Gear Selection

by mechgt

Downloads: 3,361 (5) • Reviews: 3

Version:

1.0.4

Updated:

Jan 31, 2012

Gear ratio calculated from recorded speed data

Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Wed Dec 24, 2014 4:06 pm

Is there any way to calculate the (estimated) gear ratio from speed track?

I know that in ST3 the speed data derived from GPS data overrides the recorded speed data derived from Distance track, but Garmin Fit Devices plugin makes it possible to save recorded spped data to Speed2 track of Custom data tracks.
going further with a formula I could calculate the raw gear ratio from Speed2 and cadence, but I could not assign it to estimated gears just to some "gear zones".

I'd appreciate any comments...
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby old_man_biking » Sun Dec 28, 2014 6:12 am

I've added a "Calculated tracks" feature to Custom Data Tracks plugin a few months ago.
So you can create arbitrary tracks of your own, calculating the track's data points according to a formula that you can design to your needs. It should be quite easy to calculate the crank revolutions per meter from your speed and cadence track and guess the gear from this.
Cheers,
OMB
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 6:35 am

Yeah, sorry to say but I had fully got it before your post; what I lack is the ability to depict that how much time I used eg 34/19 or 50/15 etc.

The ratio can be shown as a line chart with Custom Data Tracks plugin, but not more.
I cant see - for the time being - any integration tool between the lets say Gear_Ration by CDT plugin and the table of Gear ratio plugin.

Am I missing some tool?
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby old_man_biking » Sun Dec 28, 2014 7:14 am

There's no integration between the two plugins.

You can do a dirty little trick in Custom Data Tracks plugin:
Let's assume that you've created a calculated track as of my previous post representing either meters per crank revolution or even a gear number.
* make the "Type" of this track "Power"
* create a new power zone in Other Tasks: Select View: Categories: ...
* and abuse this to represent your gears
* assign this zone to your calculated track
--> you can view the time/distance per zone (= gear) in the Custom Data Tracks detail page.

Cheers,
OMB
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 8:53 am

A good idea, and the level of compromise is acceptable. I mean the trick is OK.

Btw what "custom" as a type means in your plugin? I wanted to use not power as type, but cadence, maybe gear ratio is closer to that, but I found no cadence, just power, speed/pace, HR, elevation and custom.
From manual "when the type is "Custom", the plugin lets you enter an arbitrary unit label"
May I use a category of cadence zones as a custom type?
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby old_man_biking » Sun Dec 28, 2014 9:03 am

Tisztul_A_Visztula wrote:A good idea, and the level of compromise is acceptable. I mean the trick is OK.

Btw what "custom" as a type means in your plugin? I wanted to use not power as type, but cadence, maybe gear ratio is closer to that, but I found no cadence, just power, speed/pace, HR, elevation and custom.
From manual "when the type is "Custom", the plugin lets you enter an arbitrary unit label"
May I use a category of cadence zones as a custom type?

The predefined types ("Speed", "Power", "HR", ...) let the plugin use the correct units for this track (e.g. display speed in km/h or mph according to your settings) and lets the plugin offer the correct subset of categories. "Custom" means: all that is in your control.
I really don't know why I didn't add "Cadence".

Cheers,
OMB
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 9:04 am

OK, a more relevant problem.

Power, cadence and heart rate zones can have 0 digits after comma. Speed can have 1 digit. Only climb zones can have at least two digits which are necessary to separate gears. Moreover they are in %

I mean 50/21 is 4.98 m, 34/14 is 5.08 m if circumference is 2090 mm.

EDIT: forget it, I will simply multiply gear ratio with 209 as cm, not 2.09 as m, and voilá....
I became a bit slow in brain to find the evident solution.
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby old_man_biking » Sun Dec 28, 2014 9:36 am

I would have suggested to use "mm" :)
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 9:37 am

old_man_biking wrote:There's no integration between the two plugins.

You can do a dirty little trick in Custom Data Tracks plugin:
Let's assume that you've created a calculated track as of my previous post representing either meters per crank revolution or even a gear number.
OMB


To be honest I have not. But now i am about to do that and I can not find Speed2 as data point in the Calculation formula/add. Again what was my original wish?

To calculate gear ratio or distance per revolution used Speed2, which is a custom data track. GFD plugin imports recorded speed data into Custom data tracks plugin. In Custom data tracks I can see Speed2 and it seems that it is what I need. But as far as I understand Custom data tracks plugin does not let me use any custom data tracks for calculating another.

I am afraid I am confused.
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby old_man_biking » Sun Dec 28, 2014 10:55 am

Ouch, you are right.
Using values of custom data tracks in the calculation formula is not yet supported - still on my to do list.

Cheers,
OMB
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 11:21 am

In the meantime i played a lot with the standard speed data points. The biggest problem is not the accuracy of speed (it is the second biggest), but the lack of 'if' function and the lack of referring to previous data point, because when you coast or partly coast (=rpm is not zero, but pedalling is not strong enough vs the actual speed), the calculation is faulty. If you partly coast even at relatively modest speed on any descents, it seems that you are in a pretty high gear, which is not true generally, if you are just over a short hill top. My method was to set a high rpm cutoff of 50 or 60 saying that under 50 or 60 there is coasting.

But I am not pleased with the result I got.

Referring to the ouch of yours instead of inserting an emoticon, let me refer to https://www.youtube.com/watch?v=FQWwaqMSAfY

;-)
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby texmurphy » Sun Dec 28, 2014 3:04 pm

Isaac will display Gear Ratio based on wheel speed sensor, tire size and cadence. So if you are using your iBike you should be able to build the gear track from an Isaac exported csv equivalent to using speed 2 and filtering for power=zero but cad>0.
Gear Ratio.jpg
Gear Ratio.jpg (232 KiB) Viewed 26844 times
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 3:59 pm

Thx Tex for the hint.

D'you mean building the gear track in excel or somewhere in ST3?
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Dec 28, 2014 4:04 pm

The ultimate solution would be that CDT plugin have all the options as Calculated Fields plugin. But to be fair the latter plugin has some drawbacks if you would like to use a calculated data field for another one too. It does not have calculation order as a facility, moreover this plugin has at least one nasty bug, because I can prove that short term peak power calculation is not consistent with underlying power data. Eg for Peak power over 5 sec the best (but not perfectly accurate!) formula is {MAXPEAKTIME(Power,4)}
Cheers,
Zoltan
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Re: Gear ratio calculated from recorded speed data

Postby Tisztul_A_Visztula » Sun Jan 04, 2015 1:58 pm

old_man_biking wrote:Ouch, you are right.
Using values of custom data tracks in the calculation formula is not yet supported - still on my to do list.

Cheers,
OMB


Aha, an after-Xmas present for a Xmas idea :-)
Cheers,
Zoltan
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