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Efficiency, getting real data
#51
Have some nice time with your relatives, see you on october.
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Si ça a déjà été fait, je peux le faire
Si ça n'a jamais été fait, donnez-moi juste le temps de trouver comment !


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#52
The search for a motor continues. After further investigation the old extractor fan motor turned out to be beyond repair. It’s a shame because it had all the right specifications.

The pressures now on to get results because I need to build the hub into a wheel as I may need to use it soon. The bearing is getting a bit loose on the 2012 hub I’m currently using. Will write more about this soon, I’m currently e-mailing Fallbrook. I also need the alternator for a wind turbine.
- Oran
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#53
This project will be delayed for a while.

The hub I was testing the efficiency of is now needed for my bicycle and has been built into a wheel. I'll have to wait and see if Fallbrook replaces my worn-out 2012 model hub.

The search for a motor will continue.
- Oran
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#54
I have now received a new hub and I’m thinking of testing its efficiency. As the efficiency seems to suffer as a hub wears out it makes sense to test one in good condition. One day maybe Fallbrook will bring out a redesigned model of the hub which will be as good as new even after 1000s of miles.

I’m aware of the breaking in period but don’t feel its really an issue. The losses due to seals are relatively small compared to the other inefficacies. Also the seal resistance can vary considerably between hubs. Wheel not spinning freely topic contains more information.

The only thing holding up this project is finding a suitable motor which is proving to be difficult.
- Oran
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#55
I know its been a very long time since I’ve done anything to this project but I found the permanent magnet generator in my workshop recently. It made me think about how much I’ve learnt over the past couple of years about Arduinos, data logging and I even have a power meter. I’m now far more equipped to make a serious attempt at measuring the efficiency of a NuVinci hub.


My initial ideas are to replace the motor with leg power and the power meter. This would give a more realistic condition to measure the efficiency under. The sprocket on the disc brake mount would drive the permanent magnet generator similar to before. This would need to increase the rpm quite a bit to get a high power dissipation at low hub ratios.

The accuracy of my power meter wouldn’t be that important as I’d have to calibrate the PMG power output measurement to equal the power meter. This takes out drive train and other unknown losses. I would do this with the hubs input locked to the output and over a range of rpms and PMG load resistances. The great thing about doing the project with my knowledge of Arduinos is that I can easily measure and log things like rpm and power measurements and do calculations on them. Once the calculations are calibrated to give 100% efficiency I could unlock the hubs input and output and see live the efficiency loss due to the hub.

When I will actually be able to work on this project I don’t know. The power meter is in Wales and my workshop and PMG are on a Scottish island.
- Oran
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