500w Motor Question

[Ebiker555]

Hi guys,

In Mph terms how fast should a 500w rear wheel motor go on your average Hybrid type ebike with a rider weight of 75kg?

Thanks in advance for your thoughts

 

[Woosh]

the short answer is 15,5mph.
legality aside, the speed depends on the gradient.
If you climb a steep hill, your speed will depend on the gradient and how much you pedal.
The 500W label simply means it can dissipate 500W guaranteed. What comes out of the motor depends on battery voltage, controller's maximum Amps and motor's winding code.
If you ride on a fairly flat road, your speed depends also on whether the bike is derestricted,
For example, the Woosh Petite and the Woosh Santana3 both have 250W motors, but the Petite has winding code 13, the Santana3 code 9. Restricted, both assist up to 15.5mph. Derestricted, the Petite goes up to 20mph on flat roads, the Santana3 27mph.

 

[Wicky]

African or European?

 

[vfr400]

the short answer is 15,5mph.
legality aside, the speed depends on the gradient.
If you climb a steep hill, your speed will depend on the gradient and how much you pedal.
The 500W label simply means it can dissipate 500W guaranteed. What comes out of the motor depends on battery voltage, controller's maximum Amps and motor's winding code.
If you ride on a fairly flat road, your speed depends also on whether the bike is derestricted,
For example, the Woosh Petite and the Woosh Santana3 both have 250W motors, but the Petite has winding code 13, the Santana3 code 9. Restricted, both assist up to 15.5mph. Derestricted, the Petite goes up to 20mph on flat roads, the Santana3 27mph.

It's impossible to say. The power that the motor produces depends on the amps that the controller and battery allow. The motor's speed is fixed by it's windings. each type of motor normally comes in different variants with different windings.

Basically, each component of the system needs to match each other for power and speed, and they all need to match your modal speed.

 

[anotherkiwi]

Here is the speed per RPM for various wheel sizes post from ES:

https://endless-sphere.com/forums/viewtopic.php?t=16114

If you look at the specs for your motor it will indicate an unloaded RPM and a loaded RPM. The chart will tell you how fast your motor will go on the flat with no wind and an average rider for a given loaded RPM. The more you pedal and correct gearing will mean you can go slightly faster than those numbers (yes, correct gearing helps hub motors too...). Your "500" Watt motor (more like +1 kW at full assist) will maintain higher speeds with a heavier load/against the wind and climb at higher speed than a 250 W motor.

Your main enemy even before hill gradient comes into play is air resistance, here is a good post on that:

https://tunedintocycling.com/2014/06/28/aerodynamics-part-1-air-resistance/

I have seen two examples of beating air resistance on TV in the last couple of days:

- Tour de France in the Alps, 77 km/h rider rolled into an egg shape on the top bar
- A guy delivering +200 kg of bananas in Burundi sitting upright on a cr@ppy Chinese bike with iffy tyres and brakes doing 70 km/h

Scientific deduction: if your roll up into an egg shape on your 500 W bike it will be faster than a 250 W bike downhill because it is heavier