gbrown
Geoff on Bkool
- Location
- South Somerset
Team BKool CycleChat
- Thread starter Peteaud
- Start date
Page may contain affiliate links. Please see terms for details.
Add
Guru
- Location
- Powys, Wales
Well, well, well! A full 18 hours in bed! NOT GOOD! And what pains me most, is listening to the sound of my wife dowstairs on the Turbo Trainer!
gbrown
Geoff on Bkool
- Location
- South Somerset
Add
Guru
- Location
- Powys, Wales
Lol! Ill, kids and wife have had it all over christmas, thought it was too good to be true that I had avoided it! Avatar is my youngest, a biker in the making I suspect.
gbrown
Geoff on Bkool
- Location
- South Somerset
Please can I ask my fellow Bkoolers help with a little experiment, should take about 10 to 15 minutes during a warm up.
Due to a fundamental disagreement between the Bkool Indoor simulator and my Powertap power meter, I've been trying to figure out how many Watts it should really take to cycle on the Bkool at a certain pace.
Please could as many of you as possible choose a flat 0% gradient (my http://www.bkool.com/profile/detail/586338?durationType=DISTANCE&lapCount=1 starts with a 0% section) and cycle at a steady 10 mph (16 kph) for a few minutes, until the power reading settles to a constant value, and note the power reading.
Then stop pedalling until speed reaches zero, and try again, getting backup up to 10 mph as quickly as possible and trying to maintain exactly that speed.
Then, if possible, repeat the experiment with 20 mph and 30 mph.
Then post the power readings here, along with your weight (although at a steady speed on a 0% gradient weight should not be a factor, just virtual "wind" and rolling resistance), so we can compare them.
Theoretically, since weight is only a factor in acceleration, and since rolling resistance and aerodynamic drag are not specified variables in the Bkool system, we should all generate the same power figures.
Also, since rolling resistance and drag should be constant at a constant speed and weight not a factor at 0% gradient, the power figure should be constant at a constant speed.
Thanks for any help on this ...
Geoff
Due to a fundamental disagreement between the Bkool Indoor simulator and my Powertap power meter, I've been trying to figure out how many Watts it should really take to cycle on the Bkool at a certain pace.
Please could as many of you as possible choose a flat 0% gradient (my http://www.bkool.com/profile/detail/586338?durationType=DISTANCE&lapCount=1 starts with a 0% section) and cycle at a steady 10 mph (16 kph) for a few minutes, until the power reading settles to a constant value, and note the power reading.
Then stop pedalling until speed reaches zero, and try again, getting backup up to 10 mph as quickly as possible and trying to maintain exactly that speed.
Then, if possible, repeat the experiment with 20 mph and 30 mph.
Then post the power readings here, along with your weight (although at a steady speed on a 0% gradient weight should not be a factor, just virtual "wind" and rolling resistance), so we can compare them.
Theoretically, since weight is only a factor in acceleration, and since rolling resistance and aerodynamic drag are not specified variables in the Bkool system, we should all generate the same power figures.
Also, since rolling resistance and drag should be constant at a constant speed and weight not a factor at 0% gradient, the power figure should be constant at a constant speed.
Thanks for any help on this ...
Geoff
Add
Guru
- Location
- Powys, Wales
The way I feel atm, I can probably manage the 10mph and 20mph at a push, but good luck getting 30 mph out of me. I'd also better move my turbo into the bathroom!
Randyberlin
Guru
- Location
- Sitka, Alaska
At 10 mph 52 to 55 watts
At 20 mph 138 to 152 watts
At 30 mph 338 watts (didn't drop back to 0- tough enough holding it steady)
206 pounds Not quite as big as Add's old avatar, but a normal weight (and normal name) in Alaska.
At 20 mph 138 to 152 watts
At 30 mph 338 watts (didn't drop back to 0- tough enough holding it steady)
206 pounds Not quite as big as Add's old avatar, but a normal weight (and normal name) in Alaska.
Last edited:
Was hanging on to see how zwift turns out. That's why I ended up buying an Elite trainer rather than being closed into bkools system. Have to say the last session on bkool makes me feels better about it, after a month faffing about!
Shanks
Well-Known Member
- Location
- Chichester
Hi , I'm here and keen to keep in the Thursday night group. Been a cc member for years but a confirmed lurker so you won't see many posts. I try to make sure the few are worthwhile though. I've had this bug all over the break so haven't been near any bike for two weeks almost. Had a tentative trip round the velodrome today and hope to ride last week's set route tomorrow if I can before the cut off. Cheers
At 10 mph 36 to 40 watts
At 20 mph 120 to 160 watts
At 30 mph 300 to 350 watts
And I weigh 170 lbs
While doing this the figures were all over the place. Not just the watts but the speed as well so it was difficult to do accurately.
johnny2names
Regular
Geoff, I've only just seen your request- I will try and do that for you tomorrow. Would it be useful to do a 10 min straight at constant pace on the velodrome?
Whilst faffing around on the internet the other day, I came across a pretty cool website, with plenty of info on the physics behind speed/power relationships in cycling, with a neat interactive comparator. Without having the tools to do a sophisticated calculation of frontal area/rolling resistance etc..., I just played around with speed,power,weight,slope using the default other settings, even though my frontal area will by default be bigger than average ( 6'3'', 95 kgs...). It's really interesting to see you much air resistance takes over at higher speeds/ gravity conquers all on steep gradients. here's the link:
http://www.gribble.org/cycling/power_v_speed.html
running the models standard numbers, with rider 75 kg, bike 8 kg, gives: 16 kph, 36W - 32 kph, 180W - 48 kph, 536W.
To get more in line with a 350W output at 30 mph, changing frontal area to 0.4 and drag coeff to 0.5 gives 30/126/355 Watts respectively.
I have no idea what bkool uses as a model, and what coeffs they use. Indeed, is it sophisticated enough a model to vary frontal area assumptions with height and weight? does it use different coeffs for the velodrome ( to reflect track bike, velodrome ideal temp, and very aggresive rider position)? One thing I can safely say is that I could never hold 44 kph for 20 odd minutes on a pan flat road on a windless day on my roadbike, which Is what I did on the 17.5k velodrome session of the other week. In fact I'm pretty sure it would be somewhere between 35 and 38 kph. Also, on my climbing effort today ( puerto mijares, mountain goats league), I'm fairly certain I would have been substantially slower in real life, perhaps 10-20% slower.
Back to the more specific bkool calibration, my data was all over the shop prior to installing new firmware- I had to make sure I ran it whilst the trainer was switched on and I had my laptop within approx 1 meter of it. If you think your data is total bogus, try uninstalling current bsim, then reinstalling as per above- hopefully that resolves that issue. I've gone from amateur 3 to amateur 9 as a result- I ain't complaining!
hope this helps
Whilst faffing around on the internet the other day, I came across a pretty cool website, with plenty of info on the physics behind speed/power relationships in cycling, with a neat interactive comparator. Without having the tools to do a sophisticated calculation of frontal area/rolling resistance etc..., I just played around with speed,power,weight,slope using the default other settings, even though my frontal area will by default be bigger than average ( 6'3'', 95 kgs...). It's really interesting to see you much air resistance takes over at higher speeds/ gravity conquers all on steep gradients. here's the link:
http://www.gribble.org/cycling/power_v_speed.html
running the models standard numbers, with rider 75 kg, bike 8 kg, gives: 16 kph, 36W - 32 kph, 180W - 48 kph, 536W.
To get more in line with a 350W output at 30 mph, changing frontal area to 0.4 and drag coeff to 0.5 gives 30/126/355 Watts respectively.
I have no idea what bkool uses as a model, and what coeffs they use. Indeed, is it sophisticated enough a model to vary frontal area assumptions with height and weight? does it use different coeffs for the velodrome ( to reflect track bike, velodrome ideal temp, and very aggresive rider position)? One thing I can safely say is that I could never hold 44 kph for 20 odd minutes on a pan flat road on a windless day on my roadbike, which Is what I did on the 17.5k velodrome session of the other week. In fact I'm pretty sure it would be somewhere between 35 and 38 kph. Also, on my climbing effort today ( puerto mijares, mountain goats league), I'm fairly certain I would have been substantially slower in real life, perhaps 10-20% slower.
Back to the more specific bkool calibration, my data was all over the shop prior to installing new firmware- I had to make sure I ran it whilst the trainer was switched on and I had my laptop within approx 1 meter of it. If you think your data is total bogus, try uninstalling current bsim, then reinstalling as per above- hopefully that resolves that issue. I've gone from amateur 3 to amateur 9 as a result- I ain't complaining!
hope this helps
