Newbie wants to build torque sensor bike

[stratohunter]

If you're looking at the TSDZ2, the first question becomes how hard are you planning on riding your bike, is it barely commuting or off-roading? I don't know if the torque sensor and the spindle of the TSDZ2 will sustain serious off-roading, but for me weighing about 75kg with my backpack, it haven't gave me any issue when standing on the pedal. Not sure how long it'll last though.

Also, the so-called 750w version will behave nowhere like a generic 750w mid motor, with the awful heat shedding design. It will peak at about 900w but anything continuous over 400w will likely cook the inside motor. I put aluminum sheets and thermal putty between the motor stator and the cover, along with a temperature sensor, to bring it up to continuous 650w. I will post about this in the future if I have time. I personally advice against buying the 1.6mm thick aluminum heatsink plate which goes between the motor base and the housing, because this depth varies among different motors due to poor QC. Mine is 0.8mm to 1.0mm and if I force a 1.6mm heatsink plate in, it will tilt the inside motor and finally break the axle. If you want to fill this space, get some high quality thermal pads instead.

Finally, it's recommended to keep a brass gear prepared, and make sure your motor comes with the older programmable controller so that you can run the OSF. Get the 36V motor and run it on 48V/52V battery if you constantly pedal above 100rpm. The stock chainring is 42T and works just fine for my 10speed cassette.

I hope these helps.

 

[machanic]

Is the Bafang SR PA211.32.st 1.8 VA7 bb torque sensor a good one and compatible with the Grin cycle analist

 

[amberwolf]

Is the Bafang SR PA211.32.st 1.8 VA7 bb torque sensor a good one and compatible with the Grin cycle analist

This one?
https://bafang-e.com/en/oem-area/components/component/sensor/sr-pa21132stc/
If so, it's specs (bolded/underlined part in specs quoted below) indicate it uses approximately the standard hall-throttle voltage output range, so it could possibly actually be directly compatible with anything that has a typical hall throttle input (including the Cycle Analyst). Depending on the response range of the throttle input on the device, you wouldn't need something that has to read a torque sensor specifically; even the CA could use it on the throttle input and not have to use it on the PAS input. (unless you want to use the cadence sensor on it as well).

SR PA211.32.ST.C

Specifications
Core Data
Type Speed & Torque Integrated Sensor
Signals (Pulses/Cycle) 32
Input Voltage(DCV) 4.5 -5.5
Output Voltage(DCV) 0.75 -3.2
Resolution (mv/N.m) 35
Operation Temperature -20 - 60℃
Shaft Standard JIS
Weight (g) 650-780
Mounting Parameters
BB Width(mm) 68
Mounting Position Bottom Bracket
Cable Length(mm), Connector Type 150 G6.5.5 / 950 G6.5.5
Tests & Certifications
IP IP X5
Certifications EN 15194 / EN 14764 / ROHS
Dimensions
Dimension A 148 mm
Dimension B 68 mm
Dimension C 2-φ44mm
Dimension D 2-BC1.37”*24T
Dimension E 47.5 mm
Dimension F 74.5 mm
Dimension G 2-17mm
Dimension H 2-M8*P1*25mm
Dimension I 31.25mm

 

[machanic]

For whom it may concern these are available on ebay Raki computers for $53.95 and sprocket spyder and sprocket for $ 19.00 shipping included. I have one and have ordered another if anyone needs additional measurements.
P.S. thanks Amberwolf, I believe that is the one but the juxtapositions of model numbers is a question.

 

[Chalo]

Let us know how long it takes to mangle the cable.

 

[machanic]

Let us know how long it takes to mangle the cable.

I usually don't build things that fail, I know that sounds like quite a boast but I have a long and successful history!

 

[amberwolf]

Oh yeah. to get the FULL Cycle Analyst experience, you will want a power metering shunt like this. This will turn your bike into a power meter too... and can manipulate the output even more based on real time power levels.

https://ebikes.ca/shunt-ca3.html

With the CA-SA model, it already comes with one.

 

[amberwolf]

To trigger some more inputs/opinions, I want to phrase my quesiton a little different:
If you have under $1,000 and must have torque sensing (NOT cadence or thumb lever), what is the best way to go about (open to DIY suggestions/kits if good instruction are provide for an able DIY (but not a bike expert).

I'd do what I already suggested; using the Cycle Analyst to convert the chosen sensor (torque in this case) to a throttle signal, and then use whatever "dumb" controller you want that has a throttle input to run the motor.

The CA just needs you to set it up for the specific sensor chosen, and do some tuning to create the throttle output response that makes the controller operate the way you want to make the bike respond the way you want.

It's a little time-consuming during initial setup, but once dialled in the way you need it, should make the bike like you just have "bionic" legs, if that's how you want it to operate. (that's pretty much what I want from my setups, just go as I pedal...but not me doing most of the work).

There is now a version of the CA firmware that allows pure torque-sensing operation without cadence sensing at all (but you may get a more natural response by using both, since boht sensors are typically included in the BB torque sensors anyway).


If you prefer to not use the CA, there are BB torque sensor setups like E-rider and the above-linked Bafang that output essentially a hall-throttle type of signal, and so they could be used (with perhaps a bit of very simple analog op-amp electronics) on the throttle input of a "dumb" no-PAS controller.

THere's a recent (last few weeks) thread here somewhere that links an Aliexpress page that sells an Erider BB torque sensor with a matching controller it directly connects to (but I don't know how that specific controller responds to it, as it uses it on a "PAS/Torque sensor" input, rather than on it's throttle input).



Note taht if you use a torque sensor on your pedals (BB style ones are pretty much all that's presently available to just go out and buy), you can't use a middrive that drives the pedal chainrings. You could use one that drives the rear wheel via a second chain, either on leftside or rightside; there are a few different ones of those, but they don't use your bike's gears this way. (it does take the unsprung mass of the motor out of the wheel, though).

Using BB torque sensors usually means using a hubmotor, either front or rear, (or both!) to provide motor power.

 

[afzal]

Note taht if you use a torque sensor on your pedals (BB style ones are pretty much all that's presently available to just go out and buy), you can't use a middrive that drives the pedal chainrings.

Using BB torque sensors usually means using a hubmotor, either front or rear, (or both!) to provide motor power.

Having never seen a mid-drive in real life yet, had to do some study on mid-drive's to understand what above means - mid-drive's need a freewheeling chainring (if connected to chainring) & there are no stand-alone BB torque sensors that does so.

 

[amberwolf]

Note taht if you use a torque sensor on your pedals (BB style ones are pretty much all that's presently available to just go out and buy), you can't use a middrive that drives the pedal chainrings.

Using BB torque sensors usually means using a hubmotor, either front or rear, (or both!) to provide motor power.

Having never seen a mid-drive in real life yet, had to do some study on mid-drive's to understand what above means - mid-drive's need a freewheeling chainring (if connected to chainring) & there are no stand-alone BB torque sensors that does so.

The BB torque sensor used shouldn't have to have anything to do with what chainrings you use (some do have special spiders on them, or special cranks, that prevent doing this, but...); as long as you can use a standard threaded righthand crank on it that can support a freewheel like these
https://www.sjscycles.co.uk/cranks/shun-alloy-104-pcd-4arm-freewheeling-cranks-170-mm-silver/?geoc=US
such as I could with my THUN or TDCM BB torque sensors, then you can prevent a motor that drives the pedal chain (but not the pedals) from directly engaging the torque sensor. So when I say "can't", it's not really a hard limitation. But it may still affect system operation.


There are multiple separate problems:

One is that the BB torque sensors for the cranks, if the crankshaft itself is driven by the motor, will be a positive feedback loop, as the motor will be causing itself to be driven harder the harder it works.

The same thing happens if the torque sensor is at the rear dropout or in the chainline itself.

If the torque sensor does not "see" any torque from the motor, then that won't happen, but:

If the motor removes the load from the cranks so that the pedals aren't producing "torque" (depends on how the sensor is setup; where it is in the BB, etc, and how it measures the pedal torque), then you have another problem, that the sensor no longer detects enough torque to keep the motor moving. If you setup the system to be sensitive enough for this to not be a problem, then it can be vastly too sensitive and too responsive for a real torque on the pedals. This is part of why systems may use both a torque and a cadence sensor--read the torque for initial acceleration and other loads like that, and read how fast you are pedalling for most of the control otherwise. (you could also design the system to "grade on a curve" so it monitors wheel speed (and perhaps what gear you are in if you want to make it that complex) and responds to the torque sensor differently for different conditions.)

There's something else I was thinking of, but JellyBean The Perfectly Normal Schmoo needed atenshunulz so I got distracted and can't remember what it was now. I'll add it later if I can.