Gravity Vehicle C

[MTV<=>Operator]

This brings up an interesting point of discussion: would it be possible to move the center of mass during the run of your vehicle? In the ready to run position, Id estimate wanting about 90% of the mass in the rear, but after the vehicle has descended down the ramp, it is more advantageous to have about 60-70% of the mass in the rear to prevent significant understeer and to aid in uniform braking. Perhaps it is possible to actually have the center of mass MOVE during the run. This could potentially be done near the end of the run (after 6-7 meters have been traveled) as a means of reducing vehicle speed. I envision a simple string wrapping around an axle after a certain distance has passed that moves the center of mass forward.
Food for thought. Id be interested to hear others' perspectives on this.

What's the legality on this, given the phrase in 3.g. "All parts of the Vehicle must move as a whole"?

I think this would be legal because technically the weight is still part of the vehicle, it isn't moving outside of the vehicle or acting as a separate object. I know there was a design in 2012 in which the mass slid from the back to the middle of the vehicle upon launch and remained in the middle for the rest of the run. However, if it significantly increases accuracy scores, could it possibly be worth it to just have the center of mass closer to the middle to begin with in exchange for a slightly greater time?

[windu34]

This brings up an interesting point of discussion: would it be possible to move the center of mass during the run of your vehicle? In the ready to run position, Id estimate wanting about 90% of the mass in the rear, but after the vehicle has descended down the ramp, it is more advantageous to have about 60-70% of the mass in the rear to prevent significant understeer and to aid in uniform braking. Perhaps it is possible to actually have the center of mass MOVE during the run. This could potentially be done near the end of the run (after 6-7 meters have been traveled) as a means of reducing vehicle speed. I envision a simple string wrapping around an axle after a certain distance has passed that moves the center of mass forward.
Food for thought. Id be interested to hear others' perspectives on this.

What's the legality on this, given the phrase in 3.g. "All parts of the Vehicle must move as a whole"?

I think this would be legal because technically the weight is still part of the vehicle, it isn't moving outside of the vehicle or acting as a separate object. I know there was a design in 2012 in which the mass slid from the back to the middle of the vehicle upon launch and remained in the middle for the rest of the run. However, if it significantly increases accuracy scores, could it possibly be worth it to just have the center of mass closer to the middle to begin with in exchange for a slightly greater time?

Yeah you could make the sacrifice, but this would be way cooler and could potentially provide a way to slow down before braking if implemented correctly.

[knightmoves]

What's the legality on this, given the phrase in 3.g. "All parts of the Vehicle must move as a whole"?

That's a curious phrase - "move as a whole" isn't very well defined. The next clause talks about no anchors or tethers, so I'd interpret that to mean "everything has to stay with the car" but I wouldn't guarantee that an ES wouldn't interpret it as "no changing mass distribution" without a clarification.

[windu34]

What's the legality on this, given the phrase in 3.g. "All parts of the Vehicle must move as a whole"?

That's a curious phrase - "move as a whole" isn't very well defined. The next clause talks about no anchors or tethers, so I'd interpret that to mean "everything has to stay with the car" but I wouldn't guarantee that an ES wouldn't interpret it as "no changing mass distribution" without a clarification.

During a run, a wingnut commonly moves within the vehicle. I dont see why other parts (a large mass) couldn't move in a similar fashion.

[AngelMB]

What's the legality on this, given the phrase in 3.g. "All parts of the Vehicle must move as a whole"?

That's a curious phrase - "move as a whole" isn't very well defined. The next clause talks about no anchors or tethers, so I'd interpret that to mean "everything has to stay with the car" but I wouldn't guarantee that an ES wouldn't interpret it as "no changing mass distribution" without a clarification.

I have a hard time believing an ES would see shifting mass as not moving as a whole. As long as no pieces physically fall off the vehicle I can't see how it wouldn't be moving as a whole. This reminds me of the moving dowel arm for some mousetrap vehicles last year, although there were moving parts on some vehicles, they still moved with the MV much like how a shifting weight would move with the GV.

[PM2017]

This brings up an interesting point of discussion: would it be possible to move the center of mass during the run of your vehicle? In the ready to run position, Id estimate wanting about 90% of the mass in the rear, but after the vehicle has descended down the ramp, it is more advantageous to have about 60-70% of the mass in the rear to prevent significant understeer and to aid in uniform braking. Perhaps it is possible to actually have the center of mass MOVE during the run. This could potentially be done near the end of the run (after 6-7 meters have been traveled) as a means of reducing vehicle speed. I envision a simple string wrapping around an axle after a certain distance has passed that moves the center of mass forward.
Food for thought. Id be interested to hear others' perspectives on this.

Legality aside, this seems a bit complicated from a technical perspective, because you'd need to have some sort of latch that starts off closed (otherwise the mass would simply slide down when in the ready-to-run). I think it definitely can be done, though. (also I don't know about the legality of this, but could it perhaps hit part of the ramp on the way down that opens the latch? Even if legal, I'm not sure it would be viable because it would take out a large chunk of momentum if not executed very well down, and have to be able to accomodate the dowel, which would likely mean assymetry, in which case any imperfection would mean the car could slightly swerve, causing some major accuracy issues)

The other issue is how much friction the moving mass would have. I wonder if you could build the whole vehicle around a linear slide as a chassis.

IDK how rational this is, but I think that much mass shifting on a vehicle should be pretty scary. OTOH, it would be pretty epic lol.

These thoughts are not fully fleshed out but I'm sort of sleepy, so we'll see what sort of glaring mistakes I've made tomorrow...

[knightmoves]

Legality aside, this seems a bit complicated from a technical perspective, because you'd need to have some sort of latch that starts off closed (otherwise the mass would simply slide down when in the ready-to-run). I think it definitely can be done, though. (also I don't know about the legality of this, but could it perhaps hit part of the ramp on the way down that opens the latch?

As was mentioned, it was done successfully last time around (and you're right - the pencil released the mass, and the mass hit the vehicle release before it slammed into the rest of the vehicle body). I'd imagine it's also quite easy to mess this up.

[knightmoves]

During a run, a wingnut commonly moves within the vehicle. I dont see why other parts (a large mass) couldn't move in a similar fashion.

That's a good point - if the rule was interpreted to mean "no changing mass distribution" then everyone's brakes are illegal, and the whole event becomes a bit silly.

[chessbucket]

I don't know if this is appropriate to put here but I wanted to get other's opinions on this:

Why would they make the distance so long? 12 meters?!?!

This may be unique to my situation but the way our team does building events is the kids do it 99% at home. Most building and testing time is done on weekends and over breaks, which is conveniently when school tends to be closed, so we can't use a hallway or anything like that to test. We don't do scioly as a club after school or during school. Where do you guys test? I've thought about a community center but having to keep transporting builds can 1) increase the chances of something breaking in transport, and 2) constantly changing testing surfaces and locations can introduce confounding variables when ur trying to get sub 5cm accuracy. For MTV, we had a continuous stretch of 8m in the common area of my house, so we always had a constant variable that didn't affect runs differently. with the 12 meter distance this year, it's a different story. I apologize if I sound like I'm whining, venting, and/or ranting but having a constant test surface has always proved to be a must in my experience.

[nicholasmaurer]

I don't know if this is appropriate to put here but I wanted to get other's opinions on this:

Why would they make the distance so long? 12 meters?!?!

This may be unique to my situation but the way our team does building events is the kids do it 99% at home. Most building and testing time is done on weekends and over breaks, which is conveniently when school tends to be closed, so we can't use a hallway or anything like that to test. We don't do scioly as a club after school or during school. Where do you guys test? I've thought about a community center but having to keep transporting builds can 1) increase the chances of something breaking in transport, and 2) constantly changing testing surfaces and locations can introduce confounding variables when ur trying to get sub 5cm accuracy. For MTV, we had a continuous stretch of 8m in the common area of my house, so we always had a constant variable that didn't affect runs differently. with the 12 meter distance this year, it's a different story. I apologize if I sound like I'm whining, venting, and/or ranting but having a constant test surface has always proved to be a must in my experience.

I agree a consistent test surface is critical. We usually use our school gym because the wood flooring is typical for what we see at most competitions. But that doesn't sound like a realistic option for you... Does your coach have the ability to request use of the school after hours or over breaks? As you note, even a hallway can be good test track.