Flow standard braking

Fortius, i-Magic , Cosmos, Flow , upgrade kits

Moderators: malfukt, Tacx support, mcorn, Tacx Moderator, Nasz, Fortius Magical Man

Post Reply
Alterastro
Posts: 2
Joined: Fri Sep 01, 2017 12:31 pm

Flow standard braking

Post by Alterastro » Fri Sep 01, 2017 12:44 pm

Hi all. Newbie Nick here!
So I have a Flow and am loving it! But I have a question - be gentle!
I’m using a mountain bike but have a tacx trainer tyre. When using the videos I have to have it in the highest gear for riding on the flat otherwise cadence is too fast, for me anyway! Only changing down a few gears for climbing. It is calibrated in the green zone. The question is, is this normal or have I set something up wrong? Even for calibrating I have to have it in the highest gear otherwise I pedal like the clappers and only just make 30kph!

Also, how does Flow work out cadence without a sensor? Will it be better/more accurate to get a sensor?

Thanks in advance!

Nick

frankhertz
Posts: 36
Joined: Sun Jun 16, 2013 4:02 pm
Location: Toronto, Canada

Re: Flow standard braking

Post by frankhertz » Fri Sep 01, 2017 2:50 pm

The relationship between speed (V) and cadence (cad) is can be approximately calculated as follows:

V = (cad/60 [to convert rpm to rev/second]) x (R [the ratio of the chain ring size to cog size. i.e. Chain ring size/cog size]) x C ([The circumference of the rear wheel with tire, which you can measure or if you have the diameter (D), use C = 3.14xD]) x 3.6 [to convert from m/s to km/h].

An example for a road wheel at 100 rpm using a 700 c (diameter approx .7 m) tire with a 53 chain ring and a 12 cog:

V=cad/60xRxCx3.6

V=(100/60)x(53/12)x(3.14x.7)x3.6

V is approximately 58 km/h. You would get a better estimate using the measured circumference C.

You can see that if the R is smaller which it usually is on a mountain bike drive train and the wheel diameter is smaller you will not go as fast for a given cadence. So it may not be unusual for you to pedal like the blazes to get a speed of 30 km/h depending on the drive train setup.

As to the second part of your question, as far as I remember I had an external cadence sensor that plugged into the brake unit. It is the same unit that also plugs in to my Fortius brake unit.

I hope I have not misunderstood your question.

Harry

mcorn
Moderator
Posts: 7436
Joined: Fri Nov 24, 2006 8:55 pm
Location: USA, Bellingham, Washington

Re: Flow standard braking

Post by mcorn » Fri Sep 01, 2017 5:39 pm

Alterastro wrote:
Fri Sep 01, 2017 12:44 pm
Hi all. Newbie Nick here!
So I have a Flow and am loving it! But I have a question - be gentle!
I’m using a mountain bike but have a tacx trainer tyre. When using the videos I have to have it in the highest gear for riding on the flat otherwise cadence is too fast, for me anyway! Only changing down a few gears for climbing. It is calibrated in the green zone. The question is, is this normal or have I set something up wrong? Even for calibrating I have to have it in the highest gear otherwise I pedal like the clappers and only just make 30kph!

Also, how does Flow work out cadence without a sensor? Will it be better/more accurate to get a sensor?

Thanks in advance!

Nick
Nick-

In order to get cadence, you need a separate sensor. However, cadence is not required for the brake to produce resistance. Even though the Flow is a modest brake in terms of the resistance it can produce, you can still get a good workout. It sounds to me like your brake is not working correctly as you should be feeling a lot more resistance. At 30kmh/20mph you should feel about between 125 watts and 350 watts of resistance, depending on the terrain.

Be sure you have the correct weight programmed into the software.

Alterastro
Posts: 2
Joined: Fri Sep 01, 2017 12:31 pm

Re: Flow standard braking

Post by Alterastro » Sun Sep 03, 2017 11:38 pm

Thanks guys.

I kind of realise a mountain bike isn’t ideal, but I think the Flow is working ok as any slope increases the braking as it should. It just seems the default braking (when cycling on the flat) isn’t enough. Is there a way to increase it on the Flow or the cycling App?

As far as cadence goes, the app shows cadence but I don’t have a sensor on the bike, so not sure how it knows...

Thanks again

Nick

mcorn
Moderator
Posts: 7436
Joined: Fri Nov 24, 2006 8:55 pm
Location: USA, Bellingham, Washington

Re: Flow standard braking

Post by mcorn » Mon Sep 04, 2017 12:08 am

Alterastro wrote:
Sun Sep 03, 2017 11:38 pm
Thanks guys.

I kind of realise a mountain bike isn’t ideal, but I think the Flow is working ok as any slope increases the braking as it should. It just seems the default braking (when cycling on the flat) isn’t enough. Is there a way to increase it on the Flow or the cycling App?

As far as cadence goes, the app shows cadence but I don’t have a sensor on the bike, so not sure how it knows...

Thanks again

Nick
I think we thought you had an older Imagic/Flow with a separate cadence sensor. You must have a Smart version with cadence sensing built into the brake. I still think something is not right as you should not be able to overpower the brake (unless you are capable of riding over 30 mph and generating 400 watts continuously for long periods).

Post Reply

Return to “Fortius - i-magic - Cosmos”

Who is online

Users browsing this forum: No registered users and 4 guests