I wrote the attached Excel calculator for the popular high-power mid-drives from Tangent, LR, and CYC:
While a gearing calculator is normally not needed for mid-drives since they can use the full cassette (indeed, that is one of their great advantages), I believe the highest-power mid-drives should be used direct/fixed, which also allows regen.
However, this introduces the challenge of gearing for desired torque/speed.
In the example below for LR Big Block w/ belt primary, fields in bold can be modified to suit your parameters. On the left: cell volts & cells (used in my example for 7Sx3 LiPo packs), amps continuous and max (for Tangent & LR, default set to motor; for CYC, default set to controller), and finally wheel and tire diameter.
The center section lists the primary (and secondary, for Tangent & CYC) reduction. For the LR BB belt, motor pulleys in 18T and 24T are offered, with a 90T driven pulley. The resulting ratios and crank RPMs are calculated.
The right section lists the final reduction. For the LR BB belt, the final drive sprocket is 22T, and I've listed out a variety of driven sprockets from 20T-40T. The final reduction is calculated, which can be compared with your current reduction to see just how (un)realistic pedaling on this setup may be. Max Hub RPM at no-load is calculated, converted to mm/h and then MPH.
So a LR BB belt on 7Sx3 LiPo with the 18T primary belt pulley and a 40T final driven sprocket gives a no-load max speed of 42mph. Switching to the 24T pulley gives 57mph:
While the LR BB belt is most desirable and thus best characterized, I included provided torque values for the Tangent and CYC. Interestingly, the CYC falls shy of the advertised 190Nm torque.
Feedback desired and appreciated.
While a gearing calculator is normally not needed for mid-drives since they can use the full cassette (indeed, that is one of their great advantages), I believe the highest-power mid-drives should be used direct/fixed, which also allows regen.
However, this introduces the challenge of gearing for desired torque/speed.
In the example below for LR Big Block w/ belt primary, fields in bold can be modified to suit your parameters. On the left: cell volts & cells (used in my example for 7Sx3 LiPo packs), amps continuous and max (for Tangent & LR, default set to motor; for CYC, default set to controller), and finally wheel and tire diameter.
The center section lists the primary (and secondary, for Tangent & CYC) reduction. For the LR BB belt, motor pulleys in 18T and 24T are offered, with a 90T driven pulley. The resulting ratios and crank RPMs are calculated.
The right section lists the final reduction. For the LR BB belt, the final drive sprocket is 22T, and I've listed out a variety of driven sprockets from 20T-40T. The final reduction is calculated, which can be compared with your current reduction to see just how (un)realistic pedaling on this setup may be. Max Hub RPM at no-load is calculated, converted to mm/h and then MPH.
So a LR BB belt on 7Sx3 LiPo with the 18T primary belt pulley and a 40T final driven sprocket gives a no-load max speed of 42mph. Switching to the 24T pulley gives 57mph:
While the LR BB belt is most desirable and thus best characterized, I included provided torque values for the Tangent and CYC. Interestingly, the CYC falls shy of the advertised 190Nm torque.
Feedback desired and appreciated.
