Motor pulley Dshape. Screw - with or without

Hello guys,

My motor has a D shape shaft and my pulley aswell this mean I just I just need to screw it in place in order to avoid sliding along the shaft.

At the moment I have it without a screw and it actually slides itself to stay adjusted with the wheel pulley.

What are your thoughts about it? Should I really tight it? I’ve rode it around 20km without problems. I think it makes less stress and friction as it adjust itself at the best position.

Same boat as you. When I mentioned the D shaped shaft, people were super confused about not needing a key. You should lock the set screw down just to keep it from sliding sideways. Less strain on your belts if it’s perfectly aligned.

When I was designing the pulley system this was my first option. D-Shape is probably the safest as you don’t rely on screws. My opinion.

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I completely agree


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If you do a stress analysis on interaction forces a D shaped shaft is significantly less strong than a keyed shaft. Because the surfaces contact at an angle that is far from tangent you get extremely high interaction forces at the mating surfaces to transfer torque. Make sure to set the pulley with a screw. It’s very easy to round the flat in the pulley if it isn’t securely locked down and permanently damage the pulley.

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