Scrambler B

[reed303]

So do the two spring launchers on the Scioly wiki page both comply with the rules?

This years rule 2.c states "c. All energy used to propel the ETV must come from a falling mass not to exceed 2.00 kg"

IMO this would not allow any springs to be involved in the propulsion of the ETV.

Many examples shown on the Wiki pages are from previous year's events, where the rules may have been quite different.

[SPP SciO]

So do the two spring launchers on the Scioly wiki page both comply with the rules?

This years rule 2.c states "c. All energy used to propel the ETV must come from a falling mass not to exceed 2.00 kg"

IMO this would not allow any springs to be involved in the propulsion of the ETV.

Many examples shown on the Wiki pages are from previous year's events, where the rules may have been quite different.

Just because a "spring" (anything elastic) is involved doesn't mean it's against the rules. Bernard posted a good description of how it works on the previous page. I recall Bro. Nigel explaining that the supervisor will be looking for slack in the string/spring before launch. If it's loose, it's okay - if there's ANY tension on it (to pull it taught), that's not okay, because it's preloaded with energy.

Think of the spring as just temporary energy storage. The falling mass "charges" the spring, and the energy is transferred to the car almost instantly when the trigger is released. This provides an advantage over a typical pulley system, where the energy is transferred to the car over a (brief but not instant) period of time while the mass is falling. However, in both cases, the total energy was gravitational potential energy (the spring just adds a conversion step).

Also - don't forget to add the mass of your spring system to the mass that falls - if it gets pulled upwards (AT ALL) before it's released, when it goes back down, it will add gravitational potential energy also.

[kdy16Dad]

So do the two spring launchers on the Scioly wiki page both comply with the rules?

This years rule 2.c states "c. All energy used to propel the ETV must come from a falling mass not to exceed 2.00 kg"

IMO this would not allow any springs to be involved in the propulsion of the ETV.

Many examples shown on the Wiki pages are from previous year's events, where the rules may have been quite different.

Just because a "spring" (anything elastic) is involved doesn't mean it's against the rules. Bernard posted a good description of how it works on the previous page. I recall Bro. Nigel explaining that the supervisor will be looking for slack in the string/spring before launch. If it's loose, it's okay - if there's ANY tension on it (to pull it taught), that's not okay, because it's preloaded with energy.

I agree so far with SPP SciO.

Also - don't forget to add the mass of your spring system to the mass that falls - if it gets pulled upwards (AT ALL) before it's released, when it goes back down, it will add gravitational potential energy also.

I don't agree with this fully. Think of this scenario where two 2kg masses are suspended on either side of a pulley with identical length strings. What is the falling mass here? Should be zero, right? Now, make one of the two masses 3 kg. What is the falling mass? It should be the delta between the 3kg mass + longer string vs the 2kg mass + shorter string, right?

In most Scrambler ETV + launcher scenarios, the mass of spring + strings on the vehicle side of the pulley outweighs the mass of the string + spring that is on the falling mass side of the pulley. (See this image http://scioly.org/wiki/index.php/File:SC-springtype.gif for reference) This means that you should actually subtract the delta from the falling mass, not add to it because the extra weight is actually trying to pull the falling mass up, not boost its energy as it is falling down.

[SPP SciO]

I don't agree with this fully. Think of this scenario where two 2kg masses are suspended on either side of a pulley with identical length strings. What is the falling mass here? Should be zero, right? Now, make one of the two masses 3 kg. What is the falling mass? It should be the delta between the 3kg mass + longer string vs the 2kg mass + shorter string, right?

In most Scrambler ETV + launcher scenarios, the mass of spring + strings on the vehicle side of the pulley outweighs the mass of the string + spring that is on the falling mass side of the pulley. (See this image http://scioly.org/wiki/index.php/File:SC-springtype.gif for reference) This means that you should actually subtract the delta from the falling mass, not add to it because the extra weight is actually trying to pull the falling mass up, not boost its energy as it is falling down.

I was thinking about it myself and it's sort of a head-scratcher - this is the logic I decided on: If there is any piece of matter which is in Position A at "Ready to Launch," and in Position B "After Launch," it must be counted towards the mass IF Position B is lower than A. If B is higher than A, it should be subtracted, for the sake of the energy calculation, but I don't think the supervisors are going to want to hear that.

That animation - the string is falling down as well, as the mass drops. If you detached the mass from the string at impound, and it was 2.0000 kg, that wouldn't be legal, since the string would need to be counted too.

I may be wrong on this - but this much I'm certain of: If you're using strings and rubber, that mass will be FAR LESS than the mass of the counterweight which drives the whole operation. Always, always, always play it safe when it comes to max dimensions - why take the chance? If you've got a 1.9kg mass, whether or not the supervisor chooses to add say 50 grams for string/rubber mass, you'll be safe. I think you'd be hard pressed to find a team that got that medal or advanced to the next level of competition by maxing out the last gram or centimeter. However, nearly everyone's got a story of the team that LOST that medal or failed to advance, because of a tiered/DQ'd device.

[kdy16Dad]

I don't agree with this fully. Think of this scenario where two 2kg masses are suspended on either side of a pulley with identical length strings. What is the falling mass here? Should be zero, right? Now, make one of the two masses 3 kg. What is the falling mass? It should be the delta between the 3kg mass + longer string vs the 2kg mass + shorter string, right?

In most Scrambler ETV + launcher scenarios, the mass of spring + strings on the vehicle side of the pulley outweighs the mass of the string + spring that is on the falling mass side of the pulley. (See this image http://scioly.org/wiki/index.php/File:SC-springtype.gif for reference) This means that you should actually subtract the delta from the falling mass, not add to it because the extra weight is actually trying to pull the falling mass up, not boost its energy as it is falling down.

I was thinking about it myself and it's sort of a head-scratcher - this is the logic I decided on: If there is any piece of matter which is in Position A at "Ready to Launch," and in Position B "After Launch," it must be counted towards the mass IF Position B is lower than A. If B is higher than A, it should be subtracted, for the sake of the energy calculation, but I don't think the supervisors are going to want to hear that.

If you want to be correct, it should be the net mass, not just the mass on the falling side of the pulley and not subtract the counterweight of the mass of the strings on the other side of the pulley.

That animation - the string is falling down as well, as the mass drops. If you detached the mass from the string at impound, and it was 2.0000 kg, that wouldn't be legal, since the string would need to be counted too.

This should not necessarily be illegal since the remaining mass of the strings on the vehicle side of the pulley is not being subtracted. Granted, if the string that falls down is made of osmium and the string+spring that goes up is made of airgel, it would make sense to weigh the string. But it should be obvious whether this is the case or not by just looking at the strings and springs. The ES should NOT ask the team to untie all the strings, unless they suspect shenanigans.

I may be wrong on this - but this much I'm certain of: If you're using strings and rubber, that mass will be FAR LESS than the mass of the counterweight which drives the whole operation. Always, always, always play it safe when it comes to max dimensions - why take the chance? If you've got a 1.9kg mass, whether or not the supervisor chooses to add say 50 grams for string/rubber mass, you'll be safe. I think you'd be hard pressed to find a team that got that medal or advanced to the next level of competition by maxing out the last gram or centimeter. However, nearly everyone's got a story of the team that LOST that medal or failed to advance, because of a tiered/DQ'd device.

Our team had all the linkages carefully calibrated and tied correctly for last year's tournament. We were ready to detach just the falling mass for the impound, but the ES forced us to also untie the strings + spring linkages and basically destroyed our device, only to find that we were fully legal. We lost our shot at Nationals because of this.

[SPP SciO]

I hear you, and it is confusing. I think the only thing you may not be considering is, with a spring launcher, once the mass has fallen, the car hasn't launched yet - it needs to be triggered, and the springs release to their "normal" positions. When the mass is at the very bottom of its descent, it has lost all of it's potential energy, and most of it was transferred to potential energy within the spring. However, since the spring was pulled upwards a little bit - and then falls back down as the car is released - it contributes a (nearly negligible) amount of gravitational energy, along with the stored elastic energy.

^ I may be totally wrong, but experience is the best teacher. Considering your experience last year, just play it safe. I know at impound there's typically a scale with a large tray, and competitors are expected to place their mass and any attaching accouterments in the tray. Designing a device that's sturdy and simple enough to easily attach/detach mass to is part of the challenge, and we have to live with rule 2.c, "Any part of the Scrambler whose gravitational potential energy decreases and provides energy to propel the ETV is considered to be part of the failing mass. The Scrambler must be impounded along with all falling mass(es) completely detached and the masses combined total not exceeding 2.00 kg."

[homeudream]

Hello, I am new to this event. After read the rules, I like to confirm the position of the bucket and the start point of ETV:
1. is it allowed that ETV starts at any point behind the start line within 2m track? or does it has to be at the center of start line?
2. is the bucket always at the midpoint between the center of start line and the center of the TB for all teams, no move?

thanks!

[Unome]

Hello, I am new to this event. After read the rules, I like to confirm the position of the bucket and the start point of ETV:
1. is it allowed that ETV starts at any point behind the start line within 2m track? or does it has to be at the center of start line?
2. is the bucket always at the midpoint between the center of start line and the center of the TB for all teams, no move?

thanks!

2. I haven't read this section of the rules in detail, but based on previous years, the bucket should be at the same position for all teams.

[cool hand luke]

On the spring falling being included in the weight.

I'd argue quite vehemently that you should NOT count the spring. lets say the spring starts perfectly horizontal. As the mass falls and the spring is stretched, it may indeed move up, and then back down. However, it started flat, ends flat, so no change in gravitational potential energy.


On where can you start the vehicle - I asked for a clarification since if you go by the letter of the wording the tip of the egg has to be ON the start point, meaning the tip of the egg is touching the ground.

I also asked if it has to be directly above the center of the little piece of tape, or can it be scooted all the way to the edge. No response yet.

[Unome]

I also asked if it has to be directly above the center of the little piece of tape, or can it be scooted all the way to the edge. No response yet.

Regarding this one; the rules are pretty clear that there is a Start Point marked on the tape that designates the start line by the event supervisor (3.a), and that the tip of the egg must be above (or rather, as in the unclear section that you noted, on) the Start Point specifically, rather than just generally above the tape (5.e).