ergomo-watss when pedaling w/ right side

How many watts did you get? Maybe this proves that the ergomo computes the right leg power for power input rather than just doubling the left leg?

mtpisgah said:

Due to nasty weather today I rode the trainer. I did a few one legged intervals and had power output when pedaling with only my right leg. It was much lower than with just the left leg but I expected it to be zero or only a few watts. Any ideas?

The pedals are connected you know!
Any slight pull up with your right leg will result in watts, which is part of the reason for doing one legged drills, is it not?

But shouldn't right leg power be transmitted directly to the chainring thus not bending the BB spindle thus not giving a power measurement? Was your left leg still connected thus giving a watts drag reading of your left leg?

"The pedals are connected you know! "

Yes, I realize the pedals are connected. According to everything I have read, the ergomo only registers watts through the left crank. It is the twist of the bottom bracket that the optical sensor reads. Pulling up on the right should not affect the readings.

My left leg was not connected when I was pedaling with only the right. The difference in wattage between left leg and right leg varied depending on the gearing. In an easy gear, spinning at 100rpm, there was more difference in the left/right readings than in a hard gear spinning at 60rpm.

Has anyone else with an ergomo tried this?

mtpisgah said:

Has anyone else with an ergomo tried this?

I have and when doing the same drill it shows zero W for the right side and about twice the W of the Tacx Basic for the left which IMHO is as it should be. Maybe you either should recalibrate or the device is not installed propely.

Speedskater said:

I have and when doing the same drill it shows zero W for the right side and about twice the W of the Tacx Basic for the left which IMHO is as it should be. Maybe you either should recalibrate or the device is not installed propely.

I've got the original ergomo and it reads less when I do right side only. Not that I do one-legged drills (specificity you know!). I might do a few strokes pulling into my driveway. Any small amount that shows up I blame on inertial loading. When spinning the right side, there will be some twist because the "free side" is connected to a mass (crank, pedal). The inertia of the mass will induce some force into the BB.

tigermilk said:

I've got the original ergomo and it reads less when I do right side only. Not that I do one-legged drills (specificity you know!). I might do a few strokes pulling into my driveway. Any small amount that shows up I blame on inertial loading. When spinning the right side, there will be some twist because the "free side" is connected to a mass (crank, pedal). The inertia of the mass will induce some force into the BB.

OK but this should be very low readings. Normally I really get zero if I pedal smoothly on the trainer. At constant rpm there should not be much effect of inertia. Outside, where youn cannot pedal like this, inertia mght be a factor, indeed.

OK, I did some testing tonight and here is what I found:

Put bike on trainer but no resistance on wheel
Perform offset. Offset ok.

Pedal in 53-11 on right: 30-60 watts when I start pedaling but it tapers to 0-8 watts and stays there
Pedal on left: 200 watts

Pedal in 39-19 on right: 30-60 watts tapers to 10-20
Pedal on left: 215 watts

I kept the rpm's the same on all tests.

I then put resistance on the wheel and the numbers were about the same.

On Sunday, I stayed in the small ring most of the time. I believe that it is a combination of the inertia tigermilk mentioned and trying to pedal 60rpm with little to no resistance. I think it is ok, I just worry too much.

mtpisgah said:

...Pedal in 53-11 .....Pedal on left: 200 watts...........
Pedal in 39-19 .....Pedal on left: 215 watts....

So your Ergomo measured 200 to 215 watts with no load on the wheel. I know it's a left hand only test but that still implies 100 watts with no load on the rear wheel. Was that a peak power reading at start up or did it read 200-215 watts after the rear wheel reached steady state? If your PM measures 100 watts with no load in steady state you've either got some really bad wheel bearings, some serious drive train problems, your brake is dragging or the Ergomo is out to lunch. I used to do the steady state spin test after setting the offset on my Ergomo and I never saw more than 10-15 watts when spinning the left crank at a steady state 60-80 rpm.

If you've installed the BB per directions including having the bottom bracket faced and the wires come out at 8 to 11 oclock when viewed from the left then something isn't kosher with your Ergomo and I'd get in touch with them.

daveryanwyoming said:

If you've installed the BB per directions including having the bottom bracket faced and the wires come out at 8 to 11 oclock when viewed from the left then something isn't kosher with your Ergomo and I'd get in touch with them.

Ergomo has restricted the installatin notes even more - at least in the German version of the manual. They now say that the cables have to come out at 9 o´clock exactly. Poor facing of the BB and cables not coming out at 9 o´clock are the two most common mistakes made with Ergomo.

I fixed it this morning and it is fine now. I had the wires coming out at around 10 or 11 o'clock which according to one manual is within spec. I changed it so they come out at 9 (per speedskater) and I am getting 0-5 watts on the right side with resistance and 0 without. Reasonable wattage on the left.

How could the angle of the wires possibly matter that much? I am sure it is not the wire itself but the sensor inside the BB and that it is in line with the wires but still, if it is an optical sensor, you would not think that it matters that much. Obviously, it does.

Thanks guys. Now I can actually start training with power and know that the data is accurate.

PS: Dave, you were right about the front derailleur the other week. I have been working on my own bikes for 10 years and always hated adjusting front derailleurs.

mtpisgah said:

I fixed it this morning and it is fine now. I had the wires coming out at around 10 or 11 o'clock which according to one manual is within spec. I changed it so they come out at 9 (per speedskater) and I am getting 0-5 watts on the right side with resistance and 0 without. Reasonable wattage on the left.

How could the angle of the wires possibly matter that much? I am sure it is not the wire itself but the sensor inside the BB and that it is in line with the wires but still, if it is an optical sensor, you would not think that it matters that much. Obviously, it does.

I have no idea how the angle affects the accuracy of a optical sensor, but it seem to work. I partly felt this 9 vs 8-11 o´clock rule a bit strange but by now there really seems to be some reason to it.

Have fun with your "real" wattage! 🙂

mtpisgah said:

How could the angle of the wires possibly matter that much? I am sure it is not the wire itself but the sensor inside the BB and that it is in line with the wires

You guessed it: apparently having the wires at 9 o'clock assures that the circuit board on which the optical sensors are mounted is vertical, such it doesn't flex (as much). Misalignment between the readings of the two sensors is therefore (largely) limited to that resulting from torque applied to the spindle, versus forces acting in other directions.