Advice on Scale Factors please.

I have two sets of Vector 3. On one set I usually get a L/R balance of approximately 48% / 52% so I decided to do a static torque test to see if there was a difference in the pedals.

The average results were L = 24.725 R = 25.03

As the mass being used was just over 15kg I am taking it that the R is more or less correct and would imply a mass of 15.0087Kg (G=9.81 and Crank = 170mm)

I decided to change the scale factor of the L pedal. I changed it to 25.03/24.725 = 1.0123.

If I do the static torque test again should I expect to see different torque results or is the scale factor only applied to calculate the power?

Nick

0 aweatherall over 3 years ago

The static torque test will report the raw value, not the value adjusted by the scale factor. The scale factor will get applied to the torque values sent to the Edge to produce the power numbers.

0 nickdodo over 3 years ago in reply to aweatherall

Thanks awetheralll

That's good as it seemed to make no difference to the static test. These tests are very difficult to do as the numbers keep changing. I guess there is no simple way of preventing this. Also trying to ensure the crank is level is not easy.

Nick

0 TriMan66 over 3 years ago in reply to nickdodo

I to have tried doing the static test and find it difficult as well. I think since we are holding the wheel by hand the imperceptible movement of our hand imparts a change that the pedal registers. It is extremely sensitive.

I think to do a really accurate test you would need an isolated stand and have the crank arm mounted firmly to the stand through the hole where it attaches to the spindle, then add the weight and wait till the whole setup stops oscillating.

The first pedals I got had a scaling factor already set but the bearing at the outer edge just underneath the battery housing got damaged. It is a very small bearing and seems to be quite fragile, a rather poor design.

Garmin has replaced the pedals twice already, on my 3rd pair. This latest pair were not calibrated at all, their scaling factors where at 1.000 for both. I was getting nearly a 10% difference between left and right 45% and 55%.

0 nickdodo over 3 years ago in reply to TriMan66

TriMan66,

I did three sets of 3 on each side. I averaged each set of three and they were very close so I figured that was about it. The scale factors worked out to 1.0123 L and 1.0 R. So they were close to correct at 1.0 (which is what I'd expect. I'd expect the factory calibration to set them to be 1.0 to be correct). That would mean that only a small drift from the factory setting for my L pedal.

I have two sets of pedals and when I did the second set they came so close to 1.0 on both sides that I left the scale factors at 1.0 on both L and R.

This was I'd expect from experience as one pair were showing me slightly less balanced than the other. Now they so close that I couldn't tell which pair I'm riding.

Nick

0 Luko79 over 3 years ago in reply to nickdodo

When i did such a static torque test with Vector1 in the past (5years ago or more), i put my bike on a wheel-on trainer, which was raised with 40cm from floor . i hanged a 20kg weight on pedals with a hook, and i played with the rear wheel to find the absolute horizontal crank position (which leads to the highest torque number), i did it 3-3 times too, averaged the values but these were very close to each (within 0.03 NM) which is 0.1% error. After it i put my bike on my Neo and did a dual measurement, and the Vectors were above Neo @200 with 1-2w which is pinpoint accuracy. It was an easy task (i made lots of such a calibration with BePros for clients)