Is there a reliable torque sensor?

[kylerlaird]

I've been using T9 BBs with some success and lots of failures. I've got a stack of dead ones. I have a couple T17 BBs "out for delivery" right now but I'm wondering if I should rethink my approach.

The more I read about torque sensors, the more I notice comments about how bad the designs are. Even the threads on the grounding issue for the ERiders give me the feeling that these sensors are operating right on the edge of failure. The rear dropout sensors look like they're even more finicky. I'm considering making a chain deflection/speed sensor because that's the only thing I can easily do myself but that's adding exposed moving parts.

I love torque control (and hate cadence control) but I want to move beyond tinkering to something that's ready for casual use. Is there a bulletproof torque sensor? I dream of a waterproof BB with CAN that just works. Is it so hard?

I'm open to suggestions.

 

[amberwolf]

What cadence control have you used?

If you have only used the on/off PAS types that almost all controllers support, you might try the Cycle Analyst variable cadence control. Works for me to reliably control the speed of the heavy heavy-cargo SB Cruiser trike. the only thing it doesn't do as easily as I'd like is get me started from a complete stop with a heavy load, but I can blip the thumb throttle for that. (I don't even actually need a throttle for it and could just use a button).

Depending on your usage and conditions, it might do what you need.


I know of no "bulletproof" sensors of any type. They're pretty much all made (like almost everything) to the lowest possible price point to maximize profit.

What specific failures have you had on your Eriders? (or any other you've used)


Since I ride generally in dry conditions, with only occasional flash floods >1 foot deep (well over the BB), my TDCM BB torque sensor's cadence sensor has been working since it was installed several years ago. I am not presently using the torque sensor, but it's voltage still reads normally in the CA setup screen for that.


If you want to make a chain-tension sensor, there's been a couple; I only remember the most widely distributed (but still out of business), BEAM TS.


There's a new one I haven't seen tried yet by Annoy Bike (what a weird name)

https://www.aliexpress.us/item/3256802830866936.html

"
Work voltage: 5V DC
Zero point output: 0.15±0.05V DC
Rated power: 0.15-3.2V DC±0.05V
Power consumption: ≤500mW
Cadence signal: 12/Circle
Rated load: 80N.m
Work temperature: -30℃~+70℃
Protection level: IP65
The structure is extremely simple and reliable
Working principle：
The bicycle flywheel and the chain drive are driven by a chain, and a torque sensor is installed between the two to make the chain a "V" shape. When a person is riding and stepping on, the "V"-shaped chain will be tensioned into a "one" shape. The degree of change in chain tension varies with the amount of pedaling force. The chain tension and torque sensor installed above the chain detects the pedaling force of the rider through the change of the chain in real time, and converts this force into an electric signal to the controller."


There are also industrial sensors like these, you might be able to adapt.

https://www.grainger.com/product/19RU08

 

[kylerlaird]

Thank you. I had found the Annoy Bike unit (while looking for a Beam TS) and it's what got me thinking about making my own. It's a little pricey for what it appears to be. (No chain speed sensor?)

My eRiders have been failing into a 2.5V output with little to no variation due to torque. It's weird. I pull out the coil and it goes to 1.5V. Replace and it's 2.5.

I've been musing about the ideal approach to this. I settled on a torque-sensing spider. Well, what do you know...they exist!

Spider Power Meters for MTB

Get your spider power meters for MTB from the #1 power meter store. Low prices and excellent customer service. Browse our huge selection today!

powermetercity.com

I want to learn more about these.

 

[Chalo]

Thank you. I had found the Annoy Bike unit (while looking for a Beam TS) and it's what got me thinking about making my own. It's a little pricey for what it appears to be. (No chain speed sensor?)

Why would you want chain speed sensing? It's totally extraneous to the purpose of a torque sensor. If you want to proportion the controller output to how hard you're pushing on the pedal (and that seems like exactly the point), then it doesn't matter how fast you're pedaling or which gear you're in.

if you don't want the motor to drive when you're waiting at a stop, either don't push the pedal, or use a brake lever cutoff switch.

 

[neptronix]

ebikes.ca has an inordinate amount of torque sensing things - sensors, motors with torque sensors built inside them, etc.
I have zero experience with torque sensors so i can't vouch for any particular piece of hardware.

 

[PaulD]

I don't have much data on these, but the dual sided magnetoelastic sensors that come from companies like Autorq, Bafang, Hyena, Mivice, PD, etc, seem pretty reliable. Not sure if they all come out of the same factory or if they are just stealing/ licencing each others designs. I know some ride share bikes have these, and those things get thrashed. Autorq claims IP67 ingress protection.
The only one of these that seems readily available to individual customers is Bafang, which you can find on aliexpress.

 

[kylerlaird]

Why would you want chain speed sensing? It's totally extraneous to the purpose of a torque sensor. If you want to proportion the controller output to how hard you're pushing on the pedal (and that seems like exactly the point), then it doesn't matter how fast you're pedaling or which gear you're in.

if you don't want the motor to drive when you're waiting at a stop, either don't push the pedal, or use a brake lever cutoff switch.

I want to know if the rider is pedaling, even if it's so light that the torque level is in the noise. If I have the chain whizzing by my torque sensor, a separate cadence sensor is extraneous.

Simple torque sensing gets a bit sketchy when standing on a bumpy downhill.

 

[kylerlaird]

I don't have much data on these, but the dual sided magnetoelastic sensors that come from companies like Autorq, Bafang, Hyena, Mivice, PD, etc, seem pretty reliable. Not sure if they all come out of the same factory or if they are just stealing/ licencing each others designs. I know some ride share bikes have these, and those things get thrashed. Autorq claims IP67 ingress protection.
The only one of these that seems readily available to individual customers is Bafang, which you can find on aliexpress.

I wonder how these differ from eRider. I have a 68mm Bafang around here somewhere. I'll find something to put it in to test.

I contacted Autorq to buy samples. They certainly make big claims about reliability.

Thanks!

 

[stancecoke]

I dream of a waterproof BB with CAN that just works. Is it so hard?

BionX used a Thun X-Cell RT with CAN interface with their IGH3 motors

I've built a bike with a Kclamber cassette integrated torquesensor about a year ago. They offer it with UART or with CAN bus.
A really tidy system and you can keep your Hollowtec crank set.

Analyse Getriebenabenmotor mit integriertem Drehmomentsensor von Kclamber

dir einen controller zur Verfügung zu stellen der das weiße Kabel des Motors auf pin11 u-art3 liegen hat:) Der Controller war ja schon vor geraumer Zeit angekommen, vielen Dank noch einmal! Jetzt habe ich die ruhige Zeit genutzt, um ihn einzubauen. Der passende REENTION Flaschenakku lag unter...

www.pedelecforum.de

Meanwhile Lishui has developed a suitable firmware for the Kclamber UART protocol, so you don't have to fiddle with my open source firmware any longer....

Steuerung für Motor mit integriertem Drehmomentsensor von Kclamber

Ich hatte mir auf der diesjährigen "Eurobike" zwei Motoren mit integriertem Drehmomentsensor von Kclamber besorgt und mir dann von meinen Kollegen 15 Controller schicken lassen zum testen, was soll ich sagen, ich bin völlig begeistert. Mit nur 3 Steckverbindungen zum Fahren wie ich mir das immer...

www.pedelecforum.de

regards
stancecoke

 

[kylerlaird]

BionX used a Thun X-Cell RT with CAN interface with their IGH3 motors

I've built a bike with a Kclamber cassette integrated torquesensor about a year ago. They offer it with UART or with CAN bus.
A really tidy system, and you can keep you Hollowtec crank set.

Analyse Getriebenabenmotor mit integriertem Drehmomentsensor von Kclamber

dir einen controller zur Verfügung zu stellen der das weiße Kabel des Motors auf pin11 u-art3 liegen hat:) Der Controller war ja schon vor geraumer Zeit angekommen, vielen Dank noch einmal! Jetzt habe ich die ruhige Zeit genutzt, um ihn einzubauen. Der passende REENTION Flaschenakku lag unter...

www.pedelecforum.de

Meanwhile Lishui has developed a suitable firmware for the Kclamber UART protocol, so you don't have to fiddle with my open source firmware....

Steuerung für Motor mit integriertem Drehmomentsensor von Kclamber

Ich hatte mir auf der diesjährigen "Eurobike" zwei Motoren mit integriertem Drehmomentsensor von Kclamber besorgt und mir dann von meinen Kollegen 15 Controller schicken lassen zum testen, was soll ich sagen, ich bin völlig begeistert. Mit nur 3 Steckverbindungen zum Fahren wie ich mir das immer...

www.pedelecforum.de

regards
stancecoke

Oh! That all sounds great! Unfortunately, I see only 68, 73, 83mm versions. I still want one.

Thank you for the references. I'm starting to feel like there might be something good out there.

 

[stancecoke]

Oh! That all sounds great!

I think, the CAN-interface was from BionX, so it is not available any longer. The Thun sensor is sold as FAG BBRTS or NTCE also.
The BionX IGH3 was used in the popular Grace Easy bikes, there is a long thread in the german forum:

Tretlager Smart oder Grace Easy 3 Gang

Hi, Im Smart bzw Grace Easy ist ein FAG bbrts 127 jis Tretlager verbaut. Meins ist hinüber... Kann mir jemand von Euch eine Bezugsquelle empfehlen? Danke im voraus.. Gruß Tom

www.pedelecforum.de

regards
stancecoke

 

[PaulD]

I wonder how these differ from eRider. I have a 68mm Bafang around here somewhere. I'll find something to put it in to test.

The Erider relies on strain gauges. I don't think this is inherently bad. Sensitivis certainly doesn't think so: Strain-Gauge & Magnetostrictive Sensor Comparison

I think perhaps the Erider has some design and QC issues. I've replaced a few on customers bikes, but most of them have 1000s of miles. Still not a very good failure rate, but it really seems to be luck of the draw.

 

[Chalo]

The Erider relies on strain gauges. I don't think this is inherently bad.

Having been a part of several prototyping projects in several different businesses that used strain gauges, I think using them is inherently bad. They're incredibly fragile, incredibly fussy and difficult to install uniformly, and they have a short operating life in real world conditions. When somebody says "strain gauge", I think, "please just no".

 

[lnanek]

I have an old Bionx hub motor with a broken strain gauge torque sensor. Always goes full throttle no matter what now. I hear it's a pretty common failure with this model.

 

[stancecoke]

I think using them is inherently bad

I have completely different experiences. If you do it the right way, strain gauges are very reliable even in rough environment. You have to prepare the surface you want to bond to very carefully and have to seal them properly. Then they will work for ever. BionX had a problem with the sealing in their derailleur motors. When the user was greasing his motor or chain, the sealing was not resistant to the oil/grease...

In the eRider/Sempu the electronic fails, not the strain gauge, I've analyzed a lot of them.

elektrotechnik:drehmomentsensoren [Wiki Pedelec-Forum]

www.pedelecforum.de

regards
stancecoke