Team BKool CycleChat

[BILL S]

I was going to do finestre tonight, but I'm on call for work at there was a problem so had to do deal with thatQUOTE]

I understand. I almost had to do some maintenance on my other bike instead of doing Finestre

 

[RickB]

Speaking of misleading marketing, and the "low power" of the realtour, this is taken directly from Elite's product marketing ...

"The electronically managed resistance unit, one of the best performers on the market, develops up to 500 W (on an average 85Kg rider's weight and 30Km/h speed)."​

Having run development departments in software companies, I am pretty sure that you are talking to first or second line support staff, who would be unlikely to be fully aware of the depths of the algorithms used in the code. They are trained to resolve setup issues, identify malfunctioning hardware or log obvious bugs. Design limitations are really down to Product Managers and Product Architects/Designers.

Unless you can get to talk to one of the senior developers or technical managers, your comments are likely to be lost in the background noise, I'm afraid.

It has also occurred to me that support for non bkool hardware with bkool software will be much less forth coming, and I wonder if swapping my trainer was a good idea?

I had a play with a certain beta today.

I'm just about to pay my bkool subscription annually ...

Geoff

Zwift not worth the wait then I take it. Where does it fall short?

 

[Richylad]

I couldn't resist reading up about magnetic Eddy Current Circular Braking (http://www.explainthatstuff.com/eddy-current-brakes.html) and gearing and torque ratios (http://en.wikipedia.org/wiki/Gear_ratio).

Please indulge me in thinking out loud again, it may all be wrong ...

It seems the electro-magnetic resistance units (like the KICKR and I believe Bkool) use fixed electro magnets floating a short distance from the surface of the conducting flywheel, which rotates within the magnetic field. When the electro magnets are on the magnetic fields generate electric current in the conducting flywheel, which can't go anywhere so manifest as eddy currents, which align in order to create there own magnetic field to resist the electro magnetic (conservation of energy, etc.). This causes the resistive force, and the stronger the current to the electro magnets the stronger the resistive force.

The KICKR has the electro magnets fixed in place on a strain gauge, which measures the rotational force applied on the electro magnets by the flywheel trying to drag them around with it. Since forces are equal and opposite this equals the force you are applying to the flywheel by pedalling, i.e. the rotational force (torque) at the back wheel hub (KICKR) or tyre (bkool). (http://www.bikerumor.com/2012/11/08...-smartphone-powered-cycling-trainer-computer/)

The torque at the back wheel in a lower gear is higher than in a higher gear due to the mechanical advantage of the gearing, in ratio to the gear ratio, as torque ratio is equal to gear ratio (http://en.wikipedia.org/wiki/Gear_ratio).

This torque is converted to a power reading using the rpm of the flywheel, which is the same as the rpm of the rear hub/wheel, to get a wattage. Therefore the higher the speed the higher the wattage (Power = Rotational Force (Torque) times RPM). So for the same wattage, if the RPM is lower then the torque (rotational force) must be higher (as torque equals Power divided by RPM). This means that doing 300W in lower gear (with a lower wheel RPM) at say 7mph will produce twice the torque than doing 300W in a higher gear at 14mph would, and four times the torque that doing 300W at 28mph would. Since the resistance unit has to resist this torque (rotation force) it has to apply a force two or four times higher to be equal and opposite.

Hence, given the same power, it's maximum resistance will be exceeded at a lower speed when in low gear (high torque, low wheel rpm/speed) than when in a higher gear (low torque, high wheel rpm/speed). That is to say, a max resistance (torque) that equates to 500W at say 30 Kmph would only equate to 250W at 15 Kmph or 200W at 10 Kmph.

Individual trainers will have differences in the resistance generated by the same current due to the differences between the tolerances of the electro magnets, the structure of the flywheel, the gaps between them, the heat they generate and can dissipate and probably loads of other factors, but the maximum resistance of each unit will be equal to the rotational force they can generate between the flywheels rotation and the opposition of the magnetic forces due to the eddy currents resisting the opposite magnetic forces in the electro magnets.

To get this maximum resistive torque specified in watts they must assume an RPM or rotational speed of the flywheel and hence the rear wheel/hub.

To get this maximum resistive torque specified as a gradient they must assume a wheel/hub speed and the weight of the rider (along with possible factors for assume air drag, rolling resistance, etc. which would apply on a real cycle and gradient).

This would seem to be born out by the Elite web site for the Real Tour trainer, which quotes a maximum gradient, AND specifies a speed and a weight.

Electronically managed resistance unit with maximum slope of 6% (500W at 30 Km/h)
The electronically managed resistance unit, one of the best performers on the market, develops up to 500 W (on an average 85Kg rider's weight and 30Km/h speed).​

This states that it can resist an 85kg rider doing 30Km/h or 18.75 mph, so if the same 85 kg rider uses the gears to get a rear wheel speed of 15 km/h, while producing the same power, they also would reach the maximum torque resistance of the unit.

If the 85Kg rider can exceed 9.375 mph up a 6% gradient they will overcome the maximum resistance of the unit, so if the gradient goes up to 7%, 12% or indeed 24% there will be no more resistance from the trainer and they can continue pedalling at the same force to continue at 9.375 mph.

Since the Bkool simulator thinks they are doing this speed at 15% they will go up the steeper slope at the same speed they could a 6% slope, and therefore in the same time.

Again, this seems to be born out in practice as an Elite Real Tour rider could ride up the incline on Cothelstone at around 11 kmph, regardless of whether the gradient was 10% or 17%, while on the Wahoo KICKR it showed fluctuating speed, in line with the fluctuating gradient.

Elite RealTour (speed stays level on the two steeper sections)
View attachment 79354

Wahoo KICKR (speed dips on the two steeper sections)
View attachment 79353

Since the max gradient is a factor of the maximum resistive torque, the maximum power therefore depends on gearing and speed and the maximum gradient also depends on the simulated weight, drag, rolling resistance and wind, as well as speed and gearing, as well as the differences between the individual trainers, and possibly the firmware and calibration, it is impossible to say at what gradient any rider and trainer will be limited

However, we can estimate that quoted at 1200W it seems the bkool would be limited at around 2.4 times the RealTour's 6% (i.e. 14% to 15%) depending on gearing, speed, weight, etc.

the KICKR is quoted at 2000W so could go as high as 24%, again depending on gearing, speed, weight, etc.

And my wife says I over analyse everything ...

Geoff

I was just going to write exactly the same thing but my ink run out in my pen

 

[LBHIFI]

Hi

Just got the Bkool Pro and have been experiencing ultra high cadence, watts all over the place, and avg watt on the low side.
Reading throught the post, it seems like what other Pro owners experienced before the latest firmware (I have the version before the latest). The latest software update, made the watts more stable but still to low in my opinion.
Is my general conception right, that the watts reported are too low, but with the latest firmware they are a bit too high.
Something like 220 watt FTP on my firmware would be 300 watt with the latest firmware, but 280 watt would be more realistic?

 

[Add]

Gutted that I didn't get a stage 1 to register in the Goat's League! I now have over an hour to make up to win it. In the process of setting up a glucose drip next to my BKool, and I have ordered a pallet of Snickers!

 

[BILL S]

Gutted that I didn't get a stage 1 to register in the Goat's League! I now have over an hour to make up to win it. In the process of setting up a glucose drip next to my BKool, and I have ordered a pallet of Snickers!

You can be well up there though Adam and there'll be many more Goat Leagues I would think. Go for stage wins if you can and try to beat Adam2. I reckon you might be onto something there with the snickers. I've not tried them with the bkool workouts but they're probably better than the gel bars that I bought a pallet load of and fortunately finished the last one doing Finestre.

 

[Rob H]

Zwift not worth the wait then I take it. Where does it fall short?

It's too computer game like if that makes sense, amazing graphics but it's hard to explain but you just get nothing from it. That being said, it is in beta still and only one very simple track, it will be interesting to see what they add in.

Right know it comes across as very much for people who just get on a turbo and want to spin miles out without getting bored, not go up crazy elevation in short distances or structured training Plans.

Right now bkool have nothing to worry about.

 

[kipster]

You can be well up there though Adam and there'll be many more Goat Leagues I would think. Go for stage wins if you can and try to beat Adam2. I reckon you might be onto something there with the snickers. I've not tried them with the bkool workouts but they're probably better than the gel bars that I bought a pallet load of and fortunately finished the last one doing Finestre.

Snickers, gels, I just have a banana close by just in case, maybe that's why my times are nowhere near yours?

 

[Rob H]

Gutted that I didn't get a stage 1 to register in the Goat's League! I now have over an hour to make up to win it. In the process of setting up a glucose drip next to my BKool, and I have ordered a pallet of Snickers!

Does it make me a bad person i actually used an energy gel last night?... I started to bonk on the last 3 miles knowing the last km was going to be a 10%er all the way

Infact thats a good comparison to my earlier post........

Bkool = Pain and resorting to enegry gels to complete.

Zwift = Dicking about with the keyboard trying to take in game selfies for Facebook..

 

[Rob H]

Hi

Just got the Bkool Pro and have been experiencing ultra high cadence, watts all over the place, and avg watt on the low side.
Reading throught the post, it seems like what other Pro owners experienced before the latest firmware (I have the version before the latest). The latest software update, made the watts more stable but still to low in my opinion.
Is my general conception right, that the watts reported are too low, but with the latest firmware they are a bit too high.
Something like 220 watt FTP on my firmware would be 300 watt with the latest firmware, but 280 watt would be more realistic?

Geoffs the man to answer this in depth but i think it may be luck of the draw with the firmware as i got mine from wiggle a few weeks ago and everything 'seems' as expected, im getting accurate cadence and my stages PM is about ranges from 10% variation at lower wattage to 2-3% when goimg for it. That was using my garmin as a comparison.

I regards to the ultra high cadence, i had that once when it picked up my hub speed sensor for some reason but a reset resolved it and i was only on the velodrome warming up but apart from that it picks up my garmin candence sensor fine.

EDIT : oh and as a premptive measure i had heard about the fan cover squeak issue so figured rather than wait for it to happen i asked wiggle for a spare and they sent one!!

ANOTHER EDIT: Just realised, Geoffs like our very own DCRainmaker

 

[kipster]

Does it make me a bad person i actually used an energy gel last night?... I started to bonk on the last 3 miles knowing the last km was going to be a 10%er all the way

Not at all, I had just never really thought about taking a gel on the turbo, mind you I try not to take them out on the road either, they are in my pocket just in case I need them. I try and fuel on bananas and fig rolls. At the end of the day it's what ever gets you to the finish line.

 

[Rob H]

Not at all, I had just never really thought about taking a gel on the turbo, mind you I try not to take them out on the road either, they are in my pocket just in case I need them. I try and fuel on bananas and fig rolls. At the end of the day it's what ever gets you to the finish line.

Id already done 2 bananas...

 

[BILL S]

To be honest I only bought the box of gel bars for the 24 hour race I did and only managed one or two of them. They're not much good in my opinion. I mostly just eat a banana or small snack before a bkool session but I'm thinking of getting a multi-save bag of snickers to try. Something tells me a snickers before a 1 hour plus bkool ride would be just about right.

 

[Rob H]

So.. deleting Finestre from my mind.. onto the next, the Moncenisio, anyone done it yet?

 

[BILL S]

So.. deleting Finestre from my mind.. onto the next, the Moncenisio, anyone done it yet?

I don't think anyone here's done it yet. Looks to be one of those where you really don't want to use up energy warming up first.