Torque sensing for person with limited leg strength?

[rocketman58]

After three years I want to replace my rear wheeled geared hub drive on my recumbent trike, with a torque sensing mid drive. Due to a reduction in leg strength, I am finding it difficult to ride with others especially on rolling hills. On up hills I have to constantly down shift to a lower gear while simultaneously bumping up the assist level. At the top of the hill I have to do just the opposite. When I had more leg strength, I could compensate more with my own power on the up hills. Juggling the gears and assist level has become too much of a chore. I need something a bit more integrated when riding with my group. They tend to ride between 15 and 17mph on average, and maintain speed up hills with their mid drive motors (Bosch for the most part.)

My concern is that as my leg strength continues to decrease, will a torque sensing motor have difficulty sensing my limited power input? How minimal can you adjust the sensor input to?

I am planning on getting a Photon Gen 2 kit. One thing that may hold me back is the lack of extension wires for the display and speed sensor. These are different than the Gen 1 motor. I also need a throttle extension wire, but I was told these are the same as before. I plan to talk to a couple of suppliers after the holidays. Thanks!

 

[RunForTheHills]

In my experience with torque sensors, it doesn't need that much pressure to activate. Although I haven't used that motor or torque sensor. I would think that if you have enough leg strength to stand and walk, you should be able to use the torque sensor.

 

[E-HP]

After three years I want to replace my rear wheeled geared hub drive on my recumbent trike, with a torque sensing mid drive. Due to a reduction in leg strength, I am finding it difficult to ride with others especially on rolling hills. On up hills I have to constantly down shift to a lower gear while simultaneously bumping up the assist level. At the top of the hill I have to do just the opposite. When I had more leg strength, I could compensate more with my own power on the up hills. Juggling the gears and assist level has become too much of a chore. I need something a bit more integrated when riding with my group. They tend to ride between 15 and 17mph on average, and maintain speed up hills with their mid drive motors (Bosch for the most part.)

My concern is that as my leg strength continues to decrease, will a torque sensing motor have difficulty sensing my limited power input? How minimal can you adjust the sensor input to?

I am planning on getting a Photon Gen 2 kit. One thing that may hold me back is the lack of extension wires for the display and speed sensor. These are different than the Gen 1 motor. I also need a throttle extension wire, but I was told these are the same as before. I plan to talk to a couple of suppliers after the holidays. Thanks!

It would seem that with declining leg strength, moving toward a torque sensor seems like moving in the opposite direction. What kind of hub motor and controller are you currently using? You could just up the power to match their speed, or let them work harder staying up with you.

 

[rocketman58]

My hub motor is a Bafang G020 / 500w / 45nm / 48v. I am using a KT controller and display. I did adjust the standard setting from the default setting of 2 to the higher setting of 3. The effect was basically like riding in a higher assist level. While this helps somewhat on the uphills, it is too much assist on level ground. I end up with a lot of ghost pedaling, and a shorter battery range. The idea is to stay with the group, so this isn't working. I was hoping torque sensing might level things out, but I'm worried that I may not eventually have the strength for some of the hills. That's why I wanted torque sensing with a throttle. Maybe I'm being too unrealistic with white am asking?

I do need to replace the rear hub motor eventually. It has developed a lot of side to side play and is starting to get noisy.

 

[2old]

IMO, torque sensing is the wrong direction and "rpm" would be far superior.Theoretically you could set the level where you would basically be ghost pedaling up a hill, especially since systems like the BBS02 are configurable.

 

[E-HP]

My hub motor is a Bafang G020 / 500w / 45nm / 48v. I am using a KT controller and display. I did adjust the standard setting from the default setting of 2 to the higher setting of 3. The effect was basically like riding in a higher assist level. While this helps somewhat on the uphills, it is too much assist on level ground. I end up with a lot of ghost pedaling, and a shorter battery range. The idea is to stay with the group, so this isn't working. I was hoping torque sensing might level things out, but I'm worried that I may not eventually have the strength for some of the hills. That's why I wanted torque sensing with a throttle. Maybe I'm being too unrealistic with white am asking?

I do need to replace the rear hub motor eventually. It has developed a lot of side to side play and is starting to get noisy.

You don’t like messing with shifting and assistance levels, but you’re moving to mid drive with means even more shifting, and no relief from adjusting assistance levels either. You have declining leg strength, but you’re choosing a system that only provides assistance proportional to leg power. Maybe you should look for a move flexible solution that doesn’t rely on leg power and a motor that requires less shifting, and tune it to your needs.

As an example, I use a motor that never requires shifting. I use a cheap dumb controller that can power the motor. I run both the throttle and PAS through a Cycle Analyst. The setup can use cadence or torque sensing PAS, but both are tuneable. For cadence, it can be setup to provide incrementally more or less assistance relative to cadence rotation speed. For torque sensing, it can be setup to deliver from zero to full power to the motor. I use a knob on my handlebar to dial up or down assistance or power, or even speed. I’m actually too lazy to shift, or even turn the knob, so I ride at a fixed assist, with power ramping based on cadence, which works for 80% of my riding, and adjust assistance levels either with throttle if I need to on hills. But I could implement assistance in a number of ways, this happens to be what works best for me, and I still get plenty of exercise.
Since you are on rolling hills, you would benefit from a direct drive hub which would allow regen (when I ran regen, I rode a few thousand mile without changing brake pads, which worked great since I had zero bike maintenance, which worked great with my laziness).

 

[docw009]

Chasing a group uphill on throttle or ghost pedalling seems like a good way to smoke a smaller motor, OP has Bafang G020 in a 20" wheel and 25A KT controller on 48V. Someone should simulate it. A rider should have the gearing set so the the motor is spinning briskly uphill.

I would expect you get about 120-140 watts in PAS 1, and 220-240 watts in Pas 2. Maybe 500 watts in PAS 5. Blipping the throttle would show 900-1200 watts on a KT display that can show watts? You can keep up on hills, if you increase the assist levels. That's how the KT works, Preset for a prorated power at each level, Your complaint is you don't like ghost pedalling and don't like changing levels. Are the handlebar controls too hard to access?

CYC gen 2 with 3x the power of the G020 probably is a safe, but pricey bet. With that kind of power, its PAS torque sensor should easily give you the same power as 250 watts (PAS2) on a 25 A KT controller. Less likely to overheat too.

A BBS02/uart version with nine level PAS could likely work too, but it is cadence sense.

I am a weak old man pedaler, and my torque sensor bikes (DM02 and TSDZ2/0SF both 350W) do tire me out on a longer ride. It's more satifying though than the BBS02B.

 

[rocketman58]

Interesting feedback.

Regarding my leg strength: I am fighting prostate cancer. The hormone treatments sap the strength out of you and make you weak. This only gets worse as time goes on. I have been dealing with this treatment for 4 years now, and I can tell the difference from when I first started riding with assist. This is something that is not going to get better. That said, I can still hang with the group on our 30 mile Saturday rides. Since I am having to use a higher assist level than when I started, my battery range has dropped from over 60 miles to around 50 miles. Not a problem yet since even our longest rides are no more than 40 miles.

 

[rocketman58]

Chasing a group uphill on throttle or ghost pedalling seems like a good way to smoke a smaller motor, OP has Bafang G020 in a 20" wheel and 25A KT controller on 48V. Someone should simulate it. A rider should have the gearing set so the the motor is sinning briskly uphill.

I would expect you get about 120-140 watts in PAS 1, and 220-240 watts in Pas 2. Maybe 500 watts in PAS 5. Blipping the throttle would show 900-1200 watts on a KT display that can show watts? You can keep up on hills, if you increase the assist levels. That's how the KT works, Preset for a prorated power at each level, Your complaint is you don't like ghost pedalling and don't like changing levels. Are the handlebar controls too hard to access?

CYC gen 2 with 3x the power of the G020 probably is a safe, but pricey bet. With that kind of power, its PAS torque sensor should easily give you the same power as 250 watts (PAS2) on a 25 A KT controller. Less likely to overheat too.

A BBS02/uart version with nine level PAS could likely work too, but it is cadence sense.

I am a weak old man pedaler, and my torque sensor bikes (DM02 and TSDZ2/0SF both 350W) do tire me out on a longer ride. It's more satifying though than the BBS02B.

My KT display shows watts being used. They are slightly less than what you stated. The handle bar controls are easy to reach on my recumbent trike. I guess I'm just getting lazy about having to constantly change gears and pas levels to match all the time. Often they do not and I find myself struggling with too high a gear and too low of an assist level. When I had a bit more strength this was not as much of a problem as it is now.

Most of my group have Catrikes with Bosch motors. Their single chainring, wide range cassette and cadence sensing have a real advantage on our rides. But while must of them are older than me, the do not have my physical issues. I was hoping to set up a system similar to what they have but still allow for my somewhat diminished leg strength.

 

[E-HP]

My KT display shows watts being used. They are slightly less than what you stated. The handle bar controls are easy to reach on my recumbent trike. I guess I'm just getting lazy about having to constantly change gears and pas levels to match all the time. Often they do not and I find myself struggling with too high a gear and too low of an assist level. When I had a bit more strength this was not as much of a problem as it is now.

Most of my group have Catrikes with Bosch motors. Their single chainring, wide range cassette and cadence sensing have a real advantage on our rides. But while must of them are older than me, the do not have my physical issues. I was hoping to set up a system similar to what they have but still allow for my somewhat diminished leg strength.

Can you provide a google maps link to an example of one of the hills you are climbing, and the distance you climb before descending on the rolling hills? With that info, it's easy to model your system on Grin's motor simulator which is a very accurate predictor of performance.

I stills recommend a system that you can tune as your needs change, with sufficient power for times where you can't contribute as much during the climbs. Also, if the rest of the group were trying to keep up with your pace, would that be a problem?

Rolling hill are perfect to regen, an you'd get back a lot of the range you're losing.

 

[OlderGiantFan]

IMO, torque sensing is the wrong direction and "rpm" would be far superior.Theoretically you could set the level where you would basically be ghost pedaling up a hill, especially since systems like the BBS02 are configurable.

That's what I do from time to time, riding along, just barely spinning the cranks. On another thread a lot of people were commenting on the BBS02's propensity to cut in late after commencing to pedal, and to keep powering along for a second of so after stopping pedaling. They explained the software 'fix' for this behavior but I actually like it that way. It makes ghost pedaling seamless and also allows me to have the bike moving with tension in the chain before the motor kicks in. Even in low PAS settings it can belt out the power.

 

[rocketman58]

This is all very interesting. The recommendations are going opposite of what I had thought. Most people are recommending I stick with cadence instead of torque sensing. Right now it looks like the BBS02 might be the best option for me if I want a mid drive. The cheapest option would be to get a replacement G020 motor. I can get a complete kit for about $300. But there are some considerations to going with a mid drive. My trike has rear suspension, and the added weight of the hub motor makes it less effective. In addition, if I were to get a flat on a group ride, it would take considerable time to fix it. This would be inconsiderate to the group.

How would riding be different between my hub drive and a BBS02? I know that's a pretty broad question, but maybe a simplified explanation? Can I reprogram the BBS02 to allow for maximum speed in each assist level (no speed cutoff), and set each assist level to deliver a specified amount of watts for assist?

 

[stancecoke]

How would riding be different between my hub drive and a BBS02?

With the hub drive, you get no accelerated wear of the chain and the sprockets, you can change gears whenever you want with a steady assist of the motor. With a simple middrive like the BBS02, you have to mount a shift sensor, that interrupts the motor power for shifting, even with a shift sensor you will have a faster wearing of the chain and the sprockets, as chain and sprockets are designed for the power of a human, not for 1000W from a motor. The only advantage of a middrive is having a high torque at slow speeds with a small motor. This advantage only matters on very steep and long ascents, that you will rarely find in roads, only on single tracks in real mountains.
You won't ride on this kind of tracks with a recumbent bike, I guess

Can I reprogram the BBS02 to allow for maximum speed in each assist level (no speed cutoff), and set each assist level to deliver a specified amount of watts for assist?

No problem for the old UART systems, with the recent CAN system, it's a kind of lottery.
Varstrom offers a tool for the CAN version, but there are only very few reports, if it really works. The Bafang Canable Tool should work for tuning your parameters also, but here the same, not many reports yet....

 

[2old]

Two other advantages of a mid are ease of tire repair, centralized weight distribution, I've operated my BBS02 for 10+ years without a shift sensor and I think that those who profess chain wear have never owned one.

 

[stancecoke]

I think that those who profess chain wear have never owned one.

I think, if you had no accelerated chain wear, you would be much happier with a hub motor, as you never have used your middrive in situations, where it can show its advantages over a hubmotor

 

[rocketman58]

I think, if you had no accelerated chain wear, you would be much happier with a hub motor, as you never have used your middrive in situations, where it can show its advantages over a hubmotor

Can you elaborate on this?

 

[stancecoke]

elaborate on this

The only advantage of a middrive is that you can climb steep, long ascents with low speed without overheating the motor, because you can use the gears to keep the motor (the cadence) in a speed range with a good efficiency. A hubmotor will have a bad efficiency and will overheat quite fast, if you use it at very low rpms...

There is a very good report on the German Pedelecforum:

https://www.pedelecforum.de/forum/index.php?threads/blick-ueber-den-tellerrand-bosch-vs-puma-versuch-eines-vergleichs.80276/

Summary, not entirely serious:

Bosch can do everything, but nothing really well.
If you operate the PUMA (=MAC) within its design (thermal) limits, it is clearly more powerful.
Another issue is that an open system allows for much greater customization, which also opens up completely new possibilities for adjustment for weaker riders or those with health impairments.

 

[docw009]

How would riding be different between my hub drive and a BBS02? I know that's a pretty broad question, but maybe a simplified explanation? Can I reprogram the BBS02 to allow for maximum speed in each assist level (no speed cutoff), and set each assist level to deliver a specified amount of watts for assist?

The older BBS02B allowed the user to set available power and speed limit for each assist level, This is superior to the KT units which have a preset power level and no speed limits. In my opinion, the speed limit should be set to the system max anyway. I've ridden a BBS02 with limits set and it's stupid. The older uart systems required the user to have a program cable, OC, or a black box to change those settings. I believe this approach is still available for the canbus models, but have read that this can now be done using advanced menus in certain displays, Check with your vendor,

 

[2old]

I think, if you had no accelerated chain wear, you would be much happier with a hub motor, as you never have used your middrive in situations, where it can show its advantages over a hubmotor

My mid as I've mentioned before is used in extreme off road activity. I ride analog MTB most of the time in those same extremes, so if the wear were accelerated much I would see it. I tested many hub systems when I evaluated them for a magazine and none would compare with a mid which is why all major OEM companies have them for all of their off road bikes..

 

[n00b]

You don’t like messing with shifting and assistance levels, but you’re moving to mid drive with means even more shifting, and no relief from adjusting assistance levels either. You have declining leg strength, but you’re choosing a system that only provides assistance proportional to leg power. Maybe you should look for a move flexible solution that doesn’t rely on leg power and a motor that requires less shifting, and tune it to your needs.

As an example, I use a motor that never requires shifting. I use a cheap dumb controller that can power the motor. I run both the throttle and PAS through a Cycle Analyst. The setup can use cadence or torque sensing PAS, but both are tuneable. For cadence, it can be setup to provide incrementally more or less assistance relative to cadence rotation speed. For torque sensing, it can be setup to deliver from zero to full power to the motor. I use a knob on my handlebar to dial up or down assistance or power, or even speed. I’m actually too lazy to shift, or even turn the knob, so I ride at a fixed assist, with power ramping based on cadence, which works for 80% of my riding, and adjust assistance levels either with throttle if I need to on hills. But I could implement assistance in a number of ways, this happens to be what works best for me, and I still get plenty of exercise.
Since you are on rolling hills, you would benefit from a direct drive hub which would allow regen (when I ran regen, I rode a few thousand mile without changing brake pads, which worked great since I had zero bike maintenance, which worked great with my laziness).

You wired in a vr for the assistance level?

 

[n00b]

Is the "KT" referenced in this thread not KunTeng?

 

[stancecoke]

for all of their off road bikes..

There a middrive makes sense for sure. But we are talking about a recumbent trike here!

After three years I want to replace my rear wheeled geared hub drive on my recumbent trike

 

[rocketman58]

Thank you all, this has all been very enlightening.

 

[2old]

There a middrive makes sense for sure. But we are talking about a recumbent trike here!

Road bikes and the few companies that make trikes (except fat tire monstrosities) too. I'm interested in assistance not conflict, so bye.

 

[stancecoke]

But keep up your hub frenzy

That's no frenzy, just simple physics
The Grin motor simulator is very helpful, to compare different setups.