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Power Transmission sketches

Power Transmission sketches are how we define dimensions pertaining to the moving aspects of the robot. This includes but is not limited to; Belt lengths, Gear sizes/ratios, and motor positioning.

Master Sketches

Power Transmissions should be a part of a subsystem's master sketch if it directly effects position of major parts of the robot, like rollers. Otherwise, Power Transmissions should have their own sketch in the subsystem's part studio.

Gears

Sketch Gears as tangent construction circles. Dimension them as the number of teeth it has, divided by twenty.

Showing Design Intent

It's best to dimension a belt with the number of teeth, divided by 20, because it helps communicate design intent. Its a lot easier to tell what size gear it is if it's dimensioned as 62/20, as opposed to 3.1.

Pulleys

To sketch a pulley, simply create a center point construction circle where you want a pulley to be. Dimension the diameter as #PulleyPD_5mm(# of teeth).

Not working?

If the #PulleyPD_5mm() function doesn't work, double check that you have origin cube at the top of the feature tree, and "5mm Belts" is enabled.

Belts

To sketch a belt, you must first have two pulleys defined to put the belt between. Make two construction lines, one on each side, tangent to both pulleys. To make sure you get the right center-to-center distance, Dimension the center of the pulleys to each other as BeltCTC_5mm(Belt teeth, Pulley 1 teeth, Pulley 2 teeth).

For example, #BeltCTC_5mm(70,24,18) would result in the center-to-center distance of a 70 tooth belt that runs between a 24 tooth pulley and an 18 tooth pulley.

Belt sizes

Make sure to use commercially available teeth numbers or ones we have on hand, commonly multiples of 5.

Chains and Sprockets

To sketch Chain and sprockets, use the same method as belts and pulleys, except use SprocketPD_25 and ChainCTC_25 instead.

See also

Gear Basics | FRCDesign.org
Belt and Pulley Basics | FRCDesign.org
Chain and Sprocket Basics | FRCDesign.org