Torque sensor BB DIY mid drive questions

Discussions related to motors other than hub motors.
This includes R/C motors, botttom bracket, roller and geared drives.
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Ronan-Carter   1 mW

1 mW
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Joined: Feb 17 2016 7:19pm

Torque sensor BB DIY mid drive questions

Post by Ronan-Carter » Aug 30 2018 9:34am

I may be asking a silly question, but I can't find any builds that answer it, does running a cyclone/gng/LR style mid drive reduction kit apply torque to the sensor of a sempu BB and render it useless, or does it not? I want to have my cake and eat it with a 2000-3000 watt mid drive that also has torque sensing without breaking more than one bank? Links to any builds would be amazing, or even just some advice!

20-20   10 mW

10 mW
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Joined: Dec 16 2017 7:35pm

Re: Torque sensor BB DIY mid drive questions

Post by 20-20 » Aug 30 2018 12:08pm

I'm running a Sempu torque sensing BB with Cyclone 3000w on my M5 recumbent. Not sure how you'd go about it on a 'regular' bike. I've split the drivetrain into two via the Cyclone double freewheel. That's allowed me to retain the original triple chainring setup. I'm using a rear derailleur as chain tensioner for the triple chainrings. Cycle Analyst V3 handles the torque sensing PAS brilliantly. I've also got throttle, which overrides PAS for when you need an extra boost. It's hooked up to a 52v 17ah battery. So far I've limited max power to 2000 watts. Max speed on the flat at WOT is 40mph - faster than I can pedal! I've done around 600 miles. So far the Sempu torque sensing BB has been working perfectly. It took some experimentation to configure in the CA, but once I got it dialled in, the torque sensing/PAS function works superbly.

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Last edited by 20-20 on Aug 30 2018 12:19pm, edited 1 time in total.

Ronan-Carter   1 mW

1 mW
Posts: 19
Joined: Feb 17 2016 7:19pm

Re: Torque sensor BB DIY mid drive questions

Post by Ronan-Carter » Aug 30 2018 12:19pm

Thank you, just knowing that the parts are compatible really helps!, Now to design a frame.....

Drum   100 W

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Re: Torque sensor BB DIY mid drive questions

Post by Drum » Aug 30 2018 6:50pm

In most builds using Cyclone / GNG etc motors, the motor does not drive the bottom bracket itself.. it drives a chainring that rotates around the bottom bracket but does not apply torque to the bottom bracket.
So yes, in a "normal" setup the only torque the bottom bracket will see is the torque applied through the pedals, and the system will work fine.

Good on you for thinking about using Torque Sensing: for off-road riding it is far superior to "Normal" PAS / cadence sensing control, and gives a very natural, instinctive riding feel and a safer, more rewarding riding experience (assuming it is well set up, of course).

Although not commonly advertised, Sempu can make a T3 model torque sensing bottom bracket which works with ISIS crank arms instead of Square Taper. Electrically and dimensionally it is said to be identical to the T4. If you would prefer the ISIS version and cannot find it for sale, PM me and I will send the link to a supplier willing to get one (on Aliexpress).

Good luck with your build.
Dave

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PaulD   1 kW

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Re: Torque sensor BB DIY mid drive questions

Post by PaulD » Aug 31 2018 6:05pm

Drum wrote:
Aug 30 2018 6:50pm
Although not commonly advertised, Sempu can make a T3 model torque sensing bottom bracket which works with ISIS crank arms instead of Square Taper. Electrically and dimensionally it is said to be identical to the T4. If you would prefer the ISIS version and cannot find it for sale, PM me and I will send the link to a supplier willing to get one (on Aliexpress).
I have 4 of the ISIS T3 sensors if anyone is interested. I am selling them because I am using T4s only now. PM me if you're interested.

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