wlsguy wrote:Balsa Man wrote: .....There’s also an implication for the “gravity supercharger” we implemented last year (if anyone's thinking about throwing that in) – a moving mass that starts at H, slides down into the vehicle, w/ vehicle released to roll just as it …joins the vehicle. At an H of 1m, it picks up/adds the kinetic energy of the mass falling ~8cm; with an overall H ~1m, ~8%. With H at, say 0.5m, the percent of the energy of that 8cm fall (vs the kinetic energy of the system- the vehicle) roughly doubles; as H goes lower, contribution/gain from the moving mass increases. Lower max m for vehicles this year means m of the moving mass will be less, and hence it’s energy will be less, but it’s still…..free additional energy into the system. It’s a pain to implement, but will definitely “pay off” at Hs <0.5m. .....
I'm not a rules expert but I'm not sure if this would be legal this year. The addition of "Entire" vehicle to 3b could be viewed to prevent vehicle and weight systems that split in 2 pieces. Also, since the vehicle must be powered only by the gravitational energy of the vehicle (3b), the highest point of the mass would be likely used for the height measurement since it is / will be part of the vehicle.
In any case, if you plan to use such a system, I recommend submitting a clarification..
With all due respect- truely;
a) All students and coaches certainly have an.....obligation to carefully read and understand the rules for any event they’re involved with. Don't know where that transitions to "expert." if you're serious about being competitive, you design, build, and perform as well as the rules allow.
b) I understand your uncertainty. But, of course, you only have a limited description on how this works to go on- the very brief summary I included, a few more detail pick-ups below; don’t know if you’ve checked out the bit more detailed description in posts last year; but even there I haven’t provided, and for obvious reasons am not going to provide, detailed drawings, or clear photos....
c) I also totally agree with Chalker’s earlier advice about pushing the limits, and getting official clarification “unless you are 100% certain whatever you are doing is legal because of either a rule or something official in writing”
d) In this case, I
am actually comfortably at that 100% level, in the way we’ve implemented it. There may well be ways using a moving mass could push/cross the limits (of the rules- 3b, and all others), but we’re not doing that. If what anyone else may be doing/considering leaves them uncertain, I would also recommend appropriate formal clarification.
With that said, if someone can see a hole in the following analysis; a basis for filing a protest based on a specific violation of any rule, I’d love to hear it…
Running through the rules that are, or may be potentially relevant:
There are “Construction Parameters” (rules 3a through 3j – how the vehicle has to be built/designed. There are then “The Competition” rules (rules 5a through 5p) – how the competition is to be done. Last, there are “Scoring” rules (rules 6a through 6g)
First, there is no general prohibition – anywhere, against moving parts per se on the vehicle, as long as they don’t fall off during the run (5e). Obviously, all vehicles have some moving parts, and some level of relaative motion between certain parts,
Second, there are no restrictions/limitations/or objective or subjective constraints on the absolute or relative movement of parts (that are attached to/ are part) of the vehicle in the Construction Parameters (rules 3a through 3j
The context of ‘the entire vehicle” in 3b is simply and only that the entire vehicle- implicitly all it’s parts- must start from a non-horizontal position, on the ramp. The wheels must be up on an inclined ramp. The term “entire vehicle’ is not used anywhere else in the rules. I suppose one could seek clarification on, “does the entire vehicle mean all it’s parts?”, but I’m comfortable with the obvious answer to that.
Also in 3b, and certainly important to look at, we have the construction parameter/rule, “all energy used to propel the vehicle must come from the gravitational potential energy derived from the mass of the vehicle.” The weight is (a securely attached) part of the vehicle; it’s mass is part of the mass of the vehicle; the energy it contributes to the vehicle is clearly (and only) “gravitational potential energy”, and it is clearly derived from the mass of the vehicle. The position of the mass before starting simply means that the center of mass of the vehicle is higher off the ground than it would be if the (moving) mass were down in the chassis (where it ends up); higher starting center of mass (and lower center of mass when it rolls off the ramp) simply maximizes the gravitational potential energy available to be harnessed from the start position.
Last, there is a requirement in 3b for “a release mechanism to hold the vehicle in place…”. Beyond fitting within dimensional limits, holding the vehicle in place (prior to it starting to move down the run), and that it be activated by a pencil, there are no further constraints on the “mechanism.” No limits on simplicity, or complexity; number of parts, number/nature of energy transfers between the process of moving the pencil, and the release of the vehicle to start moving. Obviously, for any release mechanism to work, it has to have moving parts. So, we have a multi-stage release mechanism. Pencil moves a piece on a bracket mounted to the ramp; that frees the mass to start sliding down. Vehicle is held in place on the ramp by a moveable piece (a lever, attached to the vehicle) on the underside of the vehicle. Vehicle doesn’t start to move until the moving mass engages – whacks into) the chassis; when the vehicle starts to move, the mass is down in the chassis, no longer moving around relative to the rest of the car. Technically, there’s a maybe a couple thousandths of an inch movement of the mass left/happening at the time movement of the vehicle is just starting. If there is a prohibition against ANY relative motion of any parts at these kinds of tolerances, then all vehicles would have to get DQd – axles sliding in bushings/bearings sliding on axles being the obvious. There is, of course, no such prohibition – for obvious reasons - anywhere in the rules, so, it’s a non-issue.
No ‘transfer of gravitational potential energy into an elastic devices’ (3c), is going on.
So, that’s all the rules that speak to design/construction. Nothing in violation, nothing pushing any rule limits; everything fits to what the rules say.
Let’s go on to the Competition rules. The obvious potentially relevant rule is 5e-“all parts of the vehicle must move as a whole.”
Given that there is some level of (even though small to very small) relative motion between a number of parts on ALL vehicles, the fact of such relative motion is obviously not intended to ….go outside “all parts moving as a whole.” Some level of relative motion is obviously within the intent of the rule. With our implementation, once the vehicle starts to move (when the release mechanism has…..gone through it’s movements and energy transfers, and the mass is snuggly into the receiving bay), there is no relative motion (within the intent of the rule) between the mass and vehicle- all parts do, in fact move as a whole.
Rule 5m says "vehicle height is defined as the highest point of the vehicle in the ready to launch position', 6c says vehicle height is used for H scoring, so the take that H for scoring would be the high side of the weight, before it is released, is indeed correct.
So, defense rests.
Any rebuttal testimony from the prosecution??
