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I just give up, will you ...
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Attempt at cheap homemade...
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12-04-2017, 06:42 PM
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  Attempt at cheap homemade version of Harmony
Posté par : Oran - 04-10-2016, 06:51 PM - Forum : Support and DIY (English) - Réponses (69)

I'm wanting to install an N380 on a road bike. The issue is the standard NuVinci shifter doesn't fit curved handlebars. I could find a different shifter and modify it or make a shifter but I liked the idea of experimenting with an electronic shifter. I'm wanting to learn about Arduino's and programming, so thought I would base it around one. This would also give interesting possibilities of automating the shifting.

To start with I want to get it working as a manual shifter using a potentiometer as the handlebar control. Then I will move on to the challenge of changing the potentiometer from a ratio selector to setting the desired cadence.

[Image: WP_20160405_010_zpsczujbjmg.jpg]
Very quickly put together a circuit and uploaded a basic servo control program to the Arduino, works great. The pulsed DC to voltage convertor circuits I'm hoping to use can be seen in the photo.

[Image: WP_20160409_008_zpsgr9sq263.jpg]
Next was making the mechanics so that the 180° of rotation of the servo is converted into 95mm of pull needed for the shift interface. The cable drum had to be made out of individual pieces as I have no way of turning it. This meant I could cut a cable anchor into the drum (see photo). This enables me to use second hand cable which has broken off in a shifter instead of buying two new cables.

[Image: WP_20160410_015_zpsx0lhae48.jpg]
This is how far I got with it today the servo can now control the shift interface. A couple of potentiometers just arrived in the post. One of them I'm interested in experimenting with is logarithmic. I'll set it up so that the shifter moves quickest in low ratios and slow near overdrive. This will better match the shift rate to acceleration and give better fine tuning when cruising at higher speeds. That's the theory but we'll see if its usable in practice. I expect there's a way of programming the Arduino to mimic this and in a more customizable way.

A few ideas I've got for automating the shifter. I will always want to keep the option of manual so will have a switch to select between manual and auto.
I'm currently planning to use reed switch sensors from a cycle computer and input into the Arduino as a voltage. For this I have two pulsed DC to voltage converter circuits that I made for a college project a while ago.

What I need to experiment with to find out which is best is whether to monitor wheel or crank rpm or both. I like the idea of monitoring cadence but I think it could result in a lot of unnecessary shifting. To reduce this might result in an annoying lag in shifting when accelerating. Wheel rpm would be more stable but I would need to program the Arduino so that it knows what servo position for any given speed.

Lots to think about but first I want to temporary attach it to a bike in it's current state to see how I feel about it. Then I can work on waterproofing everything.

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  Review of the N380
Posté par : Oran - 04-06-2016, 08:02 AM - Forum : General Discussions (English) - Réponses (3)

I thought it was time to get hold of an N380. I bought my first N360 4 1/2 years ago and had 3 free replacements since then. During that time stator wear has been an issue with the N360s and traction fluid leaks. Despite this the reliability of the N360s for me has been 100%, never been left walking.

The N380 is supposed to have this issue fixed and is sold as a superior and heavy duty version. I shall be testing to see if it really is suitable for cargo bikes up to 168kg. This is just an initial review, I will report back on any stator wear when I have done some miles.

First impressions are that the build quality is better. Little things like the freewheel makes a much louder more positive clicking noise. The hub spins nice and freely like a well worn in N360 does, so hopefully they have perfected the oil seals. They just seem to have perfected the manufacturing process, better quality control perhaps. Maybe all the substandard parts are going in to the N330s.

Looking inside the hub I was expecting to see some sort of major redesign of the stator and planet axles. The planet axle end caps are the same as in the 2012 model N360. The change must be in the hardness of the magnesium stator. It was definitely harder to drill the holes for the magnets. Last time I could just push the magnets in but with the N380 I had to give them a few small taps.

[Image: Aviary%20Photo_131043602879959650_zpsehvi3zeh.jpg]
No noticeable difference in the stator guide slots, accept for the small alterations to increase the overdrive ratio.
[Image: P1010056_zpskr8vxthf.jpg]
[Image: P1010062_zpsmfnczrv5.jpg]
Whilst I had the hub open I added some magnets to the stator. Should keep the traction fluid a little cleaner.
[Image: WP_20160404_004_zpsmagb75ri.jpg]

Ride experience, well my first impressions are that its more efficient especially in underdrive, seems to be less drag. Could just be that my bushing modification is making the other hub less efficient. Really want to investigate this in more depth soon.
I really like the increased ratio range because I found the 360% was never quite enough. Using the min sprocket ratio meant that top speed was around 15mph so I choose to have two chainrings. The N380 at min sprocket ratio gives a range of approx 5 - 18mph making a single chainring a much more viable option.
A future project I'm looking forward to is putting the N380 on a road bike and making an electronic shifter. I will keep the two chainrings 52/34t and 18t sprocket giving a massive speed range of 5 to over 30mph.

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  New posts to come soon.
Posté par : Oran - 03-24-2016, 01:04 PM - Forum : General Discussions (English) - Réponses (1)

Has been a while since I last posted but I haven't given up on NuVinci hubs. My modified one has done another 1000 miles without any issues. Nothing interesting to report on recently but hoping to change that soon.

I want to get an N380 and have a look inside to see what Fallbrook has done about the metal hardness issue. My modification works but isn't perfect. Regular bushing replacements, reduced overdrive ratio when they're worn and possibly reduced efficiency.

Get hold of a power meter such as Garmin Vector pedals most likely by renting. See if I can get some data that will show the hubs efficiency. Ride the same roads and keep swapping between derailleur and NuVinci. I think there will be some interesting things to learn about how the NuVinci's squishiness affects pedal stroke.

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