Possible to extend output shaft on WCP Gearbox?

[Deke]

Originally Posted by InFlight

You have a Design choice of v belts, synchronous belt, poly cord, and chain.

Using 5M HTD belt on small pulleys with only 12 teeth engaged and the small 1.5" turning diameter is not the intended or recommend use. The fact that you broke 9mm wide belts, suggests you probably were just getting by with 15mm belt with very little margin.

These HTD belts have some elasticity which reduces the effective number of teeth in mesh on the pulley. This effect is magnified when the number of total teeth is under 30.

Going to a 3M belt would provide additional margin at a given pulley diameter, as there would be more teeth engaged.

SDP-SI recommends a minimum of 6 teeth engaged and has a correction factor for less engagement: http://www.sdp-si.com/D265/PDF/D265T146.pdf

Going to 3mm belt has a significant reduction in strength. Belts are recommended to be used at 1/15 of their breaking strength (http://www.sdp-si.com/D265/HTML/D265T042.html)

3mm HTD breaking strength http://www.sdp-si.com/D265/PDF/D265P1023.pdf
6mm = 213 lbs.
9mm = 320 lbs.

5mm HTD breaking strength http://www.sdp-si.com/D265/PDF/D265P1027.pdf
9mm = 640 lbs.
15mm = 1068 lbs.

3mm HTD working strength (1/15 of breaking strength)
6mm = 14.2 lbs.
9mm = 21.3 lbs.

5mm HTD working strength
9mm = 42.6 lbs.
15mm = 71.2 lbs.

You can probably get away with more than their recommended 1/15th reserve, but that would require some testing and development.