Using the NuVinci hub on my e-bike

[tapholov]

hi,

still living with the NuVinci hub...

So far....

I think that the hub takes a lot of Hp out of the motor. It's fun to shift ratios and hear the motor humm differently...

But I really wonder whether it was that bad to only think about direction and not transmission....

After all, the electric motor is all about constant torque and in terms of transmiting that torque to the rear wheel, it really doesn't matter what gear you'r in, the motor will pull or not...

and power doesn't appear instantly. Unless you have millions of volts, it's still a bicycle, so, there must be a limit...

Riding these electric bike is a lesson in 'consistency'....

Just imagine traffic jams of electric vehicules, all needing a charge very soon....



So, right now, I'm still thinking and I have a 24" rim at my side. I'll try to reduce the ratio from motor to the wheel a little more. I want to get the full extent of the NuVinci. It might be that the motor is not powerfull enough....


I'm waiting for things, I got the 24" rim but I'm also waiting for 48V batteries. Things go on...

I'll try go figure out how to include YouTube things in here but right now,

go to YouTube.com and search for Tapholov,

and enjoy how I can get free transportation out of spending a lot of money....


Bye for now!


Hugues

[Mark_A_W]

Hugues, can you please post some more pics of your bike?

I think I have the same frame - I have a Jamis Dakar XC Comp.


Nice brakes, and what is the front wheel? It looks like a Tag wheel on an Optibike...they are $800 a pair I think?


I watched your Youtube videos. Goes really well, only downside I can see (hear?) is the noise of the motor or front chain.

[tapholov]

Hi Mark,

Thanks for the good comment.

My frame is a Jamis Jakar 20th anniversary edition 2005. I bought it from a guy in Japan and it made it all the way to Canada no problems.

It took a good part of last winter to find the usual accessories on E-Bay and I am really pleased with the results.

The wheels are simple aluminium mag wheels that a fellow on e-bay sells for the 49cc motorised schwinn but I've also seen them a little cheaper from another e-bay guy located in Taiwan (where everything is made...) I really liked the idea of going spokeless and it wasn't that expensive, maybe $225 for the set. I of course had to discard the rear wheel when I moved to the NuVinvi hub. It went on the other bike.

So, I've made my new purchases today and I'm ready to switch the 26" rear wheel for a 24" and see whether I can use the overdrive a bit more... and get more hill-clibing ability out of my motor.

And yes, a big drawback is the noise. I think it's the motor that growls. It turns heads, especially at night. Not very stealth.

Anyway, I'll let the forum know of my progress.


Bye for now, more pictures soon.


Hugues

[Mark_A_W]

Hmm...that first stage could be a belt drive...you'd have to look into the power and speed limits for a belt though.

[tapholov]

Hi,

Finally got the 24" rim on the NuVinci hub. Took a few days because one of my cats managed to hide one little spoke out of sight and I couldn't go back to the store right away to get another one.

So, esthetically, there's not that much difference between the 26" and the 24". Just more room under the fender.

One big discovery however was done while the wheel was disassembled because I did put the old wheel back for a while (got to go to work, right!)

Well, I felt I was riding a cloud. The motor pulled like crazy, went quickly to its top speed and actually got its watts at the recommended spot.

Back to the bench.

Using a tachometer, I tested the NuVinci hub. Sure enough there is that 350% difference in wheel speed depending on the setting but the motor certainly turns slower. Let's put this simply. With the wheel totally free to roll, the motor turned at a 1000rpm (read the P.S. note). Without the NuVinci hub, same size wheel, the motor turned at 1500 rpm. Ain't that amazing! The Nuvinci hub steals 33% of the power of the motor.

Translated into riding/power terms, this is why at top speed (42km/h) with the normal wheel, the motor goes from needing 1200W to a comfortable 750W. I could never attain that with the NuVinci. Top speed is 38km/h and the motor always struggles at 1200W. When I think about it, it's not so good, the motor heats up quickly, the controller probably go 'what the hell!!', etc...

On with the 24" wheel.

Well, I got the full range of the NuVinci hub, and at the almost highest ratio right now, the bike goes at 38km/h and I have correspondingly a little more underdrive. While riding up and down trails and doing some flat-ground testing, I was finally able to reduce that power demand (1200W to 750W) but then the bike only goes at 27km/h.

Everything kinda corresponds. The Nuvinci eats up 1/3 of everything, everything else being equal. It's something that might not be readily noticable at low speed but that becomes evident at higher ones.

I need more power and I'll be able to do that once I get the 48V batteries...

But then, the lightness of the regular hub tempts me a lot now and I'm debating where to go next. Using the NuVinci hasn't made the bike a lot more versatile, just heavier. There's more choices but no surprising results. I could compare this to using an automatic versus a standard transmission on a car. Both will get you going but it's really a question of attitude. Yes, the standard transmission will get you out of snowbanks easier but we usually forget that the automatic transmission has a low gear set-up.

That's what I might be aiming towards now. There only needs to be two speeds: high and low and I do know that there's a amazing long post that deals with that (from RC motors to transmissions).

It's all about having a good trail-bike or a good roadster. Different demands that lead to differend set-up/speeds. I'll definitively try the NuVinci with the 48V battery but I'm also thinking about removing the NuVinci hub from the 24" wheel and setting it up for hill-climbing/trail ride with a regular hub. Going up trails at 25/30 km/h isn't bad taking into consideration the uneven terrain. I could alternatively put another gear on the 26" wheel and depending on the situation, flip the chain from one to the other myself.

Anyway, that's in the future. Right now, I'm waiting for those batteries.

Bye for now,

Tapholov


P.S. I have part of the rpm tests on YouTube.com (search for tapholov) and for you purists, I'll mention that the motor should have been going at more than a 1000 rpm. I don't know why the tachometer only showed a 1000. Later tests showed 5000 and then an amazing 10000. It's a small gear to aim at with the laser beam. However, what is important is that all the tests were consistent within a short period, switching gears and switching wheels.

[Mark_A_W]

Apparently the NuVinci needs to run in to loosen up?

Is yours run in?

[tapholov]

Hi Mark,

I guess it's broken in, I've got about 75 km on it and I really can't see how it would spin better.

With the older wheel, a normal cassette-type freewheel with minimum friction, I wank the motor and it spins forever. With the NuVinci, the wheel stops quickly. There's just a lot of friction.

I'm a little disappointed but then, what was I expecting?

As was my intention to say before, I wish I had a strong enough motor to pull the resistance, but it's eating away my power. And it's going to do the same thing with the 48V batteries. More power but more friction that eats away that power. I'll gain but my feeling is that the 48Vs are also going to be quite an improvement with the normal wheel, maybe more so. An improvement that will negate the fact that with the NuVinci, I have a variable transmission. I really thing that I should only have two speeds: High and low, fast or powerfull.

So, this is an on-going thing and I'll see what's up as it comes.

Thank you for following this post. I'll have a pic of the whole bike in the coming days.

Hasta la vista,

Tapholov