Vex IQ Pulley

I’m trying to use pulleys to link two items together but it is slowing both down. Suggestions?

I don’t know if this will work very well because I haven’t used pulleys, but you could try two gears geared for speed on the end of the pulley. This might now work if you are using the pulleys for something that requires a lot of torque though.

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Can you tell us a bit more about your current design? Maybe show a picture?

VEX IQ is mostly a plastic construction system. We all intuitively know that plastic can deflect more than metal does. This is because plastic, on average, has a much larger elastic deformation region when looking at the stress/strain curve.

Put more basically: plastic bendy.

Are you pulling on the plastic and things are bending causing excess friction? Is the belt you are using too small for the distance you have between the pulleys? Are the pulleys on the same plane or are they offset from each other causing the shafts to bend?


The pulleys are on the same plane and the elastic (from the kit) is used. The friction of the pulley slows the motor down. Nothing is in the way of the pulley.

I’m wondering if we should rethink the design and not use the pulley.

In most cases, gears will often work better than pulleys due to their robustness and lack of friction in comparison to pulleys. I don’t know for your specific case since I don’t know what you’re doing, but gears will make the friction much less, and will make the motor spin faster and with more power.


Just because I’m curious now… Does the motor run full speed when there is no belt installed between the pulleys? If it does and is only slowed down when the belt is installed, then you have too small of a belt on there.

Now, similar to what @FRC973 said, gears are probbly a more robust solution. A big reason they would be better is because they require the gears to be on pitch and would eliminate the ability to too little/too much spacing between components. Another reason would be that under too much load, a belt can slip on a pulley and no longer transfer torque. Gears can’t really slip in the same way, and will be more reliable with less math involved.