Avanti Electra axial flux hubmotor - just for fun

voicecoils

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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:
http://endless-sphere.com/forums/viewtopic.php?f=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

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

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
View attachment 2

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.
 
riba2233 said:
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.
 
[youtube]PUhe9CLNOA0[/youtube]

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).
 
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.
 
Robbo said:
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.
 
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.
 
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.
 
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/viewtopic.php?f=2&t=68857&p=1096989&hilit=avanti#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.
 
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!)
 
Thanks to responses on the techie side of this Electra motor over the past few years. After I set my other bike up with one of Kepler's friction drives from this same forum I will return to trying to use the vesc controller and lifepo4 batteries to enhance this Electra motor, so please if anyone else has continued research please do keep posting your findings, as will I.
 
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