Which brushless hub motors have freewheel?

[frank9755]

This is why the Tongxin is out on its own. The resistance is near negligible. A year or so ago, when I was between normal bikes and Tongxin controllers I rode my bike with Tongxin in the front hub but without power on a couple of long trips. I didn't bother to change the front wheel as there was no need! I don't believe any other motors (yet) come close to that.

This means that it is viable to use a Tongxin purely as a hill-assist motor, with the rider happily doing the work on the flat or downhill. The Nano and Cytronex applications have illustrated that, both having their fervent supporters despite, on paper, not having outstanding specs.

During the Ching Challenge ride on Wednesday, there was a long (c.15 mile) gentle downhill ride alongside a river. Nick on his Cytronex and me with my Tongxin were able to do this stretch comfortably at 16-21 mph without using any power, while the Ezee bikes needed to use power to attain those speeds because they had greater motor drag. It's things like that which explain why the Nano and Cytronex are able to report such high ranges from small batteries.

 

[flecc]

Hi Flecc - all I mean is that when, there's no power, there's no porridge. As I understood it (and I write from ignorance rather than knowledge), the Heinzmann turns freely in this sense. Is this correct?

The Heinzmann is quite free running without power, certainly nothing like the drag of most three cog orbital drive motors. The Powabyke is the champ in this respect since the orbital drive is pawl free wheeled into the hub shell so it's just like a normal bike freewheel. Nothing's perfect though as ever, the pawls tick loudly as the bike is cycled without power and it is a rather noisy motor.

I was going from memory on the weight of the individual parts of the Heinzmann kit so I may have been wrong, but it being quoted as the same weight as the Bafang does puzzle me a little.

However, I see what most bike manufacturers prefer and I agree with them. For me the Suzhou Bafang motors do everything thats needed. The lack of completely free rolling without power doesn't worry me since it's an e-bike and I don't expect it to work without power.

The best modern hub motor for freewheeling seems to be the Tongxin judging by all reports from users and even those who've tried them and not bought. Bikes with the new Panasonic unit are also very good without power since the motor unit is fully freewheeled, the only extra drag over a normal bike being the extra sprocket running on the chain.
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[flecc]

The Galileo on the other hand has as good a freewheel on the front hub motor as it does on the standard rear wheel. I just assumed all hub motors were as good as this but obviously I'm wrong. I could lift the front wheel, turn the throttle up to full and watch the speedo hit 15mph then if I cut the power it would keep running and running and running and running and running ... you get the idea. If I do the same thing on the Alien it slows down quite quickly as though I've got a brake block rubbing slightly. I could hit 37mph downhill on the Galileo too! Unfortunately I don't know what motor is used in the Galileo, I could try and find out though.

It looks like the Bafang or a clone, right down to the side screw fixings.

I can do that on an eZee Torq 1 when the front wheel is lifted, it just spins on for ages and ages, but it doesn't make it the same on the road despite me recording 44 mph on a downhill stretch. When I did a later conversion on that bike, I went as far as narrow section low rolling resistance tyres and reduced the bike weight by a big margin, but it's still a pig to pedal without power, like Mussels says, stirring porridge. While it's obviously better than a bike without a freewheel in the motor, I very much doubt I'd find the Galileo much better for cycling without any power switched on than any other similar hub motor bike, since it still has to turn those same orbital gears. Of the many different geared motor ones I've tried, they've all been pigs to ride without power and no comparison with normal bikes.

P.S. I've just seen Frank's post above and his last paragraph is exactly right. That's the difference that the orbital gears make in these hub motors.
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[themutiny]

I have both a Torq 1 and a Cytronex. If you spin the front wheels by hand, without a doubt the Bafang will spin for longer, but riding them is an altogether different matter. The Tonxgin rides like a normal bike, with no perceptible drag. The only reason I swap the wheel out is for weightsaving and noise considerations, not drag. The Tongxin is quieter with the assist on than it is with it off, whereas the Bafang is silent without assist but comparatively qute noisy when it is on until you get it up to speed.

The Torq can be ridden without power, but not at speed. As Flecc says, the drag becomes very noticeable if you try.

 

[Barnowl]

I totally agree about the lack of drag on the Tongxin. Spin the wheel by hand and it makes a slushing sound and slows down to a stop alarmingly quickly. Out on the road it's a completely different story. I can't tell the difference between the Tongxin hub and a normal bike wheel. That's not to say there isn't any drag just that it's negligible and goes unoticed, even at very low speeds when freewheeling through the park. Like Nick I'm quite happy to use the bike without power (except when there's hills to go up but that goes for a normal bike too).

 

[flecc]

Thanks Barnowl and themutiny, proofs of what I've been saying all along.

Hand spinning wheels and roll speed downhill are no indication of motor drag and those tests are a waste of time. The only test is cycling without power switched on, and it's then that the drag of triple cog orbitally geared motors is very apparent, particularly as speed goes above about 13 mph. The higher the speed, the more the drag multiplies, and the effort to reach and maintain 20 mph is huge compared to that necessary on a normal bike.

The triple-roller drive Tongxin is the one exception, behaving very much like a normal motorless bike wheel.
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[Caph]

The only test is cycling without power switched on, and it's then that the drag of triple cog orbitally geared motors is very apparent, particularly as speed goes above about 13 mph. The higher the speed, the more the drag multiplies, and the effort to reach and maintain 20 mph is huge compared to that necessary on a normal bike.

I certainly didn't experience this on the Galileo. I do very much experience this on the Alien. I could easily cruise along at 18mph with the motor off and no headwind on the Galileo. As I said the free-wheel is as good in the front wheel as in the rear wheel so as long as I don't have a headwind I can power up to 18mph and keep it at that speed with little effort. At that speed the front wheel makes a rapid but quiet clicking/ratcheting sound much like my rear wheel, whereas on the Alien I can both hear and feel the gears turning due to the lack of the free wheel. I can reach a speed of 18mph on the Alien but at that speed the effort feels almost Herculean and it is a constant struggle to maintain the speed.

If a wheel slows down when you spin it off the ground then you have to counter that slow down rate to maintain any given speed when pedalling. If it slows down more at higher speeds then you have more effort to put in maintaining a higer speed. If it doesn't slow down when you spin it at any speed then you don't have to put in any additional effort countering the effect of the motor in order to maintain speed when pedalling.

A motor either exerts drag or it doesn't. You can't have a motor that exhibits drag when you spin the wheel off the ground at 15mph but does not exhibit drag when you pedal at 15mph.

Ye canne ignore the laws of physics Jim!

 

[Caph]

roll speed downhill are no indication of motor drag and those tests are a waste of time.

One final point. I've already proved that this is not true. On my Galileo the downhill speed is limited by non-motor effects such as wind resistance and tyres which is why I could get 37mph on the same hill as I used to get 34mph on a non-electric hybrid (added weight of the bike explaining the extra few mph). On the Alien, my top speed is limited by the motor drag which gets greater at higher speeds. I simply cannot get past 25mph on the Alien on that same hill.

And just in case anyone is wondering. That's going downhill not uphill!!!

 

[Caph]

I've been thinking about this some more whilst mowing the lawns (you've got to think about something right!).

Although lifting your wheel, throttling it up to 15mph and seeing if it slows down more than a normal wheel will tell you if you have motor drag, it probably gives an exagerated impression. The reason being that if you perform the same test on a non-motor wheel but with the lightest of contact from a brake block you will probably see a similar slowdown, however the slow down will not be noticeable when riding.

So the rate of slowdown has to be taken in to account. A fast slowdown means you will be having to counteract a lot of drag and will probably be noticeable when riding with the motor off (or above 15mph), a slow slowdown (if that makes sense) will probably not be noticeable when riding with the motor off (or above 15mph). Of course you would also have to take in to consideration greater slowdown at greater speed.

For comparison, my Alien slows down from 20mph to 0mph in just under ten seconds with the front wheel off the ground. That is a very fast slowdown and is noticeable when riding with the motor switched off.

I would like to add that I'm not knocking the Alien Gent's Special. I bought it as a budget interim bike that I could keep as an emergency spare when I get my other bike back but I've been really impressed with it. As a budget commuter bike I think it's spot on. I'll post a full review when I get a chance.

 

[Caph]

You can't have a motor that exhibits drag when you spin the wheel off the ground at 15mph but does not exhibit drag when you pedal at 15mph.

you will probably see a similar slowdown, however the slow down will not be noticeable when riding.

I appear to be having an argument with myself now that I re-read through the posts.

That's never a good sign.

 

[Barnowl]

I appear to be having an argument with myself now that I re-read through the posts.

That's never a good sign.

LOL. We're all out freewheeling and enjoying the sunshine

 

[flecc]

One final point. I've already proved that this is not true. On my Galileo the downhill speed is limited by non-motor effects such as wind resistance and tyres which is why I could get 37mph on the same hill as I used to get 34mph on a non-electric hybrid (added weight of the bike explaining the extra few mph). On the Alien, my top speed is limited by the motor drag which gets greater at higher speeds. I simply cannot get past 25mph on the Alien on that same hill.

Of course, that's not at all what I was saying in this thread. As you've said, the Alien is one of the few that have not got a freewheel, so very obviously it has the motor drag added.

As I've made very clear, I was referring to a test of drag of the orbital gears of freewheeled motors, refuting those who test by lifting and spinning the front wheel or checking downhill speeds between freewheeled bikes and then claim there's little or no drag.

A motor either exerts drag or it doesn't. You can't have a motor that exhibits drag when you spin the wheel off the ground at 15mph but does not exhibit drag when you pedal at 15mph.

Ye canne ignore the laws of physics Jim!

Not so, and you've reversed the way this works. The common case is the hub not exhibiting drag when spun off the ground, but exhibiting drag when pedalled on the road, not the way you've said.

And I'm afraid you've misused the laws of physics by comparing entirely different things, also ignoring what I posted about under number (3) in this post above. You are quoting the case of the drag under motor drive when the motor has orbital gear advantage, with the case of pedalling the hub motor gears around which has orbital gear disadvantage. There's also the effect of gyroscopic forces. When spun with the wheel held up, the wheel on the overrun has the usual gyroscopic momentum undisturbed by any other movement. On the road, the wheel is being continuously moved from it's existing position at any one moment which it doesn't want to do.

You can't ignore the laws of physics in these ways, and as a engineer I never do.
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[Caph]

Of course, that's not at all what I was saying in this thread.

No, you said "... roll speed downhill are no indication of motor drag". I was correcting this since it is not true.

Also, if you see drag when free spinning the wheel then you are going to have to pedal more to compensate for this when riding. How much extra work is debatable, but the extra work itself is not.

 

[AndyOfTheSouth]

Hi Caph

Before this very interesting thread fades away... Would it be possible to know more about the motor on your bike - I think you said you might be able to find out. I'd noticed earlier postings by you on the cross country rides you'd done and thought they were impressive.

Andy

 

[flecc]

No, you said "... roll speed downhill are no indication of motor drag". I was correcting this since it is not true.

I did not say "no indication of the existence of motor drag", I said "no indication of motor drag", i.e. amount of drag, so it was true.

Also, if you see drag when free spinning the wheel then you are going to have to pedal more to compensate for this when riding. How much extra work is debatable, but the extra work itself is not.

Where have I said this isn't the case?
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[daniel.weck]

For those who need a visual illustration of the reduction gear

YouTube - Planetary Gear Unit

YouTube - Electric Bike Motor planetary gear drive alternator generator rotor magnets

YouTube - Electric Bike Motor planetary gear drive alternator generator rotor magnets