NEO 550 and Pressed Pulleys

This year, our team is spending more time trying belts to do reductions (as opposed to something like VersaPlanetarys). We’ve been using GT2 belts from VexPro along with pulleys that press fit onto motor shafts.

Ours tests with 775pros and BAG motors worked pretty well, but when we tested with the NEO 550 today, we sheared the motor shaft off clean (motor was being used at a 5:1 for intake). We used calculators for tension, but there was still a lot of force on the shaft.

Have any other teams successfully used belts directly mounted to 550 shafts? The specs for the 550s look great, but the shafts are smaller than we’d like.

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Do you have any pictures of your exact setup? People have used belts with the old 550s for various things, but this is ~200 watts. Annoying/interestingly, the MiniNEO uses a larger shaft internally which is reduced with a shoulder to the 3mm diameter, matching the BB550. Pictures of the failure would also be interesting and helpful.

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OMG LOL, our team did the exact thing as you. We press fitted on to a 1/2 inch hex and then connected it to a 18T pulley up to to the 42T pulley which ran the shooter wheels. The shaft came right off. For us, we just switched up the motor with a miniCIM. The shafts are just too small for a “direct drive” type of situation. Maybe one thing you can do is have 2 plates on either side for added support and make it very hard for centrifugal or centripetal force to create a force on the shaft. The main idea is don’t use just the motor to hold up the pulley. For us , a miniCIM can very well hold up the pulley because of such a large shaft so that’s why we switched to it.

We are using them in various setups without issue. The pinions are from Vex Pro (217-5870).

I created a Center-distance calculator to help with the design process. What belt length and center distance are you using? What is your manufacturing method to control the center distances?

None of our use cases are “High Torque” conditions. we are mostly using them to move balls around internally to the robot.

How did you find the pulley pressed onto the shaft? We pressed one on and it seemed to go on a little too easy. I can gently hold the pulley and spin the back of the motor by hand and the motor spins but the pulley doesn’t. We will have it wired shortly for a proper test but I have little hope.

We found the connection to be just right. The press fit certainly needed a small arbor press (1 ton) and was secure once in place. The press technique was to “tap” on the sprocket with the motor on the plate until they self aligned and then push until it was almost bottomed (~0.010" from the hardstop). The press force was “Like Butter” I would estimate 0.0005" to 0.0008" of interference between the shaft and the pinion based on the press force. No heating/chilling was necessary.

We are mostly using these for high speed low torque applications like driving a 1" OD roller on a 3:1 reduction.

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