Talk torque please.

[LeighPing]

Pretend that you're answering someone that doesn't know much about such things please.

'Torque' - a force that tends to cause rotation.

Reading here, that 'DD' (Direct drive) motors don't have as much torque as others interested me. I have a DD motor and I thought that it did ok up the hills. But this is my first ebike. So, I really wouldn't know too much about that. I also heard someone mention a 'torque bar'. What is that exactly?

Perhaps some here could educate some of us with a discussion on ebike torque. Thanks.

I knocked up a short video for comparison purposes, not sure if it'll help or not. I did a couple of small, steep-ish hill ride ups and one static start.

 

[PH001]

That place looks awesome for sledging in the snow!

An easy way to think about it is torque for acceleration and power for top speed.

Power is really just torque x rpm.

 

[Geebee]

This article describes the idea of torque arms well, one correction to the article is that personally I would not consider a front aluminium fork without torque arm even at 250w and would strongly recommend fitting them to a rear aluminium dropout at 250w.
Keep in mind that a 250 watt motor might peak at 800 watts!
http://www.ebikeschool.com/torque-arm-need-one/

Trying to keep this simple....
Torque can be thought of as how hard the motor tries to twist the wheel.
A geared hub motor will with the same amount of power will twist harder as it is working through a gearbox like a car engine in a lower gear where as the DD is always in top gear.
A crank drive can do both as it is using the bikes gears but brings it's own issues as well.

Result of no torque arm and an aluminium dropout. Pic stolen from https://www.electricbike.com/torque-arm/

 

[LeighPing]

Cheers G. That makes things much clearer.

 

[PH001]

Another good analogy is if you think of a super tight cross-threaded bolt that you need to undo with a wrench. You can apply lots and lots of torque to it (hundreds of Nm if you put a long bar on it) but the power is limited to how many times you can turn the bolt in a minute (in rpm terms), which is probably not many.

Generally, applied torque can be any figure you like via gearing (in this case, bar length). Power is directly related to the average energy used and hence work done. That's why power = torque x rpm.

I didn't know what a torque bar was either...until I posted this thread:

http://www.pedelecs.co.uk/forum/threads/what-does-this-bit-do.24322/#post-307884

 

[RobF]

[QUOTE="LeighPing, post: 315457, member: 16250". I have a DD motor and I thought that it did ok up the hills.[/QUOTE]

Ultimately, that is all that matters - the bike does what you want it to.

You could probably get more torque by changing to a geared hub motor, but why bother if your current set up meets your needs?

Direct drive motors are whisper quiet, a geared hub motor would be significantly noisier which may or may not bother you.

 

[PH001]

I'm not sure what the difference is between a direct drive hub motor and a geared hub motor. Cam someone please explain? Is my Cyclotricity Stealth a geared hub motor?

 

[anotherkiwi]

No it is a Direct Drive.

"1000W brushless and gearless rear hub motor (comes restricted to the UK/EU regulation of 250W power and 25km/h speed by default. Reaches up to 50km/h once de-restricted to the 1000W mode.)"

Geared hubs have a reduction gear inside so that they can spin internally at high RPM where they are most efficient while providing rider compatible revs at the wheel.

 

[RobF]

I'm not sure what the difference is between a direct drive hub motor and a geared hub motor. Cam someone please explain? Is my Cyclotricity Stealth a geared hub motor?

It looks like the 250W front drive Stealth has a geared motor, but the 'dual power' 500W rear drive Stealth has a direct drive motor.

http://www.e-bikesdirect.co.uk/Item/Brands/Cyclotricity/Cyclotricity_Stealth_Electric_Bike_250w-17_Frame_36v_15ah.aspx

http://cyclotricity.com/stealth-500w-9ah/

 

[PH001]

Direct drive it is then - many thanks. I assume the geared ones don't look any different from the outside?

 

[anotherkiwi]

They are usually much smaller and a bit lighter.