FTC Mechanical design considerations 2012 edition by: Andrew Rudolph

What we’re going to talk about the rulesmanipulatorsideas

rules You’ve already read them right?

rules Only can use preformed robotics components from: Lego Tetrix Matrix

matrix Observed at World Cmp Designed to bring costs down of FTC overseas Designed off standard lego grid Different motors Different motor controllers Different Gears and wheels Possibly thinner metal Belt system CV Axles Check some of the offerings at:

matrix s/showthread.php?t=106017

rules Only COTS (Custom Off The Shelf) items allowed: Linear Slide Non-motorized Turntables and Lazy Susan Lead screws and threaded rod plus compatible nuts Servo Blocks #25 Chain and connector or half links

rules Unlimited in quantity or size of the following: Raw material available to all teams from standard distributors Standard bearings or bushings Fasteners Rope, Cord, Cable, monofilament, … Rubber bands Latex tubing Zip ties Nonslip pad without adhesive backing Electrical solder, tape and any type of glue/cement Any COTS lubricant as long as it doesn’t get on stuff

materials Extrusions Readily available from many retailers Cut and drill with simple tools Strong and lightweight Most commonly 6061 Aluminum 7075 Aluminum for higher strength

materials Sheet metal Readily available from many retailers Cut and drill with simple tools Or Water Jet, Laser Cut, CNC Break for complex parts

materials Plastics Lexan (NOT ACRYLIC) easy to find and work with Bend with heat Lots of shapes and different mechanical characteristics available Polycarbonate (lexan) Coroplast Sintra Teflon Nylon Delrin HDPE

materials Plastics You can now Rapid Prototype Parts! You can now 3D print Parts! ABS Polycarbonate PLA

materials Rope, cord, etc… Steel wire rope Solid steel wire Paracord Braided fishing line 150 lb test = 0.56mm diameter

Shoulder Bolts materials drive components Bushing McMaster for $0.75 ea! Drill rod (tool steel rod) McMaster for $2.68 for 3’ Lead screw or Acme screw Linear Bearing Lubricants

Lifts! You mastered these last year…right?

lifts We saw them last year

lifts What did we miss last year? Precision liftingVariable position liftingLifts go upLifts go down

lifts Scissor lift Short height, Wide base Lift over base Requires lots of power Lots of moving parts Difficult to synchronize two sides Difficult to lift from ground Difficult too have finite control Poor lateral loading

lifts FRC 343 circa 2000 Lead screw or Acme screw

lifts Single joint arm Simple to build Can move fast Can reach fore and aft Light weight Object orientation changes Strong Lateral load Lift outside base Object orientation changes Difficult to multi position Do not lift high

lifts multi joint arm Lots of freedom keep lift inside or outside of base complex to build heavy Lots of motors Difficult to control

lifts Four bar linkage Simple to build Light weight Object orientation stays the same Lift outside base Lots of torque required at shoulder

lifts six bar linkage twice the weight of four bar Object stays the same Higher lift than four bar Lift outside base Lots of torque required at shoulder More joints to create friction and wobbles

lifts Telescoping Straight lift multiple positions small footprint COMPLEX difficult to maintain high CG

lifts hybrid Combine multiple mechanisms

Ideas General design practices

ideas Are you going to… acquire it? manipulate it? store it? lift it? position it? release it? What tasks within my strategy do I need to perform? Let strategy drive your robot design, not the opposite

ideas What does the game piece look like from the robots POV? What are all the ways the game piece could lay? What is the most usable or stable position? How does the object react? Think like a robot about the game piece

ideas Maximize your “Acquisition Zone” other design considerations

ideas other design considerations Alignment Devices

ideas other design considerations Make it easy to drive

ideas other design considerations Will stray objects interfere?

ideas other design considerations Keep your Center of Gravity (CG) low

ideas other design considerations Design is an iterative process

Just the parts you want to work. ideas Really, simple IS better. Some design mantras You don’t have to prototype everything… Assume nothing. Sometimes wild ideas lead to champions.

Celebrity Endorsed.