Advise needed please

[Riche]

The hub on the rear of my scott bike is this,
http://techdocs.shimano.com/media/techdocs/content/cycle/EV/bikecomponents/FH/EV-FH-RM65-2535_v1_m56577569830608953.pdf

I am thinking about getting a bafang 250w(201rpm) or 500w (code 8 393rpm) rear wheel kit but the only thing that preventing me is the 9 speed cassette which I would like to keep intact and working if possible. Would I need to get the freewheel transfrered from one hub to the new hub? Can this be done?

I am quite a large lad and wondered if the 500w motor is over kill? or would a slower more torquey setup be the best option and would the 500w 393 have the same torque as the 250w 201rpm motor, both motors are 36v

Please advise.
Thanks
Rich

 

[banbury frank]

Hi Riche


You need 500 watts or more if you are Heavy like ME also look at 48 volts MORE Grunt

The cogs are different on the motor it screws on on your bike it is a cassette

You can fit a 9 speed screw on freewheel BUT it will make the motor 145 wide you will need to stretch the rear forks a 7 speed cog makes the motor 135 mm wide this is the standard

you can buy from the link below this item FW9Spd1132 it also gives you a much higher gear to keep up with the motor

The Grin Cyclery

Hope this helps

Frank

 

[flecc]

The eZee hub motor from Cyclezee is a powerful 250 watt one and can be supplied with a 9 speed freewheel. Your present 9 speed rear cluster is a cassette type which cannot be transferred onto a motor.

 

[Riche]

Thanks Frank ...
So I just couldn't take off the cassette and transfer to the new hub?
How would a 7 speed freewheel effect the gearing on my 9 speed shifters/derailiers?

I am not sure front wheel motor would work with my bike, the drop outs look pretty recessed.

I wish we had better support for this stuff in the UK. Having to buy from the US or china is a bad way to go or you really pay a premium for it buying in the UK.

Thanks
Rich

 

[NRG]

Riche, all but very very few legal 250W bikes produce in excess of 250W, the most powerful up to 1Kw. Power or grunt if you like is derived from amps and you will find the majority of bikes are equipped with 15amp 36v controllers which give, on a fully charged battery (42v), around 400W at the wheel. This is more than enough to get you up most hills especially with rider input adding another 100W or so.

The higher speed motors present a problem for hill climbing. Best efficiency coupled with high torque when climbing hills is achieved around half speed IE: if your top assist speed is 15mph then good climbing ability is achieved at ~7.5mph. Dropping below creates more losses in the motor and controller heating them up, in other words energy is being wasted in that its not being used for forward motion but for heating the components.

A higher speed motor would mean you need to ride faster up the same hill to keep losses the same, this obviously is harder to do so either the rider has to input more effort or you need to fit a higher rated controller to supply more amps....which means a stronger more capable battery and possibly a higher rated motor depending on how far you take it.

Hope this helps.

 

[Scottyf]

A code 8 has a mental top speed with almost 400rpm @ 36v.
But its really on flat speed. You'd need to travel up hills at 15mph in order to keep it in its sweet spt for best torque.

If your in norfolk and its flat go for it. Otherwise I'd suggest a different wind. Maybe a 10 or 11 @ 36v.
The higher winds will also use up less battery power than the code 8. But you'd need a hefy battery as detailed above.

Your derailer question, you'd be able to use the 7 speed cassette but you'd have 2 extra movements that wouldn't do anything apart from drop the chain on to the axel... So you'd have to remember not to drop all the gears down ...

 

[Riche]

Thanks the replies ..

Your derailer question, you'd be able to use the 7 speed cassette but you'd have 2 extra movements that wouldn't do anything apart from drop the chain on to the axel... So you'd have to remember not to drop all the gears down ...

Could you just adjust the stops on the derailer to reduce the movement of the derailer?

 

[Scottyf]

Yes, the last two movements wouldn't do anything. As you can adjust the lowest point of the stop

 

[Riche]

Thanks for all your helpfull advise

I have opted a for a 9 speed free wheel + 48v 9a Li4po Battery and 48v 500w rear kit.

I will of course let you know how I get on.

Rich

 

[Scottyf]

That'll be good for 30ish mph ;-)