No Halls (sensorless) & Internal Freewheel

[Pete1961]

I have been offered a 'no halls' motor by maker Tongxin, in the past their product has contained a freewheel meaning the motor was not ground driven when not energised (very good) BUT they then used a halls system to initally kick the motor off.
I cannot see how a motor that is not 'land driven' can provide the back emf pulses that the controller then uses to get 'in sync' with. Hence the need for halls. Either they have dropped the internal freewheel or there is something wierd here.
Xlyte have used no halls controllers but their motor always turns with the wheel (400 series)

www.bmsbatteries.com seem to offer similar items, (but nothing slower than 205 rpm) so Tongxin was my last hope, as I myself ride a 175 rpm 26'' wheel with excellent hill climbing - ideal for the older or disabled cyclist, & have been asked to 'make another bike like my own' for a friend not in the best of health. Is sensorless ie 'no halls' compatible with a freewheeling motor ??? & if so how the heck does it work???? & does it have reasonable torque at low speeds???

My motor has halls & freewheel, weighs 2.1 Kg & when combined with a small Li pack only adds about 10 lbs to the bike - so was a sorted technology for me. I could convert a folder using the 205 rpm motor - thus retaining the 17.7 lbs force at the rim but am still not sure re the sensorless & freewheel agenda. I have no argument with either company but communication on tech matters is very difficult to say the least. Sorry for all these Qs - have searched all over web but cannot answer this - so any help greatfully received PETE

 

[miuan]

I set up a bike for a friend with a geared motor with halls and a controller that could also work sensorless. He tried to disconnect the plug the other day because I was curious how it could cope, and the bike rode just like before, no power or speed loss, even at low speeds there was no hesitation. I believe the controller starts the motor by a preprogrammed phase sequence and gets it moving a tiny bit, just enough to catch a back-emf voltage signal pattern that enables the controller to initiate sensorless phase sync. So you don't really need to get it moving. There may be two problems with geared sensorless:
- gear damage if the controller starts up too harsh
- sync problems due to high commutation frequency, but we have done 45kph with a cheap chinese controller, so at your intended speed, most sensorless ebike controllers should do fine.

 

[amberwolf]

AFAIK, the only issue you might run across is that sometimes the motor may not start in the correct direction, or you might have to pedal forward just a tiny bit to get commutation started.

It's something I would like to try here, with a couple of Fusin geared motors I have with probable fried halls, but I don't yet have a working sensorless controller.


Also, is it possible the TongXin is an older brushed model? It would not have halls, either, but only two wires out instead of three.

 

[Pete1961]

Thanks guys, I think I understand the explanation you give miuan as to how this can be possible. The early version Tongxin
I am riding has three heavier phase wires between motor & controller, along with five much lighter halls wires, so it must be a sensored model. It also has an internal freewheel roller clutch (turn the wheel forward by hand = easy, turn it bacward = much harder as the motor is being 'back driven' via the planetary reduction) So this design would not be influenced by pedalling first, as doing this in a forward direction does not rotate the motor armature.

Do all or most of the geared motors have this roller clutch (as mine does) & is this sensorless tech. used by them along with this (eg Bafang) as geared motors seem to now be well established. I would like to hear from anyone who rides this combination (sensorless geared + freewheel clutch) as to how well it works in practice & who made it. I have 5+ yrs use out of my sensored Tongxin front wheel motor so no complaints there. I just fear encouraging my friend to buy something new & unproven, as we both have limited money.

 

[amberwolf]

Most geared hubs do have a freewheeling planetary set, whetehr it is gears like my Fusin, or a roller clutch like my TongXin.

Some manufacturers make a non-freewheeling version (I have one Fusin like that), and it is usually possible to disable the freewheel in most of the clutches I've seen. I am not sure how I could do that in the TongXin, though, given it's design.

 

[Pete1961]

No I would not want to disable the roller clutch as this is a great feature from several angles,
not least if the batts run out the bike is still easy to ride home - partic with the advent of lighter battpacks, I just wanted to be sure this feature had not been dropped. I do remember a P2A motor being then sold by solarbbq, this was an 'offroad' motor not including a clutch as they broke under extreme conditions.

Amberwolf, can I ask what rpm model your TongXin is & what wheel size you run it in? My choice of low rpm's is to maximise hill climbing torque for those that need it (including myself). I gather from Miles that a two mech speed hub motor is on its way? this would be great but meanwhile I can live with the 13.7 mph top speed, as the hill assist really works.
Plus for higher speeds I think suspension & disc brakes are an asset, also there is a 15 mph limit on my local shared footway/cycleway system.

 

[amberwolf]

Mine isn't in a wheel, as it was donated to my projects by another member here; it has a slipping problem IIRC., which I might be able to fix but I havne't tested it under enough torque to make it slip yet (just by hand). I don't know what RPM it is, but this is a thread I made for analyzing it:
http://www.endless-sphere.com/forums/viewtopic.php?f=2&t=25188&p=363939
If I get the chance sometime, I'll test the RPM and post it there.