Lightweight setup for 700C front wheel power boost?

[djk]

I do recreational riding of a nice lightweight road bike... and although perhaps it seems odd for me to look into a motor assist, I'm intrigued by the idea of just adding some reserve juice on the hills so I can stay with the faster younger guys.   Am I crazy?    Is this practical?   What kit would be best?   Seems to me that a powered front wheel with a thumb control would work fine... adding just 200 Watts at key points (i.e short hillclimbs) in the ride would be plenty of power to add to my own.

So what kit would you recommend?   Build my own front wheel assembly? or use a prebuilt wheel?   what is the width of the hub?  does it fit standard front forks, such as Cervelo carbon fork?

Thanks

David

[Bikemad]

Hi David andto the forum.

It sounds like you might be wanting a geared minimotor (shown below), rather than a direct drive motor, mainly because the minimotor has an internal freewheel device which completely eliminates any magnetic drag from the motor when it is not being used.

The internal gears greatly increase the torque output from the small motor, which unfortunately gives a lower top speed, but the minimotor has the advantage of being both smaller and lighter than the direct drive motors.



I think the width requirement between the dropouts is ~100mm, but I'm not so sure that carbon forks are going to be suitable for transmitting the axle torque, as the dropouts are not usually designed to withstand any torsional load whatsoever.
I would suggest that you use steel forks to greatly reduce the possibility of dropout failure.

A pre-built wheel would be the simplest option, but if you wanted to build your own, that's entirely up to you.

Perhaps one of the forum members who use a minimotor can provide more information regarding what speed and assistance you are likely to get with different voltages.

This will hopefully have given you something to think about in the meantime.

Alan
 

[Andrew]

Hi David,  unfortunately you will add about 2.5kg's of weight with the mini motor and another 3-6kg's of weight with a lithium battery pack depending on what range and power you want from the motor.  You maybe be able to get a custom made battery pack made to your personal requirements.  my better half has a front wheel mini motor on her mountain bike with a 54v 10ah custom made lithium pack(3kg's) and controller fitted in a large frame bag for good balance on the bike. 
This enables her to tackle hills whilst pedalling. This set-up lacks any real power but it is great as an 'assistance' on hills. 

Here's her bike with the battery/controller/wires all hidden in the frame bag and with the motor up front.



If you are an avid mountain biker you will not like a battery pack mounted over the rear wheel as it makes the bike top heavy and the rear unbalanced and bouncy.  A battery pack inside a rear pannieer is better as it sits lower on the bike with  the battery at the bottom of the bag.

Andrew

[GM Canada]

Hi David,  unfortunately you will add about 2.5kg's of weight with the mini motor and another 3-6kg's of weight with a lithium battery pack depending on what range and power you want from the motor.  You maybe be able to get a custom made battery pack made to your personal requirements.  my better half has a front wheel mini motor on her mountain bike with a 54v 10ah custom made lithium pack(3kg's) and controller fitted in a large frame bag for good balance on the bike. 
This enables her to tackle hills whilst pedalling. This set-up lacks any real power but it is great as an 'assistance' on hills. 

Here's her bike with the battery/controller/wires all hidden in the frame bag and with the motor up front.



If you are an avid mountain biker you will not like a battery pack mounted over the rear wheel as it makes the bike top heavy and the rear unbalanced and bouncy.  A battery pack inside a rear pannieer is better as it sits lower on the bike with  the battery at the bottom of the bag.

Andrew

Great looking bike! What Ebike? Very clean and simple look.

Gary

[Andrew]

Thanks Gary,  I'm lucky that i  had a custom made small battery pack put together by member DirtyGinge that would fit in the frame bag with the excess wires and external controller.  The bike only has to do a 8 mile round trip so the pack has been made accordingly.