I don't like hub motors - (crappy ones)

[ElectricEd]

Lucky_Hoodlum: <edited with acknowledgement to mud2005>
not offering much factual information just puting down something
that has become very obvious you know little about.

I have previously worked as an engineering fitter and turner over 10 years. IMHO opinion I think I know a little more about transmission backlash than the average joe. I have recently been involved with industrial robots where the elimination of backlash is critical.

put together a quality rc motor electric bike and do some real world comparisons with your hub motor bike, or all you will have are opinions.

They are not just opinions but real world experience. My brother's bike has a separate chain driving the rear wheel. As there is no freewheel, there is a large transmission backlash when going into regen. As I mentioned earlier regarding huskydave's proposed setup, if he is driving the bicycle chain he is driving the freewheeling cluster so backlash is not a problem. It's probably a universal law of engineering somewhere, but backlash doesn't occur with a freewheel because there is nothing to load up against.


Let's get it clear here, I have all along just explained my preferences and pointed out what I thought were the factors that made me choose one way or the other.
1/ I like a smooth transition between drive and regen. It is not possible for a simple gear system to do this. Ask any drivetrain engineer.

2/ The only part to wear out on a hub motor are the bearings. Not so with a chain drivetrain. You have chain stretch and shark-toothing sprocket wear. If using a derailleur system, the chain will start to jump with the extra load that a motor places on it after it has worn and stretched a bit. You'd have to be a fair weather rider to make it last much longer. The better Shimano clusters have hard chrome facing, but once you get through this with the silicon grit paste that comes from the road surface in wet weather, they don't last much longer than the cheapies. Using hub gears is a completely different matter. They are much more forgiving with chain stretch due to the more robust sprocket.

3/ When younger and a lot fitter and commuting 20Km each way through Winter, it'd take about 6 weeks for the chain to stretch. At 8 weeks the chain would start to jump. I'd need to get a new cluster and chain. I found that alternating 2 chains with one cluster I could extend the life of the drivetrain a bit. Maybe we have tougher silicon over here :wink: , but noting Toshi's and zoot kat's experiences with ice and salt, I reckon that would make up for any difference in grit composition.

4/ I like regen. If Jason says that I may only get 10%, I'll be happy with that. An extra 3 or 4 kilometres on my range may make the difference between smiles and that long walk home. Not to mention that it also closes the gap between the efficiencies of the 2 motor types.

5/ recumpents 1000 miles may not be enough to get a good feel for wear if he only rides in fair weather. It takes me a bit less than 6 weeks to do that much. Since taking up ebiking, I have done nearly 2800 miles (4500Km) using the same chain and cluster. I obviously don't pedal as hard as I used to. I also try to avoid heavy downpours with a fully charged 48V LiFePO4 just at my butt. Going by my experience, if you are riding in all weathers and driving a bike's chain drive with a motor that will be delivering at least twice the power that a human can deliver, the drivetrain must wear more quickly.

6/ And finally, fewer parts to go wrong.

 

[mud2005]

mud2005:
not offering much factual information just puting down something
that has become very obvious you know little about.

interesting quote, but I didn't say it.

The only part to wear out on a hub motor are the bearings

really? very debatable.

I like regen

cool, enjoy

And finally, fewer parts to go wrong.

again, debatable.

 

[Miles]

As far as over heating goes, there's so much surface area on a hub motor that it shouldn't be a problem. Considering that an RC motor is developing a similar power in a smaller volume, cooling probably is an issue on warmer days or in a hot climate.

Heat dissipation is usually the limiting factor for both low speed/high torque and high speed/low torque motors. Remember that heat generation is proportional to torque output not power output.... also, that a smaller volume has a proportionately greater surface area....

 

[mud2005]

if 2 bikes were coasting down a hill one with freewheel and one with cogging/regen, I'm imagining the bike with freewheel gaining more speed and coasting very far. on the other hand the regen/cogging bike wont coast as far but gain back some power so it can drive to where the freewheel bike coasted? you might get a little more than that, but with regen/cogging its never going to pedal around without drag, like a bike, in my opinion.

 

[Miles]

Whether a regen. set-up is better than a freewheeling one depends on your riding requirements and the terrain/situation that it is used in.

No doubt, the ability to have both will eventually come. Locking freewheel or coreless motor are both possible ways...also see http://www.users.bigpond.com/pflemming/rewsc.htm

 

[TylerDurden]

As Fechter would say; "there is always room for improvement"... that goes for both schools:

In the case of hubbies, the benefits of simplicity restrict the ease of improvements in areas such as: gearing, cooling, weight, power and efficiency.

In the case of non-hubbies, their complexities also ease advances in gearing, cooling, weight, power and efficiency; via a more open-architecture where the community contributes improvements in parallel.

The RC solutions are not currently plug-N-play, but I expect to see something <1yr.

 

[Ypedal]

everyone is entitled to their opinion.. :lol:

Hub motors used within their limitations are excellent, outside their comfort zone they suck.. same thing goes for geared systems.

I can honestly say i have put my money where my mouth is on this one and there is no perfect solution for all situations. Brushed, brushless, geared, direct drive, cyclones, RC setups(currently installling to a bike !!! stay tuned for that one ! )

If you live in a place that allows a hub motor to climb all the hills you have to climb without hitting the current limitter on full throttle, they are as efficient as it gets. The speed of the hub will slow down as the power increases in proportion to the grade of hill being climbed, given that you canot shift, the hub just takes as much power as is required without incurring drivetrain losses 100% of the time.

My decision to go with an RC setup has nothing to do with efficiency and all to do with performance, the motor itself is very high efficiency ( astroflight 3210 ) but the belt, chain, Nuvinci hub, chain tensioners, freewheels, etc.. all take their share, i really don't give a hoot however, as i'm going to carry enough battery to more than make up for it ! lol

 

[Doctorbass]

I second Ypedal on that.

By my side what i appreciate about my hub motor is that :

-They are silent eventhough their great torque or speed
-easy and quick to install
-Can take alot of power due to their mass
-requier low maintnence (only one moving parts)


But..
-they are heavy,
-have lower efficiency at low speed

For me i still think that for my needs, the 5305 combined with electric transmission (Delta Wye) runing at high voltage is the best solution.

That give me incredible torque
and i can still run around 75km/h in WYE and will get like 100km/h+ in Delta when i'll transfer this contactor to my electric beast. still using the old crystalyte 72V 35A controller (mooded)

If i would restart that project, i would certainly choose that setup again. I dont like high pitch gear sound!!

But I more prefer this sound style!! it really rock!! :twisted: http://www.youtube.com/watch?v=6_41btVawMc

Doc

 

[Lucky_Hoodlum]

Sound the same as brushless outrunner rc motor to me

http://www.youtube.com/watch?v=nIdjVSWZsHo&feature=PlayList&p=2F5262BDF695E75C&playnext=1&playnext_from=PL&index=15

 

[dnmun]

doc,

why not try the latching relays like flip found for your C'lyte? they are the largest current relays we could find on ebay, and if they will carry the C'lyte, they should work for anyone. and then there is no coil current too. i may test the smaller relays yet.

do you think it will make a difference to back off the throttle when switching to the delta or is it best to maintain the controller current at the same level?

you can switch the latching relay with a 2P2T switch with the leads from opposite sides of the switch reversed, then add a momentary switch inline to pulse the current to reverse them when the 2P2T is reset to the opposite configuration.

 

[ElectricEd]

As far as over heating goes, there's so much surface area on a hub motor that it shouldn't be a problem. Considering that an RC motor is developing a similar power in a smaller volume, cooling probably is an issue on warmer days or in a hot climate.

Heat dissipation is usually the limiting factor for both low speed/high torque and high speed/low torque motors. Remember that heat generation is proportional to torque output not power output.... also, that a smaller volume has a proportionately greater surface area....

? a smaller volume also has a smaller surface area.
It depends on the way you look at it.
Consider:
The 2 different motor types and assume they have the same efficiency rating at a given speed for the vehicle being driven.
They are both drawing the same amount of power from a given power source.
Assume in this case that the RC motor's drivetrain has no resistance.
Each motor must be dissapating the same amount of heat.
With a much smaller surface area, the RC motor will not loose heat as effectively as the hub motor.

We should look up real world efficiencies of the different motor types and drive trains. I don't know about the RC motors, but I've just found an independant test of a 408 on Brett White's website that gives a max efficiency of 83% (a little worse than the graph supplied by Crystalyte - funny about that).

With all of this sort of stuff the devil is in the detail. A careful examination will give a better idea as to the relative merits of either system as far as efficiencies go.
The rest is up to personal preference determined by route, weather and the depth of pockets. :wink:

 

[TylerDurden]

With a much smaller surface area, the RC motor will not loose heat as effectively as the hub motor.

Not necessarily... the RC motor likely has forced convection in rpm ranges in the thousands, with openings to the atmosphere.

 

[Lucky_Hoodlum]

With a much smaller surface area, the RC motor will not loose heat as effectively as the hub motor.

Metal type and thickness of metal has alot to do with speed of heat dissipation. RC motors are smaller yes but possibly
thinner casing compared to hub motors and differing alloy, the thicker metals would retain the heat longer than thinner. Hub motors
have no inetrnal airflow, rc motors do, out runners have complete housing spinning. I think it is not as cut and dry as simple size of the motor.

 

[ElectricEd]

With a much smaller surface area, the RC motor will not loose heat as effectively as the hub motor.

Not necessarily... the RC motor likely has forced convection in rpm ranges in the thousands, with openings to the atmosphere.

That's my point, all things being equal, the RC motor will probably need to have some form of extra cooling. As they have a fan or something to induce airflow through them prooves it.

It looks like I'll have to rush out and get an RC motor and do some relative tests. How much is lost by the fan and drive train compared with what is gained or lost with a hub motor would be worth finding out for different ride profiles.

Really, this thread is trying to compare apples and oranges, or a Toyota Camry (got one these too) with a Ferrari. Remember that dust, rain, grit and slush are not good for highly tuned mechanical devices without protection.

The other thing I like about my 408 is that it is very quiet. It makes a great cat killer :wink: I've seen some fantastic leaps by moggies when they suddenly realise that they are about to get run over.

 

[ElectricEd]

With a much smaller surface area, the RC motor will not loose heat as effectively as the hub motor.

Metal type and thickness of metal has alot to do with speed of heat dissipation. RC motors are smaller yes but possibly
thinner casing compared to hub motors and differing alloy, the thicker metals would retain the heat longer than thinner. Hub motors
have no inetrnal airflow, rc motors do, out runners have complete housing spinning. I think it is not as cut and dry as simple size of the motor.

Certainly, although hub motors have their complete housing spinning too. :wink: And looking at the inside if my 408, there'd by a fair bit of air turbulence which would help to transfer heat from the windings to the outer case. I don't know how an anodised casing would compare with a painted casing for dissapation, but going by my commute home with a fairly decent climb at the end, the 408 is only warm to the touch but not hot. If the windings were stinking hot, I'd probably feel heat at the axle (as this is pressed in to the armature), but I don't.

 

[recumpence]

Efficiency is an issue too. The RC motors tend to have higher efficiency overall. Plus, they spin very fast. That added RPM gives better cooling.

Matt

 

[Lucky_Hoodlum]

^^what recumpence say he pro hehe

How do the inrunner and outrunner compare with cooling in your opinion recumpence?

ElectricEd yes true hub motor housing spin but have they venting holes? Aside from heat transfer through hub housing which
would not be super good lets be honest here, has it got any vents to release heat? I have seen no hub motor other than picture
i see RC motor only smaller one though in local hobby shop they are very open for ventilation.

 

[swbluto]

If the windings were stinking hot, I'd probably feel heat at the axle (as this is pressed in to the armature), but I don't.

And how fast were you going up the hill and what's the hill's percent grade and climbing altitude? From my experience climbing an 8% hill for a 400 ft. rise on an 85 degree fahrenheit day at an average speed of 6 mph(That includes pedaling!), the motor definitely overheats and that's with a puny 20-amp controller, too. By comparison, a powerful outrunner ran by the appropriate batteries would be chugging up at least 20 mph which means significant cooling and vastly improved efficiency(You'll see a slow hub motor often sucks in efficiency - it's typically, what, 50-60%?).

I think we've covered that hubs work great for modest speeds and relatively flat terrain. Its good to know your obvious bias stems from your flat locale. I, on the other hand, have tried both a hub motor and outrunner, and I already have experience to compare the two.

But, I encourage you to be biased! If it means you actively think of more elements to compare, then everyone gets a better detailed picture of how hub motors and RC motors compare. Be brave! Be Bold! Challenge the status non quo. :lol:

 

[The Stig]

Reliability is important. I was also wondering how easy it would be waterproof an RC system?

 

[ElectricEd]

If the windings were stinking hot, I'd probably feel heat at the axle (as this is pressed in to the armature), but I don't.

And how fast were you going up the hill and what's the hill's percent grade and climbing altitude? <snip>

I think we've covered that hubs work great for modest speeds and relatively flat terrain. Its good to know your obvious bias stems from your flat locale. I, on the other hand, have tried both a hub motor and outrunner, and I already have experience to compare the two.

Averaging 20Kmh for 4 km gaining 200M . It varies between a rolling hill to some lamp-post climbing grades back to a gradual rise. On the steep bits I'm out of the saddle in the middle ring and drawing 20 amps which is the limit that I set in the CA. I suppose that "flat locale" is relative. It doesn't compare with the Rockies, but my commute home starts in the city of Dandenong and finishes in the Dandenong Ranges east of Melbourne. The flat-landers in the inner burbs wouldn't call my area "flat".
I agree that an RC setup is better at climbing steep hills, in this area an RC motor is the clear winner.

I must say, this thread has been interesting. When I saw "I don't like hub motors" I thought that was a pretty bold statement just asking for response.
I just posted why I like hub motors and everyone jumped out accusing me of bias and not knowing what I was talking about. Gee, tetchy lot you RC motor afficionados.
(Ducks for cover...)

 

[swbluto]

Reliability is important. I was also wondering how easy it would be waterproof an RC system?

Ideally, it wouldn't be water-proofed. Water would help with the cooling. :lol:

But, I'd suggest, replacing the bearings to ones that can withstand water and then... uhhh.... I can't think of anything else that really would be needed to be waterproof. The wire itself is insulated so the electrical part would be impervious to water. If you wanted to add hall sensors, then it'd be as simple as coating the hall sensors' legs which would be easy since they're accessible.

As far as the controller goes, that's your own deal with whatever controller you choose just like it is with hub motors.

Anyways, time is the only proof of reliability. We'll see how things go after Endless Sphere gets a bit more data points from this summer - I suspect we'll see a lot more reports within the next couple of months. It seems the "budget motors" fare worse than quality motors(Like the Astros) as it seems the magnets come unglued after 400-1000 miles or so(It hasn't happened yet for me), but recumpence's has lasted quite a long time and I wouldn't doubt the astros would fare similarly.

 

[The Stig]

Wow you can just let the motor get wet... They are corrosion resistant? Do they mind getting dust and dirt in them? Probably wouldn't like mud.

 

[swbluto]

I don't know if they're corrosion resistant. Theoretically, it seems like they could be made that way(such metal exists, right?), but I wouldn't expect it since I'm guessing most RC guys don't fly their electric helis in the rain. But, it seems the only moving parts in contact is the shaft and the bearings, so it seems like it wouldn't matter how much rust the rest of it gets. After a decade of rusting, sure, it'd matter but until then...

Yeah, it probably wouldn't be good to get it muddy. But the open design makes outrunners pretty easy to clean out with a garden hose to get all the grime out should that even happen. I suspect the bearings would be the first things to replace with continued exposure to water, but once you get water-resistant ones, it's all golden from there.

 

[johnrobholmes]

Just get a marine motor treatment to keep it corrosion free. CorrosionX is a great electric motor treatment that can allow a motor to run fully submerged with no worry about rust.


Inrunner vs outrunner, the inrunner has an easier time dissipating heat since the windings are by the exterior surface. So far inrunners have an efficiency advantage too, but we may see them even out in the future.

 

[recumpence]

Alot of guys run outrunners in monster trucks. That is a terribly dirty environment. They hold up fine.

Outrunners are good because they move air directly to the windings. But, they also inhale air and dirt through the inside of the motor. It is a trade-off I guess.

Matt