2WarningThis presentation was prepared using draft rules. There may be some changes in the final copy of the rules. The rules which will be in your Coaches Manual and Student Manuals will be the official rules.
3TASK Build a vehicle Impound – yes Eye protection - #5 Uses a non-metallic, elastic solidTravels a distance quickly and accuratelyImpound – yesEye protection - #5Things are going to stretch – and possibly break
4Construction Goals Travel 7.00m to 11.oom 1.0m increments – Regional0.5m increments – State0.1m increments - NationalDoes not stray from Center Line
5Powered By Non-metallic, elastic solid Rubber bands, bent fishing poles, bungee cords, etc.Must be impoundedExtra device may be impoundedAnything else used to power the device must start at lowest energy statePre-loaded energy storage devices may be used for other functions, such as braking systemMay NOT be used to propel vehicle
6Elastic Device All materials are elastic to some extent Must be a solid materialMay not use metal to store energyMay consist of more than one partMust be impounded with vehicleSecond elastic device may be impoundedMay be left unattached until the runUse simple machines to multiply distance it stretches or bendsMay warp chassis if too strong or chassis too weak
7Size - lengthDistance between center of rotation of the front-most axle and rear-most axle must not be greater than 70.0cm – don’t push the limit – responsible for much down tiering
8Length¼ dowelMeasurement Point to within 1 cm of the floor70 cm
9The Dowel & Measurement Point Laser beamMeasurementPoint to within 1cm of floor30cm 35cm
10Measurement PointMust be a paper clip attached to the front end of the dowelMust be the end point of the paper clipEasily accessible to the Event SupervisorMust extend out beyond all other parts of the vehicle (including the elastic device)Must extend down to within 1.0cm of the track’s surfaceResponsible for most of the down tiering
11Size - width Vehicle’s track width may not exceed 30.0cm. Measured perpendicular to the direction of travel between the outermost left side and outermost right side of the widest part of the track that would be left in or on the surface by the vehicle’s tires, treads, wheels, CD, etc.Don’t push the limit – responsible for much down tiering
12The Vehicle’s Track Measured between outermost wheel/tire surfaces Measured on the widest axleMay not exceed 30 cm
13Part(s) exchangeOnce impounded, only the elastic solid (with any connected attachment device) or aligning device, may be removed or added to the vehicle
14TriggerMust use an unsharpened #2 pencil with an unused eraser (provided by the Event Supervisor)Must be designed so that actuation is perpendicular (vertical) to the floorNon-vertically actuated trigger is a Construction ViolationStudents must not hold, constrain, or push vehicleMust be able to remain at starting position without being touched until triggered
15Contact with floorOnly the wheels and drive strings, if any, may contact the floor at any timeIf a piece falls of the vehicle during the run, it is a Construction Violation
16BrakesIf the following slide does not show you a YouTube video of the braking system, you can go to YouTube and call up the following:Axle and wing nut
17Brakes Stopping mechanism must work automatically Must not be remotely controlled or tethered
18ElectricalElectrical components and electronics, if used, must not use their electronic properties on the vehicle or its sighting/alignment devicesE.g. batteries may be used as counterweights, but not to power something electronically
19The trackSmooth, level, and hard surface (or whatever they give the Event Supervisor)It is recommended that at least 0.5m is provided on both sides of the Center Line (a bit more is better)Tape used for Center Line, Starting Line, 0.5m line, 6.5m line, and Target LineTarget line will be marked with a point on the inside edge where the Target Line meets the middle of the center line.Photo gates, if used, will be placed between 30.0cm and 35.0cm from the floor (rule 3.e)
20The TrackLasersTarget line0.5m line6.5m lineStart Line7m m
21Competition - Impound Vehicle and interchangeable parts Tools, test date, measuring/calculating devices used to make adjustments need not be impoundedPower tools requiring an electrical outlet must not be allowed
22Competition – outside help Once competitors enter the event area to compete, they must not leave the area or receive outside assistance, materials, or communications until they are finished competing.All assistant coaches and parents should be made aware of this and reminded often.
23Event Time – 8 minutes Can measure distance if desired Load energy into vehicleMake up to 2 runsMay adjust vehicle between runse.g. Change speed, distance, directional control, changes from impounded partsEvent Supervisor measurement time does not count in these 8 minutes
24MeasurementTeams may use their own measuring device to measure track or the distance from the Measurement Point to the line - as part of their 8 minutesMay not roll the vehicle on or adjacent to the track at any time prior to or during the competitionMay not roll the vehicle from where it stopped to the finish line to establish correction – may measure thoughMay be a way to preset the braking system
25Sighting/aiming devices Sighting and aiming devices may be placed on the track but must be removed before the vehicle begins to runAligning and sighting devices mounted on the vehicle may be removed at team’s discretion prior to each run
26It goes down the track Competitors must not follow Must wait until called by Event Supervisors8 minute timing begins again when they pick up the vehicleMay do own measurements but it is part of their 8 minutes
27What happens if?No movement- students may ask for another try at same run – their 8 minutes – ask the Event Supervisor before touching the vehicle – Not counted as a runVehicle veers and does not pass through photogate or cross the 6.5m lineTier 2 – time measured by timing persons, distance measuredVehicle passes 0.5m line but not the 6.5m line
28What happens if? Time and/or distance cannot be measured Starts before Event Supervisor is readyMoves but does not go at least 0.5mCompetitors pick it up before it is measuredTravels in wrong directionTier 2 with a score of 5000
29ScoringRun Score = sum of Time Score, Distance Score, and Center Line BonusRun Time = time between 0.50m line and 6.50m line, rounded to nearest 0.1 secondTime Score = Run Time x 5Distance Score = distance from Measurement Point to Target Line in centimeters to the nearest 0.1cmThis is a point to line measurement
30Scoring Center Line Bonus -20 points if the center line remains completely within the vehicle’s track while vehicle travels between the Start Line and the Target Line.Awarded even if the tip of the fixed point or entire vehicle crosses the Target LineFinal Score = run which gives team the better rankTie breakersBetter non-scored timeFaster time on the second run
31Tiers Tier 1 – run with no violations Tier 2 – run with competition violationsTier 3 – run with construction violations or both construction and competition violationsTier 4 – any vehicle not impoundedTeams who cannot complete a run or have 2 failed runs will be given participation points
32That was the easy partNow that we’ve covered the rules, we get into how to build one of these.Many of the following photos come from my old Mousetrap Vehicle as there are many similarities in construction, so ignore the mousetraps.Many slides came from the 2007 powerpoint of Erv Zimmerman
33Body / Chassis Connects all of the other parts/systems together Determines wheelbaselonger wheelbase means it is easier to keep vehicle in the laneMay provide more room to ‘stretch’ the elastic material
34Wide Chassis Wide chasses tend to go straighter. Can add more weight. Would make it easier to get the center line bonus.Adds additional stress to powered axle.
35ChassisAlmost no chassis –frame has few, thin members – this can help make a very light vehicle.Should increase speed due to lower mass to move.Easy to warp.
36Narrow Chassis Very lightweight May be difficult to run a straight line.
37AxleAxle has a ball bearing insert where it passes through chassis to reduce friction.Thin axle will bend under stress.Can be purchased in many sizes from local RC (radio control) stores or hobby shops.
38Wheels and Axles Wheels are difficult to make exactly round Large diameter WheelRevolves fewer times to travel a given distance.Vehicle travels fasterRequires stronger elasticElastic needs to stretch/bend lessHeavierOptimum size is somewhere in between
39Wheels It takes energy to turn a wheel The greater the mass of the wheel, the more energy it takes to turn itSoUse smaller wheelsIf possible, cut or drill mass out of wheelsEspecially out near the rim of the wheelUse lighter materials3 inches or less is good but
40Wheels Smaller drive wheels = greater speed May spin out on take-off Larger drive wheels = greater distanceMay be too heavy for decent speedMust balance the two to get the 12 meters if that is the length of the trackRemember – speed for 0.5 to 6.5 meters, then accuracy
41WheelsCD – size can add mass requiring more energyDrilled holes reduce the mass, getting a better effect from the mousetrap’s energyEven if smaller CD wheels used, think about removing some mass out near rim.
42Wheels Very light chassis, fragile Large, heavy wheels add mass and take a lot of energy to turn
43Wheels - FrictionThe wheels will tend to spin without grabbing floor unless the friction is increased between the wheel and floor.Wheels to left are bare and may not give a good start as they might spin.Wheels to right have something added to increase friction – often a stretched balloon.
44OK, so maybe it is just a tidge big and heavy, but it sure is beautiful.
45How Far Will It Go?1. Divide diameter of the wheel (Output) by diameter of the axle (Input) to get the IMA of the Wheel & Axle.2. Multiply the length the elastic changes (L) by the IMA of the Wheel & Axle to find the distance your vehicle will travel.3. To calculate how much the elastic must change to travel the Target Distance (10 meters), divide 10 meters by the results found in step #1.
46“Transmission”Use IMA of simple machines to “multiply” the stretch of the elastic so the vehicle can go the Target DistanceExample uses a “Wheel & Axle”String wrapped around the axle transfers the energyRemember to convert all dimensions to the same units.
47GearingJump start off the larger axle and then build up speed by switching to a smaller diameter axle.
48GearingSomewhat fancierSomewhat simpler, with up to four levels
49GearingA simple practice axle to determine the amount of raise you wish to add to the axle and the width of the different levels.
50Steering Difficult to keep properly aimed. Good way to make small, but lasting changes
51Lengthen out one or two slots on long arm of chassis right beneath axle attachment. Attach one end of turnbuckle to long arm of chassis and other to axle.Can make minor but lasting changes to angle of travel.
52Distance Measuring Usually implemented by counting turns of wheels. May have scale marked on circumference of wheels.May apply brake
53Brakes None – Coast to a stop Easy to implement Distance unpredictable Positive LockEasier to makeMay cause wheels to skid and distance to be unpredictable.Always stops in the same position.Combine with friction type for best results.Friction – Gradual applicationDifficult to makePrevents wheel skidFinal stopping position unreliableCombine with positive lock for best results.
54BrakingBobby’s 2nd car – brake would apply itself in center of vehicle to avoid a pull to one sideBobby’s 1st car – brake would apply itself on one side of the vehicle and cause a change of direction.
55Braking Small felt pad to absorb some of the shock of braking. Wing nut rides between two rods to eliminate shaking and to help ensure accuracy.
56Elastic attachmentSome students wish the elastic to come free when it has expended its energy and need to make arrangements to allow the string to slide off and vehicle to coast. What is shown here was fine for Mousetrap but probably will not be strong enough for Wheeled. (But the idea is a starting point.)Others have enough elastic on the axle to allow the vehicle to coast without the elastic coming free. Possible problem - elastic entangle-ment which stops the vehicle short.Perhaps a drop of CA glue to keep the zip-tie from slipping.