Avanti Electra axial flux hubmotor - just for fun

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voicecoils
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Avanti Electra axial flux hubmotor - just for fun

Post by voicecoils » Apr 24, 2015 12:23 am

Back in 2010, Liveforphysics made a thread asking if anyone had one of the hubmotors made for the Avanti Electra. Here's the original thread:
https://endless-sphere.com/forums/viewto ... =2&t=22255

Apparently about 1000 of them were made and sold around the year 2006. The actual motor development was done by a company called IMT Motors from the Northern Territories which had a background in motor development for solar car racing.

The complete bikes looked pretty ordinary:
Avanti_Electra-complete-bike.jpg
Avanti_Electra-complete-bike.jpg (99.69 KiB) Viewed 1422 times


Fast forward to today and I've got one which came with a blown controller and a bit of a wobble in the rim. Although I don't have any immediate need for an ebike with an 8kg front wheel, this motor has so many interesting design characteristics compared to most conventional hubmotors, I thought it would be fun to play around with.

First, here's photos of the wheel from both sides:
Avanti-Electra-axial-flux-drive-side.jpg
Avanti-Electra-axial-flux-drive-side.jpg (150.81 KiB) Viewed 1422 times
Avanti-Electra-axial-flux-non-drive-side.jpg
Avanti-Electra-axial-flux-non-drive-side.jpg (145.58 KiB) Viewed 1422 times
Some items of note externally:
* the silver right side (drive side) rotates while the entire black left side is stationary
* attaches to the bike fork with a quick release skewer
* one long bolt on the stator appears to connect to the bicycle's fork to act as torque arm
* drive side spokes radiate 2 cross from near the centre of the hub
* non-drive side spokes connect at the hub's perimeter and are also 2 cross but banded in pairs with stainless rings

Here's some internal photos from the thread I linked to above, showing magnets (rotor) and the windings (stator):
avanti-magssmall.jpg
avanti-magssmall.jpg (47.29 KiB) Viewed 1422 times
avanti-coilssmall.jpg
avanti-coilssmall.jpg (59.07 KiB) Viewed 1422 times
Anyone know how many pole pairs the motor has? I count 16 magnets and 48 stator slots. Normally I would have thought 16 magnets means 8 pole-pairs but with so many stator teeth in the axial-flux design I'm not so sure.

I plan to fool around with the motor first using the GrinTech ASI FOC controller which can do both sensored and sensorless control.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by voicecoils » Apr 24, 2015 12:26 am

*Reserved* for initial findings

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by riba2233 » Apr 24, 2015 1:55 am

Yeah it's 8 pole pairs :)

Nice find, testing will be very interesting :mrgreen:

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by voicecoils » Apr 24, 2015 4:36 am

riba2233 wrote:Yeah it's 8 pole pairs :)

Nice find, testing will be very interesting :mrgreen:
Cool, thanks for the confirmation. I've had a little chance to play around with the motor with the ASI controller in sensorless mode. Interestingly, it does not want to start when the software is set to 8 poles. It judders as if it's firing phases in the wrong order. However, if I set it to a higher multiple of 8, like 96 poles it will spin up smoothly provided the hub is already turning at a low speed.

On a ~40v battery, it spins at least 1100 rpm according to the Cycle Analyst external speedo. Perhaps that's because it was designed to run on a 12v13Ah lead acid battery :lol: I'll need to mount the motor more sturdily before holding open full throttle and finding out exactly what the max RPM is (and hence RPM/volt) with the controller set to zero field weakening.

Here's some no load power consumption stats I took:

RPM Watts
220 12
380 21
540 45
660 60
760 85
(this is in a 700c wheel with tyre & tube)

ASI's BACDoor software suit polls the motor during setup so here's a few more electrical stats:
Ls 42-43 uHenrie
Rs 37-38 mOhms

I will also try to tap into the motor's hall sensors in the next few days and try sensored startup which will hopefully improve low speed operation.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by voicecoils » Apr 24, 2015 5:16 am



First spin-up. Sorry for the vertical video and shaky Cycle Analyst. On the CA screen where it show's km/h it's giving RPM/10 (the speedo has been set to 1666mm wheel dimeter).

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by riba2233 » Apr 24, 2015 8:20 am

Interesting sound.. I would love to see some graphs, especially efficiency from 0 to 100% rpm :)

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by Robbo » Sep 10, 2015 5:10 pm

Voicecoils, have you any updates on testing this motor?

I have acquired the same hub motor/wheel also with a blown controller. I am about to start testing it with a VESC controller.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by voicecoils » Sep 11, 2015 6:39 am

Robbo wrote:Voicecoils, have you any updates on testing this motor?

I have acquired the same hub motor/wheel also with a blown controller. I am about to start testing it with a VESC controller.
No, it was on loan (I'd hoped somewhat permanently :lol: ) but the owner asked for it back.

Additional thoughts:

24-36v is plenty unless you plan to run a really small diameter rim. The motor has very high rpm/volt.

Would be fun to run this on the rear wheel of a single sided swingarm bike or using 2, drive the front 2 wheels of a tadpole trike.

Motor was built to run in a bike with modest lower of 150-200w and low speeds. So, motor performance & safety is unknown at higher speeds and at higher levels of motor heating.

Motor deserves a FOC controller.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by Robbo » Sep 12, 2015 5:25 am

I am starting testing on 12v and will work up from that but agree I will lose a bit of speed through not using FOC. By the way the original controller it came with was a space vector controller which would have been quite advanced for its time and would have been part of the technology coming from its solar car racing origins. I was initially thinking about a new space vector controller so part of the rational for using the VESC controller was that it was open source and it was developed with a view of implementing FOC in the future.

I had wondered how I could mount the hub as a rear wheel but hadn't thought about a single sided swing arm. Given that one side doesn't rotate it is probably easier to do this rather than machine a spacer. I wasn't lateral enough in my thinking.

I reckon there must be a growing number of these motors out there sitting in sheds un-used with a battery and/or controller that has died and people will be told they can't be fixed at least by the mainstream bike shops. I hope they don't send them to the tip.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by tennisfiend » Jun 07, 2016 8:26 pm

hi all
i have acquired the motor in a 26" rim, and fitted it to my mountain bike - works a treat. i was very interested to read your research, especially if a controller or any aspect dies and i might need some know-how or lateral-thinking to repair.
in the meantime, would you have any recommendation for battery-type with deep-discharge and re-charge characteristics, with perhaps 20Ah - ebike batteries are notoriously expensive, so need to get best recommendation possible.
thanks so much, and i really look forward to reading more about your research on this particular motor.
cheers
ian.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by Robbo » Sep 14, 2016 8:07 am

Sorry Tennisfiend I missed your post as I hadn't looked at the forum for a while. It's great to hear that you have the same motor still going strong. I made the following post back in October last year which tells you a little bit about what I was doing.
I have just started testing a BLDC bike hub motor using a VESC from Enertion. Currently I am running it on a cycle trainer where I know the speed power curve which is used to load to the motor. Currently I am not using Hall sensors and are using 12v which is the original voltage for the motor. It does need a bit of a push to get it spinning most times.

This thread discusses the motor that I am using https://endless-sphere.com/forums/viewt ... i#p1096989.

My motor already came in a 700c wheel the same as pictured in the linked thread. I have it running unloaded at speeds between 3 and 52km or 22 to 400 rpm. This corresponds to a duty cycle between 5 to 89%. It can probably go a bit faster.
As the motor has 8 poles eRPM is 8 times the wheel RPM.

Because the motor is already in a wheel the extra weight or inertia has resulted in the BLDC auto configuration sequence not working as it is expecting the motor to spin up quickly given a burst of power. Therefore I set the motor parameters manually taking values from a discussion on e skateboard hub motors Min eRPM = 80, eRPM for Integrator limit = 1000, Integrator limit = 60.

Under load the motor is working well between 50 and 255rpm or 6 to 33 kmh with maximum power of 211W with a motor current limit set to 25A. As this is rev 1.10 FW this would probably increase with rev 1.12 FW.

As for other people using a VESC for an ebike, Vedder mentioned in one of his postings that he has a friend who has tried it and there are a couple of you tube videos of ebikes powered by a VESC. They are using much higher voltages and power settings than me.
The VESC firmware version I was using didn't support FOC and without FOC the motor was rather rough and noisy compared to Voicecoil's video. I presume your motor and original controller are also quiet?

I just started testing FOC last week. It took me a while to upgrade the VESC to a version that would support FOC due to my board not having a bootloader and then the pinouts being wrongly labelled on the programmer I bought. I still have the same problem with motor testing not working automatically and have to tune the parameters manually. FOC does seem to be much smoother and quieter but I still haven't got it running properly yet. I also need to try the Hall probes.

As for batteries the above testing is still being done on the cycle trainer using a rather heavy 12 volt lead acid battery. Once I had it working at 12v I was going to try slightly higher voltages as I now think FOC will require a higher voltage for higher speeds. As for the eventual battery to use on the bike, I was thinking about using a RC LiPo battery as they are relatively cheap. There are many threads discussing these (and other) batteries on the forum but LiPo batteries do need to be handled carefully, charged with a correct charger and have the cell voltages monitored by a BMS.

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Re: Avanti Electra axial flux hubmotor - just for fun

Post by electriceel888sgm » Dec 27, 2017 12:46 am

Someone mentioned in this thread that there must be a few of these hub motors sitting in garages...
I am one of them who has bought a (used) Avanti Elactra some few years back. I blew the controller by just applying a slight over-voltage.
I'd love to make this bike go again as an e-bike ( just changed the wheel and used is as an ordinary bike).
So a FOC controller is the best for this bike? Any particular one? I'd love to run this bike at 1000W continually.
What battery and voltage should I use? (I know lead acid is ridiculous for this bike!)

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