Power readings in Bkool

[gbrown]

Continued from FAQ thread ...

Has anyone compared the power that the bkool displays against an actual power meter?

https://www.cyclechat.net/threads/bkool-faq.191965/post-4053014

Possibly, I am just reporting what I have found on my classic with v2.04 firmware (iirc). For me, my current ftp on bkool of 199w, came off of a ride average of 210w. The vectors reported 201w for a 20 minute average on the same session (a PB), one of the T100 stages. At lower to flat gradients I am getting an over read of up to 30w compared to the vectors.

I find, with my set up, that acceleration up to any speed and the power readings are almost identical. Once I am no longer accelerating and I am just holding a steady speed the power differences start to come in. How much depends on slope, cadence, speed and weight. The thing is it is a pretty consistant, for me, with my setup.

A 5% over read on bkool compared to your Vectors is not bad at all.

One thing with the Vectors is that they are measuring power at the pedal, whereas the Bkool is estimating power at the rear wheel, and a powertap is measuring it at the rear hub. There would always be some loss of power through the drive train, I understand this can be in the order of around 3%! So you might expect the Vectors to be around 3% higher than a reading from the rear wheel...

I would guess that most people are interested in the power they are applying to the pedal/crank, the fact that it is slightly higher than at the rear wheel is a psychological bonus!

Here I tried to speculate on why the trainers have limits on maximum gradient simulated and why this varies from person to person and trainer to trainer, not just due to the weight of the rider, but also the speed at which they climb and which gear they use.

https://www.cyclechat.net/threads/team-bkool-cyclechat.144689/post-3525607

Geoff

 

[theboxers]

I found that the power readings and resistance settings have not changed much since the firmware update on the trainer. I still max out resistance wise at about 6%. It is just that I can now turn a higher cadence or higher gear than I could before. Signs of improvement.

The difference I have found is the the speed reporting. Prior to the firmware update when going above 6% the speed numbers would turn blue and go down. The edge and speed sensor would report 5mph and bkool would go as low as 1.5mph. Makes going up Alpe d'Huez a 2 hour slugfest . Now the reporting says what I am actually doing for the most part.. It's still difficult but I can complete sessions in a reasonable time now

 

[gbrown]

I found that the power readings and resistance settings have not changed much since the firmware update on the trainer. I still max out resistance wise at about 6%. It is just that I can now turn a higher cadence or higher gear than I could before. Signs of improvement.

The difference I have found is the the speed reporting. Prior to the firmware update when going above 6% the speed numbers would turn blue and go down. The edge and speed sensor would report 5mph and bkool would go as low as 1.5mph. Makes going up Alpe d'Huez a 2 hour slugfest . Now the reporting says what I am actually doing for the most part.. It's still difficult but I can complete sessions in a reasonable time now

I wonder if the blue speed numbers were an attempt to compensate for the lack of resistance and estimate a speed if the gradient at your weight were fully simumlated with the correct resistance. A great idea in theory, but as you say, it would make a long steep climb like Aple d'Huez a marathon!

I wonder why it stopped doing the blue speed, did they give up on the idea, I wonder?

How's the weight coming down?

Geoff

 

[g00se]

The blue numbers mean that the system is 'estimating' what the speed should be - not taking it from the resistance unit. It usually comes into play on decents - which it estimates the freewheeling speed down a slop.

Not sure what it could be going up.. Possibly head winds with the simulated weather?

 

[borchgrevink]

Anyone measured and compared different bkool turbos?

 

[theboxers]

I wonder if the blue speed numbers were an attempt to compensate for the lack of resistance and estimate a speed if the gradient at your weight were fully simumlated with the correct resistance. A great idea in theory, but as you say, it would make a long steep climb like Aple d'Huez a marathon!

That was what I thought about the drop in speed. The only problem as far as I could see was the mismatch in cadence. I thought I was doing well maintaining the cadence but that was only at a lower actual gradient.

I wonder why it stopped doing the blue speed, did they give up on the idea, I wonder?

It could be that people complained about the time taken to do some of the steeper or longer sessions due to the speed drop. I know I was glad when the updated firmware allowed me to complete sessions in a reasonable time. I would still be at max resistance after only 6% but the speed was a true wheel speed.

In the T100 league I re-did 10 or so of the sessions to try and improve my times after the update, In every case I managed to improve my time. On Cheddar Gorge I went from 27 to 17 minutes, on the shorter sessions it was only seconds of improvement, but still better.

How's the weight coming down?

Geoff

About as quickly as the power is going up....Slowly

The blue numbers mean that the system is 'estimating' what the speed should be - not taking it from the resistance unit. It usually comes into play on decents - which it estimates the freewheeling speed down a slop.

Not sure what it could be going up.. Possibly head winds with the simulated weather?

Yes that is my understanding of the blue numbers too. However prior to the firmware update the speed estimation would occur on the upslope as well, in my case lugging 135kg up a hill resulted in a very low speed going up something over 6%.

On the other had I can gain a bit on the downhills, if I play it right

 

[borchgrevink]

At my 77.5 kg it I haven't noticed that the resistance maxes out, or maybe I'm just to absorbed...

 

[gbrown]

It could be that people complained about the time taken to do some of the steeper or longer sessions due to the speed drop. I know I was glad when the updated firmware allowed me to complete sessions in a reasonable time. I would still be at max resistance after only 6% but the speed was a true wheel speed.

I guess that was what the slope reduction was for, but that doesn't work for league sessions.

About as quickly as the power is going up....Slowly

Keep climbing those hills and it will keep coming down!

I couldn't believe how many calories I could burn in an hour on a Mountain goat session, almost 1,000/hour at just under 300 Watts. No wonder it got warm...

At the moment I have to limit myself to around 120 Watts, so I've no chance of getting up any slope of any significance.

Geoff

 

[theboxers]

I guess that was what the slope reduction was for, but that doesn't work for league sessions.

Keep climbing those hills and it will keep coming down!

How I feel after some of the sessions

At the moment I have to limit myself to around 120 Watts, so I've no chance of getting up any slope of any significance.

Geoff

Hope you can get back to something sensible.

 

[theboxers]

At my 77.5 kg it I haven't noticed that the resistance maxes out, or maybe I'm just to absorbed...

It took me a while to work it out for my situation. It's not a major issue for me as I am still trying to get somewhere sensible performance wise. A big part of that is weight loss.

 

[Mr. P]

Has anyone compared Zwift figures with Bkool, as both power & speed on similar % inclines seem to be quite varied, yet on the flat they're not so far apart.

 

[g00se]

Be aware they on Zwift, the default setting is to effectively reduce slopes by 50%. It does this by slowing you down for the power you output, similar to giving you a much lower gear.

That's why if you're pedaling gently on a hill, you can effectively come to a stand still.

 

[Mr. P]

Be aware they on Zwift, the default setting is to effectively reduce slopes by 50%. It does this by slowing you down for the power you output, similar to giving you a much lower gear.

That's why if you're pedaling gently on a hill, you can effectively come to a stand still.

Sounds about right. Bkool seems more realistic on uphills for both speed and power output.

 

[g00se]

Sounds about right. Bkool seems more realistic on uphills for both speed and power output.

You can change the effectiveness of the slope in Zwift in the user settings

 

[T.M.H.N.E.T]

You can change the effectiveness of the slope in Zwift in the user settings

Slap it onto max and grit your teeth