal.

We have a standard Hinged Counterweight Trebuchet with no rails. The sling is attached to the heavier side. It makes no motion at all when no counterweight is attached. You just reminded me that we could add some weight to the side where the counterweight is attached to make it more balanced.

JSGandora wrote:I just had States yesterday and we got 2 kilogram counterweight with 40 gram projectile. Our treb came in second with about 11.5 meters and we came in 2nd overall. There's a slim chance we'll go to nats.

I would have thought it would have taken a lot more than that to place that high at State. I would expect to see two or three trebs that reach the 20 meter mark at those masses at my State tournament. Good luck, hope that you guys can make it to nationals.

yeah, I thought our treb was failing when it got 11.5 meters. I pretty sure we wouldn't place...but then after seeing some of the other trebs...