Sorry, Another Question

[Biggles]

What stops my rear wheel drive motor at is maximum revs? Also what is the plate that looks a bit like a cooling fan without gaps?

 

[VictoryV]

What stops my rear wheel drive motor at is maximum revs? Also what is the plate that looks a bit like a cooling fan without gaps?

There is an electrical motor effect called "back emf". When your motor starts running it also then acts as a generator to produce a voltage in the reverse effect of the power you are applying. If left to freely run the motor will get faster until the back emf balances the power supplied plus any applied power needed to overcome efficiency losses in the system. It will self balance. So the motor is applying max power at standstill (no back emf) and virtually no power except that required to cover losses at max speed. If you run a petrol engine at full throttle off load it is likely to overspeed to destruction becuase there is no balancing "back emf" to self balance the input energy.

 

[flecc]

And you need to tell us what bike you have to answer the "cooling plate" question.
.

 

[Deleted member 4366]

What stops my rear wheel drive motor at is maximum revs? Also what is the plate that looks a bit like a cooling fan without gaps?

If it maxes out at 15 - 16 mph, it's the controller's programmed speed limit.

 

[Biggles]

Hi, its an e-wayfarer. I was BTW talking about the rear wheel speed with no load on it, i.e. spinning in mid air.

 

[VictoryV]

Hi, its an e-wayfarer. I was BTW talking about the rear wheel speed with no load on it, i.e. spinning in mid air.

That is what I was expaining about "back emf" above (Electro-Magnetic Force - EMF)

 

[Biggles]

So it's self limiting not governed by the controller.

 

[Deleted member 4366]

How fast does it go in the air?

 

[Biggles]

Not sure, I haven't put a rev counter on it, or speed computer.

 

[VictoryV]

So it's self limiting not governed by the controller.

It could be limited by the controller if the absolute wheel top speed limit caused by the balance of battery emf versus back emf is higher than that allowed by the controller - hence d8veh's question about rpm - knowing the rpm and the size of the wheel you can work out the mph at that maximum unloaded speed

 

[Deleted member 4366]

If the motor hits a wall at its maximum, it'll be limited by the controller. If the power reduces gradually to the maximum, it's limited by the motor. Another wsy to tell if it's the motor that's limiting it is if the maximum speed is 25% less with an empty battery compared with when it's full or 12.5% less when half full (or half empty).