10-25-2011, 11:57 AM

I have what should be a reasonably simple question to answer,

and this looks like a nice in depth forum full of experienced people.

All I'm looking for is how much "Energy" is needed

to maintain a speed of 20-MPH on a simple bicycle...

Leaving out the many many variables of a lessor degree,

and utilizing some generic major values for an approximation.

And forming an answer in an

accepted measurement format

like the topic heading indicates:

Pound/Inch Torque

Newton/Meter Torque

Watts (IMHO too vague)

1 - A standard 180-Lb person

2 - Standard street tread 26" wheels

3 - 60-70-SPM pedaling cadence

4 - Standard bike/handlebars/clothing

5 - No additional wind force or road drag (level grade)

The problem is I'm having a hard time pinning this down

to any reasonable average value of some kind to utilize,

and none of my Google hits agree on where to test for this.

The closest, and possibly most accurate I found indicated

that it takes about 280-watts of equivalent 85%-Eff motor.

This was determined by building in a tensor sensor into a

an emptied out hub motor (by a hub motor manufacturer)

to sense the hub force required to maintain the US 20-MPH limit.

I think more of this test because it eliminates the gear ratio factor,

as it was a direct test of the force applied to the hub via freewheel.

When that same tensor sensor was connected to their hub motor,

and the rim's RPM was held at the same speed needed for 20-MPH,

the required wattage to maintain the same force was 280-Watts.

It was not one of the planatary-reduction hubs to be clear on this.

I took an 11-tooth gear and put it on an old crappy (China)

MY-1016 24-Volt 350-Watt motor I got on eBay for about $16,

and fed a 65-tooth excer-cycle sprocket on a 26" rear wheel.

(1523-RPM = 20-MPH for this setup)

I only needed ~200-watts (24.81-Volts x ~8.1-Amps)

to maintain a 20-MPH average speed in my tests.

Don't get me wrong, this motor sucks,

and I will buy a real one next, heheh...

But is there a known value that people agree upon (for the most part)

that equates to a given speed and weight of rider perhaps please ?

Thanks

and this looks like a nice in depth forum full of experienced people.

All I'm looking for is how much "Energy" is needed

to maintain a speed of 20-MPH on a simple bicycle...

Leaving out the many many variables of a lessor degree,

and utilizing some generic major values for an approximation.

And forming an answer in an

accepted measurement format

like the topic heading indicates:

Pound/Inch Torque

Newton/Meter Torque

Watts (IMHO too vague)

1 - A standard 180-Lb person

2 - Standard street tread 26" wheels

3 - 60-70-SPM pedaling cadence

4 - Standard bike/handlebars/clothing

5 - No additional wind force or road drag (level grade)

The problem is I'm having a hard time pinning this down

to any reasonable average value of some kind to utilize,

and none of my Google hits agree on where to test for this.

The closest, and possibly most accurate I found indicated

that it takes about 280-watts of equivalent 85%-Eff motor.

This was determined by building in a tensor sensor into a

an emptied out hub motor (by a hub motor manufacturer)

to sense the hub force required to maintain the US 20-MPH limit.

I think more of this test because it eliminates the gear ratio factor,

as it was a direct test of the force applied to the hub via freewheel.

When that same tensor sensor was connected to their hub motor,

and the rim's RPM was held at the same speed needed for 20-MPH,

the required wattage to maintain the same force was 280-Watts.

It was not one of the planatary-reduction hubs to be clear on this.

I took an 11-tooth gear and put it on an old crappy (China)

MY-1016 24-Volt 350-Watt motor I got on eBay for about $16,

and fed a 65-tooth excer-cycle sprocket on a 26" rear wheel.

(1523-RPM = 20-MPH for this setup)

I only needed ~200-watts (24.81-Volts x ~8.1-Amps)

to maintain a 20-MPH average speed in my tests.

Don't get me wrong, this motor sucks,

and I will buy a real one next, heheh...

But is there a known value that people agree upon (for the most part)

that equates to a given speed and weight of rider perhaps please ?

Thanks