Non-drag hub motors

[eHomer]

Now that the decent weather is at last here I've been giving my electric bikes a good testing around the country lanes.

I built both myself, one with a freewheeling planetary geared 250w front hub motor and the other with a direct drive 1000w rear hub motor.

I'm now looking to make up a compromise between the two.

I can see the big difference in drag between the two when pedaling unassisted.

Is it possible to buy a 36 volt front hub motor on a 700c rim that sounds a little less like a milk float pulling away ?

Is it unavoidable that direct drive hubs will always have drag when pedaling unassisted ?

Does the amount of drag vary between makes of motor ?

Failing that, would a planetary geared motor of a higher wattage, (say 500 watts) make less noise than the 250 ?

 

[Deleted member 4366]

Interesting questions!
The higher the load on a geared motor, the more noise they make, so a 500w one running at half-power will be fairly quiet.

High quality geared motors are a bit better than cheap ones.

Some direct drive motors have more drag than others, but they all have it, and usually more than a geared motor.

We tested a geared hub-motored bike hear in China with one of the new generation sine-wave controllers, and it was much quieter, which shows that the noise is electrical and not from the gears. These controllers will be generally available soon.

Sent from my GT-N7100 using Tapatalk 2

 

[KirstinS]

Any chance you could please explain what a sinewave controller does that's so different so a standard ?

And in simple terms for non-engineer me !

 

[Deleted member 4366]

Any chance you could please explain what a sinewave controller does that's so different so a standard ?

And in simple terms for non-engineer me !

A sine wave controller gives its pulses of power in smooth waves like you get on water. A normal controller gives its power pulses in a square pattern, which has sharp corners. As sound, a sine wave is a smooth tone like a note from a musical instrument, while as a square wave would be a rasping sound. You can find examples with Google to hear the difference.

Sent from my GT-N7100 using Tapatalk 2

 

[KirstinS]

Thanks , even I can understand that

 

[Marctwo]

As well as being quieter, the sine wave should be less aggressive in shaking your nuts and bolts loose, too.

 

[eHomer]

These controllers will be generally available soon.

Thanks Dave, it sounds a really good solution all round.

I like the idea of just changing the controller.

Where you say "available soon", do you have any of your very educated guesses on how soon (weeks, months ?) which suppliers, and rough cost ?

 

[Deleted member 4366]

I think they're already available. The bike we tried was a production bike. I'll see what I can find out tomorrow if we have time.

Sent from my GT-N7100 using Tapatalk 2

 

[eHomer]

26 minutes !

Thanks Dave, much appreciated.

I tried Googling and got nowhere...

 

[billadie]

As well as being quieter, the sine wave should be less aggressive in shaking your nuts

Damn it, that's the bit I enjoy.

 

[Scimitar]

As well as being quieter, the sine wave should be less aggressive in shaking your nuts and bolts loose, too.

Ooh, my nuts would thank the controller for that.

 

[eHomer]

Damn it, that's the bit I enjoy.

Trouble is though, when you're a "heavy" bloke like me, it sounds like a fork lift truck pulling away.

 

[Deleted member 4366]

Trouble is though, when you're a "heavy" bloke like me, it sounds like a fork lift truck pulling away.

I'm hoping to get some sine wave controllers to test. They are available at stockists now, but I couldn't get a price. I can get at least one soon after I get home.

Sent from my GT-N7100 using Tapatalk 2

 

[eHomer]

I'd be very interested in one Dave, if you get the opportunity of one to sell on.

It's for 36 volts, and the current motor is 250 watt, but if the choice came up I'd go a bit higher on the wattage to enable me to upgrade the motor if necessary later.

 

[kemi]

Wouldn't the solution for hub motors, be to program the controller with the profile for a normal wheel. I know that this feature would require extra power beyond the 25 Km/h, but all it does is to make the bike behave like a normal bike. So I don't see any harm in doing so.

 

[103Alex1]

^^ the solution to what ?

 

[kemi]

^^ the solution to what ?

The drag that comes after the bike hits 25 Km/h

 

[Scimitar]

I'm hoping to get some sine wave controllers to test. They are available at stockists now, but I couldn't get a price. I can get at least one soon after I get home.

Now, that sounds interesting. I fancy one of the Conhismotor controllers with the display panel, and if they're bringing out a sine wave version later on, it would be worth my while waiting to upgrade and do both steps at once.

 

[amigafan2003]

Ah, you mean after 25km/h just add the minimum amount of power to over come the drag of the motor?

I think people are overestimating the amount of drag geared motors have. Most of the "drag" when hitting the 25km/h "wall" is wind resistance, not motor resistance.

 

[SRS]

Ah, you mean after 25km/h just add the minimum amount of power to over come the drag of the motor?

I think people are overestimating the amount of drag geared motors have. Most of the "drag" when hitting the 25km/h "wall" is wind resistance, not motor resistance.

Program it to overcome motor drag and wind resistance. Then you have an option that really does work.