Power input of the rider

[mark.ai]

I found this equation if it's correct?

Power (kW) = Torque (Nm) x Speed (RPM) / 9.5488

So if you know the cadence of the pedals (RPM) and the torque on the shaft between the pedals that would give you the total power being applied (by rider + motor) ?

The sensor would do the measuring of the torque and then the meter part would be the display of the power I guess.

 

[khorn]

This is the the most common formula:

HP = RPM x TORQUE ÷ 5252


(Copied from the Internet)

By definition, POWER = FORCE x DISTANCE ÷ TIME (as explained above under the POWER heading)

Using the example in Figure 2 above, where a constant tangential force of 100 pounds was applied to the 12" handle rotating at 2000 RPM, we know the force involved, so to calculate power, we need the distance the handle travels per unit time, expressed as:

Power = 100 pounds x distance per minute

OK, how far does the crank handle move in one minute? First, determine the distance it moves in one revolution:

DISTANCE per revolution = 2 x π x radius

DISTANCE per revolution. = 2 x 3.1416 x 1 ft = 6.283 ft.

Now we know how far the crank moves in one revolution. How far does the crank move in one minute?

DISTANCE per min. = 6.283 ft .per rev. x 2000 rev. per min. = 12,566 feet per minute

Now we know enough to calculate the power, defined as:

POWER = FORCE x DISTANCE ÷ TIME
so
Power = 100 lb x 12,566 ft. per minute = 1,256,600 ft-lb per minute

Swell, but how about HORSEPOWER? Remember that one HORSEPOWER is defined as 33000 foot-pounds of work per minute. Therefore HP = POWER (ft-lb per min) ÷ 33,000. We have already calculated that the power being applied to the crank-wheel above is 1,256,600 ft-lb per minute.

How many HP is that?

HP = (1,256,600 ÷ 33,000) = 38.1 HP.

Now we combine some stuff we already know to produce the magic 5252. We already know that:

TORQUE = FORCE x RADIUS.

If we divide both sides of that equation by RADIUS, we get:

(a) FORCE = TORQUE ÷ RADIUS

Now, if DISTANCE per revolution = RADIUS x 2 x π, then

(b) DISTANCE per minute = RADIUS x 2 x π x RPM

We already know

(c) POWER = FORCE x DISTANCE per minute

So if we plug the equivalent for FORCE from equation (a) and distance per minute from equation (b) into equation (c), we get:

POWER = (TORQUE ÷ RADIUS) x (RPM x RADIUS x 2 x π)

Dividing both sides by 33,000 to find HP,

HP = TORQUE ÷ RADIUS x RPM x RADIUS x 2 x π ÷ 33,000

By reducing, we get

HP = TORQUE x RPM x 6.28 ÷ 33,000

Since

33,000 ÷ 6.2832 = 5252

Therefore

HP = TORQUE x RPM ÷ 5252

Note that at 5252 RPM, torque and HP are equal. At any RPM below 5252, the value of torque is greater than the value of HP; Above 5252 RPM, the value of torque is less than the value of HP.



Karsten

 

[Gary]

Many ordinary power meters on road bikes(Stages, Pioneer etc) use string gates that measures the amount of flex in the crank arms by the torque that the rider put into the pedals - I have a few myself and its quite accurate.

Karsten

Yeah. I'm well aware of that . Which is why I'm interested to know what mechanical means the power is measurd by in emtb motors.

 

[khorn]

Yeah. I'm well aware of that . Which is why I'm interested to know what mechanical means the power is measurd by in emtb motors.

I think quite a few have answered you, the heart of any emtb system - The torque sensor!

Karsten

 

[Gary]

Just saying the words "torque sensor" doesn't explain how it measures the torque from the riders pedalling inputs

 

[Gary]

It's fine to say "I don't know" BTW

 

[khorn]

It's fine to say "I don't know" BTW

???

 

[mark.ai]

This picture explains everything! (If your eyesight is good enough to see it - sorry can't find a bigger version.)

It's from this link how sensors work - torque transducers, but my brain turns off reading it too much ...

 

[khorn]

well, if you are too lazy to google “torque sensor” then I rest my case.......

Karsten

 

[Gary]

I'm an E bike owner. Aren't we all lazy?

 

[khorn]

I'm an E bike owner. Aren't we all lazy?

Not really............ I have rheumatoid arthritis and my hips, knees, ankles and fingers does not work any more. Emtb is my best medicine to keep my body alive!

Karsten

 

[Gary]

It was a joke mate. I'm not lazy either.

Let me rephrase the question for you Karsten.

Where exactly is the torque sensor for measuring rider pedal power situatd on the Brose motor. And how does it work? (i. what sort of sensor is it)

 

[Kiwi in Wales]

IF Blevo only shows average and max power of the rider during a ride (like in screenshot), the usefulness of that info is questionable, but IF the rider power info would be available as real time data, using same ANT+ power meter profile as any other separate power meter, then THAT would totally replace a separate power meter. I don't understand why manufacturers don't do that.

View attachment 7455

The numbers in this screenshot are somewhat interesting, as rider input in ECO and TRAIL is lower than in TURBO... isn't it "normally" the opposite - you push all out of your legs until they explode, then switch to TURBO/BOOST and try to recover. I would expect that TURBO shows lower RIDER Watts than ECO. At least in my riding style it certainly would?!?

Both the 'biker' and 'motor' power readings are available as real time data. See my first screen shot of the display.
As you can image in post 3, it is not easy to screen shot whilst riding so that it why both readings are faily low.

 

[Kev Henson]

Hi, I think there are lots of wrong assumptions here.
Yes, Specialized bikes output real-time data of both rider power and motor power. According to all available tests they seems to be quite accurate (apart from random spikes) and even Specialized mention rider power reading as accurate "with same precision or better than current power meters on market".
I don't see why this can't be used for training as with power meters on non-ebikes. Its the same thing, you just have additional motor power to increase your speed (if you want). The truth is that because I wanted to ride with power meter was just another reason to buy Levo as it just already have this sensor included in package.

I don't need to add anything related to this to Ebike Field, as Rider power data are available as standard ANT+ power sensor, so Garmin can connect to this sensor and draw power graph alone (higher device models). I only added possibility to choose to show rider power value on Ebike Field - Nerd Style.

But this discussion is about Shimano motors and I don't think they support ANT+ connectivity at all, so no data for Garmin devices if I have correct info. It is shame really that only Specialized have ANT+ connectivity in their bikes. I will be more than happy to know that something is changed there.

i get ant + connection on my wahoo although it only shows it as a Di2 and displays the gears but looks like it is a option looking at this article Garmin® announces SHIMANO STEPS support on Edge® cycling computers to help enhance the eBike riding experience | Garmin Newsroom

 

[Kiwi in Wales]

I'm an E bike owner. Aren't we all lazy?

I think I may be confusion people with my read out screens above as I may be I riding my ebike slightly different to most people.

IF Blevo only shows average and max power of the rider during a ride (like in screenshot), the usefulness of that info is questionable, but IF the rider power info would be available as real time data, using same ANT+ power meter profile as any other separate power meter, then THAT would totally replace a separate power meter. I don't understand why manufacturers don't do that.

View attachment 7455

The numbers in this screenshot are somewhat interesting, as rider input in ECO and TRAIL is lower than in TURBO... isn't it "normally" the opposite - you push all out of your legs until they explode, then switch to TURBO/BOOST and try to recover. I would expect that TURBO shows lower RIDER Watts than ECO. At least in my riding style it certainly would?!?

I am doing the exact opposite as that is the way I ride when I am dong Solo. 70% of my rides are Solo.

I push in Turbo until I explode and then I recover using Eco and Trail.

Let me explain...
I ride to the trails in Eco (mostly) and Trail. When I get to the specific part of the trail I 'enjoy' the most I flick over to Turbo and 'ride it like I just stole it'. When I finish that part of the trail that I 'enjoy' the most I cruise off to the next part of the trail recovering in Eco (mostly) and Trail. I repeat this method until I have completed my normal 20-30km circuit.

I am not doing this for training, I am doing this as I enjoy it. I just get the 'training' benefits as a default. Have a look at a couple of screenshots below of two of my more intense rides.

All the outputs noted below are Real Time outputs. I like having the info displayed in Real Time as it assists me with...

How the bike is performing
Motor temprature
Battery temprature
Battery % left
Motor output
Current Speed

How I am performing
Heart rate
Biker Power output
Cadence
Meters climbed
Duration of ride

Other live info
Time of day
Phone battery left
GPS signal

Nerd I may be but this is why I love Blevo. Best money I have ever spent on an App.

Blevo also has a 'Smart Heart rate' function and 'Smart Power' function which I havent had the time to look at yet but will get there eventually.

 

[Gary]

I think I may be confusion people with my read out screens above as I may be I riding my ebike slightly different to most people.

Did you mean to quote me? As already explained, that was just a joke playing on the sterotype of the Ebiker.

We ALL ride our Ebikes differently. I did a 15mile XC ride in the rain last night with mine switched off the entire ride just because my Ebike was already dirty and had my bar light fittings on it. I didn't switch it on as I was riding with my GF who's a beginner to night riding and wanted to try it for the first time. I'd already ridden 30 miles to the nearest Halfords on my roadbike earlier on to get a helmet light mount for her to use the bikehut light as a headtorch. I'm far from lazy on any bike. Not that this matters. We all enjoy riding bikes. not all in the same manner or manor. but it's all good non?

 

[Kiwi in Wales]

Did you mean to quote me? As already explained, that was just a joke playing on the sterotype of the Ebiker.

We ALL ride our Ebikes differently. I did a 15mile XC ride in the rain last night with mine switched off the entire ride just because my Ebike was already dirty and had my bar light fittings on it. I didn't switch it on as I was riding with my GF who's a beginner to night riding and wanted to try it for the first time. I'd already ridden 30 miles to the nearest Halfords on my roadbike earlier on to get a helmet light mount for her to use the bikehut light as a headtorch. I'm far from lazy on any bike. Not that this matters. We all enjoy riding bikes. not all in the same manner or manor. but it's all good non?

Not sure what happened there dude, I wasnt quoting you.... must have got mixed up with my other response.
For sure all good here dude How is the GF liking the night rides?

Would be good to get some confirmation back if the in built power meter is actually accurate. Not sure who could do that though....
Would be great to get someone on here from Brose to confirm how accurate it is? What say you @Rob Hancill ?
I get an almost identical reading from both the Specialized App and also the Blevo App for max power output.

 

[khorn]

Would be good to get some confirmation back if the in built power meter is actually accurate. Not sure who could do that though....
.

I do have a Tacx Neo hometrainer that is rated within 1% accuracy. It’s is actually mounted already with a 11 speed cassette and the Levo should fit even I have not tried yet. It can handle 2000+ watts so it should be sufficient for me + the Levo. I can then data log simultaneously the produced power from both the Levo and the Hom trainer. Only question is if I can set my 2018 Levo to 0 power assist and still turned on?

Karsten

 

[khorn]

I just need to buy this I guess:

Køb Tacx T2835/2840 Neo / Flux thru axle adapter | ROSE Bikes

Karsten

 

[Gary]

How is the GF liking the night rides?

She loved it. Fell off once, just a comedy fall on wet logs my retard of a mate thinks constitutes sustainable "trailbuilding" over a quagmire. and struggled to get back on the bike. Oh how we laughed

This one might be a keeper
(I might have said that before tho )

 

[JanCapek]

i get ant + connection on my wahoo although it only shows it as a Di2 and displays the gears but looks like it is a option looking at this article Garmin® announces SHIMANO STEPS support on Edge® cycling computers to help enhance the eBike riding experience | Garmin Newsroom

What I understand in the meantime is that ebike specific ANT data should be supported by some new shimano accessory. And if Garmin promoted that, that is good news, as it means that it will hopefully follow communication by standard. In that case, my apps are ready for it!

 

[100 Cols]

What I understand in the meantime is that ebike specific ANT data should be supported by some new shimano accessory. And if Garmin promoted that, that is good news, as it means that it will hopefully follow communication by standard. In that case, my apps are ready for it!

Yes, but unfortunately Garmin announced support only for newer STePS incarnations, E6100 and E7000?!

E8000 is NOT in the list of supported models, maybe because that unit does not transmit the needed ANT+ channels?

 

[100 Cols]

I do have a Tacx Neo hometrainer that is rated within 1% accuracy. It’s is actually mounted already with a 11 speed cassette and the Levo should fit even I have not tried yet. It can handle 2000+ watts so it should be sufficient for me + the Levo. I can then data log simultaneously the produced power from both the Levo and the Hom trainer. Only question is if I can set my 2018 Levo to 0 power assist and still turned on?

Karsten

THAT would be a super cool thing to do, Karsten. However, there might be a small problem that needs to be solved (IF your Levo is similar to Shimano motors): the speed sensor and corresponding magnet attached to a spoke... you need to provide that speed signal to the motor/controller somehow, otherwise it will stop assisting.

Tacx Neo's flywheel is full of strong magnets (if I'm not mistaken), which might interfere with the speed sensor pretty badly, if you just try to glue the speed sensor magnet there...

But I do encourage you to go ahead with the project, as you already have all the instruments and players in the band. Highly interested hearing the results!

 

[khorn]

THAT would be a super cool thing to do, Karsten. However, there might be a small problem that needs to be solved (IF your Levo is similar to Shimano motors): the speed sensor and corresponding magnet attached to a spoke... you need to provide that speed signal to the motor/controller somehow, otherwise it will stop assisting.

Tacx Neo's flywheel is full of strong magnets (if I'm not mistaken), which might interfere with the speed sensor pretty badly, if you just try to glue the speed sensor magnet there...

But I do encourage you to go ahead with the project, as you already have all the instruments and players in the band. Highly interested hearing the results!

You are right about the speed sensor but my plan was not to measure power output from the motor but only from the legs. Big question is now if I can set the ECO mode to 0/0 in BLevo and then ride without the magnet and still get power output(power meter) from the Brose motor. I guess that there is only one way to find out and that is to do the setup in BLevo, remove the magnet from the wheel and go for a ride while looking at my Garmin Edge and see if there is a power output from the power meter.

Karsten

 

[JanCapek]

Yes, you can. I am using it like this when I feel empowered enough myself. And you don't need to have valid data from speed sensor to get power data. So go for it.

 

[bigdaddy46]

Resurrecting this to see if there is anything new in 2021, just ordered a commencal w/ ep8. My usage for a power meter is that I'm dealing with Lyme/cfs and overdoing it causes me to crash for sometimes weeks. Being able to put a number to my output would help me have fun ok my bike and stay below that threshold I think!

 

[beutelfuchs]

Hi bigdaddy,
Same here. Awaiting my rise and I would love to get power readings from it.
I have a kenevo with the build in PM which I compared to my kickr core and it was spot on.

For the shimano the only options which are confirmed to work are pedal systems (garmin, SRM) or the power tab hub.
Pedals are not for me as I want to ride flats. Also the SRM have really poor customer reviews.
The hub is probably not ideal as it can account for the power lost by the drive train and especially the motor.

I was asking the guys at P2M if the have something which fits but they denied.
Just today I was mailing to stages. Stil awaiting response.

 

[Trail Doug]

Thread resurrection with FYI for anyone else trying to find a way of getting rider power on Shimano.

Tried the Stages XT crank off my XC bike on the E8000 and the power meter sensor doesn't get anywhere near clearing the motor housing.

 

[beutelfuchs]

I think for now its either clipless pedals or nothing.
For me being a flat pedal guy this kicked the Shimano out.

 

[berny]

Newbie here. After reading this whole thread, my take is the new EP8 still doesn't support power meter connectivity to any app, and thus is not able to output the power information to Stava. Is that right?